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R&D Publications
Accounting for scale effects in genetic evaluation of dairy cattle / Lopez-Villalobos, N.; Garrick, D.J.; Harris, B.L.; Blair, H.T. 1994.
Proceedings of the New Zealand Society of Animal Production v.54 p.275-279
Lactation records of dairy cows calving between 1986 and 1989 were obtained from the Livestock Improvement Corporation of the New Zealand Dairy Board. There were milkfat yields from 2,004,854 lactations in 83,805 contemporary groups. The data were divided into three equal-sized subsets based on average level of production (scale) in the contemporary group; these being (kg milkfat ± sd) High (H), 172 ± 28; Medium (M), 152 ± 26; and Low (L), 139 ± 25. The objectives of this study were to provide evidence of heterogenous variance and to identify the best of three methods to stabilise the variance of milkfat yields for use in the genetic evaluation of New Zealand dairy cattle based on a best linear unbiased prediction procedure using an across breeds animal model which will be implemented in July 1996.
The methods investigated for the accounting of scaling were adjustment based on: contemporary group standard deviation (SD); contemporary group means (MEAN); and logarithmic transformation (LOG) of milkfat yield. The overall correlation between contemporary group means and standard deviations was 0.44. This value was reduced to 0.31 in SD-transformed data, -0.27 (MEAN) and -0.24 (LOG).
Correlations between breeding values for sires estimated from the independent data sets using a mixed model but without adjustment for scale were 0.76, 0.73 and 0.78 in the L-M, L-H and M-H comparisons. These were lower than expected correlations of 0.85, 0.85 and 0.87, reflecting inaccuracies in sire evaluation when scaling is ignored. Calculated correlations were similar for SD and MEAN (0.78, 0.75 and 0.80; 0.78, 0.74 and 0.78), but LOG reduced the calculated correlations (0.73, 0.69 and 0.75).
Results confirm the problem of scaling on genetic evaluation of New Zealand dairy cattle and indicate other methods need to be studied to correct the scaling problem.
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Across breed evaluation of dairy cattle / Harris, B.L.; Clark, J.M.; Jackson, R.G. 1996.
Proceedings of the New Zealand Society of Animal Production v.56 p.12-15
Genetic analysis of dairy cattle has been undertaken using an animal model including pedigree records since 1940 and performance records since 1986. The animal model analyses all breeds and breed crosses simultaneously allowing accurate estimation of hybrid vigour effects for milk production, liveweight, four survival traits and 16 linear type traits. The animal model allows the effects of induction, age at calving and herd- year-season to be taken into account when estimating an animal’s breeding and production values. The breeding value estimates of all animals regardless of breed are on the same scale allowing direct comparison of Holsteins and Jerseys, for example. The results of the animal model analysis are expressed in terms of individual animal performance, eg. kg of milk fat per cow. Three selection indices have been developed to identify the most economically efficient animals under New Zealand pasture based farming systems. To identify the best animals for breeding herd replacements in the future the breeding worth index is used. To rank cows on lifetime profitability the production worth index is used and to rank cows on current lactation profitability the lactation worth index is used. The indices have been developed using a whole farm model which takes into account the future revenue and cost streams to rank the animals on net income per unit of feed.
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The across breed evaluation of dairy cattle in New Zealand / Garrick, D.J.; Harris, B.L.; Johnson, D.L. 1997.
Proceedings of the Association for the Advancement of Animal Breeding and Genetics v.56 p.12-15
New Zealand dairy cattle are genetically evaluated using an cross-breed animal model fitted to production records every three weeks. The traits evaluated and included in economic indices are milk volume, fat and protein yields, lactating cow liveweight and survival. Some additional traits (e.g., animal and udder conformation) are evaluated but not included in any economic index. This evaluation system, which replaced the previous systems as from June 1996, incorporates three major research findings. First, a new methodology to predict total lactation yields from individual test-day information. This accounts for any number of herd tests over any testing frequency and allows for variable information among herdmates and for the effects of culling. Second, a mixed model routine to calculate breeding values using a single trait repeatability model equation, allowing for heterogeneous subclass variation and including fixed breed and group effects. Third, an economic model to derive relative economic values parameterised to a fixed feed supply. Economic indexes describe animal profitability per unit of fee and account for the variation in body size and individual productivity that is a feature of across-breed evaluation. A programme of industry consultation was integral to these developments over some five years, in tandem with an educational campaign targeted at all 14,500 farmers plus other industry players.
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Analysis of herd life in Guernsey dairy cattle / Harris, B.L.; Freeman, A.E.; Metzger, E. 1992.
Journal of dairy science v.75 p.2008-2016
Genetic parameters of 48- and 72-month herd life were estimated with multiple-trait Restricted Max. Likelihood (REML) from sire models incorporating sire relationships. For each age, 2 traits were defined: true herd life (or total longevity) and functional herd life (a measure of herd life when cows are subjected to involuntary culling only). The h 2s of 48- and 72-month herd-life traits were low (0.02-0.07); genetic correlations among herd-life traits were 0.82-0.95, and phenotypic correlations of herd-life traits with 1st-lactation milk, fat and protein yields were 0.37-0.81; those for functional herd life were lower than for true herd life. Multiple-trait REML from sire models, which included sire relationships, was used to estimate genetic and phenotypic correlations of 48-month true and functional herd life with linear type traits for registered Guernsey cattle. The genetic correlations were used to compute weights for indirect predictions of true and functional herd-life transmitting abilities from linear type trait transmitting abilities. These predictions are equivalent to multiple-trait BLUP evaluations with no observations for herd life
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Analysis of management traits in the New Zealand dairy cattle population / Winkelman, A.M.; Harris, B.L.; Montgomerie, W.A. 2001.
Journal of dairy science (accepted for publication
Dairy farm profitability is influenced by the production and non-production traits of the cows. In New Zealand (NZ), cows in Livestock Improvement’s Sire Proving Scheme (SPS) herds are measured for 17 non-production traits known as traits other than production (TOP). Four of these traits are scored by the farmer and are considered to be management traits. The remaining 13 traits are scored by inspectors and related to conformation characteristics of the cow. Scoring for all TOP is done on a linear scale from 1 to 9. The national selection index introduced in 1996 (Harris et al., 1996) included the breeding values (BV’s) for milk, fat, and protein yields, live weight, and survival. Survival was measured as binary traits from lactations 1 to 2, 2 to 3, 3 to 4 and 4 to 5, with each resulting BV weighted by its economic value. As part of a project to enhance the survival BV, research was undertaken to determine the associations between the TOP and survival, with a veiw to determining whether the accuracy of the prediction of survival BV could be enhanced using information on these traits. Associations between the TOP and survival traits were assessed using two methodologies. Linear model methodology was used to estimate genetic and phenotypic correlations between the TOP and survival for each lactation. This work is a continuation of the work initiated by Cue et al. (1996) with six additional years of data and inclusion of survival p to the fifth lactation. Survival analysis (see, for example, Klein and Moeschberger, 1997) was used to examine the degree to which the TOP influenced longevity measured as days of age from first calving to last known herd test. Results for the linear model analysis and survival analysis are reported for the four management and four conformation traits. The four conformation traits chosen were the ones with the highest genetic correlations with survival up to the 5th lactation.
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Animal model for New Zealand dairy cattle evaluation / Harris, B.L. 1994.
Interbull bulletin no.10
This paper reports on the animal evaluation project which is responsible for developing an appropriate animal evaluation system for use in New Zealand. Since the introduction of the current sire evaluation system over 20 years ago there have been a number of developments which together justify a thorough review of the entire system used for providing genetic evaluations of dairy cattle in New Zealand. A detailed description of the current sire evaluation system used in New Zealand is given by Wickham & Stitchbury (1980).
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Anionic and cationic components from protein aggregates in bovine seminal plasma and their effects on sperm motility / Al-Somai, N.; Vishwanath, R.; Molan, P.C.; Shannon, P. 1994.
Molecular reproduction and development v.39 p.328-336
Bovine seminal plasma proteins are in an aggregated form of high molecular weight in their native state. By immobilisation on a cation exchanger with exposure to disaggregating conditions (i.e., acetonitrile and low pH), the high-molecular-weight aggregates could be dissociated to slowly release the low-molecular-weight components. The anionic component released from the cation exchanger during disaggregation was collected by adsorption on a hydrophobic interaction column. The cationic component remaining on the cation exchanger was eluted with NaOH. Both components were found on gel permeation chromatography to be < 5 kDa. SDS-PAGE of the various fractions showed that components of low molecular weight were still in an aggregated form. These components resulting from the disaggregation process have detrimental effects on sperm motility and the effects were more substantial compared with that of whole seminal plasma. All the cationic components were significantly detrimental to sperm motility, especially the fractions of low molecular weight. The anionic fractions reduced sperm motility when in an aggregated state. The isolated anionic peptide was not detrimental in its free form. In all fractions the peptides tended to re-aggregate to a higher molecular weight under neutral conditions, however, the isolated anionic peptide (molecular weight < 1,500) failed to do so.
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Application of Transvaginal Ultrasound for Performing Amniocentesis in Cattle / Bellow, M.S.; Feeleus, W.N.; Ohlrichs, C.L.; Johnson, D.L.; Looney, C.R. 1996.
Theriogenology v.45 no.1 p.225
This study determined if transvaginal ultrasound-guided aspiration could be used to perform amniocentesis on pregnancies at less than 80 days of gestation. Pregnant crossbred beef recipients (n=24) were assigned to one of two groups. Group A (n=9) and Group B (n=15) ranged from 40 to 59 and 60 to 75 days of gestation, respectively. The pregnancies used in this study were the results of transfers of frozen demi embryos or natural service. Recipients were restrained, administered an epidural and the perianal region thoroughly washed. An Aloka SSD-500V ultrasound (Corometrics Medical Systems, Inc., Wallingford, CT) with a 5 MHz convex array transducer fitted in a custom-made plastic probe housing a stainless steel needle guide was utilized for aspiration. The probe and transducer were covered with a sanitary latex cover (Cone Instruments, Solon, OH) before each procedure. The pregnant uterus was supported per rectum in one hand, the transvaginal probe and needle were manipulated in the other hand. A 17-gauge, 60 cm echogenic single lumen needle (RAM IVF Supply, Madison, WI) was used to penetrate the vaginal wall, uterus and subsequent amniotic cavity. The aspirate was collected using 10 ml Air-Tite syringes connected to medical grade Teflon tubing (FR 6.3/70cm; Cook Veterinary Products, Spencer, IN) via a three way stopcock. The initial 3 ml of amniotic fluid was discarded to ensure that the needle was devoid of any maternal cells which may have been aspirated during penetration of the vaginal wall. The lever on the three-way stopcock was repositioned towards a second syringe and 6 to 8 ml of additional aspirate were then retrieved. The entire transvaginal ultrasound-guided amniocentesis (TUA) procedure took approximately 5 min.
Following aspirations, samples were transferred into 15 ml conical tubes and centrifuged at 400 g for 10 minutes. Cytological examination of cells was not performed, however, a cell count was done on random samples and number of cells ranged from 0.5 × 105 to 2.2 × 106 for Group A and B, respectively. All recipients were subsequently scanned using a 7.5 MHz rectal transducer once weekly for a period of 2 weeks to assess fetal viability via fetal heartbeat. In Group A, 1 of 9 [47 d] and in Group B 3 of 15 [67 d (n=2), 75 d (n=1)] of the recipients aborted 1 to 2 weeks following the TUA procedure. In each of the TUA procedures that resulted in abortions, blood was present in the amniotic sample. This may have indicated possible damage to the fetal placenta unit and that may have lead to subsequent abortion. As pregnancies advanced, positioning became more difficult due to the size of the reproductive tract; however, the amniotic cavity was larger, making it easier to penetrate and allowed for positioning the fetus further away from the incoming needle. Transvaginal ultrasound-guided amniocentesis is a nonsurgical procedure which may be performed on pregnancies 40 to 75 days of gestation with minimal risk to the fetus.
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Approximate reliability of genetic evaluations under an animal model / Harris, B.; Johnson, D. 1998.
Journal of Dairy Science v.81 p.2723-2728
A method was developed for calculating approximate reliability for national systems of evaluation. The method combined the reliability of three information sources: parent average, animal’s own records, and progeny records. This method provided good approximation to the actual values with minimal upward bias and was considerably better than the current national method of New Zealand genetic evaluation or Meyer’s method for all accuracy measures. Our method had an average absolute bias of 0.006 compared with 0.026 and 0.035 for the current national method and Meyer’s method, respectively. Our method was less computationally demanding than the current New Zealand method. One of the major advantages of the method is that it can be extended to accommodate more complex models by altering the selection index equations within the method. An example is given for which the method was extended to account for a genetic correlation other than unity between an incomplete lactation and a complete lactation yield.
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Artificial breeding of yearling dairy heifers: an economic analysis / Rendel, J.M.; Xu, Z.Z.; Burton, L.J. 1998.
Proceedings of a Seminar of the Society of Dairy Cattle Veterinarians of the New Zealand Veterinary Association v.15 p.259-262
Dairy farmers have been mating yearling heifers to Artificial Insemination (Al) for some time. It is the believed that this practice increases the rate of genetic progress thereby increasing farm profitability. Products are available which enable heifers to be synchronised making the mating process more convenient. There appears to have been very little research done into the economics of mating yearlings to Al. The rate of genetic progress per year is a function of selection intensity, accuracy of selection, generation interval and the amount of variation (van Vleck, Pllak et al. 1987). The generation interval is the average age of parents when their offspring are born. This involves four reproductive pathways. Two are associated with breeding young bulls to progeny test; cows to breed sons and bulls to breed sons. A third pathway; bulls to breed daughters’ is associated with Al companies selecting bulls to market and farmers bull purchasing decisions. The fourth pathway is concerned with farmers selecting cows as dams of heifer calf replacements; cows to breed daughters. The pathways that contribute most to the genetic progress in dairy cattle are those that are controlled by Al companies, which are the cow to son, bull to son and bull to daughter pathways. Mating yearling heifers to Al, rather than using natural mating, impacts on the cow to daughter pathway.
The selection intensity is a function of the proportion of animals selected from those available (the smaller the proportion selected the higher the selection intensity and the greater the genetic progress). The accuracy is a function of herd recording and herd testing.
Cows (including heifers) and bulls are identified as parents of the next generation of cows and bulls using a breeding objective. The breeding objective used in New Zealand, is concerned with identifying animals that are the most efficient converters of feed into net farm income (Livestock Improvement 1996).
The Breeding Worth (BW) is used as a measure of the national NZ breeding objective and is the economic worth of animals as parents of the next generation. It is measured as dollars of net farm income pr 4,500 kg of Dry Matter (DM). The BW is a measure of the “economic efficiency” rather than the net or gross output from the animal. Those animals that produce greater quantities of valuable product or reduce costs will contribute most to the net farm income. The 4,500 kg DM is the estimated intake of an average New Zealand cow and her proportion of the replacements.
The traits that are combined together in the BW are those traits that have been identified as having a major influence on farm profitability and have a genetic basis. These traits are milkfat yield, protein yield, milk volume, liveweight and survival.
The BW represents the Net Present Value (the value of some future net cash flow in today’s dollars) from breeding replacements from an animal. It includes future prices and costs as well as the terminal value of the animals present after 20 years. Therefore, economic analyses of different mating strategies can be done directly on the change in BW of parents.
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Assesment of female traits for genetic improvement in dairy cattle / Grosshans, T.; Xu, Z.Z.; Burton, L.J. 1996.
Proceedings of the New Zealand Society of Animal Production v.56 p.27-31
The objective of the present study was to investigate the suitability of various fertility traits for describing the reproductive performance of dairy cows in New Zealand. Using a data set from herds participating in the Livestock Improvement Sire Proving Scheme over the 1986/87 to 1992/93 seasons, the following female fertility traits have been investigated. Based on the start of mating (STOM) in a particular herd, the intervals from STOM to first mating (SMFM) and to the successful mating (SMCO) were calculated and compared to the internationally used traits that are based on the calving date, such as, calving to first mating (CFM) and calving to successful mating (days open, DO). Further traits considered are age at calving (AC), number of matings per conception (NS), first to successful mating (FMCO), calving interval (CI) and two traits that indicate whether a cow became pregnant within 21 or 42 days of STOM (PR21, PR42). The traits defined for the unique conditions in New Zealand, SMFM, SMCO, PR21 and PR42 emphasize the economic importance of reproduction to dairy production. The comparison to overseas studies using DO, FMCO and CI showed that New Zealand dairy cows had a better fertility performance than overseas cows
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Assessing the changes in translational and rotational velocities of bull sperm under aerobic and anaerobic conditions after cold shock using the TTLV laser machine / Prendergast, E.; Vishwanath, R.; Shannon, P.; Molan, P.C. 1996.
Proceedings: Australian Society for Reproductive Biology p.14
Progressive movement in spermatozoa is an important function enabling them to reach the site of fertilisation. Propulsion requires a supply of ATP which can be generated either in the presence of oxygen by respiration coupled with oxidative phosphorylation or anaerobically by fructolysis. When the available oxygen drops below a critical level, transition from one system to the other is clearly evident using the TTLV laser machine (1) resulting in a sharp decrease in both Translational velocity (TV0 and Rotational velocity (RV). Cold shock immobilises sperm by causing plasma lemma damage, allowing it to become leaky. In this study the TTLV laser machine was used to monitor the differences in motility of bull sperm stored in 3 cationic lipoprotein diluents that have been described previously (2). The diluents were under test for their relative abilities to protect against cold shock. Measurements of progressive velocity (v) and rotation frequency (f) were taken before and after cold shocking the sperm to 0ºC for 20 minutes, under both aerobic and anerobic conditions. Semen collected from 3 bulls was diluted to 200 million sperm/ml in 14G citrate buffer containing 5% egg yolk (2) or one of the lipoprotein diluents at the equivalent protein concentration (8.15 mg/ml). Assessments were performed at 39ºC, with the semen diluted to 20 million sperm/ml with 14G buffer and v and f were measured using six-2 minute alternate runs for each. To obtain anaerobic conditions all diluents were saturated with nitrogen gas and semen samples were incubated anaerobically at 37ºC for 45 minutes prior to assessment and cold shock.
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Assessing the value of breeding technologies to dairy farmers / Rendel, J.; Jackson, R.; Harris, B.; Allison, T.; Shannon, P.; Burton, L.; Tempero, H. 1996.
Proceedings of the New Zealand Society of Animal Production v.56 p.22-24
The adoption of technologies for breeding dairy cattle requires estimating the financial return to dairy farmers in conjunction with assessing the financial implications to the breeding company. This paper describes a procedure currently used by the Livestock Improvement Corporation.
The net on-farm income generated as a result of the new technology is calculated. This is discounted to a Net Present Value allowing for the cost of the technology. A positive NPV indicates the adoption of the technology is of benefit to the dairy farmer.
The breeding company also should assess the funding implications of any change. Typically this is expressed in terms of the increase/decrease in price of products and services.
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Associations between milk protein genetic variants and production traits in New Zealand dairy cattle / Winkelman, A.M.; Wickham, B.W. 1997.
Proceedings of the IDF seminar "Milk protein polymorphism II": Palmerston North p.38-46 Records on 7574 first lactation cows were used to investigate the associations between milk protein genetic variants and 305-day milk, fat, and protein yields. Friesians, Jerseys and Ayrshires and their crosses were represented in the data. Milk samples were type for three casein (Cn) proteins µs1-Cn (B,C), ß-Cn (A1, A2), Â-Cn (A, B), and one whey protein ß-lactoglobulin (Lg) (A,B). The model used to describe the data included the additive genetic effect of animal and the four protein phenotypes. Hypotheses testing involved a test of the breed by protein phenotype interaction for each of the four milk proteins, and, where appropriate, a test to determine whether the difference between the homozygotes was significantly (P<0.05) different from 0, as well as a test to determine whether the heterozygote was significantly different from the midpoint of the two homozygotes.
The interaction between breed and ß-Cn phenotype was significant for milk, fat and protein yields, while the interaction between breed and Â-Cn phenotype was significant only for protein yield. The interaction associated with Â-Cn was a scale effect, while the interactions associated with ß-Cn resulted from reranking of breed across the protein phenotypes. Across breed µs1-Cn BC cows produced 1.9% less milk and 0.6% more protein than BB cows, while the differences between the phenotypes for fat production were small. The ß-Cn A2 allele was associated with increased production in the Friesians, with A2 A2 cows producing approximately 2% more milk, fat and protein than A1 A1 cows. The opposite effect was found in Jerseys, where A2 A2 cows produced 3-4% less milk, fat, and protein that A1 A1 cows. The B allele of Â-Cn was associated with a 0.6-3.5% increase in production. The ß-Lg BB phenotypes produced approximately 1.3% less milk and protein and 1.2% more fat than the AA phenotypes.
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Associations between milk protein genetic variants and production traits in New Zealand dairy cattle / Winkelman, A.M.; Wickham, B.W. 1996.
Proceedings of the NZ Society of Animal Production v.56 p.24-27
Records on 7574 first lactation cows were used to investigate the associations between milk protein genetic variants and 305-day milk, fat, and protein yields. Friesians, Jerseys and Ayrshires and their crosses were represented in the data. Milk samples were typed for 3 casein (CN) proteins as1-CN (B,C), b-CN (A1, A2), k-CN (A,B) and 1 whey protein b-lactoglobulin (LG) (A,B). The model used to describe the data included the additive genetic effect of animal and the four protein phenotypes.
The interaction between breed and as1-CN phenotype and between breed and b-CN phenotype was significant (P<0.05) for milk, fat and protein yields while the interaction between breed and k-CN phenotype was significant (P<0.05) only for protein yield. The interactions associated with the as1-CN and k-CN phenotypes were scale effects while the interactions associated with b-CN resulted from reranking of protein phenotype across the breeds. Friesian and Jersey as1-CN BB cows had higher (2.8% and 0.8%, respectively) milk production and lower (0.3% and 1.2%, respectively) protein production than BC animals while the differences between the phenotypes for fat production were small. The b-CN A2 allele was associated with increased production in the Friesians with A2A2 cows producing approximately 2% more milk, fat and protein than A1A1 cows. The opposite effect was found in Jerseys where A2A2 cows produced 3-4% less milk, fat, and protein than A1A1 cows. The B allele of k-CN was associated with a 0.6 to 3.5% increase in production.
The b-LG BB phenotypes produced approximately 1.3% less milk and protein and 1.2% more fat than the AA phenotypes. The dominance effect was not significant (P<0.05) for any of the protein phenotypes.
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Associations of b-lactoglobulin A, B and C variants with production traits in New Zealand dairy cattle / Winkelman, A.M. 1997.
Proceedings of the IDF seminar "Milk protein polymorphism II": Palmerston North p.83-86 Records on 2742 first lactation cows were used to investigate the associations between ß-lactoglobulin phenotype and 305-day yields of milk, fat and protein. The data consisted mainly of Jersey and Jersey cross cows. Milk samples were typed for the A, B and C variants. The frequencies of the A, B, and C variants were 0.31, 0.62 and 0.07, respectively. Thus, frequency of C variant cows was low (19CC cows). For all traits, AA cows produced the highest yields while CC animals produced the lowest yields, with AA cows producing 4.9%, 4.3% and 6.8% more milk, fat and protein, respectively, than CC cows. However, the low number of CC animals resulted in large standard errors of the difference (SED) between the phenotypes so that contrast was significant (P<0.05) only for protein yield. Production of AC and BC animals was 1-2% lower than that of AB and BB animals.
While the SEDs were large, the results suggest that the C variant is associated with a reduction in milk, fat and protein production. Further work is needed to quantify more accurately the association between the C variant of ß-lactoglobulin and production traits.
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Breeding dairy cattle for economic efficiency: a New Zealand pasture-based system / Harris, B. L. 1998.
6th World Congress for Genetics applied to Livestock Production v.25 p.383-386 Dickerson (1970) stated that the performance criteria used for evaluating the efficiency of milk production could be improved upon. He argued that including estimated energy intake in the selection objective would dampen the enthusiasm for the larger cow per se and thereby reducing costs associated with cow maintenance. Almost 30 years later, a large number of traits are evaluated in dairy cattle populations including: milk production, survival, linear conformation traits and to a lesser extent fertility, health and liveweight traits. Most countries proivde indices based on gross milk income as well as separate indices including conformation traits (Leitch 1994). The majority of the indices do not include the feed costs associated with increased production of the individual milk components from genetic improvement. Furthermore, exclusion of other major components of net income such as feed requirements for maintenance can favor higher producing larger cattle over comparatively lower producing, smaller cattle (Visscher et al. 1994) rather than cattle which maybe more economically efficient. In a pasture based system the objective is maximise the net income per hectare or more explicitly maximise the net income per unit of feed consumed, thus the first definition of efficiency is applicable.
Two main methods have been developed to allow selection on the breeding objective. The most common method is the use of a selection index that combines individual trait breeding values with economic weights to provide a single measure on which to select animals. The second method measures the breeding objective (e.g. net income per cow) directly and provides genetic evaluations for this measure (Line and Allaire 1977; Visscher and Goddard 1995). The advantage of the second method is that it includes a number factors such as lactation length, health status and survival into a single measure. However, the procedure requires net income to be computed on individual cows which involves estimation of feed costs and variable farm costs which are then allocated to individual cows. Such a procedure requires a number of assumptions to be made which may account for the low to moderate heritability estimates being reported. The low to moderate heritability estimates limit the usefulness of this approach. This report will focus on the application of selection index procedures to breed for economic efficiency in a New Zealand pasture based system.
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Breeding objectives - future directions / Harris, B.L. 1993.
Proceedings A.L. Rae symposium on animal breeding and genetics: Massey University p.30-37 Breeding objectives can be considered as a function used as the basis for genetic evaluation. Livestock are selected as parents of the next generation based on their aggregate genotype so the aggregate genotype can be considered more broadly as a breeding objective. Breeding organisations are selling technological change to producers, primarily as semen, embryos or offspring from highly selected animals. A major goal of breeding organisations must be to supply genetic material which helps individual producers to improve their net income (Rae 1982). The adoption of genetic improvement constitutes a continuous process of change which will affect the net income of the producer throughout the life of the farm business. Economic methods used to value technological improvement (Peterson and Hayami 1977) provide a logical basis for determining the economic weightings in the aggregate genotype.
Several factors should be considered when modelling the economics of genetic gain: the genetic changes in any other correlated traits; the flow of genetic improvement through the producer herd over time; and the consequences of long-term selection on all traits of economic importance (which will affect the ultimate value for the accrued genetic gain for traits being selected). A model which accounts for the flow of genetic improvement in traits in the breeding objective over time is required. Ideally the model of a farm enterprise should include all sources of revenue and cost so that the net income will be accurately predicted. Modelling of the producer enterprise is necessary since the breeding objective via the aggregate genotype should maximise a function of the net income of the producer enterprise (Allaire and Thraen 1985). Constraints on the available resources and constraints concerning production processes are required for this model to be realistic. Because genetic improvement is a continuous process, any economic analysis of genetic gain cannot be done with a static economic model – rather, an inter-temporal economic model is required. If the breeding goals is to maximise a function of the net income of the farm enterprise then a key question is-what is the economic contribution of a one unit genetic improvement in the traits in the breeding objective to the net present value of the producer net income
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Calving difficulty in two genetic lines of Holstein-Friesian cows differing in mature live weight / Garcia-Muniz, J.G.; Holmes, C. W.; Garrick, D. J.; Lopez-Villalobos, N.; Spelman, R. J. 2000.
Proceedings of the 6th World Congress on Genetics Applied to Livestock Production v.25 p.39-42
Calving difficulty (CD) records (O = no difficulty, 1 = difficult calving) were collected over a 10-year period from 1987 to 1996 from a dairy herd used to develop two genetic lines of Holstein-Friesian (F) cows differing in mature live weight (LW). Cows from the base herd (B, n – 157), the heavy (H, n = 53), and light (L, n = 49) LW selection lines provided 508, 110, and 101 calving records, respectively. Nationally evaluated across breeds, the average breeding values (BV’s) for LW were 41.3 kg (B), 18.5 kg (L), and 92.5 kg (H), for maternal grandsires (MGS), and 47.4kg (B), 32.1 kg (L), and 87.3 kg (H) for sires. Stepwise logistic regression was used for variable selection and to estimate the regression coefficients and odds ratio (OR) of variables related to CD. Variables considered were calf sex, parity, age, genetic line, sire of calf breed, an index for farm profitability termed “Breeding Worth” (BW), and the BV’s for production traits and traits other than production (TOP) for sires and MGS. Primiparous (n = 228 calvings) and multiparous (n = 490 calvings) cows were analysed separately. There was no effect of genetic line (H or L) on CD of primiparous or multiparous cows. For primiparous cows, calves were more difficult to deliver if i) sired by F than by Jersey (J) bulls (P < 0.05; OR = 2.3), ii) if they were males (P < 0.005; OR = 2.7), or iii) if their MGS BV for rump angle was one standard deviation (SD) below average (P<0.11; OR = 1.7) more difficult to deliver than females. Calves were more difficult to deliver if calved by younger cows (P < 005; OR = 1.6), sired by bulls with BW one SD below average (P < 0.05; OR = 1.5), or if from bulls with BV for rump width one SD above average (P < 0.01; OR = 1.4).
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Changes in susceptibility of bovine sperm to in situ DNA denaturation during prolonged incubation at ambient temperature under conditions of exposure to reactive oxygen species and nuclease inhibitor / Krzyzosiak, J.; Evenson, D.; Pitt, C.; Jost, L.; Molan, P.; Vishwanath, R. 2000.
Reproduction, fertility and development v.12 no.5&6 p.251-261
Sperm were incubated for up to 9 days in the presence or absence of exogenous hydrogen peroxide, phenylalanine, catalase and aurintricarboxylic acid to assess the influence of reactive oxygen species and inhibition of deoxyribonucleases on sperm chromatin stability. The assessment of sperm DNA susceptibility to in situ acid denaturation by the sperm chromatin structure assay did not detect any difference in chromatin stability between sperm incubated for 9 days under aerobic and anaerobic conditions in a diluent called 14G. Exposure to exogenous hydrogen peroxide under both aerobic and anaerobic conditions and to phenylalanine under aerobic conditions (which produces hydrogen peroxide by a reaction catalysed by the aromatic amino acid oxidase present in sperm) was detrimental to sperm chromatin stability, increasing its DNA susceptibility to in situ acid denaturation over the incubation time. This effect was eliminated if catalase was present in the diluent. Inclusion of the general deoxyribonuclease inhibitor aurintricarboxylic acid in the diluent severely decreased sperm chromatin stability under both aerobic and anaerobic conditions. Aurintricarboxylic acid was mildly cytotoxic, as revealed by viability assessment, under aerobic, but not under anaerobic, incubation conditions. Exogenous hydrogen peroxide, either directly added to the diluent or generated through the enzymatic oxidation of phenylalanine, was detrimental to sperm motility and the integrity of the plasma membrane.
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Characterization of ovarian follicular cysts and associated endocrine profiles in dairy cows / Hamilton, S.A; Gaverick, H.A.; Keisler, D.H.; Xu, Z.Z.; Loos, K.; Youngquist, R.S.; Salfen, B.E. 1995.
Biology of reproduction v.53 no.4 p.890-898
It is generally accepted that ovarian follicular cysts (cysts) are nonovulatory follicular structures that contribute to extended calving intervals. Follicle/cyst dynamics and the etiology of cysts are unclear. The present study was conducted to characterize follicle/cyst dynamics and to define endocrine changes (etiology) associated with cyst development. Thirty-two dairy cows were studied: controls (n = 6), cows with spontaneously occurring cysts (n = 14), and cows in which cysts were induced by exogenous steroid treatment (n = 12). Ovaries of cows were scanned daily by ultrasonography to record follicle/cyst dynamics. Blood was collected to determine endocrine changes associated with follicle/cyst life span. Three ovarian responses in cows with cysts were observed: persistence of cysts, turnover of cysts, or spontaneous recovery (self-recovered; turnover of cysts and replacement with a follicle that ovulated). Mean maximum size of cysts was larger (p < 0.05) than that of ovulatory follicles (2.80 +/- 0.19 vs. 1.60 +/- 0.05 cm). Mean interval from initial detection of follicle/cyst wave to detection of a new follicle/cyst wave in cows with cysts was longer (13.0 +/- 1.1 days; p < 0.05) and more variable (6 to 26 days; p < 0.05) than in controls (8.5 +/- 0.5 days and 6-14 days, respectively). Cysts grew at the same rate as follicles but continued to grow for an additional period of time. A transient increase in FSH preceded detection of all follicle/cyst waves
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Comparative reproductive performance. Chapter 3 of: Reproductive management of grazing ruminants in New Zealand; ed by E.D.Fielden & J.F.Smith; NZ Society of Animal Production / McMillan, W.H.; Shackell, G.H.; Vishwanath, R. 1998.
This chapter aims to compare and contrast various aspects of the reproductive biology and patterns of reproduction in sheep, cattle, deer and goats. As well as providing estimates of mean levels of reproductive performance, estimates are provided of the variation about these mean values. Furthermore, the implications of this variation for the successful management of reproduction in the four target species are highlighted. Performance data recorded in New Zealand flocks and herds is used widely, but overseas data is also used where New Zealand data is lacking. Where appropriate, data from males and females of each of the species is presented. The objective is to provide descriptive material, much of it in tabular (16 tables) and graphic form (15 figures), for easy reference. Other chapters are cross-referenced when more detail or additional material on techniques may be useful.
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Comparisons between fertility and survival of strains of Holstein-Friesian cow, Jersey cows and their crosses in New Zealand / Harris, B.L.; Holmes, C.W.; Winkelman, A.M.; Xu, Z.Z. 2000.
British Society of Animal Production occasional publication The survival and fertility of strains of Holstein–Friesian (HF) cows, Jersey cows and their crosses was investigated. Parametric survival analysis was used to model the number of days between first calving and last known herd test. The analysis was stratified by breed and included explanatory variables for production and nonproduction traits and proportion of overseas (i.e. not of New Zealand origin) HF genetics. Linear model analyses were used to investigate the genetics of fertility measures of first–lactation cows and their associations with production, live weight and survival. The HF Jersey crossbred cows had a lower risk of culling than the parental breeds. The risk of culling increased with the proportion of overseas HF genes in both the HF and HF Jersey crossbred cows. The heritabilities for the fertility traits ranged from 1.3% to 5.4% with days from start of mating to first mating (DFM) having the highest value. Antagonistic relationships, in terms of genetic correlations, between fertility and production were largest for DFM. DFM was negatively correlated with survival. Declining fertility and survival were found as the proportion of overseas HF increased.
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Comparisons of fertility measures in strains of Holstein-Friesian cows, Jersey cows and their crosses / Harris, B.L.; Winkelman, A.M.; Burton, L.J. 2000.
Dairyfarming annual p.71-78
The objective of this study was to investigate the survival and fertility of Jersey cows, strains of Holstein-Friesian (HF) cows and their crosses reared under the seasonal pastoral dairy farming system of New Zealand (NZ).
Linear model analyses were used to investigate the genetics of fertility measures and their associations with production traits, live weight and survival. The data was obtained from 104,862 first-lactation cows participating in Livestock Improvement’s Sire Proving Scheme herds (LSPS) in seasons 1987 to 1999. The fertility measures were days to first mating (DFM), calf born to artificial insemination (CAI) and two measures of returning to heat after first artificial insemination (AI).
The heritabilities of the fertility traits ranged from 1.3% to 5.6%, with DFM having the highest value. Antagonistic genetic relationships were found between production and fertility traits. The genetic correlation’s between fertility and production were largest for DFM (rg = 0.19, 0.13, 0.09 for milk, fat and protein yields, respectively). The two fertility traits DFM and CAI were strongly genetically correlated (rg = -0.840). Both CAI and DFM were correlated with survival from lactation 1 to 2 (rg =0.84 and –0.44, respectively) and survival from lactation 1 to 5 (rg = 0.80 and –0.48, respectively). Crossbreeding increased production and liveweight and had a favourable effect on the fertility traits DFM and CAI. Declining fertility and survival were found as the proportion of overseas HF genetics increased.
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Controlled breeding technologies / MacMillan, K.L.; Vishwanath, R.; Xu, Z.Z. 1997. From: Milk composition, production and biotechnology p.363-371
Artificial insemination (AI) is recognised as an integrated process initially involving off-farm routines for collection, processing, storage and distribution of semen from selected sires which have usually been progeny tested to confirm their genetic merit for milk production. The on-farm routines include detection of oestrus so that the insemination procedure allows the stored semen to be prepared appropriately within minutes of using a standardized palpation technique to pass an inseminating pistolette through the cervix. The sperm are deposited in the lumen of the uterus while the inseminated animal is in oestrus but has not ovulated. This total process is the product of research on each of the steps from semen collection to sperm desposition (Peters and Ball, 1987). Initial research focused on methods for semen collection and processing. Aspects of oestrus detection were largely understood because of well-recognised cow-cow and bull-cow behavioural interactions occurring at around 21-day intervals for individual cows until they had conceived. Current research on semen collection, processing and storage is limited to using standardized equipment to produce semen straws for storage in liquid nitrogen (Peters and Ball, 1987). A notable exception is in New Zealand where the marked peak in demand for inseminations, because of the highly seasonal nature of the pasture-based dairy industry, is best accommodated through the development of unique diluents which allow relatively low numbers of sperm (1 x 106 total sperm) to be inseminated after being stored at room temperature in CaprogenTM for several days (Shannon and Vishwanath, 1995).
Increasing emphasis has been placed on genetic aspects of the AI process, partly because maximising the rate of genetic progress is considered a desirable objective, but also because modern marketing techniques are used to promote sales of semen. Sire selection methods first focused on comparing progeny statistics to accurately identify the superior sires but then moved onto producing young sires whose genotypes were expected to increase their profitability of retention for widespread use as a progeny tested sire. This aspect of young sire production has also been associated with increasing selection differentials within the female population through increasing embryo numbers, first by superovulation and most recently by in vitro embryological techniques (Peters and Ball, 1987).
Two original reasons for promoting the use of AI were to remove the safety risks associated with having to maintain mature sires for herd breeding, and to reduce the transmission of veneral diseases. The use of AI is now widespread and these reasons tend to be forgotten. However, the reproductive performance of cows in many dairy industries is steadily declining. This is not because of clinical reproductive disorders so much as reduced emphasis on differences among sires in their fertility, difficulties in monitoring reproductive performance with decentralised recording combined with herd staff inseminating within a single herd (DIY inseminating), and the negative consequences of increasing the milk production potential and the daily milk yield on fertility (Macmillan, 1985; Macmillan et al, 1996). The ideal postpartum interval to conception still coincides with peak daily milk yield. An animal’s energy deficit appears to compromise its ability to conceive as well as its display of oestrus (Lehrer et al., 1992). Among cows in high producing commercial herds in North America, oestrus detection rates of around 50% can be found with pregnancy rates around 40% to produce a pregnancy rate profitability associated with an individual oestrus or ovulation of about 20% (Macmillan et al., 1996).
This diminished level of reproductive performance could not be tolerated in New Zealand’s dairy herds because cows which fail to conceive during a breeding period of 12-14 weeks will be culled from the herd and replaced by younger animals. The annual production cycle is centred on a herd owner’s choice of a date in late winter when cows should commence calving so that the lactational peak in production coincides relatively closely with the spring peak in daily pasture growth rates. Selecting this date then dictates the date to commence breeding cows by AI in that herd, irrespective of an individual cow’s calving date. Since none or very few cows may be milked during the 6 weeks preceding the date selected for the planned start of calving (PSC), lactation length is also dictated mainly by calving dates relative to a herd’s date of PSC (Macmillan et al., 1991).
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Deleterious effect of seminal plasma in the cryo-preservation of bovine spermatozoa / Martinus, R. D.; Molan, P. C.; Shannon, P. 1991.
New Zealand Journal of Agricultural Research v.34 p.281-285
The effect of seminal plasma on spermatozoa was studied during freezing in a buffered diluent. The effect was assessed after thawing, both by visual assessment of motility and by colorimetric assay of aromatic L-amino acid oxidase activity. The presence of seminal plasma caused damage to the spermatozoa, as reflected by an increase in the release of the amino acid oxidase (increased from 39.6 to 86.1% of that released from maximally damaged spermatozoa) and a reduction in the motility of the spermatozoa (reduced from 29.6 to 2.7% motility). Very little of the damage was incurred in the cooling of the spermatozoa to 5ºC before freezing; this tends to suggest that the effect of seminal plasma on spermatozoa during freezing is distinct from its known effect in cold shock of spermatozoa.
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Do sperm cells age? A review of the physiological changes in sperm during storage at ambient temperature / Vishwanath, R.; Shannon, P. 1997.
Reproduction, fertility and development v.9 no.3 p.321-331
In a liquid environment, at high dilutions, fertility of bull sperm is maintained for 3–5 days when stored at ambient temperatures (10–21°C), after which time it steadily declines at a rate of 3–6% per day. This decline in fertility occurs irrespective of whether the sperm are stored at 5°C or at 15°C, but the rate is greater once storage temperatures exceed 25°C. Sperm motility can be maintained for extended periods in an environment where the extracellular oxidative stress is minimized by reducing the oxygen tension, by addition of antioxidants and chelating agents; however, this will not prevent a significant drop in fertility after five days of storage at ambient temperature. The requirement of energy by the sperm-motility apparatus demands a high level of respiratory activity. This system is very active and the free radicals produced in vivo during this process could lead to chromatin damage. As no internal repair mechanism exists in sperm, an extraneous supply of protectants, or an environment where damage is minimized, is essential to maintain its fertilizing potential. The lack of extended storage potential of sperm, even in the presence of antioxidants, seems to suggest that although oocyte-penetrating ability of the sperm could still be intact, the high rate of intracellular metabolic activity could lead to mitochondrial DNA damage and chromosomal abnormalities that would compromise the viability of the resulting conceptus.
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Economic considerations of protein variants in the design of breeding schemes / Rendel, J.M.; Harris, B.L. 1997.
FIL/IDF Milk Protein Polymorphims Conference: Christchurch p.461-466 The major mechanisms for altering the frequencies of milk protein genetic variants in the national dairy cattle population are the selection of cows and bulls to be parents of the next generation, and the culling of cows.
The objective of this study was to investigate the economics of several options for including selection for a protein variant in a breeding programme. When considering adding traits to a selection programme, the economic benefits of the additional traits need to be weighed against both the lost in genetic gain in the current traits and any further costs associated with the added traits.
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Economic value of response from sire selection in dairy cattle - a linear programming model / Harris, B.L.; Freeman, A.E. 1994.
Agricultural systems v.44 p.65-89
A linear programming model that accounts for the economic consequences of response to selection in milk production, type, somatic cell score, days open (a reproductive trait), and liveweight to the producer enterprise over a given planning horizon is described. A procedure is given in detail for defining upper and lower bound constraints on variables that are correlated in the linear programming model. This procedure enabled the linear programming model to construct a feasible hyperspace that reflects the relationship between the variables in terms of the trend in the relationship and the variation around this trend. The linear programming model was used to compute optimal rates of rseponse to selection for all traits in the model for four planning horizons. The optimal response to selection per year for the production traits was closest to the maximums achievable from a gene-flow model. Of all the nonproduction traits, days open had the greatest proportion of its maximum achievable from a gene-flow model. The linear programming model was used to compute relative economic weights ( REVs ) for the nine traits for each planning horizon. The REVs for milk, fat and protein production were considerably larger than the REVs for the nonproduction traits for all planning horizons. Somatic cell score had the largest REVs of the nonproduction traits in all planning horizons.
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Economic weights for milk yield traits and herd life under various economic conditions and production quotas / Harris, B.L.; Freeman, A.E. 1993.
Journal of dairy science v.76 p.868-879
A linear programming model was used to derive economic weights for yield traits and herd life for a farm system. Different milk markets, protein to fat price ratios and feed costs were considered. The model allowed optimisation of the system over time, while simultaneously optimising management resource and capital allocation and optimising future genetic merit of the animal. The change from fluid to manufacturing use of milk had considerable effect on the economic weights for yield traits but had little effect on the weights for herd life. The effect of changes in feed costs was greatest on the economic weights for herd life. Changes in protein to fat price ratio had little effect on the economic weights for milk carrier yield and herd life, but affected the relative magnitudes of economic weights for fat and protein yields substantially. Economic weights were computed with milk carrier quota, fat quota and milk carrier plus fat quotas, assuming constant herd size and prices and costs prevailing in midwestern USA. Economic weights for the yield traits under quota were negative while those for herd life increased substantially under production quotas. Economic weights were also computed when enterprise rescaling was taken into account. The optimum for rescaling the enterprise depended on the economic severity of the system
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The effect of chelating agents and free radical scavengers on survival of bull spermatozoa at ambient temperature / Vishwanath, R.; Munday, R.; Curson, B.; Shannon, P. 1992.
12th international conference on animal reproduction: The Hague: v.1 p.547-549
The addition of Desferal, an iron chelator, and BHT, an antioxidant, improved the survival of sperm incubated at 37ºC in egg yolk diluents. Desferal and BHT were effective at low concentrations and their effect was additive with that of catalase. It is suggested that the beneficial effect of Desferal is attributable to chelation of iron, thereby preventing iron-mediated free radical production.
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The effect of Holsteinization on intensive pastoral dairy farming in New Zealand / Harris, B.L.; Kolver, E. 2001.
Journal of dairy science v.84, electronic supplement.
Papers from 2000 Joint ADSA/ASAS Annual Meeting During the last 20 yr, the percentage of Holstein Friesian (HF) cows in the New Zealand (NZ) herd with North American Holstein genetics has increased from 2 to 38%. The use of North American Holstein genetics was increased to broaden the genetic base of the HF population in NZ and to incorporate traits for high productivity. Analysis of the national database and several comparative studies have shown that, in general, North American-derived Holstein cows were heavier, produced more milk volume and protein yield, had lower concentrations of fat and protein, and had poorer fertility and survival than NZ HF cows. Failure to get in calf and maintain a 365-d calving interval appears to be one of the key reasons for the reduced survival of North American Holstein cows within a seasonal dairying system. Analysis of the productive, reproductive, and survival characteristics of North American Holstein and NZ HF cows revealed an average advantage of $NZ 4950 per farm per year in favor of NZ HF cows, which represented approximately a 12% difference in economic farm surplus. If the population of Holstein genetics outside New Zealand is to be used in NZ pastoral dairying systems, these results suggest that fertility traits should be included in the national breeding objectives.
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Effect of inaccurate parameter estimates on genetic response to marker-assisted selection in an outbred population / Spelman, R.J.; Van Arendonk, J. A. M. 1997. Journal of dairy science v.80 no.12 p.3399-3410 The effect of inaccurate estimates of variance and of the location of the quantitative trait locus on the genetic response to marker-assisted selection was studied by simulation of an adult multiple ovulation and embryo transfer nucleus breeding scheme. Two genetic models were simulated for the quantitative trait locus: a total of 10 alleles or 2 distinct alleles per base parent. For both models, the locus explained either 5 or 10% of phenotypic variance. A polygenic component was simulated, and the two genetic components were summed to 35% heritability for a trait measured on females. Overestimation of variance of the quantitative trait locus had minimal effect on genetic gain for marker-assisted selection over the short term, but decreased long-term response. The long-term loss was reduced when variance of the quantitative trait locus was reestimated after four generations of marker-assisted selection. Selection for favorable alleles at a nonexistent quantitative trait locus resulted in first generation losses of 3 and 7% for postulated quantitative trait loci, explaining 5 and 10%
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