Call number: LD2668 .T4 1978 O36 / Master of Science

Call number: LD2668 .T4 1984 G728 / Master of Science

Genomic selection (GS) has been adopted by the dairy cattle breeding industry and the opportunity exists to implement this technology in UK beef and sheep breeding. However, these sectors do not appear so readily predisposed to GS implementation. Following an introduction to GS in Chapter 1, Chapter 2 investigated the structure of the little-studied UK beef breeding sector. This provided estimates of key commercial and pedigree population parameters, for use in modelling genetic gain from GS. Terminal traits were found to be the dominant selection goals, with 85% of beef-sired commercial matings resulting in progeny being slaughtered at a prime age. Pedigree bulls disseminated the majority of genes in the sector via natural service. The correlation between the terminal selection index (TI) and the sale price of breeding bulls was moderate, suggesting a modest uptake of genetic technology in the sector. Chapter 3 estimated selection intensity for TI, generation interval and the dissemination rate of improved genes in the pedigree Limousin population. In order to predict the genetic gain achievable in using GS in beef and sheep breeding, Chapters 4 to 6 undertook deterministic selection index simulations, incorporating genomic information as correlated traits. In Chapter 4, GS was modelled for terminal beef traits, when incorporating carcass information and accounting for likely genotype by environment interaction. Using a training population of 2000 sires, this concept was predicted to offer 40% greater genetic gain than existing BLUP selection using pedigree phenotypes. Gene flow methodology projected the commercial value of this gain to offer a substantial return net of genotyping costs. Chapter 5 explored GS for maternal beef traits within the concept of a nucleus breeding scheme. Whilst greater genetic gain was predicted with GS than with conventional BLUP, the economic value of this gain was projected to be too low to justify such a scheme in the UK. Chapter 6 proposed a synergy between computer tomography (CT) phenotypes and GS in sheep breeding. Developing a genomic predictor from male selection candidates with CT phenotypes and conventional performance records was predicted to increase genetic gain by 55% over BLUP selection without CT traits. Introducing GBV contributed most of the accuracy in this scenario, suggesting that the existing performance recording structure in UK sheep breeding could in the future be replaced by GS using CT. In the general discussion, the potential for GS in other beef and sheep traits was considered in the light of the outcomes of these simulations. Given the lack of vertical integration in UK beef and sheep sectors, the drivers for implementation of GS are examined. Finally, the options for international cooperation and the possibilities offered by future genotyping technology are considered. It was concluded that implementation of GS incorporating beef carcass phenotypes was merited and could provide a platform for future GS implementation in other novel traits. Sheep GS with CT traits was considered a higher risk strategy, due to the lack of evidence for uptake of existing EBV technology.

Call number: LD2668 .T4 1986 W74 / Master of Science / Animal Science and Industry

Typescript (photocopy). / Digitized by Kansas Correctional Industries

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One thousand Holstein-Friesian heifer calves were studied to evaluate the effects of colostrum-derived 24 to 48 h serum Ig concentrations on growth and survival. The rate of growth increased as 24 to 48 h serum Ig concentrations increased. Calves born to first-calf heifers had higher 24 to 48 h serum Ig concentrations and gained weight at a higher rate of gain than heifers born to 3-year-old and older cows. The concentration of serum Ig at 24 to 48 h in the dairy heifer is a significant source of variation affecting average daily gain through the first 180 d of life. Seasonal factors were also significant in influencing rate of gain from birth to 6 months. Age of dam was a significant source of variation in calf weight gains, but only for the first 35 d of life. Approximately 28% of the calves absorbed less than 12 mg/ml of maternally-derived antibody. Heifers in this category suffered a death loss of 6.78% compared to only a 2.59% loss for heifers absorbing greater than 40 mg/ml Ig. Both season and age of dam were significant in affecting the concentration of 24 to 48 h serum Ig acquired. Forty-nine percent of the variation in 35 d serum Ig can be attributed to the variation found at 24 to 48 h. The data presented here indicate that proper management of factors influencing the absorption of colostral immunoglobulins by the neonatal dairy heifer would enhance the replacement rearing program.

Data on 5130 registered Hereford cattle owned and managed by the San Carlos Apache Indian tribe were used to study cow productivity in terms of Most Probable Producing Ability and fertility. Analyses of variance and regression analyses were utilized to investigate sources of variation in the weaning weights of the calves and in their day of birth (which was a measure of cow fertility). Heritability estimates for various weights and gains and correlations (genetic, environmental and phenotypic) for weights, gains and MPPA were also calculated. Large year effects caused the most variation in weaning weight. Important too, were the effects of age of dam, interaction between year and age of dam and regression of weaning weight on day of birth. The repeatability of weaning weight was .25. This value was low compared to the average usually seen. Heritability estimates for weaning weight were .05 for males and .18 for females. Not much progress could be made selecting for weight at that stage. The heritability of postweaning weights were higher. The values for 20-month-weight were .46 for males and .31 for females, indicating reasonable progress could be made selecting for weight at that age. Twelve-month-weight had heritability estimates of .21 (males) and .17 (females). Since a weight loss occurred during the period between weaning and the 12-month-stage, the trait being measured may be a response to nutritional stress. The genetic correlations between weights at various stages were high. Some of the same genes are responsible for weights at various stages of growth. Correlations (genetic) between the weights and MPPA were generally low except the correlation of 12-month-weight with MPPA (.41). Day of birth measured as a trait of the calf was a reflection of gestation length. Heritability estimates for day of birth were .26 for calves of cows dry during the breeding season and .04 for the calves of lactating cows. When calculated as a trait of the cow, day of birth was considered a measure of cow fertility with a resulting heritability of .09. In evaluating overall cow productivity both MPPA and fertility must be considered jointly, perhaps in the form of a selection index or through independent culling levels.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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