Doctoral Dissertations

Date of Award

6-1985

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

Will T. Butts

Committee Members

Karl M. Barth, Benny R. Bell, Robert A. McLean

Abstract

Estimates of heritability (h2) of the partial nutritional efficiency of cow-calf pairs during the lactation period (ratio of estimated total digestible nutrients (ETON) consumed by the cow and calf during lactation to calf weight at weaning (LWEFF)) and over the entire 365-d period (ratio of 365-d ETON consumed by the cow and calf to calf weight at weaning (365-d WEFF)) were obtained from intake and performance records of 146 cows by 56 sires raising 266 calves by 46 sires. Intake data on 113 cow-calf pairs were from individual feeding on a grass silage diet. Intake data on 153 cow-calf pairs were from weekly, inert marker estimates of forage intake of pairs grazing fescue or fescue-clover pastures. In addition to cow-calf pair efficiency, estimates of h2 of cow-calf pair forage ETON intake during the lactation period (LETDN), 365-d ETON intake of the pair and mean daily milk in-take were obtained by paternal half-sib analyses (sire of cow) by Henderson's Mixed-Model Procedure. The structures of the genetic influences on LWEFF, 365-d WEFF, LETDN intake, 365-d ETON intake and calf mean daily milk intake were examined by sequential addition, as covariables, phenotypic traits of the cow-calf pair, to models estimating sire components of variance. From records adjusted for year-treatment, sex of calf and age of calf, estimates of h2 obtained by Henderson's Mixed-Model Procedure of LWEFF, 365-d WEFF, LETDN intake, 365-d ETDN intake and calf mean daily milk intake were .70 ± .260, .69 ± .260, .13 ± .214, .09 ± .210 and .83 ± .267, respectively. After the addition of terms for cow weight and fat thickness, recorded at weaning of her previous calf, cow weight change during the year, calf weight at weaning and mean daily milk intake (where applicable) the estimates of h2 of LWEFF, 365-d WEFF, LETDN in take, 365-d ETON intake and calf mean daily milk intake were .13 ± .221, .08 ± .216, .30 ± .238, .07 ± .215 and .32 ± .238, respectively. From records adjusted for year-treatment, sex of calf and calf weaning age, estimates of genetic correlations between LWEFF and mean daily LETDN intake, mean daily milk intake, cow weight, cow fat thickness and 365-d WEFF were .13 ± .332, -.70 ± .221, .26 ± .244, .25 ± .309 and 1.03 ± .028, respectively.

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