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|Title:||Genetic and Genetic-Feeding Regimen Interaction Effects on Lactation, Growth and Carcass Traits in Dairy Cattle|
|Department / Program:||Dairy Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Animal Culture and Nutrition|
|Abstract:||Average daily gan (ADG), usually estimated from initial and final body weights, ignores information provided by intermediate body-weight measurements. Alternative methods to obtain a more precise estimate of ADG were developed and compared using simulation. Estimated generalized least-squares regression of body-weight on age was a better estimator of ADG (gave lower mean square error of ADG and variance components) than the usual estimator, which itself was better than ordinary least-squares regression.
An experiment to study genetic and genetic-feeding regimen interaction effects was conducted on Holstein and Brown Swiss heifers and steers in the University herd. Procedures to estimate covariances between traits measured on different animals of the same genetic group were derived for a mixed model with two random factors. Procedures to estimate sampling errors of genetic correlation were derived for the mixed model, only for traits measured on the same animal.
Estimates of heritabilities were small or moderate. Estimates of genetic correlations of lactation with carcass traits were moderately negative or large positive. Genetic correlations of lactation traits and estimated ADG could not be estimated. Sampling errors of estimates of genetic parameters were large.
Feeding low level of energy until 64 weeks of age (wks) and continuing until 2 months prior to calving (low-low) was not significantly different from a medium-low regimen for lactation traits. Feeding high level until 52 wks and continuing until 80 wks (high-high) was less favorable than a medium-high regimen for backfat thickness, kidney-pelvic fat weight and yield grade in Holstein, but not in Brown Swiss steers. Feeding a higher level of energy gave significantly higher estimated ADG than a lower level in heifers and steers.
Sire with feeding level interaction variance, relative to sire variance, was large for estimated ADG. Similarly sire with feeding regimen interaction variance was large for backfat thickness, chilled carcass weight, dressing percentage, maturity score and yield grade.
Results indicate that differences in feeding effects are small for lactation traits but may be large for ADG and some carcass traits. Sire with feeding interaction may need consideration in genetic studies or in sire evaluation for some carcass traits and ADG.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-16|