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|Title:||Interactions of Sires With Feeding and Management Factors in Illinois Holstein Cows|
|Author(s):||Mohemmad, Waheed Abdul|
|Department / Program:||Dairy Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The objectives of this research were to estimate components of phenotypic variation in milk yield due to the interactions between sires and several feeding and management factors and to examine the implications of the estimated interactions in sire evaluation for milk yield. Data on feeding and management practices in Illinois Holstein herds on official DHI and DHIR testing programs were obtained by questionnaires. Milk yield data were first lactation records, begun in 1973, of purebred or grade Holstein heifers. Part records were extended to 305-day records and then adjusted for age and month of calving. The feeding and management practices were source of roughage for milking herd during summer, amount of grain fed to heifers between 12 and 18 months of age, amount of grain fed to heifers during two months before calving, and ideal weight for breeding heifers. Variance components were estimated by Methods 1 and 3 of Henderson.
Results indicated that sire-herd interaction component of phenotypic variance of milk yield was about 10%. Estimates of the sire component of variance were less than 3%. A probable explanation for the low estimate of sire variance is that sires were selected for high milk production. Estimates of the components of variance due to interaction between sires and three feeding and management factors, namely, source of roughage for milking herd during summer, amount of grain fed to heifers between 12 and 18 months of age, and amount of grain fed to heifers during two months before calving, were negative. Interaction between sires and ideal weight for breeding heifers accounted for 3% of the phenotypic variation in milk yield. Sire evaluation by Best Linear Unbiased Prediction procedures indicated that consideration of sire-herd or sire-ideal weight for breeding heifers interaction appeared to affect the magnitude of estimated breeding values. Product-moment and rank correlation coefficients between estimates of breeding values when sire-herd or sire-ideal weight for breeding heifers interaction was considered or ignored in the model were, however, high, 0.99. It appeared that evaluation of sires, ignoring sire-herd and sire-ideal weight for breeding heifers interaction, was adequate for selection of sires for breeding.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.
|Date Available in IDEALS:||2014-12-14|