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Analysis of reproductive traits in sheep and of productive traits in river buffaloes
Abstract
Records on reproductive traits from 22,938 matings of sheep were analyzed. Performance of ewes for six basic and seven composite traits were analyzed. Ewe performance of five breeds and two synthetic lines were compared. Linear fixed models were fitted to detect significant effects among years, ages and breeds of ewe, hormone treatment and seasons of breeding. A genetic animal model was used to estimate variance components. Other random effects fitted in the model were maternal genetic, permanent environmental and mate of the ewe effects. Estimates of heritabilities were mainly small. Genetic and environmental correlation estimates were computed. Breeding values of sires for four basic and two composite reproductive traits with categorical distributions were also estimated with a mixed model adaptation of the Grizzle-Starmer-Koch method. Three breeds were considered: Finnsheep, Dorset, and Rambouillet. Traits were analyzed with a sire model. Restricted maximum likelihood estimates of parameters were obtained through expectation maximization algorithm. The solutions are estimates of the probability for each sire to have progeny in each category within each level of the fixed factor. Buffalo breeding in Italy has economical importance because of the high price of mozzarella cheese that is produced with buffalo milk. Restricted maximum likelihood was used to estimate genetic parameters for milk, protein, fat and mozzarella yields and for protein and fat percentages for the Italian buffalo population. Fixed effects included in the model were herd and year combination, month of parity and times of milking per day. Records were adjusted for age of buffalo cows in months using a cubic covariate and for days in dry period by a quadratic covariate. Estimates of heritability were smaller than those usually estimated in dairy cattle for the same traits. Phenotypic and genetic correlations among all traits were estimated showing the possibility of developing selection schemes to increase characteristics of milk favorable for production of mozzarella cheese.
Subject Area
Livestock
Recommended Citation
Rosati, Andrea, "Analysis of reproductive traits in sheep and of productive traits in river buffaloes" (1996). ETD collection for University of Nebraska-Lincoln. AAI9725134.
https://digitalcommons.unl.edu/dissertations/AAI9725134