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GENETIC CONTROL OF TEST-DAY MILK YIELD IN SAHIWAL CATTLE

G. BILAL, M. S. KHAN, I. R. BAJWA AND M. SHAFIQ1

Department of Animal Breeding and Genetics, University of Agriculture, Faisalabad; 1Research Centre for Conservation of Sahiwal Cattle, Jhang, Pakistan

Abstract

    Heritabilities of test-day (TD) and 305-day milk yield were estimated using performance records of 780 first lactation Sahiwal cows, following two models. In the first model, estimated 305-day lactation milk yields were analyzed through an individual animal model with period-season of calving as fixed effect and additive genetic effect as random factor. The second model was a repeatability model where monthly milk yield records were analyzed using period-season of calving as fixed effect and additive genetic effect and permanent environmental effect as random factors. The age at calving, ratio of days in milk to 305-day (as linear and quadratic components) and their reciprocal logs were used as covariables. The heritability estimates for 305-day and TD milk yields were 0.082 and 0.024, respectively. Heritability estimates of individual TDs ranged from 0 to 0.274. The relative proportion of permanent environment variance to total variance was 0.498. Heritability of individual test-day milk yield was highest in the mid-lactation (TD6-TD8). Lower genetic control of test day and lactation milk yield in the present study needs validation using larger data sets with accurate pedigree recording. 

Key words: Genetic parameters, Sahiwal cattle, test day model.
 
   

ISSN 0253-8318 (Print)
ISSN 2074-7764 (Online)



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