Abstract   

    Data on 8948 performance records of Sahiwal cows kept at the Livestock Experiment Station, Jahangirabad (Khanewal) were used in the present investigation. The heritability was estimated by using Restricted Maximum Likelihood (REML) procedure fitting an Individual Animal Model. The heritability estimates by univariate analysis were 0.013+0.022 for first lactation milk yield, 0.062+0.039 for first lactation length and 0.028+0.027 for first dry period. The heritability estimates considering all lactations (repeatability model) 'were 0.052+0.032, 0.027+0.013 and 0.029+0.018 for milk yield. lactation length and dry period, respectively. Pedigree and performance recording of dairy animals for more precise genetic evaluation programmes is suggested.    

Key words: Animal Model, Heritability, Pedigree, Sahiwal, cattle.