بررسي تاثير پدر، فصل زايش ، سن مادر (زايش )، جنس گوساله و نحوه زايش (تك قلو يادو قلو) بر روي وزن تولد گوساله هاي هلشتاين

Influence of sire, season of birth, parity, sex and twinning on birth weight of Holstein calves

The influence of sire, season of parturition, paricty, sex and twining on birth weight of Holstein calves were studied. The data used in this study was obtained from the birth weight of 1645 calves born during years of 1995 - 2000 in Kenebist dairy farm, Astan e Ghods Razavi. Results showed the effect of sire was significant (p <0.0001) and birth Weight in winter was significantly (p<0.0001) higher than Spring, Autumn and Summer (39.9 ± 0.55 , 38.31 + 0.51 , 37.66 f 0.54 and 36.08 f 0.49 Kg respectively). The birth weight was increased while the age of dam increased (Until 5th calving). The birth weight of male calves was significantly (p<0.01) higher than female calves (39.7 + 0.48 Kg vs 36.27 ± 0.44 Kg, respectively) and single calves had higher weight than twin calves (42.23 f 0.38 Kg vs 33.75 f 0.61 Kg, respectively) ; the difference were significant (p<0.0001). According to these results all of these factores had significant effect on birth weight of calves and calculating of correction factores for each of them can make the birth weights comparable and thus they can be use in selection of the best replacement heifers or breeding bulls.