Abstract

Data collected on purebred Friesian Heifers imported from Netherlands were used in this research to estimate genetic and non-genetic parameters. The average age at first calving (AFC), gestation period (GP), number services per conception (S/C), calving interval (CI), total milk yield (TMY), daily milk yield (DMY) and lactation length (LL) ranges were 24.9±2.34 - 26.50±2.84 months, 274.21±55.57 - 273.3±4.03 days, 3.92±2.77 -2.3±1.7, 468.90±116.32 - 445.4±92.81 days, 5533.14±1546.03 - 3748.2±1095.2 kg, 15.10±3.58 - 11.00±2.42 kg, and 376.74±15.89 - 349.0±86 days respectively.

Results showed that parity number had a significant (p < 0.05) effect on (S/C). Also age at first calving had a significant (p < 0.05) effect on milk yield per lactation and daily milk yield (p < 0.01). Year of calving presented a significant (p < 0.05) effect on DMY,S/C and (CI) (p < 0.001). Whereas place of birth had a highly significant effect (p < 0.001) on TMY and significant (p < 0.01) effect on AFC.

Repeatability estimates for GP, S/C, CI, TMY, DMY and LL were found to be 0.170±0.045, 0.090±0.044, 0.361±0.047, 0.420±0.061 and 0.094±0.044, respectively. While heritability estimates by paternal half-sib method ranged from 0.003±0.078 for LL and 0.190±0.140 for AFC. Whereas, estimates calculated by daughter-dam regression were found to be 0.710±0.456, 0.320±0.168, 0.106±0.120, 0.100±0.150, 0.174±0.136 and 0,055±0.224 for AFC, GP, S/C, TMY, DMY and LL, respectively.

Regarding phenotypic correlations among parameters, age at first calving was negatively correlated with other traits except for S/C and DMY. Whereas S/C exhibited positive phenotypic correlation with all the traits studied. Total milk yield was found to have positive correlation with DMY and LL. Concerning genetic correlations among traits were either inestimable or overestimated.

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