Productive and reproductive records of 1509 Holstein Friesian were collected from private farm to study the influence of genetic (heritability (h2), phenotypic correlation (r P), genetic correlation (r G), and estimated breeding value (EBV)) and environmental factors such as days in milk (DIM), dry period (DP), calving interval (CI), parity, season of calving, days open (DO) and age at first calving (AFC) on 305-day milk yield (305-DMY) and total milk yield (TMY). This study recorded highly significant (P ≤ 0.01) effect of all studied variables on TMY trait. DIM and DP had significant effect on 305-DMY. Nevertheless, the effect of parity and DO on 305-DMY were non-significant (P≥ 0.05). The average EBV for DP and CI were higher in dam than in cow, and sire. Also, for 305-DMY and DIM, they were higher in cow than in dam and, sire. For TMY, it was higher in sire than in cow and, dam. Medium heritability estimates for TMY, DIM, CI and DO were (0.32, 0.33, 0.29 and 0.29, respectively), while low heritability estimate (0.07) was recorded for DP. Finally, there were positive phenotypic correlation (r p) between all studied traits except 305-DMY had negative r p with DP and CI. Cattle breeders must consider the environmental factors in manage mental program because they greatly affect the farm profitability, and they must select individuals with higher breeding values to be the parents of the next generation |
