The Effect of Early or Late Breeding on Milk Production in High Producing Lactating Dairy Cows

The objective of this study was to compare the effect of early or late breeding on milk production in high producing dairy cows. In this aim, the cows with previous average peak milk yield above 45 kg/d (n = 48) were divided into two groups; Group1 (early bred) included the cows (n = 21) were inseminated between 45 to 75 days in milk (DIM) and Group2 (n = 27; late bred) were inseminated between 76 to 124 DIM. The cows that became pregnant at their first insemination following first estrus selected for the study. Milk yield was recorded every 5 days after calving for the first 45 days then continued for every 15 days for every each cow. Average DIM in early and late bred cows at insemination were 66 (min, 45; max, 75) and 99 (min, 76; max, 124), respectively. Average milk yield up to 271 d was similar between groups, however, average milk yield from 227 to 271 d was lower ( P < 0.04) in early bred cows with 26.7 kg/d compare to late bred cows with 30.3 kg/d. Even, there was no relationship between average milk yield up to 271 d, peak milk yield and day of insemination, it may be concluded that milk yield continues with more pronounced stability through the end of