مهدی حسین یزدی

This research paper addresses the effect of different grouping strategies of fresh cows on total lactational and reproductive performance. Hundred-sixty multiparous Holstein cows were enrolled in a completely randomized design and assigned to one of following treatments: 21 d in fresh pen with 12.5 kg concentrate (C21, n = 60), 10 d in fresh pen with 12.5 kg concentrate (C10, n = 50), and 10 d in fresh pen with 10 kg concentrate (L10, n = 50). Although there was no differences among treatments within first 10 days in milk (DIM), C10 and L10 cows tended to produce more milk than C21 from 10 to 21 DIM. In addition, greater milk yield was obtained in C10 and L10 cows during 22 to 28 DIM and 29 to 70 DIM. Higher production in early lactation resulted in a tendency for greater milk production for C10 and L10 cows throughout a 305 d lactation. There was no difference in productivity between C10 and L10 groups at any time point. No blood metabolites (Ca, P, non-esterified fatty acids and beta-hydroxy butyrate) were affected by treatments. Pregnancy at first, second and third service was 38, 39, and 40%, respectively, which were not influenced by the days in fresh pen or concentrate allowance. Collectively, our results for the first time suggest that fresh cow grouping strategy has a long-term effect on productivity but that adding 2.5 kg concentrate has no effect on milk yield in fresh pen.