Effect of different levels of concentrate supplement on the reproductive performance of dairy cows maintained to pasture

This experiment was carried out with the objective of evaluating the effects of different levels of concentrate supplement in the pre and post-parturition periods on the reproductive performance of dairy cow. 54 cows in a completely randomized design, distributed in 3 x 2 factorial arrangement, being 3 treatments, 2 periods and 9 repetitions for treatment, were used. The treatments with different levels of concentrate supplement (in dry basis) in the pre-parturition periods (PRE), were: PRE1 = 0% of body weight (BW); PRE2 = 0.5% of BW; PRE3 = 1.0% of BW; and in the post-parturition (POS), were: POS1 = 1kg for each 2.5 kg of produced milk; POS2 = 1kg for each 2.0kg of produced milk and POS3 = 1kg for each 1.5kg of produced milk, above 6 kg of milk a day. The ultrasonography evaluation and body score were evaluated every seven days. 20 animals presented estrus and 13 animals became pregnant in the evaluated period. The average interval between parturition-first estrus was of 53.13 days, varying from 19 to 105 days. The amount of animals that entered in the estrus in the 120 days of evaluation increased with the post parturition supplementation level, being of 2, 4 and 7 animals for the treatments 1, 2 and 3, respectively. For the conception, the only treatment in that all the animals became pregnant, was the treatment PRE3 and POS3. There was higher number of conceptions among the animals that received treatment 2 and 3, so much in the pre as in the post-parturition, in relation to animals that received the treatment 1. The increasing supplement level in the treatments pre and post-parturition caused lineal decrease of the number of weeks for beginning of follicular activity (BFA) and beginning of follicular growth (BFG). There was negative Correlation among BFA (-0.34), BFG (43 1) and body score to the parturition. It can be concluded that the increasing supplement level in the pre and post-parturition treatments, increases the amount of animals that manifest estrus and become pregnant in the first 120 days post-parturition, as well as, in the pregnant maintenance. Lineal decrease occurred in the time for BFA and BFG as increases the supplement level in the pre and post- parturition, being these correlated with the body score to the parturition.