Effect of feed supplementation on the productive and reproductive performance of Brahman heifers grazing in the humid tropics of Mexico

Abstract

The effect of pre-breeding feed supplementation was studied in 90 Brahman heifers, 1 000 d of age and 340 kg of live weight (LW) initially, kept in prairies of Santo Domingo star (Cynodon nlemfuensis). During 130d, 45 animals (group with SUP) received 2.8 Mcal ED / kg and 18% CP at a rate of 1% of PV daily, the same number did not receive it (group without SUP). Ovarian activity was recorded every third day in 30 of the 90 heifers (15 with and 15 without SUP), by ultrasonography and plasma progesterone level. Oestrus observation was carried out twice a day. The daily gain of LW was greater with SUP (0.4 vs. 0.2 kg) and in body condition (CC, scale from 1 to 5), the increase was half a point more with vs. without SUP (2.1 to 3.6 vs 2.2 to 3.1, P <0.05). the mean duration of the estrous cycle in 252 observed estrus was: 19.4 d, while based on 58 progesterone elevations (> 1 ng / mL) it was 18.4 d. 66.3% of the observed follicular population measured 3-5 mm, 28.6% measured 6-9 mm, and 5.1% measured> 9 mm. General means of 2.6 services per conception and 73.3% of the total pregnancy rate were obtained. Although SUP improved productive performance, it did not affect (P> 0.05) any of the reproductive criteria studied. It did not benefit ovarian activity or the establishment of pregnancy. The CC also did not relate (P> 0.05) with these reproductive variables.