Desempenho produtivo, reprodutivo e perfil metabólico protéico de vacas de corte suplementadas no pós-parto

Abstract

The objective of this work was to evaluate the effect of supplementation of beef cows, kept on nature pasture, with wheat meal at level of 0.7% of the body weight, with or without urea inclusion in supplement, between calving and weaning, on milk production and composition, interaction with protein metabolic profile, productive and reproductive performance, before and after weaning, at 63 days after calving. 115 cows from Charolais (C), Nellore (N), crossbreds with Charolais predominance (CN) and crossbreds With Nellore predominance (NC) genetic groups were used. The cow age varied from 3 to 13 years, being divided into three classes of age: young (3 to 4 years), adult (5 to 7 years) and old (+ than 8 years). The cows were divided this way: PN cows with calves kept exclusively on nature pasture; FTR cows with calves kept on nature pasture, receiving 0.7% of body weight from wheat meal supplementation; FTRU cows with calves kept on nature pasture, receiving 0.7% of body weight from wheat meal supplementation + urea (12.5 g/100 kg of body weight). Daily milk production and protein milk content were bigger at two first periods, decreasing at weaning moment. Nellore and CN cows presented lactose content (5,02%) bigger than NC cows (4,83%), with Charolais being at middle (4,90%). Dry extract content was bigger to Nellore and NC cows (12,25 and 12,16%, respectively) than Charolais and CN cows (11,35 and 11,61, respectively). There was a significant interaction (P<0,10) between treatment and genetic group for serum urea nitrogen (SUN) level, being supplemented cows with urea at concentrate presented SUN level higher than cows not supplemented and supplemented only with wheat meal (18,19 vs 14,54 e 12,48 mg/dL, respectively). Serum albumin and milk urea nitrogen (MUN) levels didn t differ significantly (P>0,10) between treatment and period. SUN and MUN presented a positive and highly significant (P<0,0001) correlation of 49%. Conception rate wasn t influenced by SUN and MUN levels, wherever the treatment they were submitted. Supplemented cows presented an average daily gain (ADG), since calving until end of matter season, superior (P<0,05) than not supplemented cows, besides they presented a bigger weight gain (P<0,0002) during the supplementation period. The ADG from cows wasn t influenced by genetic group (P>0,05), however the Charolais had a better body condition (P<0,05) during the experimental period, being Nellore with an inferior body condition and the crosses with a middle value. The calving rate didn t present a significantly difference between periods (P>0,05).