Uréia em suplementos protéico-energéticos para bovinos de corte durante o período da seca: características nutricionais e ruminais

Abstract

RESUMO -Objetivou-se avaliar o consumo, a digestibilidade, o pH e a concentração de amônia do líquido ruminal, a concentração de nitrogênio sérico e urinário e a síntese microbiana em novilhos recebendo suplemento durante o período da seca. Utilizaram-se quatro novilhos mestiços Zebu × Holandês, castrados, com peso médio inicial de 430 kg, fistulados no esôfago, rúmen e abomaso e distribuídos em quatro piquetes de Brachiaria decumbens, cada um com 0,40 ha. Cada animal recebeu 4,0 kg/dia de suplemento, constituído de milho moído, farelo de algodão, mistura mineral e uréia/sulfato de amônia em quatro níveis (0; 1,2; 2,4 e 3,6% na matéria natural). Os consumos de matéria seca total, 2,0% (10,9 kg/dia), e de pasto, 2,3% (7,1 kg/dia), matéria orgânica, 2,2% (9,7 kg/dia), matéria orgânica do pasto, 2,3% (6,3 kg/dia), proteína bruta, 1,9% (1,3 kg/dia), extrato etéreo, 3,6% (0,4 kg/dia), fibra em detergente neutro, 1,9% (5,8 kg/dia), carboidratos totais, 2,3% (8,2 kg/dia), e carboidratos não-fibrosos, 2,9% (4,1 kg/dia), foram influenciados de forma quadrática pelos níveis de uréia nos suplementos. Apenas a digestibilidade total da matéria orgânica foi afetada, de forma linear positiva, pelos níveis and non-fiber carbohydrate (NFC) presented quadratic behavior. The maximum responses on the urea levels were: 2.0%(10.9 kg/day), 2.3% (7.1 kg/day), 2.2% (9.7 kg/day), 2.3% (6.3 kg/day), 1.9% (1.3 kg/day), 3.6% (0.4 kg/day), 1.9%(5.8 kg/day), 2.3% (8.2 kg/day) and 2.9% (4.1 kg/day), respectively, for TDM, DMP, OM, OMP, CP, EE, NFD, TC and NFC. The OM digestibility was affected with a linear behavior. No differences were observed for the pH values. However, ammonia concentration increased linearly as the urea level in the supplement increased. The urea level in supplement increased linearly the nitrogen in serum and urinary excretion of nitrogen from urea. No effect from the urea level on the microbial efficiency, expressed by different forms, was observed.

Substitution of soybean meal for cottonseed meal in multiple supplements for grazing beef heifers in the dry season

“…The average EMPS value among the different treatments was 122.9 g CP/kg DOM, which is very close to the 120 g CP/kg DOM recommended by Valadares Filho et al (2010) for cattle managed under tropical conditions. These results are similar to those reported by Moraes et al (2009).…”

Levels of mineral mixture and urea in supplementation of crossbred heifers, with Gyr predominance, reared at pasture during the dry season

“…Similar results were found by Restle et al (2001), Magalhães et al (2003) and Moraes et al (2009), by utilizing increased levels of urea in the supplement. These results can be justified by the absence of replacement effect of pasture by supplement, which is common in elevated levels of supplementation, although in the 10:10 diet there was the greatest intake of supplement (0.62 kg), around three times greater than the intake of supplement of the other diets containing urea.…”

Physicochemical composition and fatty acid profile of milk from F1 Holstein x Zebu cows fed with increasing concentrations of urea

“…Thus, ruminal microorganisms are probably able to adequately process the changing diets, since other variables (i.e., milk casein) also behaved similarly in all treatment groups. Indeed, previous work using urea as a supplement for pasturing calves did not find variations in ruminal microbe efficiency (MORAES et al, 2009). The physicochemical characteristics of milk found here (Table 2) lie within the ranges recommended in guideline number 62 (BRASIL, 2011).…”