Níveis de uréia em suplementos múltiplos para terminação de novilhos em pastagem de capim-braquiária durante o período de transição águas-seca

Abstract

RESUMO -Avaliaram-se os efeitos de suplementos múltiplos com diferentes níveis de uréia sobre o desempenho produtivo e os parâmetros nutricionais de bovinos em fase de terminação mantidos em pastagem diferida de capim-braquiária (Brachiaria brizantha cv. Marandu) no período de transição águas-seca. A disponibilidade estimada de matéria seca das pastagens variou de 16.360 a 9.358 kg/ha. Para avaliação do desempenho produtivo, utilizaram-se 20 novilhos mestiços não-castrados, com 20 meses de idade e 376 kg de peso vivo. Os animais foram agrupados em lotes com pesos semelhantes, segundo um delineamento inteiramente casualizado, em quatro piquetes de 1,5 ha, onde receberam 1,5 kg/dia de suplemento isoprotéico (20% de PB), constituído de grãos de milho e soja moídos, mistura mineral e uréia nos níveis 0,0; 1,6; 3,2 ou 4,8% na matéria natural. O ganho médio diário -valor médio foi de 0,570 kg/dia -não foi influenciado pelos níveis de uréia do suplemento. Os parâmetros nutricionais foram avaliados utilizando-se quatro animais mestiços Holandês × Zebu, não-castrados, com peso médio inicial de 320 kg, fistulados no esôfago, rúmen e abomaso. Os animais receberam as mesmas quantidades de suplemento fornecidas aos animais do experimento de desempenho. Os níveis de uréia não afetaram significativamente o pH e a concentração de amônia ruminal. Para obtenção de ganhos de 0,5 a 0,6 kg/dia, pode-se utilizar apenas milho, uréia e mistura mineral em suplementos múltiplos para terminação de bovinos em pasto diferido.Palavras-chave: consumo, digestibilidade, milho, soja integral, suplementação Urea levels in multiple supplements for finishing beef cattle on palisade grass pasture during the rainy to dry transition ABSTRACT -The effects of multiple supplements with different urea levels on the productive performance and nutritional characteristics, for finishing beef cattle kept in deferred pasture of palisade grass (Brachiaria brizantha cv.Marandu) in the transition period of rainy to dry season were evaluated. The estimated dry matter availability of the pasture ranged from 16,360 to 9,358 kg/ha. In the performance trial, 20 crossbreed bulls, 20 months old and initial 376 kg BW were used. The animals were grouped in lots of similar weights to a completely randomized design, in four paddocks of 1.5 ha, where they received 1.5 kg/d of isoproteic supplements (20% CP), consisting with corn grain, grounded soybean, mineral mix and urea in the levels of 0.0; 1.6; 3.2 and 4.8% as-is basis, respectively. The average daily gain (mean value of 0.57 kg/d) was not affected by the urea levels in the supplements. The nutritional characteristics were evaluated using four crossbred (Holstein × Zebu) bulls, with initial 320 kg BW, with esophageal, ruminal and abomasal cannula, were used. The animals were fed the same amounts of supplements fed to the animals of the experimental performance. Urea levels did no affect the ruminal pH and the ammonia concentration. Weight gains 0.5 to 0.6 kg/d could be obtained using only corn, urea and mineral mix in ...

Nutritional requirements of energy, protein and macrominerals for maintenance and weight gain of young crossbred Nellore × Holstein bulls on pasture

“…The lowest kg value may have been due to low concentration of energy on the diets for the animals. Sales (2008), working in situations similar to the present study found a value of kg of 29%. found values of kg which ranged from 27% to 37% for diets with TDN of 62.49 and 75.55%, respectively, which also shows the lowest kg for less energy diets.…”

“…that there was greater participation of fat in the composition of weight gain when compared with the protein, although non-castrated males deposit more lean tissue in the body than castrated males and females (Vandewert et al, 1985;Berg & Butterfield, 1976). The value of 242.47 g/kg EBWG/day of MPg, for 250-kg LW animals was 6.14% lower than the 257.36 g/kg EBWG/day found by Sales et al (2010), working in similar conditions. While these authors observed an increase of 8.0% in requirement for MPg (from 200 to 350 kg BW), in the present experiment, this increase was 18.19%, but when there was a change in the requirement of MPg of an animal from 350 to 400 kg of BW, the increase was only 0.49%, whereas the increase in requirement for MEg was 10.55%.…”

“…When comparing the ratios obtained in this study with those used with grazing animals, data from this study are numerically superior to those found by Zervoudakis et al (2002), Fregadolli (2005) and Moraes et al (2009), who reported values of 0.8575; 0.8746 and 0.8877, respectively, although close to the value of 0.8997 found by Sales (2008), who carried out experiments in conditions similar to this research.…”

“…Requirements of rumen-undegradable protein (RUDP) were reduced from 21.07 and 12.71% (% of CP), respectively, for animals with 200 and 400 kg, which allows to infer that animals, especially in the finishing stage, need little RUDP, as noted by Sales et al (2008), who used levels of urea in multiple supplements for animals at this stage of production, on deferred pasture, and found that urea can be used to replace soybean meal, for gains up to 600 grams/day.…”

“…CSIRO (2007) has recommended that the maintenance requirements for beef cattle raised on pasture be from 10 to 50%, and in function of the distance traveled, the availability of pasture and slope of the terrain. Some studies on nutritional requirements for cattle raised on pasture (Zervoudakis et al, 2002;Fregadolli, 2005;Moraes et al 2009;Paixão, 2008;Sales et al 2010;Sales et al, 2011) have been developed in Brazil, but the amount of information available is still considered small for the development of equations that are considered as reliable for use in diet formulation programs, especially regarding the supplementation of these animals.…”