Associação de diferentes fontes energéticas e protéicas em suplementos múltiplos na recria de novilhos mestiços sob pastejo no período da seca
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Data
2005-10-27
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Revista Brasileira de Zootecnia
Resumo
Dois experimentos foram realizados com o objetivo de avaliar diferentes fontes protéicas e energéticas em suplementos múltiplos para bovinos. No primeiro experimento, estudou-se o desempenho de novilhos em fase de recria em pastagem de Brachiaria brizantha, no período da seca. Utilizaram-se 20 novilhos mestiços Holandês x Zebu, não-castrados (17 meses de idade e 265±18 kg de peso vivo inicial), distribuídos em quatro piquetes de 1,5 ha. Os suplementos foram fornecidos diariamente na proporção de 0,75% do PV. Empregou-se como fonte protéica grão de soja (GS) ou caroço de algodão (CA) inteiros e farelo de trigo (FT) ou farelo de arroz (FA) como fonte de energia, em esquema fatorial 2 x 2. Não foram verificadas diferenças no ganho médio diário (GMD), no peso vivo final (PVF) e no ganho de peso total (GPT). A suplementação propiciou aos animais GMD de 0,589; 0,530; 0,620 e 0,606 kg/dia, respectivamente, nos tratamentos GS/FT, GS/FA, CA/FT e CA/FA. No segundo experimento, determinaram-se as frações dos carboidratos da pastagem e dos ingredientes utilizados na formulação dos suplementos e estimaram-se as respectivas taxas de digestão das frações pela técnica de produção de gás. A forragem apresentou altos teores da fração indigestível (C) e baixos da potencialmente digestível (B2). Entre os concentrados, o FA apresentou menor fração C. O GS e o FT destacaram-se pela elevada proporção de CNF. O CA, embora tenha demonstrado fração C superior aos demais, apresentou rápida taxa de digestão da fração B2. As taxas de digestão dos CNF foram 35,06; 14,86; 17,83 e 58,80, respectivamente, para FA, FT, GS e CA. A opção por uma das fontes protéicas ou energéticas estudadas depende, portanto, do preço e da disponibilidade no mercado, pois não influenciou o desempenho dos animais. Os carboidratos estruturais (B2 e C) são responsáveis pelo alto teor de carboidratos totais presentes na Brachiaria brizantha no período da seca, pois correspondem a aproximadamente 80% de sua composição. Observaram-se variações entre as frações dos carboidratos, assim como na taxa de degradação das fontes energéticas e protéicas estudadas.
Two trials were conducted to investigate different protein and energy sources in multiple supplements fed to growing crossbred bulls. In the first experiment, performance of 20 crossbred growing bulls averaging 17 months of age and 265±18 kg of body weight was evaluated in the dry season. Animals were maintained in 1.5 ha paddocks of Brachiaria brizantha with supplements being offered daily in a proportion of 0.75% of the body weight. A completely randomized design with a 2 x 2 factorial arrangement was used. Supplements contained whole soybean (WSB) or whole cottonseed (WCS) as the protein sources and rice bran (RB) or wheat bran (WB) as the energy sources. No significant differences on the average daily weight gain (ADG), final body weight (FBW), and total weight gain were observed among diets in this trial. The ADG and FBW averaged 0.589 and 318.2, 0.530 and 317.2, 0.620 and 319.6 and 0.606 kg/day and 323.6 kg for animals fed supplements containing WSB/WB, WSB/RB, WCS/WB, and WCS/RB, respectively. The objective of the second study was to estimate the carbohydrate fractions of the pasture and that of the feeds used in multiple supplements as well as their digestion rates using the gas production technique. Forage had higher indigestible fraction (C) and lower potentially degradable fraction (B2) compared to the supplements. Among supplements, WCS had the lowest C fraction while WSB and WB had the highest proportion of non-fiber carbohydrates (NFC). Although WCS had the highest content of C fraction, it also showed the fastest rate of digestion of the B2 fraction. Digestion rate of NFC were: 35.06, 14.86, 17.83 and 58.80, respectively for RB, WB, WSB and WCS. The choice of each protein and energy source will depend on market price and availability because there were no significant differences among treatments. The structural carbohydrates (B2 e C) are responsible for the high concentrations of total carbohydrates in Brachiaria brizantha during the dry season, which averaged 80%. It was observed variations in the carbohydrate fractions as well as in the degradation rates across supplements.
Two trials were conducted to investigate different protein and energy sources in multiple supplements fed to growing crossbred bulls. In the first experiment, performance of 20 crossbred growing bulls averaging 17 months of age and 265±18 kg of body weight was evaluated in the dry season. Animals were maintained in 1.5 ha paddocks of Brachiaria brizantha with supplements being offered daily in a proportion of 0.75% of the body weight. A completely randomized design with a 2 x 2 factorial arrangement was used. Supplements contained whole soybean (WSB) or whole cottonseed (WCS) as the protein sources and rice bran (RB) or wheat bran (WB) as the energy sources. No significant differences on the average daily weight gain (ADG), final body weight (FBW), and total weight gain were observed among diets in this trial. The ADG and FBW averaged 0.589 and 318.2, 0.530 and 317.2, 0.620 and 319.6 and 0.606 kg/day and 323.6 kg for animals fed supplements containing WSB/WB, WSB/RB, WCS/WB, and WCS/RB, respectively. The objective of the second study was to estimate the carbohydrate fractions of the pasture and that of the feeds used in multiple supplements as well as their digestion rates using the gas production technique. Forage had higher indigestible fraction (C) and lower potentially degradable fraction (B2) compared to the supplements. Among supplements, WCS had the lowest C fraction while WSB and WB had the highest proportion of non-fiber carbohydrates (NFC). Although WCS had the highest content of C fraction, it also showed the fastest rate of digestion of the B2 fraction. Digestion rate of NFC were: 35.06, 14.86, 17.83 and 58.80, respectively for RB, WB, WSB and WCS. The choice of each protein and energy source will depend on market price and availability because there were no significant differences among treatments. The structural carbohydrates (B2 e C) are responsible for the high concentrations of total carbohydrates in Brachiaria brizantha during the dry season, which averaged 80%. It was observed variations in the carbohydrate fractions as well as in the degradation rates across supplements.
Descrição
Palavras-chave
Bovino de corte, Cinética ruminal, Desempenho, Suplementação, Taxa de digestão