Exigências nutricionais e validação da seção HH para predição da composição corporal de zebuínos
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2002-08-13
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Universidade Federal de Viçosa
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O presente trabalho foi desenvolvido buscando determinar: a composição corporal, as exigências de energia, proteína, cálcio, fósforo, magnésio, potássio e sódio, bem como as eficiências de utilização da energia metabolizável para mantença e ganho de peso, e validar a seção HH como técnica indireta para predição da composição física e química da carcaça e, conseqüentemente, do corpo vazio de animais zebuínos. Foram utilizados 19 bovinos anelorados, castrados, com peso vivo médio inicial de 270 kg. Quatro animais foram abatidos no início do experimento, compondo o grupo referência, três foram alimentados ao nível de mantença e os demais distribuídos uniformemente em delineamento inteiramente casualizado, em três tratamentos, com três níveis de concentrado nas dietas (5, 35 e 65%, na base da MS total). Como volumoso utilizou-se o pré-secado de capim-braquiária (Brachiaria brizantha), que foi substituído, no terço final do experimento pelo pré-secado de capim-tifton 85 (Cynodon spp). Após o abate dos animais, todas ixas carcaças direita foram dissecadas completamente. A composição química do corpo vazio foi obtida pela análise química de todos os tecidos corporais. As exigências líquidas para ganho de peso de cada nutriente foram determinadas a partir da derivada das equações de estimativa do conteúdo corporal de proteína, energia, cálcio, fósforo, magnésio, potássio e sódio. A exigência líquida de energia para mantença foi estimada como o anti-log da intercepta da equação obtida pela regressão linear entre o logaritmo da produção de calor e o consumo de energia metabolizável. As eficiências de utilização da energia metabolizável para mantença (k m ) e ganho de peso (k f ) foram estimadas a partir da relação entre os teores de energia líquida, para mantença ou ganho, respectivamente, e de energia metabolizável da dieta. A comparação entre as composições física e química observadas na carcaça e aquelas estimadas pela seção HH foram efetuadas por intermédio do ajuste do modelo de regressão linear simples (REG 1) dos valores estimados sobre os valores observados, através do programa estatístico SAS (1997). Os níveis de concentrado (NC) das dietas influenciaram (P<0,05) a composição física e química da carcaça. Com o aumento do NC, a porcentagem do tecido adiposo e o conteúdo de extrato etéreo da carcaça aumentaram linearmente, enquanto os tecidos muscular e ósseo decresceram linearmente, sendo o mesmo comportamento observado para os teores de Ca, P e Na da carcaça. Os teores de PB, Mg e K da carcaça não foram afetados pelo NC das dietas, apresentando valores médios de 17,77; 0,04 e 0,23 %, respectivamente. A seção HH estimou de forma satisfatória a composição física da carcaça de animais zebuínos, o mesmo não ocorrendo para a composição química. Os teores de proteína, água, cinzas, fósforo, magnésio, potássio e sódio da carcaça foram estimados adequadamente pela seção HH, enquanto que o teor de gordura foi superestimado e o de cálcio subestimado. Foram ajustadas equações de regressão entre os teores de gordura observados na seção HH e na carcaça, bem como para os teores de cálcio, no intuito de se estimar o conteúdo dessas frações na carcaça a partir da análise química da seção HH: % EE carcaça = 1,0709 + 0,7854 % EE na seção HH (r 2 = 0,97) e % Ca carcaça = -0,2433 + 1,2832 % Ca na seção HH (r 2 = 0,69). De forma análoga, foram geradas equações entre os teores de gordura, proteína, água e cinzas no corpo vazio xem função dos teores desses mesmos constituintes na seção HH. O requisito energético para mantença foi de 74,51 kcal/PCVZ 0,75 ou de 68,60 kcal/PV 0,75 . Para a estimativa da energia retida (ER) diária, em Mcal, obteve-se a equação: ER = 0,0718 PCVZ 0,75 * GDPCZ 0,9658 , enquanto para proteína retida (PR) , em g/dia, a equação obtida foi: PR = -37,0401 + 213,024 GPVJ – 17,1430 ER. Para conversão das exigências para ganho de peso de corpo vazio em exigências para ganho de peso vivo, deve-se multiplicar o ganho de PCVZ pelo fator 0,90, obtido neste trabalho. A k m foi de 0,66 e a k f variou de 0,26 a 0,46. As relações g Ca/100g de PR e g P/100g de PR foram iguais a 10,92 e 5,26, respectivamente. As exigências dietéticas de Ca e Mg foram semelhantes às recomendadas pelo NRC (1996) ao passo que as de K e Na foram inferiores e as de P superiores às recomendadas pelo referido conselho.
The present work was done aiming at determine the body composition, the energy, protein, calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K) and sodium (Na) requirements and the metabolizable energy efficiencies of utilization for maintenance and weight gain, and validate the 9-10-11 th rib cut as an indirect method for estimating the physical and chemical carcass and, consequently, empty body composition of Zebu cattle. Nineteen Zebu steers, averaging 24 months of age and 270 kg body weight (BW) were used. Four were used as reference steers, been slaughtered at the beginning of the trial, three were fed for maintenance, and the remaining were uniformly allotted to a completely randomized design, with three treatments with 5, 35 and 65% of concentrate in total dry matter (DM) basis. The roughage used was Brachiaria brizantha haylage, that was substituted by Cynodon spp. haylage in the latest 30 days of the trial. After chilling, the right side of each carcass was physically separated into lean, fat and bone. The empty body chemical composition was xiiobtained by the chemical analysis of all the body tissues. The net requirement for weight gain of each nutrient was estimated by deriving the regression equations of the logarithm of protein, fat, energy, Ca, P, Na, Mg or K body content, in function of the logarithm of empty BW (EBW). The net energy requirement for maintenance was estimated as the intercept anti-log of the equation obtained by linear regression between the logarithm of heat production and the metabolizable energy intake (MEI). The metabolizable energy efficiencies of utilization (MEEU) for maintenance (k m ) and weigh gain (k f ) were estimated from the relationship between the net energy concentration, for maintenance or gain, respectively, and the metabolizable energy (ME) content of the diet. The comparison between the observed and predicted (by the 9-10- 11 th rib cut) physical and chemical carcass composition was done by regression equation (REG 1) fitted for the predicted values in function of the observed ones, using the SAS (1997). The concentrate level (CL) in the diet influences (P<0.05) the carcass physical and chemical composition. Increasing the CL, fat percentage and the content of ether extract of the carcass increased linearly, while, lean, bone, Ca, P and Na contents had a linear decrease. The protein, Mg and K carcass contents were not affected by the CL, averaging 17,77; 0,04 e 0,23 %, respectively. The physical carcass composition of zebu steers was well predicted by the 9-10-11 th rib, what was not true for the chemical composition. The contents of protein, water, ash, P, Mg, K e Na were adequately predicted by the 9-10-11 th rib cut, while the fat content was overestimated and the calcium content underestimated, respectively. Regression equations involving the fat (EE) and calcium (Ca) contents observed in the 9-10-11 th rib cut and the respective contents observed at the carcass were developed: % EE carcass = 1,0709 + 0,7854 % EE 9-10-11 th rib cut (r 2 = 0,97) and % Ca carcass = -0,2433 + 1,2832 % Ca 9-10-11 th rib cut (r 2 = 0,69). Similarly, regression equations between the contents of fat (EE), protein, water and ash determined in the empty body and the contents of this components obtained in the 9-10-11 th rib cut were developed. The net energy requirement for maintenance was 74,51 kcal/EBW 0,75 or 68,60 kcal/LW 0,75 . To estimate the daily retained energy (RE), in Mcal, it is suggested to use the equation: RE = 0,0718 EBW 0,75 * EBW gain 0,9658 , while for daily retained protein xiii(RP) the equation obtained was: RP = -37,0401 + 213,024 EBW gain – 17,1430 RE. To change the EBW gain requirements into LW gain requirements, it is necessary to multiply the EBW gain for 0,90. The k m estimated was 0.66 and the k f ranged from 0,26 to 0,46. The relationships g Ca/100g of RP and g P/100g of RP were 10,92 and 5,26, respectively. The Ca e Mg dietetic requirements were similar to those of the NRC (1996), while the K e Na requirements were, respectively, lower and greater than that recommended by NRC (1996).
The present work was done aiming at determine the body composition, the energy, protein, calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K) and sodium (Na) requirements and the metabolizable energy efficiencies of utilization for maintenance and weight gain, and validate the 9-10-11 th rib cut as an indirect method for estimating the physical and chemical carcass and, consequently, empty body composition of Zebu cattle. Nineteen Zebu steers, averaging 24 months of age and 270 kg body weight (BW) were used. Four were used as reference steers, been slaughtered at the beginning of the trial, three were fed for maintenance, and the remaining were uniformly allotted to a completely randomized design, with three treatments with 5, 35 and 65% of concentrate in total dry matter (DM) basis. The roughage used was Brachiaria brizantha haylage, that was substituted by Cynodon spp. haylage in the latest 30 days of the trial. After chilling, the right side of each carcass was physically separated into lean, fat and bone. The empty body chemical composition was xiiobtained by the chemical analysis of all the body tissues. The net requirement for weight gain of each nutrient was estimated by deriving the regression equations of the logarithm of protein, fat, energy, Ca, P, Na, Mg or K body content, in function of the logarithm of empty BW (EBW). The net energy requirement for maintenance was estimated as the intercept anti-log of the equation obtained by linear regression between the logarithm of heat production and the metabolizable energy intake (MEI). The metabolizable energy efficiencies of utilization (MEEU) for maintenance (k m ) and weigh gain (k f ) were estimated from the relationship between the net energy concentration, for maintenance or gain, respectively, and the metabolizable energy (ME) content of the diet. The comparison between the observed and predicted (by the 9-10- 11 th rib cut) physical and chemical carcass composition was done by regression equation (REG 1) fitted for the predicted values in function of the observed ones, using the SAS (1997). The concentrate level (CL) in the diet influences (P<0.05) the carcass physical and chemical composition. Increasing the CL, fat percentage and the content of ether extract of the carcass increased linearly, while, lean, bone, Ca, P and Na contents had a linear decrease. The protein, Mg and K carcass contents were not affected by the CL, averaging 17,77; 0,04 e 0,23 %, respectively. The physical carcass composition of zebu steers was well predicted by the 9-10-11 th rib, what was not true for the chemical composition. The contents of protein, water, ash, P, Mg, K e Na were adequately predicted by the 9-10-11 th rib cut, while the fat content was overestimated and the calcium content underestimated, respectively. Regression equations involving the fat (EE) and calcium (Ca) contents observed in the 9-10-11 th rib cut and the respective contents observed at the carcass were developed: % EE carcass = 1,0709 + 0,7854 % EE 9-10-11 th rib cut (r 2 = 0,97) and % Ca carcass = -0,2433 + 1,2832 % Ca 9-10-11 th rib cut (r 2 = 0,69). Similarly, regression equations between the contents of fat (EE), protein, water and ash determined in the empty body and the contents of this components obtained in the 9-10-11 th rib cut were developed. The net energy requirement for maintenance was 74,51 kcal/EBW 0,75 or 68,60 kcal/LW 0,75 . To estimate the daily retained energy (RE), in Mcal, it is suggested to use the equation: RE = 0,0718 EBW 0,75 * EBW gain 0,9658 , while for daily retained protein xiii(RP) the equation obtained was: RP = -37,0401 + 213,024 EBW gain – 17,1430 RE. To change the EBW gain requirements into LW gain requirements, it is necessary to multiply the EBW gain for 0,90. The k m estimated was 0.66 and the k f ranged from 0,26 to 0,46. The relationships g Ca/100g of RP and g P/100g of RP were 10,92 and 5,26, respectively. The Ca e Mg dietetic requirements were similar to those of the NRC (1996), while the K e Na requirements were, respectively, lower and greater than that recommended by NRC (1996).
Descrição
Palavras-chave
Exigências, Seção HH, Validação, Zebuínos
Citação
PAULINO, Pedro Veiga Rodrigues. Exigências nutricionais e validação da seção HH para predição da composição corporal de zebuínos. 2002. 150 f. Dissertação (Mestrado em Zootecnia) - Universidade Federal de Viçosa, Viçosa. 2002.