Composição Corporal e Requisitos Líquidos e Dietéticos de Macroelementos Minerais de Bovinos Nelore Não-Castrados

Abstract

RESUMO -Foram utilizados 40 novilhos Nelore inteiros, com peso vivo médio inicial de 240 kg, sendo quatro novilhos de referência, quatro alimentados para mantença e o restante distribuído em oito tratamentos, com quatro diferentes níveis de concentrado nas dietas (20, 40, 60 e 80%) e dois níveis de proteína bruta (PB) (15 e 18%). A fase de recria foi avaliada até 360 kg de peso vivo e a fase de engorda, até 450 kg de peso vivo. O volumoso utilizado foi feno de gramímea Cynodon dactylon (L) Pears. cultivar Tifton 85. Após o abate, todas as partes do corpo do animal foram pesadas e amostradas. As amostras foram liofilizadas para determinação de matéria seca, pré-desengorduradas com éter e, posteriormente, moídas e determinados os teores de macroelementos minerais. Os conteúdos de proteína, gordura e energia retidos no corpo foram estimados por meio de equações de regressão do logaritmo do conteúdo corporal dos macroelementos minerais, em função do logaritmo do peso de corpo vazio (PCVZ). Derivando-se as equações de predição do conteúdo corporal dos macroelementos minerais, em função do logaritmo do PCVZ, foram obtidas as exigências líquidas destes, para ganho de 1 kg de PCVZ, a partir de equação Y' = b. 10 a . X b-1 , sendo a e b a intercepta e o coeficiente de regressão, respectivamente, das equações de predição dos conteúdos corporais dos macroelementos minerais. Houve diminuição nas concentrações dos cinco macroelementos estudados no corpo vazio e no ganho de corpo vazio, com a elevação do peso vivo. As relações g Ca/100 g de proteína retida e g P/100 g de proteína retida foram iguais a 6,44 e 4,78.Palavras-chave: exigências, macrominerais, Nelore Body Composition and Net and Dietary Macrominerals Requirements of Nellore BullsABSTRACT -Forty Nellore bulls, with 240 kg initial live weight (LW), were used. Four were reference bulls, four were fed for maintenance, and the remaining were allotted to eight treatments, with four different concentrate levels in the diets (20, 40, 60, and 80%) and two levels of crude protein (CP) (15 and 18%). The growing phase was evaluated up to 360 kg of LW and the fattening phase, up to 450 kg of LW. Cynodon dactylon (L) Pears. (cv Tyfton 85) grass hay was used as roughage. After slaughter, all animal body parts were weighed and sampled. The samples were freeze dried to determine the dry matter, pre-degreased with ether, grinded and the concentrations of macrominerals were determined. The Ca, P, Na and Mg contents in the body were determined in function of their concentrations in the several body parts. The macrominerals contents retained in the body were determined by regression equations of the logarithm of the macrominerals contents in the body, in function of the logarithm of empty body weight (EBW). By deriving the prediction equations of macrominerals body content, in function of the logarithm of empty body weight (EBW), the net macrominerals requirements, for gains of 1 kg of EBW, were obtained by means of the equation Y' = b. 10 a . X b-1 , being "a" and "b" the intercep...

Macro mineral requirements by grazing zebu bovines

“…Dietary requirement of Ca for 1.0 kg of gain of a 400-kg BW animal, found in this study (Table 6), were close to the value 21.49 g/kg BWG estimated by Silva et al (2002b).…”

“…For the same 400 kg and by using net requirements of protein, and Ca and P obtained by BR-CORTE (Valadares Filho et al, 2010) for Zebu animals in Brazilian conditions, we obtain the relationships 9.25 g Ca/100 g CP retained and 4.89 g P/100 g CP retained , which are close to the ones in this study. In this research, net requirements of Mg for a 400-kg BW animal were close to the ones estimated by Silva et al (2002c) and by BR-CORTE (Valadares Filho et al, 2010). On the other hand, net requirement of Mg were much lower than the constant value of 0.45 g/kg recommended by ARC (1980).…”

“…Net requirements of Ca (13.02 g/kg EBW) estimated for a 400-kg BW animal, were higher than the ones observed by Silva et al (2002b) and given by BR-CORTE (Valadares Filho et al, 2010) for Zebu animals in Brazil. In addition, the value in the present study was smaller than the one recommended by AFRC (1991) for a 400-kg LW animal (11.90 g/kg EBW).…”

“…Silva et al (2002b) obtained 6.44 g Ca/100 g CP retained and 4.78 g Pa/100 g CP retained . For the same 400 kg and by using net requirements of protein, and Ca and P obtained by BR-CORTE (Valadares Filho et al, 2010) for Zebu animals in Brazilian conditions, we obtain the relationships 9.25 g Ca/100 g CP retained and 4.89 g P/100 g CP retained , which are close to the ones in this study.…”