Composição corporal e exigências nutricionais de macroelementos minerais (Ca, P, Mg, Na e K) de bovinos Nelore e Caracu selecionados para peso aos 378 dias de idade / Body composition and nutritional requirements of macrominerals (Ca, P, Mg, Na and K) of genetic improved Nellore and Caracu bulls to weight at 378 days of age

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The experiment was accomplished in the Experimental Station of Colina, Zootecnia Institute, Sao Paulo, Brazil, with the objective of evaluating the body composition and the net and dietary requeriments of calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and potassium (K) of Genetic Improved Nellore (GIN) and Genetic Improved Caracu (GIC) for weight at 378 days of age and Genetic Non Improved Nellore (GNIN). Fifty six bulls with average age of 18 months were used. After a period of adaptation of 28 days, twelve animals were slaughthered as reference to estimate the empty body weight (EBW) and the initial body composition of the 44 remaining, being 16 GIN, 16 GIC and 12 GNIN with initial average live weight (LW) of 392, 421 and 337 kg, respectively. The animals were uniformly distributed to a completely randomized design in a 3 x 2 factorial arrangement, with three genetics groups and two dietary levels. One of dietary levels was the restricted, in which the consumption was of 65 g of DM/LW0.75 per day and the other level was the ad libitum, with feed supply twice per day. The roughage used was corn silage and the concentrate ingredients were ground corn, cottonseed meal, urea, rumensin, mineral mixture, with roughage/concentrate ratio of 50/50. The slaughter occurred when the animals presented 4.0 millimeters of subcutaneous fat thickness, measured by ultra-sound, in the area among the 12th and 13th ribs. After the slaughter, all animals body parts were weight 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, Mg, Na and K contents in the body were determined as a function of their concentrations in the several parts of the body. The macrominerals contents retained in the body of the animals were determined by regression equations of the logarithm of Ca, P, Mg, Na and K body content as a function of the logarithm of EBW. The net macrominerals requeriments for gain of 1 kg of EBW were obtained by deriving the prediction equations of macrominerals body contents as a function of the logarithm of EBW. The requirements of Ca, P, Mg, Na and K for maintenance were estimated based in the recommendations of ARC (1980) and of NRC (1996). The identity test of models indicated that there were no differences (P>0.05) between the regression equations for P, Mg and Na for GIN and GNIN, which differed of the equations for GIC. For Ca and K, there were no differences between the equations for GNIN and GIC, which differed of those referring to the GIN. The body concentrations and the requeriments of all macrominerals studied increased with the increase of EBW of the animals. For a 400 kg LW animal, the body concentrations of Ca, P, Mg, Na and K (g/kg of EBW) were, respectively: GIN (16.99; 7.89; 0.30; 1.28 and 2.18); GNIN (15.27; 7.89; 0.30; 1.28 and 1.72) and GIC (15.27; 7.32; 0.26; 1.12 and 1.72). The net requeriments of Ca, P, Mg, Na and K (g/kg of EBWG) for one bovine with this same weight were, respectively: GIN (17.09; 9.33; 0.43; 1.64 and 2.78); GNIN (15.37; 9.33; 0.43; 1.64 and 2.60) and GIC (15.37; 8.52; 0.35; 1.54 and 2.60). The respective total dietary requeriments (g/day) were: GIN (45.51; 22.73; 9.50; 4.74 and 46.56); GNIN (42.16; 22.73; 9.50; 4.74 and 46.38) and GIC (42.16; 21.58; 9.08; 4.63 and 46.38), for the same macrominerals sequence.

ASSUNTO(S)

beef cattle composição corporal nutrição animal animal nutrition nutritional requirements bovino exigências nutricionais nutricao e alimentacao animal body composition

ACESSO AO ARTIGO

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