Influence of low crude protein diets in nitrogen balance and tissue retention of growing swine / Efeito de nÃveis de proteÃna da raÃÃo no balanÃo de nitrogÃnio e composiÃÃo corporal de suÃnos em crescimento

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Three experiments were conducted in the DZO/UFLA to evaluate the effects of crude protein content in nitrogen balance, body composition and blood and urinary metabolites of swine. In the first experiment, 12 crossbred barrows, housed individualy in stell metabolic cages were used. The animals were allotted to four treatments consisting of isocaloric and isolysine diets formulated with the ideal protein concept but with different crude protein contents (16, 14, 12 and 10%). The amount of diet fed was of 3.5 times as high as maintenance energy calculated as 106 kcal of ME/Kg BW0.75 and adjusted daily according to the expected weight gain. The experiment was carried out in two consecutive 12-day periods. The seven first days were utilized for animalâs adaptation and the five remaining utilized in the total collection of feces and urine. Ferric oxide was used as a fecal marker. The experimental design was the changeover balanced in two periods. In the second experiment were utilized 38 crossbred barrows (initial BW 32.7 +- 1.5 kg) and with a high ability for lean deposition. Eight pigs were slaughtered at the begin of the experiment and used as a reference for the calculation of the protein retention rates and lipid deposition. The 30 remaining crossbred barrows were individualy housed in compacted -floored pens and distributed into five treatments. The experimental treatments were four isolysine and isocaloric diets containing different contents of crude protein (10, 12, 14 and 16%). A fifth treatment was included to verify whether the supplementation of non essential amino acids (L-glutamate, L-glycine and L-proline) in the diet with the lowest protein content would influence protein retention (10+NEN). The amount of diet fed was 3.5 as high as the amount of maintenance energy calculated as 106 kcal of ME/Kg LW0.75. The animals were weighted twice a week to establish diet consumption. The experimental design utilized was that of randomized blocks. In the third experiment were utilized 12 crosbreed barrows (initial BW 32.0 Â 1.05 kg), housed individualy in compact floored pens. The animals were distributed into four treatments, which consisted of isocaloric and isolysine diets but containing different crude protein contents (10, 12, 14 and 16%). The amount o diet given was 3.5 as high as maintenance energy calculated as 106 kcal of ME/KgLW0.75 and adjusted daily according to expected weight gain. The experiment was done in two consecutive 7-day periods, on the seventh day, blood collection was proceeded. In the first experiment, it was found that there was a linear reduction (P<0.01) in nitrogen excretion with decreasing crude protein content of the diets. At every percent point of reduction in the diet crude protein, 10.8% less nitrogen is eliminated in the urine. Nitrogen retention decreased linearly (P<0.01) with decrease of protein content. Diet 10 provided around 80% of nitrogen retention of diet 16. However, efficiency of use of nitrogen consumed increased proportionally with decrease of crude protein of the diet. The metabolizability coefficient of the diets were similar (P<0.05) but the ratio between digestible and metabolizable energy was inversely proportional to the concentration of protein of the diets. In the second experiment, the swine of the 10 + NEN and 10 diet swine presented lower weight gain (P<0.05) and worse feed conversion (P<0.05) than the swine submitted to the other treatments. The weight of organs (liver, kidneys, pancreas and heart) was not altered by the protein content of the diets. The weight of the intestinal tract (INT) and the summation of the weights of the INT and organs were higher (P<0.01) in treatments 14 and 16 as compared with treatments 10 + NEN and 10. The body protein retention rate was higher (P<0.05) in the diet 14 and 16 diets swine as compared with treatments 10 + NEN and 10. The protein retention provided by diet 12 was intermediary relative to the others. The animals consuming diet 16 shown less (P<0.05) body deposition of lipids than the swine consuming diet 10 + NEN. In the other treatments, fat deposition was similar between each other and intermediary in relation to the diet 16 and 10 +NEN swine. There was a linear effect (P<0.05) of protein content upon the urea concentration in the blood and urine. In conclusion the reduction of four percent points in crude protein content with its adequate supplementation of synthetic aminoacids enables decrease in nitrogen elimination in the urine without altering the performance and protein retention of growing pigs. However, low protein diets result into increase in body fat deposition. The blood and urine urea concentrations reflect the protein content of the diets.

ASSUNTO(S)

zootecnia nitrogen balance crude protein balanÃo de nitrogÃnio growing swine body composition proteÃna bruta composiÃÃo corporal suÃnos em crescimento

ACESSO AO ARTIGO

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