Fontes de proteína e concentração de fósforo em suplementos para bovinos consumindo feno de baixa qualidade

Abstract

The study was conducted through two experiments carried out at the Experimental Farm of Iguatemi (FEI), belonging to the Universidade Estadual de Maringá - UEM, from June 2008 to February 2010. The first experiment was carried out to evaluate the effect of protein supplements with two protein sources at two doses of supply, on intake, ruminal fermentation and kinetics, nutrients apparent digestibility and blood parameters. Five Nelore steers, cannulated in the rumen with 366 kg ± 55 kg body weight (BW) were used. The experimental design was a Latin square 5 x 5, and the animals were allocated into five experimental diets based on hay (Brachiaria humidicola cv. Llanero) chopped, supplemented or not with two doses and two protein sources. The treatments were: hay without supplementation (FSS), hay + 1 g urea supplement/kg body weight (1U), hay + 2 g urea supplement/kg body weight (2U), hay + 1 g soybean meal supplement/kg body weight (1FS) hay + 2 g soybean meal supplement/kg body weight (2FS). The use of supplements increased intake, omasal and fecal flow, ruminal and nutrients total digestibility, serum concentration of urea nitrogen, concentration of N-NH3 and total concentration of short chain fatty acids in rumen. The supplement containing soybean meal had the highest omasal flow of CP, increased total digestibility of DM, OM and NDF, increased intestinal digestibility of CP, and also had the highest rate of disappearance and digestion. The urea was responsible for the increased fecal flow of OM and NDF, the highest rate of dilution of the diet and increased recycling rate. Between doses of supplementation, higher responses were found with the highest doses at supplementation. The second experiment was conducted to evaluate the influence of increasing phosphorus concentration in protein supplements for cattle on intake, rumen fermentation and kinetics, efficiency of microbial synthesis, disappearance and apparent absorption of P, apparent digestibility of nutrients and blood parameters. Five Holstein steers castrated with 254 kg ± 22 kg body weight were used. The animals were allocated into five experimental diets based on hay (Brachiaria humidicola cv. Llanero) chopped, supplemented with increasing doses at P in experimental design 5 x 5 Latin square. The treatments consisted of the use of supplements containing: 2.5 g P/kg body weight (2.5 P), 5 g P/kg body weight (5P), 10 g P/kg body weight (10P ), 15 g P/kg body weight (15P) and 20 g P/kg body weight (20P). The supply of phosphorus in increasing doses increased linearly intake, omasal and fecal flows and total apparent absorption of phosphorus and linearly decreased the rate of recycling in the rumen. The total apparent digestibility of DM and NDF showed a quadratic response in percentage of phosphorus in supplement and the pH was cubically. There was no treatment effect on blood parameters, the concentration of NNH3, SCFA and microbial efficiency.