Glicerina residual da produção de biodiesel em dietas com elevado teor de concentrado para ovinos

Abstract

The objetctive were to evaluate, for sheep, the inclusion of glycerin from biodiesel soybean in high-concentrate diets, with cotton boll, on the intake of nutrients and water, total tract apparent digestibility, nitrogen balance, pH, ruminal ammonia, blood glucose concentrations, production (Pmic) and microbial efficiency (Efmic). The design was a 5x5 Latin square with five castrated male sheep, cannulated in the rumen, with 52.2 ± 5.5 kg. Animals were fed with diets (11.2% CP) formulated to contain 0, 5, 10, 15 e 20% of glycerin (on dry basis), with 25% forage and 75% concentrate. Water, feed, refusal and total fecal output were collected to obtain intake and digestibility. Rumen fluid was collected to measure the pH values and ruminal ammonia, at the feeding moment up to 8 h. The glucose blood concentrations were measured with Accu Chek®. Estimates of Pmic, Efmic and the derivatives of purine were obtained in 24 h urine collection from the estimates of purine excretions. The glycerin had a quadratic effect on intake of dry matter, organic matter, crude protein and total digestible nutrients. The ether extract intake linearly increased (P<0.01), while for non-fiber and total carbohydrates, a linear reduction in intake and digestibility was observed. The glycerin increased dry matter, organic matter, crude protein, ether extract and neutral detergent fiber digestibilities. Intake of water support about 2.3 L/kg DM without glycerin effect. The pH values were quadratically affected (P<0.03) by glycerin and collection times, with the maximum of 5.57 observed for 8.63% glycerin, and minimum of 5.39 about 4.78 hour after feeding. The increase amounts of glycerin did not affect the blood glucose concentrations. The inclusion of glycerol to the diet quadratically increased the nitrogen intake, fecal urinary and the uptake, with maximum values of inclusions of 14.22; 11.53; 11.86 and 15.52%, respectively. There was a linear decrease (P<0.01) on ruminal ammonia of 0.16 mg/dL for each 1% of glycerin added. The excretion of purine derivatives were not affected, except for xanthine + hipoxatina which was linearly increased (P <0.01), with excretion of 9,85 mmol/day for total purine, resulting in 55,03 g/day Pmic, and 48.35 g CP/kg TDN of EFmic. The maximum intake of dry matter and crude protein was estimated at 13% glycerin inclusion. The digestibility and nutritional components were not negatively influenced by low ruminal pH values. Inclusions of glycerin can be made up to 20% without compromising the nitrogen balance, protein and microbial efficiency, even with the reductions in the concentrations of ruminal ammonia.