-Two studies were conducted to evaluate the effects of crude glycerin on feed intake, performance, carcass characteristics, and total digestibility of Nellore bulls. In experiment 1, cattle (n = 30) were fed a control diet without crude glycerin and diets containing 7.5, 15, 22.5, and 30% crude glycerin, for 103 d. Animals were harvested and data of carcass characteristics were collected. In experiment 2, a digestibility trial was performed using indigestible acid detergent fiber (iADF) as internal marker, and five rumen-cannulated steers. Both experiments were conducted as a randomized complete block design and data were analyzed using mixed procedures. In experiment 1 no differences were observed among treatments on dry matter intake, and performance variables. Regarding carcass characteristics, no effect was observed, except for carcass fat estimates, which were greater in treatments with crude glycerin. In experiment 2, crude glycerin promoted a decrease in digestibility of fibrous fractions NDF and HEM, and increased digestibility of crude protein by 6%. Although it caused negative effect on digestibility of fibrous fraction of diets, crude glycerin can be a good energy source for Nellore bulls, since no losses are observed on performance and carcass characteristics when animals are fed up to 30% of this by-product.

This study aimed to evaluate the effects of glycerin supplements in the diet of beef cattle by assessing intake, apparent nutrient digestibility, ruminal pH, ruminal ammonia concentrations, and blood parameters. The study was conducted at the São Paulo State University (UNESP, Jaboticabal campus) using five crossbred cattle in an experiment employing a 5 x 5 Latin square design. Cattle diet treatments included zero, 50, 100, 150, and 200 g kg -1 dry matter of glycerin. Feed, leftover feed, and faeces were collected to determine intake and digestibility. Samples of ruminal liquid were collected at -1, 0, 1, 2, 4, 6 and 8 h after feeding to determine pH and ruminal ammonia. Blood was collected four hours after the morning feeding from the coccygeal vein. Replacing maize with glycerin resulted in lower concentrations of ether extract and non-fibre carbohydrates in the diets, leading to a linear decrease in the intake of these nutrients (P<0.05). The digestibility of neutral detergent fibre and nonfibre carbohydrates also decreased linearly with increasing dietary glycerin concentrations (P<0.05). The results for ruminal fermentation parameters showed a linear decrease (P<0.05) in the ruminal concentration of N-NH 3 with increasing dietary levels of glycerin; however, ruminal pH was not affected (P>0.05). Serum concentrations of urea, triglycerides, cholesterol, and plasma glucose concentrations were within normal ranges based on the literature. The inclusion of glycerin in the cattle diet altered rumen fermentation, reducing the concentration of N-NH 3 , the digestibility of neutral detergent fiber and non-fiber carbohydrates. g kg -1 de glicerina na MS. Para determinação do consumo e digestibilidade foram realizadas colheitas de alimentos, sobras e fezes. Para determinação do pH e amônia ruminal foram colhidas amostras de líquido ruminal nos tempos -1, 0, 1, 2, 4, 6 e 8 horas após a alimentação. As colheitas de sangue foram realizadas 4h após a alimentação matutina via veia coccígea. A substituição do milho pela glicerina resultou em menores concentrações de extrato etéreo e carboidratos não fibrosos nas dietas, o que levou a redução linear no consumo desses nutrientes (P<0,05). As digestibilidades da fibra em detergente neutro e de carboidratos não fibrosos apresentaram redução linear com o aumento da concentração de glicerina na dieta (P<0,05). Em relação à fermentação ruminal, houve decréscimo linear (P<0,05) na concentração ruminal de N-NH 3 com o aumento da inclusão desse subproduto, mas o pH ruminal não foi influenciado (P>0,05). As concentrações séricas de ureia, triglicerídeos e colesterol ficaram dentro dos níveis considerados normais pela literatura assim como as concentrações plasmáticas de glicose. A inclusão de glicerina na dieta de bovinos alterou a fermentação ruminal, reduzindo a concentração de N-NH 3 , a digestibilidade da fibra em detergente neutro e dos carboidratos não fibrosos. Palavras-chave: Biodiesel, fermentação ruminal, metabolismo, subproduto

Crude glycerin, a potential energy source for ruminant animals, has been evaluated, mainly, in diets with high starch content. However, a limit number of studies have evaluated the inclusion of crude glycerin in low starch diets. This study aimed to evaluate the effects of the association of crude glycerin with corn grain or citrus pulp on carcass traits and meat quality of Nellore bulls ( n = 30, 402 ± 31 kg initial weight). The treatment consisted of: CON = control, without crude glycerin; CG10 = 10% of crude glycerin and corn grain; CG15 = 15% of crude glycerin and corn grain; CP10 = 10% of crude glycerin and citrus pulp; CP15 = 15% of crude glycerin and citrus pulp. The performance parameters and carcass traits were not affected by treatments ( P > 0.05). The inclusion of crude glycerin decreased yellow color intensity and increased fatty acids pentadecanoic and heptadecenoic in meat ( P < 0.05), without affecting neither the concentration of polyunsaturated fatty acids nor the relationship of saturated and unsaturated fatty acids. The association of crude glycerin with corn or citrus pulp has no adverse effects on carcass characteristics and meat quality.

Crude glycerin, the main by-product of biodiesel production, can replace dietary energy sources, such as corn. The objective of this study was to evaluate the inclusion of up to 30% of crude glycerin in dry matter (DM) of the total diets, and its effects on meat quality parameters of feedlot Nellore bulls. Thirty animals (227.7 ± 23.8 kg body weight; 18 months old) were housed in individual pens and fed 5 experimental diets, containing 0, 7.5, 15, 22.5 or 30% crude glycerin (DM basis). After 103 d (21 d adaptation) animals were slaughtered and the Longissimus muscle was collected. The characteristics assessed were chemical composition, fatty acid profile, cholesterol, shear force, pH, color, water-holding capacity, cooking loss and sensory properties. The increasing inclusion of crude glycerin in the diets did not affect the chemical composition of the Longissimus muscle (P > 0.10). A quadratic effect was observed when levels of crude glycerin were increased, on the concentration of pentadecanoic, palmitoleic and eicosenoic fatty acids in meat (P < 0.05), and on the activity of the delta-9 desaturase 16 and delta-9 desaturase 18 enzymes (P < 0.05). The addition of crude glycerin increased the gamma linolenic fatty acid concentration (P < 0.01), and altered the monounsaturated fatty acids in Longissimus muscle of animals (Pquad. < 0.05). Crude glycerin decreased cholesterol content in meat (P < 0.05), and promoted higher flavor score and greasy intensity perception of the meat (P < 0.01). The inclusion of up to 30% crude glycerin in Nellore cattle bulls`diets (DM basis) improves meat cholesterol and sensory attributes, such as flavor, without affecting significantly the physical traits, the main fatty acid concentrations and the chemical composition.

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