No abstract

An increasing worldwide interest in alternative fuel sources and in a more diversified energy matrix has provided incentives for the biodiesel industry, generating large amounts of the by-product crude glycerin, a potential alternative feed for dairy cows. A replicated 3×3 Latin square study was conducted to evaluate the effects of high concentrations of crude glycerin on dry matter intake, milk yield and composition, milk fatty acid profile, and blood metabolites of medium-yield cows. Ruminally cannulated Holstein cows (n=6; 587 ± 39 kg of body weight; 114 ± 29 d in milk; and 20 ± 1.5 kg/d milk yield) were used in the study. The experimental period included 2 wk for adaptation and 1 wk for data collection. Cows were fed diets containing 0 (control), 15, or 30% crude glycerin (83% glycerol). Cows were milked, milk weights were recorded twice daily, and milk samples were collected for milk quality analyses at d 18 and 19 in each experimental period. Feeding cows with crude glycerin linearly decreased dry-matter intake, the 3.5% fat-corrected milk, and the solid-corrected milk yield. Hepatic enzymes were not affected by dietary treatments, except gamma-glutamyl transferase, which was decreased with the 15% crude glycerin diet. Serum glucose and albumin showed quadratic effect with increasing inclusion of crude glycerin. Plasma cholesterol as well as total protein linearly decreased with increasing inclusion of crude glycerin. Milk fat concentration and yield showed a quadratic effect of treatments. Solid yield decreased linearly with increasing inclusion of crude glycerin. Odd-chain fatty acids and conjugated linoleic acid in milk fat linearly increased with addition of crude glycerin in the diets. Together, these results suggest that crude glycerin has potential to replace corn; however, feeding diets in which corn is replaced with crude glycerin at 30% of dietary DM greatly reduces animal performance.

-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.

As the biodiesel industry produces a large surplus of crude glycerin, this by-product is increasingly being considered as an attractive source of energy to replace corn in livestock diets. The objective of this study was to evaluate how the inclusion of up to 30% crude glycerin in Nellore cattle diets affects ruminal parameters such as pH, ammonia, and volatile fatty acids as well as greenhouse gas production, and concentration of the protozoal and bacterial fractions. Five ruminally cannulated Nellore steers were randomly assigned in a 5 Â 5 Latin square design and fed diets containing 30% corn silage and 70% concentrate composed of sunflower meal, corn grain, soybean hulls, minerals, and 0, 7.5, 15, 22.5, or 30% crude glycerin (860 g glycerol/kg). After 14 d of adaptation, animals were submitted to rumen content sampling for 7 d. With the supplementation of glycerin in the diets, total VFA and acetate concentrations decreased (linear, P¼ 0.03, Po 0.0001, respectively), and propionate concentrations increased (linear, P¼ 0.007; quadratic, P ¼0.008), leading to an acetate to propionate ratio decrease (linear, P o 0.0001). The rumen ammonia was not affected while pH was quadratically affected and was lesser for glycerin treatments (quadratic, P¼ 0.04). Methane production was reduced (linear, Po 0.0001) when glycerin was added, as well as the CO 2 (linear, P o0.0001; quadratic, P ¼0.0001; cubic, P o0.0001). The concentration of liquid phase microorganisms was not affected, while the concentration of particle-associated bacteria fraction was decreased by the addition of crude glycerin in the diets. The inclusion of up to 30% of crude glycerin in diets for beef cattle decreased ruminal concentration of total VFA and acetate, increased propionate, reduced concentration of particle-associated bacteria, and decreased production of methane.

Este experimento foi realizado para avaliar o efeito de dois níveis de casca de soja (CS) e de três fontes de nitrogênio sobre a digestão total e parcial aparentes no rúmen e nos intestinos. Seis novilhos Holandês x Zebu com idade média de 12 meses e 229 kg de PV foram fistulados no rúmen e no abomaso e distribuídos em quadrado latino 6x6 e alimentados individualmente ad libitum. O consumo e as digestibilidades totais e parciais dos nutrientes foram avaliados. Não houve efeito da fonte de proteína sobre o consumo, quantidades de matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), fibra em detergente neutro (FDN) e da fibra em detergente ácido (FDA) no rúmen, no abomaso e nas fezes e sobre os coeficientes de digestibilidades destes componentes. O aumento, porém, do nível de casca de soja elevou os coeficientes de digestibilidade de todos os componentes estudados nos locais do trato digestivo, com exceção nos intestinos, onde o nível de casca de soja não afetou a digestão da PB, FDN e da FDA. Os resultados indicam que a casca de soja pode substituir tanto o milho como, parcialmente, a fração volumosa nas rações de ruminantes. A farinha de subproduto avícola e a amiréia podem substituir o farelo de soja nas rações de bovinos sem reflexos negativos sobre a digestão de seus componentes nutritivos.