ABSTRACT The objective of this study was to evaluate the effects of adding crude glycerin with food additives (sodium monensin or essential oils) to the diets of beef cattle on feed intake, ruminal parameters, in vitro digestibility, and production of greenhouse gases. Five ruminally cannulated Nellore steers were randomly assigned in a 5×5 Latin square design. The treatments were: control, without crude glycerin and additives; with essential oils and without crude glycerin; with sodium monensin and without crude glycerin; with essential oils and crude glycerin; and with sodium monensin and crude glycerin. The addition of crude glycerin caused a reduction in dry matter (DM) intake, increase in vitro dry matter digestibility, and decrease in vitro crude protein digestibility, regardless of the food additive. All treatments were effective in maintaining the rumen environment with pH values above 6.2 and ammonia nitrogen concentrations above 10 mg dL−1. No difference was observed in the production and quality of protozoal and bacterial fractions. The addition of crude glycerin at 200 g kg−1 DM in the total diet can partially replace corn grain and soybean hulls and be combined with either sodium monensin or essential oil without impairing the rumen fermentation, being effective in reducing gas methane production and, when combined with sodium monensin, enables more efficient utilization of the diet by the animal. Therefore, feedlot experiments at large scales of production should be evaluated to prove these positive results.

RESUMO: A crescente disponibilidade de glicerina bruta proveniente da produção de biodiesel tem gerado grande estoque nas indústrias. Para resolver esse problema, a glicerina bruta está sendo utilizada na alimentação animal como fonte energética. O objetivo deste estudo foi avaliar os efeitos da associação da glicerina bruta (10% da MS das dietas) com diferentes volumosos sobre o pH e amônia ruminal, degradabilidade, digestibilidade da matéria seca e nutrientes, e produção de gás de efeito estufa. Seis novilhos da raça Nelore foram distribuídos aleatoriamente em um quadrado latino 6×6. Os tratamentos avaliados foram cana-hidrolisada associada ou não à glicerina, silagem de milho associada ou não à glicerina ou feno de Tifton 85 associado ou não à glicerina. A concentração de amônia ruminal e pH não foram afetados pela associação glicerina bruta com volumosos e consumo de matéria seca, mas reduziu o consumo de FDN para dietas com cana-hidrolisada e silagem de milho, e reduziu a digestibilidade de MS, MO, FDN, EE, CNF e amido para dietas com Feno de Tifton 85, além de reduzir a degradação efetiva na taxa de 8% h-1 nesta dieta. A associação glicerina bruta com cana-de-açúcar hidrolisada reduziu a produção de CH4 e de CO2 em mL g-1 de MS. A associação da glicerina bruta afeta a utilização de nutrientes, independente do volumoso utilizado. Além disso, promove a mitigação de gases de efeito estufa em dietas com cana-de-açúcar hidrolisada e, quando associada à silagem de milho, mostrou melhores condições de fermentação ruminal e utilização dos nutrientes.

ABSTRACT: The increasing availability of crude glycerin from biodiesel production has generated great stock in the industries. To solve this problem, crude glycerin is being used as an energy source to replace corn in livestock diets. This study evaluated the effects of the association of crude glycerin (10% on DM of diets) with different roughages in Nellore cattle diets on ruminal pH and ammonia, degradability, digestibility of dry matter and nutrients, and greenhouse gas production. Six ruminally cannulated Nellore steers were assigned to a 6×6 Latin square design. The following treatments were evaluated: Hydrolyzed Sugarcane associated or not with crude glycerin, Corn Silage associated or not with crude glycerin or Tifton-85 Hay associated or not with crude glycerin. Association of crude glycerin with roughages did not affect the rumen ammonia concentration and pH and dry matter intake, but reduced the intake of NDF for diets with Hydrolyzed Sugarcane and Corn Silage and reduced the digestibility of DM, OM, NDF, EE, CNF and starch and decreased the effective degradation at the rate of 8% h-1 for diets with Tifton-85 Hay. The association crude glycerin with Hydrolyzed Sugarcane reduced the production of CH4 and CO2 in mL g-1 of DM. The inclusion of crude glycerin affects differently nutrient utilization in diets with Corn Silage, Hydrolyzed Sugarcane or Tifton-85 hay. Moreover, promotes mitigation of greenhouse gases in diets with Hydrolyzed Sugarcane. Association of crude glycerin with Corn Silage in Nellore cattle diets showed better conditions of ruminal fermentation and utilization of nutrients.

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.