Performance and methane emissions of grazing Nellore bulls supplemented with crude glycerin.

Supplementation of grass-fed cattle with low-cost feeding alternatives may be an attractive way to improve efficiency of cattle production. We hypothesized that inclusion of crude glycerin (CG) in supplements provided to grass-fed cattle could improve feed conversion without negative effects on growth performance while reducing methane emissions. Our hypothesis was tested using Nellore bulls grazing tropical pasture ( = 50; initial BW of 427 ± 19.41 kg; age of 17 ± 2 mo) supplemented with increasing concentrations (0, 70, 140, 210, and 280 g/kg DM basis of supplement) of CG and corn gluten replacing corn grain. A second experiment was conducted using 10 ruminally cannulated Nellore steers (490.1 ± 47.8 kg BW; age of 25 mo) to assess the impact of different concentrations of glycerin in the supplement on ruminal VFA concentration. Inclusion of CG did not affect total DMI ( = 0.53), DMI of forage ( = 0.41), supplement DMI ( = 0.47), organic matter intake ( = 0.50), crude protein intake ( = 0.24), NDF intake ( = 0.49), GE intake ( = 0.50), NDF digestibility ( = 0.17), final BW ( = 0.17), LM area ( = 0.50), rib fat thickness ( = 0.87), or carcass gain ( = 0.13). The inclusion of CG in the supplement linearly increased ( < 0.001) the molar proportion of propionate, butyrate, and valerate; linearly decreased acetate ( = 0.001); and did not affect the molar proportion of isovalerate ( = 0.31) and isobutyrate ( = 0.63), thereby reducing the acetate to propionate ratio ( < 0.001). The increase of CG supplementation of young bulls in pasture had a quadratic effect on BW gain ( = 0.002), with lower BW gain with 140 g/kg DM of CG in the supplement and tended ( = 0.06) to improve G:F. Inclusion of CG did not affect ruminal CH emission expressed in kilograms per year ( = 0.74), grams per kilogram of DMI ( = 0.69), and grams per kilogram of carcass gain ( = 0.48). Crude glycerin supplementation was not effective as a strategy to reduce CH emission in grass-fed cattle. However, CG can be effectively used as a partial energy source in supplement of grazing cattle, promoting an improvement in feed efficiency.

Fatty acid profile, carcass and meat quality traits of young Nellore bulls fed crude glycerin replacing energy sources in the concentrate.

Carcass and meat quality traits of 60 Nellore young bulls fed diets without crude glycerin (CG); with CG replacing corn (CGc; 10% of dry matter - DM) in the concentrate; and with CG replacing soybean hull (CGsh; 10% of DM) in the concentrate were evaluated. Diets were evaluated at two concentrate levels (CLs). The CL did not affect cold carcass weight (CCW; P=0.6074), cold carcass dressing (CCD; P=0.9636), rib fat thickness (RFT; P=0.8696) and longissimus muscle area (LMA; P=0.7524). Animals fed diets with CGc or CGsh showed meat with greater deposition of monounsaturated fatty acid (MUFA; P=0.0022) and CLA (18:2 cis-9, trans-11) contents (P=0.0001) than animals fed diets without CG. The inclusion of 10% of CG in diets CGc or CGsh does not affect the carcass and meat quality traits; however, it increases the MUFA and CLA contents in beef, although these changes are very small in nutritional terms.