Crude glycerine as an alternative energy feedstuff for beef cattle grazing tropical pasture

The purpose of the current study was to evaluate the effect of different levels of crude glycerine (CG, 810.9 g glycerol/kg) replacing dry ground maize on intake, digestibility, microbial nitrogen (N) synthesis and N utilization in grazing beef cattle. Five Nellore bulls (332 +/- 29.6 kg initial body weight (BW)) were used in a 5 x 5 Latin square design. The animals grazed five Marandu grass (Urochloa brizantha cv. Marandu) paddocks of approximately 0.32 ha. Five supplements were evaluated: mineral supplementation (control, only ad libitum access to a mineral mixture) and 4 g of protein-energy supplementation/kg of BW with four levels of CG (0, 330, 660 and 1000 g/kg) replacing dry ground maize. Bulls that received protein-energy supplementation had greater organic matter (OM) pasture and digested OM (DOM) intakes than the control. No differences were observed among CG levels with regard to OM pasture, neutral detergent fibre and DOM intakes. However, ether extract intake increased linearly as CG levels increased. Protein-energy supplementation enhanced efficiency of microbial N synthesis, N balance and ammonia concentration, but they were not influenced by the CG levels. In conclusion, partial or total replacement of dry ground maize by CG in protein-energy supplements for grazing beef cattle exerted no changes on pasture intake, digestibility and N utilization. Therefore, the use of CG as an energy source in supplements for grazing cattle can be recommended.