Effect of forage/concentrate ratio and dietary coconut oil level on methane output and performance of finishing beef heifers

Intake, animal performance and methane (CH4) output was investigated using 36 finishing Charolais cross heifers (mean starting weight 462 kg, S.D.+/-16) fed ad libitum over an 11-week period. Six dietary treatments were investigated in a randomised block design experiment with a factorial arrangement of treatments. The six experimental diets consisted of three forage/concentrate (F/C) ratios (0.65:0.35, 0.40:0.60 and 0.10:0.90) supplemented with two levels of coconut oil (0 or 350 g/ day). Rumen protozoa numbers were significantly (P<0.001) lower for diets containing coconut oil at the end of the trial. Reducing the F/C ratio resulted in significantly (P<0.001) increased rates of live weight gain (LWG) and carcass gain (CG), but coconut oil had no effect on animal performance. Methane output in litres per day was significantly modified (P<0.001) by both the F/C ratio and level of coconut oil. Maximal CH4 output was recorded on the 0.40:0.60 diet, with coconut oil reducing daily CH4 output regardless of the F/C ratio. Methane output per unit of animal product (per kg of LWG and carcass gain) was significantly reduced by lower F/C ratios and the dietary inclusion of coconut oil (P<0.001 and Pless than or equal to0.003, respectively). No significant (P>0.05) interaction between the F/C ratio and coconut oil level was identified although coconut oil significantly reduced dry matter intake (DMI), CH4 l/day and LWG on the 0.65:0.35 F/C ratio diet. (C) 2003 Elsevier B.V. All rights reserved.