The effect of dietary coconut kernels, whole cottonseeds and sunflower seeds on the intake, digestibility and enteric methane emissions of Zebu beef cattle fed rice straw based diets

Methane emissions from ruminant livestock are problematic with respect to the energy utilization efficiency of animal feed as well as environmental sustainability due to such emissions being a major greenhouse gas source. The objective of this experiment was to determine the methane emissions and feeding performance of two breeds of Zebu beef cattle fed rice straw based diets with oil plant inclusion. Eight mature bulls (four Thai native and four Brahman crossbred beef cattle weighing 290 +/- 10.2 and 401 +/- 29.7 kg (mean +/- SD), respectively) were assigned to a replicated 4 x 4 Latin square design with 21 day periods. The following dietary treatments were assigned: 1=control diet, 2=whole cottonseed diet, 3 = whole sunflower seed diet and 4=coconut kernel diet. The animals were individually placed in metabolic cages and respiration chambers to determine feed intake, total tract digestibility and methane emissions. The two cattle breeds were not different in their dry matter intake per body weight (or metabolic body weight) and digestibility, but the corresponding values for the oil plant dietary treatments were less (P < 0.001) than those for the control diet. All of the oil plant treatments decreased (P < 0.001) the dry matter and NDF digestibility compared to the control diet, but the oil plants had no effect on ruminal pH, ammonia nitrogen or total volatile fatty acid concentration. The methane emissions of the Brahman crossbred beef cattle were greater (P < 0.001) than those of the Thai native cattle (135.4 and 171.5 L/day), but there was no difference (P>0.05) when corrected for dry matter intake, organic matter intake, metabolic size or gross energy intake. The methane emission rate was reduced (P<0.001) by up to 50.1% by the oil plant feeding strategy compared to the control diet. The methane emission rate of the base line typical feeding system in the control diet (10.4%) appeared to be much greater than the Intergovernmental Panel on Climate Change value of 6.5% for cattle fed low-quality crop residues or by-products. Our results demonstrated that methane emissions did not differ between Zebu beef cattle when corrected for metabolic body weight and feed or gross energy intake. The inclusion of oil plants in the diets, such as the coconut kernel, sunflower seed and cottonseed, affects intake, digestibility and potentially be used as an enteric methane mitigation feeding strategy. (C) 2014 Elsevier B.V. All rights reserved.