Potential of various fatty feeds to reduce methane release from rumen fermentation in vitro (Rusitec)

The effects of coconut oil and whole crushed oilseeds (rapeseed, sunflower seed and linseed) on rumen fermentation, as well as on methane and hydrogen release, were evaluated in vitro employing the rumen simulation technique (Rusitec). A low-fat diet served as the negative control and a diet with rumen protected fat as the positive control. By using two different proportions of concentrate in the diet, 6% and 9% of total lipids were supplied with each of the five fat supplemented diets, whereas the control diets contained about 3% total lipids. The 12 diets were provided at daily amounts of 11 g and 22 g dry matter. Rumen-protected fat as well as rapeseed had small effects on fermentation pattern and methane formation, which presumably resulted from the exchange of carbohydrates by fat. In contrast, coconut oil, sunflower seed and linseed significantly reduced protozoa count and methane release. An increased fat supply by the higher concentrate proportion further supported the suppressing effects of these types of fat on protozoa and methane. Coconut oil completely eliminated protozoa from rumen fluid after four to nine days of application, and this period was shorter by more than 30% on average at the higher level of supply. As compared with the low-fat treatment, coconut oil suppressed methane by 43% with medium and 57% with high concentrate level. The maximum methane reduction with sunflower seed and linseed accounted for about 40%. An increase in hydrogen release was found with coconut oil and oilseeds which, however, was considerably lower than the hydrogen quantities that were less incorporated into methane. In these situations, hydrogen recovery, as calculated from hydrogen balance, was reduced. (C) 1998 Elsevier Science B.V.