Linseed suppresses enteric methane emissions from cattle fed barley silage, but not from those fed grass hay

Abstract

This study investigated potential effects of feeding ground linseed on enteric CH4 production, ruminal fermentation and nutrient digestibility in cattle when it was added to diets containing grass hay or barley silage. Twelve non-lactating ruminally cannulated Holstein cows were used in a replicated 4×4 Latin Square design experiment with four diets and four 21d periods. Experimental diets (500:500 forage to concentrate ratio; dry matter (DM) basis) were used in a 2×2 factorial design using either chopped grass hay or whole crop barley silage as the forage source with or without ground linseed at 150g/kg ration DM as a partial replacement for barley grain. Diets were fed once daily as total mixed rations. Rumen contents were collected on days 14 and 21 of each period. In situ ruminal digestibility of grass hay and barley silage was measured at 24 and 48h of incubation on days 15 and 16. Apparent total tract digestibility of dietary nutrients was estimated by collecting fecal samples from the rectum of each cow twice daily from days 15 to 21. Indigestible aNDF was used as an internal marker to estimate apparent diet digestibility in the total tract. Enteric CH4 production was measured from days 17 to 19 using the sulfur hexafluoride tracer gas technique. Without linseed inclusion, cows fed the diet based on grass hay produced 31% less CH4 as g/hd/d and up to 30% less CH4/kg of DM, digested DM or digested organic matter intake, or as MJ CH4/MJ gross energy intake (forage×linseed interaction, P<0.01) versus cows fed the diet based on barley silage. Including linseed in the hay based diet did not suppress CH4 emissions, whereas including linseed in the silage based diet reduced enteric CH4 emissions by 36% as gCH4/hd/d, by 33% as gCH4/kgDM intake, by 28% as gCH4/kg digested DM and by 37% as MJCH4/MJ gross energy intake (forage×linseed interaction, P<0.01). Linseed inclusion lowered CH4 emissions of cows fed the silage based diet by depressing ruminal fermentation (i.e., reduced protozoal population, decreased total volatile fatty acid concentration (forage×linseed interaction: P<0.01), ruminal digestion (i.e., lower 48h in situ silage fibre disappearance; linseed effect: P≤0.05) and total tract diet digestibility (linseed effect: P≤0.03). Depressive effects of linseed on these variables were less pronounced for the hay based diet. Results show that including ground linseed in a barley silage based diet can mitigate enteric CH4 emissions, but not in a grass hay based diet.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.