The objective of this experiment was to assess the effects of a partial replacement of ryegrass (Lolium perenne) by red clover (Trifolium pratense) or alfalfa (Medicago sativa) supplemented with 0 or 41 g Acacia mearnsii extract (containing 0.615 g/g condensed tannins)/kg dietary dry matter on nitrogen turnover and methane release by sheep, using the respiration chamber technique. Across all variables, there was no significant interaction between basal diet and tannin supplementation. The partial replacement of the grass by the legumes remained without effect on the amounts of nitrogen excreted through faeces or urine. Nitrogen and energy utilisation was lower (P < 0.05) with ryegrass–alfalfa than with ryegrass alone, and methane release (kJ/MJ gross energy intake) was higher (P < 0.05) with ryegrass–red clover than with ryegrass alone. Tannin supplementation decreased (P < 0.05) ruminal ammonia concentration and urinary nitrogen excretion without affecting body nitrogen and energy retention, and reduced (P < 0.001) methane release by 13% on average. The results suggest that supplemented Acacia mearnsii tannins can be useful in mitigating methane and potential gaseous nitrogen emissions, whereas a replacement of grass by legumes obviously shows no advantage in this respect.

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Machmüller, A. and Kreuzer, M. 1999. Methane suppression by coconut oil and associated effects on nutrient and energy balance in sheep. Can. J. Anim. Sci. 79: [65][66][67][68][69][70][71][72]. Three different diets with increasing proportions of coconut oil (0, 3.5 and 7%) were fed to six sheep in an incomplete Latin square experiment with four replicates per diet. The diets were composed of hay and concentrates either without or with coconut oil. Concentrate comprised 28.8 and 54.6% of the diet DM in the treatments containing 3.5 and 7% coconut oil, respectively. Wethers on all treatments were fed at 1.2 × maintenance. Gaseous exchange was measured in respiratory chambers. Protozoa counts were reduced (P < 0.05) by 88 and 97% when diets contained 3.5 and 7% coconut oil, respectively, whereas bacteria counts increased (P < 0.05). Supplementation of coconut oil at proportions of 3.5 and 7% suppressed (P < 0.001) methane production by 28 and 73%, respectively, as related to the unsupplemented diet. This proportionately reduced (P < 0.001) the amount of gross energy lost through methane from 7.5 to 5.7 and 2.5%, in diets containing 0, 3.5 and 7% coconut oil, respectively. Assuming a linear suppressive effect of coconut oil, about half of the additional methane reduction with the 7% coconut oil diet as compared with the 3.5% diet was attributed to the substitution of concentrate for hay. Digestibility of cell wall constituents was numerically decreased by coconut oil. Apart from this and its effect on methane emissions coconut oil had no major influence on digestion or on energy and nitrogen balance. Trois différentes rations alimentaires contenant des teneurs croissantes d'huile de coco (0, 3.5 et 7 %) ont été distribuées en expérience carré latin incomplet à six moutons avec quatre répétitions pour chaque ration. Les rations étaient composées de foin et de concentré, ce dernier sans ou avec l'huile de coco. Les concentrés ont compris 28.8 et 54.6 % de matière sèche de la ration respectivement pour les traitements contenant 3.5 et 7 % d'huile de coco. Les animaux ont été nourris à 1.2 × des besoins d'entretien. Les échanges gazeux ont été mesurés en chambre respiratoire. Le nombre de protozoaires a été réduit (P < 0.05) de 88 et 97 % respectivement pour les rations contenant 3.5 et 7 % d'huile de coco, tandis que celui des bactéries a augmenté (P < 0.05). La supplémentation de 3.5 et 7 % d'huile de coco a diminué (P < 0.001) la production de méthane de 28, respectivement 73 % en comparaison avec la ration sans huile de coco. La perte d'énergie brute sous forme de méthane a ainsi été réduite proportionnellement (P < 0.001) de 7.5 à 5.7 et 2.5 % respectivement pour les rations contenant 0, 3.5 et 7 % d'huile de coco. En supposant une diminution linéaire par l'huile de coco, environ la moitié de la diminution de production de méthane constatée avec la ration contenant 7 % d'huile de coco, par rapport à celle avec 3.5 %, est attribuable à la substitution du foin par le concentré. L'huile de coco a numériquement diminué...

K RE UZ E R. 1999. Diets containing either coconut oil or rumen-protected fat (54 g kg −1 dry matter each) were supplied to Rumen Simulation Technique fermenters filled with faunated and defaunated rumen fluid in a 2 × 2 factorial design. Defaunation immediately reduced methane formation by about 40% with each diet. With coconut oil, methane gradually declined in faunated and defaunated rumen fluid. Finally, the extent of methane suppression was similar, both with coconut oil and with defaunation. Independently of the status of protozoa, the population of methanogens in rumen fluid was significantly reduced by coconut oil. The results suggest that defaunation and coconut oil independently and additively suppress rumen methanogenesis.