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Various supplements and unconventional feeds (supplement-type: Acacia tannins, Yucca saponins, extruded linseed, lauric and myristic acid; medicinal-type plant parts: garlic bulbs, hop cones, grape seeds, maca hypocotyls; legumes: lupine seeds and lucerne meal) were screened with the in vitro Hohenheim gas test for their methane mitigating potential in an incubation period of 48 h. The control diet consisted of maize silage and concentrate (0.85:0.15). Replacing 150 g/kg dry matter of the control diet with garlic bulbs (Allium sativum) decreased methane by 50% and the methane-to-total gas ratio by 15 to 17% at 75 and 150 g garlic/kg DM. This was accompanied by a decline in acetate proportion of total short-chain fatty acids. Methane formation tended to be reduced by 15% with a high-tannin extract from Acacia mearnsii (50 g/kg diet). The methane-tototal gas ratio was not significantly affected by the other treatments. Accordingly, garlic turned out most promising for the mitigation of methane without negatively affecting rumen microbial fermentation.

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Ryegrass with high contents of water-soluble carbohydrates (WSC) was recently bred and tested for its potential beneficial effects as feed for ruminants. The objective of the present study was to determine the effect of feeding high-WSC ryegrass hay on the fatty acid composition of the milk as compared to low-WSC ryegrass hay and a maize silage-based diet. The diet type had no significant effect on feed intake and gross milk composition. Milk yield was highest for cows fed the low-WSC hay. Vaccenic acid and conjugated linoleic acids were higher in the milk fat of hay-fed cows compared to those receiving the maize diet. Milk fat from cows fed low-WSC hay showed the highest proportion of α-linolenic acid, while that from cows fed the maize diet showed the lowest proportion. Total polyunsaturated fatty acids were also highest in milk from cows fed low-WSC hay and lowest in milk from cows fed the maize diet. The milk from cows fed the high-WSC hay showed intermediate values for both. In conclusion, the high-WSC hay diet compared to the low-WSC hay had no beneficial influence on the proportion of functional fatty acids in cow milk.