Susanne Sinz

The methane mitigating potential of various plant-based polyphenol sources is known, but effects of combinations have rarely been tested. The aim of the present study was to determine whether binary and 3-way combinations of such phenol sources affect ruminal fermentation less, similar or more intensively than separate applications. The extracts used were from Acacia mearnsii bark (acacia), Vitis vinifera (grape) seed, Camellia sinensis leaves (green tea), Uncaria gambir leaves (gambier), Vaccinium macrocarpon berries (cranberry), Fagopyrum esculentum seed (buckwheat), and Ginkgo biloba leaves (ginkgo). All extracts were tested using the Hohenheim gas test. This was done alone at 5% of dry matter (DM). Acacia was also combined with all other single extracts at 5% of DM each, and with two other phenol sources (all possible combinations) at 2.5%+2.5% of DM. Methane formation was reduced by 7% to 9% by acacia, grape seed and green tea and, in addition, by most extract combinations with acacia. Grape seed and green tea alone and in combination with acacia also reduced methane proportion of total gas to the same degree. The extracts of buckwheat and gingko were poor in phenols and promoted ruminal fermentation. All treatments except green tea alone lowered ammonia concentration by up to 23%, and the binary combinations were more effective as acacia alone. With three extracts, linear effects were found with total gas and methane formation, while with ammonia and other traits linear effects were rare. The study identified methane and ammonia mitigating potential of various phenolic plant extracts and showed a number of additive and some non-linear effects of combinations of extracts. Further studies, especially in live animals, should concentrate on combinations of extracts from grape seed, green tea leaves Land acacia bark and determine the ideal dosages of such combinations for the purpose of methane mitigation.

Diets excessive in crude protein (CP) are unfavourable in terms of metabolic and environmental load. Dietary phenols, often binding to dietary proteins, may alleviate these problems. In an experiment with 60 lambs (3.2 ± 1.6 months of age; 29.7 ± 5.1 kg body weight), kept in pairs, five diets were tested. A diet with 157 g CP/kg dry matter (DM) served as negative control. Four diets with on average 229 (225–233) g CP/kg DM remained either non-supplemented or were supplemented with 13 g/kg DM of Acacia mearnsii extract, grapeseed extract, or a combination of both (26 g extract/kg DM). The analysed concentrations of total extractable phenols were 7.1, 8.1, 14.3, 16.6 and 25.4 g/kg DM for low (CP^‒) and high CP (CP⁺), and high CP with acacia (CP^+A), grapeseed (CP^+G) and acacia plus grapeseed (CP^+AG), respectively. Diets were fed for 10 weeks, and for 6 d faeces and urine were collected and subsequently stored as complete manure for 8 weeks. In blood plasma, phenol concentrations and activities of enzymes indicating liver and kidney stress were analysed. The CP⁺ diet increased apparent digestibility of N and its removal with the urine, with the expected increase in gaseous N emissions from the manure (13.5 vs 6.5 g/lamb per day during 8 weeks) compared to CP^‒. However, no clear signs of metabolic stress were detected. Supplementing the extracts did not impair intake, growth performance and digestibility. Only the supplementation with both extracts decreased urinary N proportion of manure N, and the concomitant weak decline in gaseous emission from the manure was not significant. At least part of the phenols of both extracts seem to be bioavailable as their supplementation elevated blood plasma phenol concentrations by 15% to 40% compared to CP⁺. A combination of both extracts did not result in a further increase. Further studies have to identify the minimally effective dosage for reducing N emissions, which, at the same time, does not cause adverse side effects in performance.