Svenja Marquardt

Milk and dairy products considerably contribute to the nutritional value of human diets. In order to benefit human nutrition bovine milk fatty acid composition and phenol content are effectively manipulated by the cow’s diet. However, response times taken for these alterations to occur have not...

To maintain species‐rich swards from which forage of a high nutritional quality can be produced, it is essential to adapt grassland fertilization strategies. In this study, we investigated how different long‐term mineral fertilization treatments affect dry‐matter (DM) yield, plant species composition, and nutrient and mineral concentrations of forage from mountain grasslands. During 2 years, forage was sampled from three different long‐term fertilization experiments located at 930 (L), 1,190 (M) and 1,340 (H) m a.s.l. at different sites in Switzerland. At each site, three mineral fertilization treatments (0, PK and NPK) had been maintained for three to six decades, with two (L and M) or three harvests (H) per year. Yield, the botanical composition and concentrations of net energy, utilizable crude protein and different phenolic fractions were determined. Nutrient and mineral concentrations were also determined. For all three sites (L, M and H), unfertilized swards had lower annual DM yields (3.39, 5.17 and 2.73 t/ha) compared to PK (6.33, 7.17 and 4.44 t/ha) and NPK fertilized swards (7.69, 7.22 and 7.44 t/ha), respectively. Long‐term fertilization had little effect on the gross nutrient and phenolic composition, but forage P and K concentration increased. The decades‐long fertilization of either PK or NPK of up to 85 kg N, 80 kg P₂O₅ and 240 kg K₂O/ha reduced plant species richness only at site H. Fertilization of PK may allow to simultaneously increase forage productivity and maintain forage quality in mountain grasslands.

The influence of phenol-rich dietary grapeseed extract on performance, energy and N balance and methane production was determined in sixteen lambs and thirteen goat kids (body weight 20·5 and 19·0 kg, 2 months of age, day 1 of study). Half of the animals received a concentrate containing grapeseed extract, and the others received concentrate without grapeseed extract (total extractable phenols analysed 27 v. 9 g/kg dietary DM; concentrate and hay 1:1). Diets were fed for 7 weeks with 1 week for determining intake, excretion and gaseous exchange in metabolism crates and respiration chambers. Overall, there was an adverse effect of the phenolic diet on apparent N digestibility and body N retention. Faecal N loss as proportion of N intake increased while urinary N loss declined. Relative to N intake, total N excretion was higher and body N retention lower in goat kids than lambs. Diets and animal species had no effect on methane emissions. The saliva of the goat kids had a higher binding capacity for condensed tannins (CT). Goat kids on the phenolic diet had higher CT concentrations in faeces and excreted more CT compared with the lambs (interaction species × diet P < 0·001). The lambs had overall higher (P < 0·001) urinary phenol concentrations than the goat kids (2·19 v. 1·48 g/l). The negative effect on body N retention and lack of effect on methane emissions make the use of the extract in the dosage applied not appealing. Species differences need to be considered in future studies.

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.

Polyphenols are known to affect digestion of ruminants, whereas there is little information about their metabolic effects. In a 2 × 2-factorial experiment, the effects of supplementing a phenolic grapeseed extract were compared in 11 East Friesian dairy sheep and 9 Saanen goats. The concentrate, supplemented with 7.4 g/100 g DM grapeseed extract, had contents of 3.5 g additional phenols/100 g DM and was compared with a low phenolic control concentrate. Performance, total phenols in blood, milk, urine and feces, antioxidant capacity of the blood, and saliva properties were examined. The experiment lasted for 11 wk from parturition to late lactation, with an initial adaptation phase of 1 wk. Milk yield was measured daily after weaning at about 7 wk after parturition. Blood, milk, saliva, feces, and urine were sampled 4, 3, 2, 2, and 2 times per animal, respectively. The phenolic diet increased phenol concentrations in blood (+10% and 17% in weeks 5 and 11, respectively) and in milk (+32% in week 5) in some of the sampling weeks. There were no clear species differences in phenol concentrations in blood plasma, milk, urine, and feces. However, at the end of the experiment, the supplemented goats had higher (P < 0.05) urinary phenol concentrations than the nonsupplemented goats. A weak relationship (P < 0.05) was found between phenol intake and phenol excretion with milk for sheep but not goats. The phenolic diet did not influence blood antioxidant capacity and tannin-binding capacity of the saliva. The saliva of the goats had a higher tannin-binding capacity than sheep saliva. The effects of the extract on milk yield were inconsistent between sheep and goats. In general, goats had higher feed and nutrient intakes, were heavier, and yielded more milk. Additionally, milk protein and lactose contents were lower and milk urea content was higher in goats than sheep. In conclusion, supplementing grapeseed extract to sheep and goats elevated phenol concentrations in milk and blood to a certain extent, but most of the phenols were lost via urine. The study gave another indication that goats seem to have developed coping mechanisms like a higher salivary tannin-binding capacity, mechanisms which are less pronounced in sheep.

In order to identify new ways to mitigate methane emissions from ruminants, six medicinal plants, Achyranthes aspera, Azadirachta indica, Andrographis paniculata, Helicteres isora, Tinospora cordifolia and Piper longum, were evaluated in vitro with respect to ruminal fermentation and methanogenesis. A three-stage approach with n = 6 per treatment was applied. Two 24-h Hohenheim gas test experiments were performed by incubating the plants first as sole substrate and then added to a basal diet (10 g/kg diet DM). Finally, in a 10-day Rusitec experiment, A. paniculata, P. longum and T. cordifolia were supplemented individually and in all binary combinations to a basal diet (25 g/kg DM). Provided as sole substrate, all plants, except P. longum, decreased methane and carbon dioxide production (P < 0.05), and reduced the methane : short-chain fatty acid ratio (P < 0.05) in the Hohenheim gas test. In Rusitec, none of the individual supplements decreased methane production. The combination of A. paniculata with P. longum as a supplement was effective in mitigating the methane : carbon dioxide ratio and simultaneously maintaining feeding value. In conclusion, all medicinal plants incubated as sole substrate, except P. longum, possess anti-methanogenic properties, especially T. cordifolia, A. indica and H. isora. When supplemented at the levels investigated, they were mostly neutral with respect to rumen fermentation and nutrient digestion. Combining A. paniculata with P. longum mitigated methane without side effects on general ruminal fermentation. Further investigations, carried out in vivo, will demonstrate how useful this plant combination is in ruminant nutrition.