Monday, 16 April 2018

Supplementation of Pelleted Hazel (Corylus avellana) Leaves Decreases Methane and Urinary Nitrogen Emissions by Sheep at Unchanged Forage Intake

Sci Rep. 2018; 8: 5427. Published online 2018 Apr 3. doi: 10.1038/s41598-018-23572-3 PMCID: PMC5883041 PMID: 29615655 Shaopu Wang,1 Melissa Terranova,1 Michael Kreuzer,1 Svenja Marquardt,1 Lukas Eggerschwiler,2 and Angela Schwarmcorresponding author1 1ETH Zurich, Institute of Agricultural Sciences, Animal Nutrition, Universitaetstrasse 2, 8092 Zurich, Switzerland 2Agroscope, Tioleyre 4, 1725 Posieux, Switzerland Angela Schwarm, Email: hc.zhte.sysu@mrawhcs.alegna. corresponding authorCorresponding author. Author information ▼ Article notes ► Copyright and License information ► Disclaimer Go to: Abstract This study is the first to quantify the effects of hazel (Corylus avellana) leaves on methane and urinary nitrogen emissions, digestibility, nitrogen and the energy balance of ruminants. Four experimental pellets were produced with 0, 30% and 60% hazel leaves, the latter also with 4% polyethylene glycol. Hazel leaves gradually replaced lucerne. The diet was composed of the pellets and grass hay (80%: 20%). Six adult sheep were allocated to all four treatments in a 6 × 4 crossover design. Including hazel leaves did not affect the feed intake, but it decreased the apparent digestibility of organic matter and fibre, especially at the high level. Methane emission was reduced by up to 25 to 33% per day, per unit of intake and per unit of organic matter digested. Urinary nitrogen excretion decreased by 33 to 72% with increasing levels of hazel leaves. The treatment with polyethylene glycol demonstrated that tannins in hazel leaves caused significant shares of the effects. In conclusion, the current results indicated a significant potential of hazel leaves as forage for ruminants to mitigate methane and urinary nitrogen emissions. Even high dietary hazel leaf proportions were palatable. The lower digestibility needs to be compensated with easily digestible diet ingredients. Go to: Introduction Methane (CH4) from the livestock sector was calculated to account for 28% of the total global anthropogenic emissions, and is predicted to rise further due to an increasing worldwide demand for meat, milk and other animal-source products1,2. Manipulating the rumen fermentation by nutritional approaches with the aim of reducing CH4 and nitrogen (N) emissions from ruminant husbandry at concomitantly unchanged or even improved feed intake and digestibility are among the most important goals of current animal nutrition research. Various nutritional attempts to mitigate CH4 emission from ruminants have been undertaken, as reviewed by Beauchemin et al.1 and Hristov et al.3. Special attention has been given to plants or extracts rich in plant secondary compounds (PSC), such as tannins, essential oils or saponins. A number of screenings provided promising plants of at least moderate nutritional value that are effective in mitigating noxious emissions4–6. Different from synthetic compounds, the public’s growing concern about food safety is met by PSC-based forages7. Tannins are a complex group of polyphenolic PSC with widely varying molecular weights that are found in many representatives of the plant kingdom8. When provided at high dosages, tannins were predominantly found to be antinutritional because of their adverse effects on feed intake and nutrient utilisation9. In recent years, however, they have been recognised as useful phytochemicals when provided at moderate dosages. Tannins can be beneficial modulators of rumen microbial fermentation promoting metabolic protein supply, animal productivity and animal health10,11. The feeding of tannin-containing plants or extracts from such plants to ruminants was found at times, but not always, to substantially reduce enteric CH4 emissions12–14. The effectiveness varies depending on the source, structure and supplemented level of the tannins5. In addition, tannins bind to proteins and thus protect at least part of the dietary protein from being degraded in the rumen. These bonds are cleaved in the abomasum, and thus the protein becomes at least partially digestible in the small intestine or, otherwise, will be excreted with the faeces14,15. Feeding diets containing tannins, therefore, is an efficient means to reduce the amount of dietary N to be excreted via urine and with that the N emission potential of the manure16,17. The shrub hazel (Corylus avellana) grows wild in Europe and western Asia, but it is also cultivated for its nuts. Its leaves are considered a potential means of antioxidant and antibacterial effects because of their richness in phenolic compounds18,19. Besides, among the plant materials tested in the extensive EU screening project “Rumen Up”20, hazel leaves were found in vitro to depress CH4 production (mmol/g dry matter (DM) incubated) by 25%. Another recent in vitro screening confirmed the CH4 mitigation potential of hazel leaves and indicated their concomitantly favourable forage potential21. Hazel leaves were also found to inhibit the proteolytic activity in rumen fluid20. However, the effect of replacing part of the diet by hazel leaves on intake, total tract digestibility and mitigation of CH4 and urinary N losses in live ruminant livestock has not yet been determined. In addition, it is unclear yet whether the active ingredients of the hazel leaves are indeed represented by the tannins or also by other PSC. The objective of the present study was to determine the quantitative effects of replacing lucerne (Medicago sativa) with hazel leaves at different proportions in forage-only diets fed to adult sheep. The following predictions were made: (i) Hazel leaves contain PSC which affect digestion in a way that CH4 and urinary N formation are mitigated in a dose-dependent way. (ii) These changes happen without major adverse effects on intake, nutrient and energy utilisation. (iii) The main active ingredients in hazel leaves responsible for the observed effect are the tannins, rather than other PSC like flavonoids. For this purpose, polyethylene glycol (PEG), which binds to tannins and inactivates them22,23, was added to one of the diets