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.
Highlights
Hazel leaves (% of pellets) Pellet ingredients (% of dry matter (DM)) Lucerne (% of total pellets) Hazel leaves (% of total pellets) Polyethylene glycol (PEG, % of total pellets) Analysed composition (% of DM) Organic matter Crude protein Ether extract Neutral detergent fibre Acid detergent fibre Acid detergent lignin Gross energy (MJ/kg DM) Total phenols Non-tannin phenols Total tannins Condensed tannins Hydrolysable tannins
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
The lignification of the fibre was low in the hay, intermediate in the lucerne and high in the hazel leaves
Summary
Hazel leaves (% of pellets) Pellet ingredients (% of dry matter (DM)) Lucerne (% of total pellets) Hazel leaves (% of total pellets) Polyethylene glycol (PEG, % of total pellets) Analysed composition (% of DM) Organic matter Crude protein Ether extract Neutral detergent fibre Acid detergent fibre Acid detergent lignin Gross energy (MJ/kg DM) Total phenols Non-tannin phenols Total tannins Condensed tannins Hydrolysable tannins. 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. It is unclear yet whether the active ingredients of the hazel leaves are represented by the tannins or by other PSC. (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 them[22,23], was added to one of the diets
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