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Abstract: This paper reports effects of chestnut and mimosa tannins on N utilisation in sheep. Tannins were added to grass either at ensilage or incorporated into grass silage at feeding. The study used an 8×5 incomplete Latin Square design with eight mature wether sheep and five 21-day periods. Tannin additions reduced in vivo apparent digestibilities of dry matter (DM), organic matter (OM) and neutral detergent fibre (aNDFom) compared with the untreated control silage (P<0.001). Reductions ranged from 7.6% for DM to 8.5% for aNDFom. Chestnut compared to mimosa tannin silages produced higher values for DM intake (734g/day versus 625g/day) and in vivo digestibility for DM, OM and aNDFom (0.66, 0.68 and 0.69 versus 0.61, 0.63 and 0.62; P<0.001). A substantial shift occurred in the pattern of N excretion in sheep fed the tannin versus control silages. As a proportion of daily N intake, urinary N losses were lower (56.4g/100g N versus 65.1g/100g N intake) and faecal N losses were higher (40.2g/100g N versus 29.8g/100g N intake) for sheep fed the tannin silages compared with those fed the control grass silage (P<0.001). Nitrogen intake was higher in sheep fed the chestnut compared to mimosa tannin silages (16.2g/day versus 13.4g/day; P<0.001), reflecting the lower DM intake of sheep fed the mimosa silages. However, faecal N loss was lower for chestnut compared to mimosa tannin silage fed sheep (38.2g/100g N versus 42.1g/100g N intake; P<0.01), resulting in higher N retentions with the chestnut compared to the mimosa silage fed sheep (5.49g/100g N versus 1.38g/100g N intake). Faecal N losses were also higher when tannins were added during ensiling rather than at feeding (P<0.05). Although there was no overall effect of tannins on N retention in mature wether sheep, it is likely that productive ruminants with higher protein requirements would retain more N from silages containing chestnut tannins. Tannins added externally to grass silages may generate some benefits on N utilisation and environmental N excretions in sheep fed the silages. [Copyright &y& Elsevier]

Abstract: The effects of various fats on nitrogen digestion and metabolism of lambs and their manure were investigated in six isoenergetic diets (n =6) with similar contents of absorbable protein. Treatments were either a control diet or diets containing 25 g/kg of additional ether extract from rumen-protected fat, coconut oil, rapeseed, sunflower seed or linseed. Fat supplementation resulted in trends for higher apparent nitrogen digestibilities (significant with coconut oil; P <0.05, post hoc test) and body nitrogen retention (P <0.1). Urinary nitrogen losses and their proportion of manure nitrogen did not differ significantly among groups as was also true for C/N ratio, dry matter, nitrogen and ammonia nitrogen contents of the manure. In the first week of manure storage, most fat supplements tended to decrease gaseous nitrogen emission as assessed by respiration chamber and mass balance measurements. These differences tended to be mitigated after 7 weeks of manure storage. Only the coconut-oil treatment still resulted in numerically lower nitrogen emissions. In conclusion, addition of fat source in the diet, in addition to increasing dietary energy and suppressing methanogenesis, can under certain circumstances decrease gaseous nitrogen emission from the manure. [Copyright &y& Elsevier]