Effect of rare earth elements on feed digestibility, rumen fermentation, and purine derivatives in sheep

Abstract

The experiment was conducted to evaluate the effect of rare earth elements (REE) on feed digestibility, rumen fermentation, and urinary purine derivatives (PDs) in sheep. Eight sheep (44.58±2.9 kg of body weight) fitted with ruminal cannulas were used in a replicated 4×4 Latin square design 20-day experiment. Sheep were fed a basal diet containing 100, 200 and 300 mg REE-citrate per kg dry matter (DM). Mixture of REE mainly consisted of cerium (56.8%), lanthanum (35.0%) and praseodymium (6.5%). Ruminal pH value was linearly (P<0.01) and quadratically (P<0.01) decreased, and ammonia N concentration (9.73 to 11.83 mg/100 mL) was quadratically (P<0.05) decreased, whereas total volatile fatty acids concentration was linearly increased with increasing REE supplementation (P<0.05). The ratio of acetate to propionate was linearly (P<0.01) and quadratically (P<0.01) decreased due to increase of propionate concentration (P<0.05). In situ ruminal neutral detergent fibre (aNDF) degradation of Leymus chinensis was improved (P<0.01), but the in situ ruminal crude protein (CP) degradation of soybean meal was decreased by feeding REE (P<0.01). Moreover, digestibility of DM, organic matter, aNDF, acid detergent fibre and CP in the total tract and urinary excretion of PD were also linearly (P<0.01) and quadratically (P<0.01) increased with increasing REE addition. In conclusion, supplementation of the basal diet with REE improved rumen fermentation and feed digestion in sheep. It was suggested that REE stimulated rumen microbial activity, digestive microorganisms or enzyme activity in a dose-dependent manner. The optimum supplemental dose of REE was about 200 mg/kg dietary DM in sheep. © W. Xun et al., 2014.