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The effects of milk replacer allowance and weaning age on the performance, nutrients digestibility, and ruminal microbiota communities of lambs

Zhang, Qian, Li, Chong, Niu, Xiaolin, Zhang, Zhian, Li, Fadi, Li, Fei
Animal feed science and technology 2019
Roseburia, Ruminococcaceae, Ruminococcus, acid detergent fiber, average daily gain, body weight changes, carcass weight, crude protein, digestibility, early weaning, fat intake, feed conversion, feed intake, fermentation, growth performance, lamb feeding, lambs, males, milk replacer, nutrients, rumen development, rumen fermentation, rumen microorganisms, starch
There has been a recent shift in raising lambs towards early weaning and intensive feeding, with the aim of improving growth rates and feed utilization efficiency of the lamb. This change has prompted studies on the effects on rumen development, which is influenced by a complex interaction between the host, solid feed, ruminal microbiota and fermentation. In this study, 30 male Hu lambs were divided randomly into four treatment groups in a 2 × 2 factorial-design with two different weaning ages (21 or 35 d) and two different milk replacer (MR) feeding allowance (2% or 4% average body weight). This study aimed to examine the effects of weaning age and MR levels on: 1) ruminal morphology, fermentation and microbial composition; and 2) feed intake, growth performance and nutrient digestibility from pre-weaning to post-weaning in lambs. Results showed that weaning age and MR levels had limited effect on apparent digestibility of nutrients, ruminal microbiota and fermentation at 50 d. The digestibilities of dry matter (DM), crude protein (CP), fat and acid detergent fiber (ADF) declined progressively from 8 d to 49 d. There was an interaction between weaning age and MR treatment on the abundance of Firmicutes (P = 0.020), Ruminococcaceae UCG 014 (P = 0.033) and Roseburia (P = 0.032). The 21 d weaning groups had a significantly higher (P = 0.035) relative abundance of Ruminococcus 1 than the 35 d weaning groups. Lambs weaned at 35 d had greater starch intake (P = 0.004), fat intake (P < 0.001), total average daily gain (ADG) (P = 0.001), final body weight (BW) (P = 0.013) and carcass weight (P = 0.008) than 21 d weaned lambs, and lambs given 4% levels of MR had greater fat (P < 0.001), CP intake (P = 0.019), total ADG (P = 0.013) and carcass weight (P = 0.036) than lambs consuming 2% levels of MR. In conclusion, weaning age and MR levels had limited influence on apparent digestibility of nutrients, ruminal microbiota and fermentation at 50 d. Feeding a high level of MR and later weaning age provided a large amount of easily absorbed nutrients which led to greater ADG and BW, and had a sustained positive effect on lambs’ body weight gain.