Pelleted total mixed ration improves growth performance of fattening lambs

Twenty-four fattening lambs were randomly assigned to two groups (completely randomized design) to assess effects of feeding a pelleted total mixed ration (PTMR) on growth performance and rumen fermentation characteristic of lambs. Dietary treatments were PTMR and unpelleted total mixed ration (UPTMR). During a 56-d fattening period, growth and digestibility were measured and samples of blood and rumen fluid were collected. At the end of the fattening period, lambs were slaughtered and digestive tracts were collected and evaluated. Dietary PTMR increased dry matter intake and average daily gain (P <  0.001) of lambs, but did not significantly affect feed conversion rate, increased apparent digestibility of dietary crude protein (P <  0.001), ash-free acid detergent fiber (P <  0.001), ether extract (P < 0.01), and starch (P <  0.001), but did not change apparent digestibility of dietary dry matter and amylase-treated ash-free neutral detergent fiber. Feeding PTMR increased concentrations of high density lipoprotein cholesterol (P <  0.05) and decreased low density lipoprotein cholesterol in plasma (P <  0.05) and hence was beneficial to health of lambs by modulating cholesterol metabolism. Feeding PTMR altered rumen fermentation and increased the ratio of acetate to propionate in rumen fluid (P<0.001). Furthermore, PTMR increased rumen papilla height and density (P < 0.001), decreased crypt depth of duodenum (P <  0.05) and hence increased the ratio of villus length to crypt depth and mucosal layer thickness of duodenum (P < 0.001), jejunum (P <  0.01), and ileum (P <  0.01). In conclusion, feeding PTMR increased growth performance of fattening lambs; this was attributed to improvements in gastrointestinal tract development, rumen fermentation characteristics and cholesterol metabolism.