Effects of diets with various levels of forage rape (Brassica napus) on growth performance, carcass traits, meat quality and rumen microbiota of Hu lambs

Abstract BACKGROUND Apart from being an oil crop, forage rape ( Brassica napus ) can be used to feed ruminants. The objective of this study was to investigate the effects of pelleted total mixed ration (TMR) diets with various levels of forage rape on growth performance, carcass traits, meat quality, meat nutritional value and rumen microbiota of Hu lambs, which was important for the efficient utilization of forage rape and alleviating the shortage of high‐quality forage in China. RESULTS Lambs fed on diets with 200–400 g kg −1 forage rape had greater average daily gain (ADG) and lower feed conversion ratio (FCR) than those fed on diets with 0–100 g kg −1 of forage rape ( P < 0.05). As dietary forage rape levels increased, the content of intramuscular α‐linolenic acid and a variety of amino acids in the muscle increased linearly ( P < 0.05). No difference was found in carcass traits or meat quality among the dietary treatments ( P > 0.05). However, the inclusion of forage rape increased the relative abundance of cellulolytic bacteria and short‐chain fatty acid producers, including Succiniclasticum , Fibrobacter and members of the Lachnospiraceae. Besides, Succiniclasticum was found to be positively correlated with the final body weight of lambs. CONCLUSION TMR diets that included 200–400 g kg −1 forage rape could improve the growth performance of lambs, and elevated the content of intramuscular α‐linolenic acid and a variety of amino acids in the muscle, accompanied by increased abundance of cellulolytic bacteria in the rumen.