Effects of forage rape at various levels on growth performance, carcass traits, meat quality, rumen fermentation and rumen microbiota of Hu lambs

Abstract Background : The objective of this study was to investigate the effects of forage rape ( Brassica napus ) in total mixed ration (TMR)-based diet on growth performance, carcass traits, meat quality, rumen fermentation and rumen microbiota of Hu lambs. Methods : A total of 50 Hu lambs (20.86 ± 3.00 kg, three-month-old) were randomly allocated into five dietary treatments: Ctrl, T1, T2, T3 and T4 with 0, 10%, 20%, 30% and 40% of forage rape, respectively. Each treatment had 10 replicates of one lamb each and the study lasted for 60 days. Results : The results showed that T2, T3 and T4 increased the average daily gain (ADG) and decreased the feed conversion ratio (FCR) significantly compared with Ctrl and T1 ( P < 0.05). Moreover, the final body weight and ADG were increased, and the FCR were decreased linearly ( P < 0.05) along with increasing forage rape levels. The relative weight of liver was increased in T3 and T4 compared with Ctrl ( P < 0.05). With increasing forage rape levels, the relative content of intramuscular heptadecenoic acid and α-linolenic acid, and the composition of various amino acids in the muscle of lambs were increased linearly ( P < 0.05), while ruminal concentration of ammonia nitrogen was decreased linearly ( P < 0.05). No difference on carcass traits, meat quality or ruminal profile of short-chain fatty acids were observed among groups ( P > 0.05). In addition, the inclusion of forage rape altered the rumen microbial community, and increased the relative abundance of cellulolytic bacteria and short-chain fatty acid producers, including genera Family_XIII_AD3011_group and Anaerovorax in T1, Succiniclasticum and Fibrobacter in T2, Ruminiclostridium_5 in T3, and members of family Lachnospiraceae and genus Shuttleworthia in T4. Conclusion : TMR included with forage rape could improve growth performance, meat nutritional value and rumen microbial community of Hu lambs.