Effects of feeding different Sorghum-Sudangrass hybrids silages on growth performance, fatty acid composition of longissimus dorsi muscle, ruminal bacteria and volatile fatty acid formation of weaned Small-Tailed Han lambs

This study aimed to determine the effects of feeding different ensiled Sorghum-Sudangrass (SSG) hybrids on growth performance, muscle fatty acid (FA) composition, ruminal bacteria and volatile fatty acid (VFA) formation of weaned lambs. Thirty healthy weaned Small-Tailed Han female lambs at 4 months old with BW 32.2 ± 2.4 kg (mean ± SD) were randomly assigned to five groups of six lambs each. Lambs in the control (CON) group fed 400 g/kg dry matter (DM) of corn silage, while lambs in other treatments had access to the same concentrate and premix as those in CON, plus 400 g/kg DM of ensiled Combination 3 (C3), Combination 4 (C4), Wancao No.007 (W7) and Wancao No.008 (W8), respectively. Live weights were measured before the start and end of the study. The experiment lasted 60 d, and DM intake of feed, faece and urine were weekly recorded after 15 d adaptation. Lambs were sacrificed at end. Fresh C3 had higher levels of crude protein (p = 0.013) and hydrogen cyanide (p = 0.007), but C4 had higher plant height (p = 0.031), leaf length (p = 0.001) and width (p < 0.001), fresh weight (p < 0.001) as well as DM content (p = 0.018), while W7 had more tiller number (p < 0.001). There was no differ DM intake and daily BW gain between CON and W7, despite the BW gain of CON was higher than that of other treatments (p = 0.001). Compared with CON, lambs fed the ensiled SSG hybrids had lower levels of saturated FAs (p = 0.032) but higher unsaturated FAs (p < 0.001) in longissimus dorsi muscle. In addition, the ensiled hybrids decreased ruminal total VFA concentration (p = 0.002) while increased pH value (p = 0.017). Furthermore, lambs fed the SSG hybrids silages were poorly enriched with rumen VFA-producing bacteria such as Clostridium (p = 0.019), Butyrivibrio (p < 0.001), Lactobacillus (p < 0.001), Streptococcus (p = 0.009), Prevotella (p = 0.047), Bacteroides (p = 0.004), Parabacteroides (p < 0.001), Ruminobacter (p < 0.001), Bifidobacterium (p = 0.011) and Fibrobacter (p < 0.001). In conclusion, the W7 silage may substitute corn silage in diet of the weaned lambs since it could improve muscle FAs composition without statistically significant growth performance, despite SSG hybrids silages could reduce the relative abundance of ruminal VFA-producing bacteria.