Stall-Feeding of Sheep on Restricted Grazing: Effects on Performance and Serum Metabolites, Ruminal Fermentation, and Fecal Microbiota

SIMPLE SUMMARY: The global demand for mutton products has increased due to changes in consumer lifestyles, consumption concepts, and socio-economic developments. The feeding systems are widely acknowledged to significantly affect the growth, development, and body health of livestock. In this study, we evaluated the effects of different feeding methods on growth performance, serum biochemical indexes, rumen fermentation parameters, and fecal microorganisms of Huang-huai sheep. The results show that indoor feeding with restricted grazing artificial grassland can improve fattening performance, antioxidation and immune function activity, and rumen fermentation, as well as change fecal microbiota composition. ABSTRACT: This study investigated the effects of three feeding systems, indoor feeding (CONT), indoor feeding with time-restricted grazing artificial pasture (4 h/day, G4H), and indoor feeding with an eight-hour daily grazing artificial pasture (G8H), on the growth performance, serum metabolites, ruminal fermentation, and fecal microbiota composition of lambs. Average daily gain showed a tendency (p = 0.081) to be higher for the G4H group compared with the CONT group. Moreover, feeding systems did not have a significant effect on most of the serum biochemical indicators in lambs. Concentrations of serum glutathione peroxidase and immunoglobulins (IgA, gG, and IgM) were significantly lower (p < 0.01) in the CONT group. Additionally, a tendency towards higher levels of volatile fatty acids, acetate, and butyrate was found in animals of the G4H group compared to the CONT group. Furthermore, fecal microbiota composition was altered in G4H and G8H groups, resulting in the increased relative abundance of Firmicutes and Ruminococcaceae UCG-005, as well as the decreased relative abundance of Ruminobacter compared with the CONT group. Overall, these results suggest that indoor feeding with restricted grazing time does not significantly affect fattening performance or rumen fermentation but enhances antioxidation and immune function activity and also alters fecal microbiota composition.