This study aimed to investigate the effects of active dry yeast (ADY) on rumen microbial composition and slaughter performance of beef cattle. Thirty-two finishing beef cattle (simmental crossbred cattle ♂ × cattle-yaks ♀), with an average body weight of 110 ± 12.85 kg, were randomly assigned to one of four treatments: the low plane of nutrition group (Control), low plane of nutrition group + ADY 2 g/head/d (ADY2), low plane of nutrition group + ADY 4 g/head/d (ADY4) and high plane of nutrition group (HPN). ADY supplementation increased average daily gain ( P 0.05). The serum glutamic-pyruvic transaminase activity in control and ADY4 group was higher than HPN group ( P =0.001). The neutral detergent fiber ( P =0.022) and acid detergent fiber ( P =0.043) digestibility in HPN group was greater than control, but no difference was obtained among ADY2, ADY4 and HPN group ( P >0.05). The rumen ammonium nitrogen content in control was greater than ADY2 and ADY4 group ( P =0.003), and no difference was obtained ADY2, ADY4 and HPN group ( P >0.05). The propionic acid content in the rumen in ADY2, ADY4, and HPN group were greater than control group ( P <0.001). The simpson ( P =0.014) and shannon ( P =0.045) indexes in control and HPN group were greater than ADY4 group. At the phylum level, the relative abundance of Firmicutes in the HPN group was higher than ADY4 group ( P =0.015). At the genus level, HPN and ADY4 were clustered together, and the relative abundance of Ruminococcaceae UCG-002 in ADY4 group was higher than control and HPN group ( P =0.004). In conclusion, supplementation ADY 4 g/head/d shift the rumen microbial composition of beef cattle fed low plane of nutrition to a more similar level with cattle fed with HPN diet, produced comparable carcass weight with HPN diet.

Heat stress is a major environmental stressor in poultry production that reduces growth performance and induces oxidative stress, inflammatory responses, and lung tissue injury. This study investigated the protective effects of dietary supplementation with Ginkgo biloba extract and tea polyphenols against heat stress-induced lung injury in broilers. A total of 320 one-day-old broilers were reared under standard management conditions until 21 days of age. Subsequently, 300 birds with similar body weight were selected and randomly allocated into six groups: a thermoneutral control group, a heat stress group, a heat stress group supplemented with 300 mg/kg tea polyphenols, and three heat stress groups receiving 300 mg/kg tea polyphenols combined with 100, 300, or 600 mg/kg Ginkgo biloba extract. The analysis of the results showed that heat stress significantly reduced the average daily gain and feed intake while increasing the feed conversion ratio. It also markedly increased serum lactate dehydrogenase activity and malondialdehyde levels, while decreasing antioxidant-related indicators, indicating the occurrence of oxidative stress and inflammatory responses. Histological examination revealed lung injury characterized by alveolar wall thickening, epithelial cell shedding, and disruption of the endothelial barrier, accompanied by upregulated expression of heat shock proteins and inflammation-related signaling genes. Supplementation with tea polyphenols alone partially alleviated these changes. Notably, the combined supplementation of Ginkgo biloba extract and tea polyphenols exerted more pronounced protective effects, significantly enhancing antioxidant capacity, attenuating inflammatory responses, and maintaining pulmonary barrier integrity. Among the tested levels, the groups receiving 300 mg/kg Ginkgo biloba extract in combination with tea polyphenols showed the most evident improvements. These findings suggest that the combined use of these plant-derived extracts effectively mitigates heat stress-induced lung injury in broilers.

The intestinal microorganisms make an important contribution to the development of the host immune system and resistance to pathogen infections, especially