Shuo Zhang

Slaughter performance is a critical economic trait that varies across breeds, yet the rumen metabolic mechanisms driving these phenotypic differences remain unclear. The study involved 30 healthy 12-month-old beef cattle, with 10 animals from each of the three breeds: Chinese Simmental (ST), Taihang Yun (TY), and Charolais (CL). The cattle were randomly assigned into three groups using a completely randomized design, and the average initial body weight was 549.78 ± 59.45 kg. A 130-day feeding trial (10-day pre-feeding period, 120-day main trial period) was conducted. By comparing the slaughter performance, relative organ weight, and rumen fluid metabolomic profiles, the study investigated breed-specific differences in meat quality and potential underlying metabolic patterns. The results showed that CL exhibited a superior carcass yield, with a significantly higher dressing percentage (62.38%, p = 0.013) and net meat percentage (56.54%, p = 0.028) than ST and TY, and a significantly lower backfat thickness (p = 0.006); ST had the highest proportion of premium cuts, relative to carcass weight (72.97%, p = 0.014), with prominent economic value, while TY had significantly higher weights of visceral organs, such as liver, kidney, small intestine and omasum, than CL (p < 0.05). Metabolomic analysis revealed that CL and ST had elevated levels of purine metabolism, nucleotide synthesis and cofactor biosynthesis compared to TY. In conclusion, CL and ST possess advantages in carcass yield supported by upregulated anabolic metabolism in the rumen, whereas TY prioritizes visceral organ development. These findings provide valuable insights into the physiological and metabolic divergences regulating the slaughter performance and regional adaptability across cattle breeds.

Annual greenhouse gas emissions from livestock (CO₂ equivalent) are estimated at approximately 7.1 billion tons, accounting for 14.5% of global emissions, with beef and dairy cattle production contributing 41% and 20% of total emissions, respectively. Greenhouse gases released by ruminants not only lead to feed energy loss but also result in environmental degradation. Therefore, reducing greenhouse gas emissions from ruminants is crucial for the sustainable development of the ruminant industry. The primary greenhouse gases produced by ruminants include nitrous oxide from ruminant manure storage and methane generated in the rumen via the action of methanogenic archaea. Tannins, a class of polyphenolic compounds present in many plants, play a significant role in animal feed. Recent studies have shown that incorporating certain tannins and their metabolic products into diets can modulate protein metabolism and the ruminal microbiome, thereby regulating greenhouse gas emissions from ruminants. This review summarizes the types and properties of dietary tannins, as well as the latest advancements in understanding the impacts of tannins and their metabolites on cattle nutrient digestion and greenhouse gas emissions, concluding that dietary tannin supplementation can reduce greenhouse gas emissions from ruminants. Future research should focus on identifying the optimal concentrations of different tannins and their metabolites in diets to minimize ruminant greenhouse gas production while maintaining animal performance and health.

The present experiment aimed to investigate the effects of harvest stages on the fermentation quality and nutritional value of sorghum stalk silage. Sorghum stalks were harvested at the three stages (milk, dough, and ripe), chopped, and ensiled for 60 d. Each treatment had five replicates, and the silages were evaluated for fermentation quality, nutritional composition, in vitro rumen fermentation characteristics, and bacterial community profiles. The results showed that the crude protein, neutral detergent fiber, and acid detergent fiber contents decreased significantly with harvest maturity (p < 0.05). Consequently, silage from the ripe stage possessed the highest dry matter, relative feed value, and total digestible nutrients (p < 0.05). In vitro rumen fermentation indicated that the ripe stage silage exhibited the greatest gas production, and the lowest concentrations of ruminal ammonia–nitrogen (p < 0.05). Microbial analysis revealed a shift from dominant epiphytic Proteobacteria to fermentative Firmicutes post-ensiling, with the ripe stage community co-dominated by Lactobacillus and Leuconostoc, in contrast to the milk stage’s enrichment with Klebsiella. In conclusion, harvesting sorghum at the ripe stage is the optimal strategy as it establishes a beneficial microbial community, resulting in silage with superior nutritional value and rumen fermentation efficiency.

High prolactin (PRL) concentration has been shown to induce the apoptosis of ovine ovarian granulosa cells (GCs), but the underlying mechanisms are unclear. This study aimed to investigate the mechanism of apoptosis induced by high PRL concentration in GCs. Trial 1: The optimal concentration of glutathion was determined according to the detected cell proliferation. The results showed that the optimal glutathione concentration was 5 μmol/mL. Trial 2: 500 ng/mL PRL was chosen as the high PRL concentration. The GCs were treated with 0 ng/mL PRL (C group), 500 ng/mL PRL (P group) or 500 ng/mL PRL, and 5 μmol/mL glutathione (P-GSH group). The results indicated that the mitochondrial respiratory chain complex (MRCC) I–V, ATP production, total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and thioredoxin peroxidase (TPx) in the C group were higher than those in the P group (p < 0.05), while they were lower than those in the P-GSH group (p < 0.05). Compared to the C group, the P group exhibited elevated levels of reactive oxygen species (ROS) and apoptosis (p < 0.05) and increased expression of ATG7 and ATG5 (p < 0.05). However, MRCC I–V, ATP, SOD, A-TOC, TPx, ROS, and apoptosis were decreased after the addition of glutathione (p < 0.05). The knockdown of either L-PRLR or S-PRLR in P group GCs resulted in a significant reduction (p < 0.05) in MRCC I–V, ATP, T-AOC, SOD and TPx, while the overexpression of either receptor showed an opposite trend (p < 0.05). Our findings suggest that high PRL concentrations induce apoptotic cell death in ovine ovarian GCs by downregulating L-PRLR and S-PRLR, activating oxidative stress and autophagic pathways.

Prolactin (PRL) has been reported to influence reproductive performance and cell apoptosis. However, its mechanism remains unclear. Hence, in the present study, ovine ovarian granulosa cells (GCs) were used as a cell model to investigate the relationship between PRL concentration and GC apoptosis, as well as its possible mechanisms. We examined the relationship between serum PRL concentration and follicle counts in sexually mature ewes. GCs were isolated from adult ewes and treated with different concentrations of PRL, while 500 ng/mL PRL was selected as the high concentration of prolactin (HPC). Then, we applied the transcriptome sequencing (RNA-Seq) combined with a gene editing approach to explore the HPC contributing to cell apoptosis and steroid hormones. The apoptosis of GCs gradually increased at PRL concentrations above 20 ng/mL, while 500 ng/mL PRL significantly decreased the secretion of steroid hormones and the expression of L-PRLR and S-PRLR. The results indicated that PRL regulates GC development and steroid hormones mainly through the target gene MAPK12. The expression of MAPK12 was increased after knocked-down L-PRLR and S-PRLR, while it decreased after overexpressed L-PRLR and S-PRLR. Cell apoptosis was inhibited and the secretion of steroid hormones increased after interfering with MAPK12, while the overexpression of MAPK12 showed the opposite trend. Overall, the number of follicles gradually decreased with increasing PRL concentration. HPCs promoted apoptosis and inhibited steroid hormone secretion in GCs by upregulating MAPK12 through reducing L-PRLR and S-PRLR.