To study shifts in the intestinal microbiota during estrus synchronization in ruminants, we characterized the intestinal microbiota in grazing Simmental cows and the possible mechanism that mediates this shift. Fourteen postpartum Simmental beef cows were synchronized beginning on day 0 (D0) with a controlled internal release device (CIDR), and cloprostenol was injected on D9 when the CIDR was withdrawn. Synchronization ended with timed artificial insemination on D12. Serum and rectal samples harvested on D0, D9, and D12 were analyzed to assess the reproductive hormones and microbiota. Reproductive hormones in the serum of the host were measured using enzyme-linked immunosorbent assay. The microbiota was characterized using 16S rRNA sequencing of the V3–V4 hypervariable region, alpha diversity and beta diversity analyses (principal coordinate analysis, PCoA), cladogram of the linear discriminant analysis effect size (LEfSe) analysis, and microbiota function analysis. Levels of the reproductive hormones, except gonadotropin-releasing hormone (p > 0.05), shifted among D0, D9, and D12 (p < 0.05). Decreased community diversity (Chao1 and ACE) was observed on D12 compared with D0 (p < 0.05). The beta diversity (PCoA) of the microbiota shifted markedly among D0, D9, and D12 (p < 0.05). The LEfSe analysis revealed shifts in the intestinal microbiota communities among D0, D9, and D12 (p < 0.05 and LDA cutoff >3.0). The KEGG pathway analysis showed that carbohydrate metabolism, genetic information and processing, the excretory system, cellular processes and signaling, immune system diseases, and the metabolism were altered (p < 0.05). Reproductive hormones (especially estradiol) were correlated with the alpha diversity indices, beta diversity indices, and an abundance of biomarkers of the shifting intestinal microbiota (p < 0.05). In conclusion, the structure, composition, and function of the intestinal microbiota were shifted during estrus synchronization in a grazing Simmental cow model, and these shifts were mediated by reproductive hormones.

The diet energy level plays a vital role in the energy balance of transition cows. We investigated the effects of high dietary energy density on body metabolism. Twenty multiparous Angus cows were randomly assigned to two treatment groups (10 cows/treatment), one receiving a high-energy (HE) diet (NEm = 1.67 Mcal/kg of DM) and the other administered a control (CON) diet (NEm = 1.53 Mcal/kg of DM). The results indicated that feeding a high-energy diet resulted in higher plasma glucose concentration and lower concentrations of plasma NEFA and BHBA on d 14 relative to calving in the HE-fed cows compared to the CON-fed ones. The postpartum plasma levels of T-AOC were lower in cows that received the CON diet than in cows in the HE group, while the concentration of malondialdehyde (MDA) showed an opposite trend. Among the 51 significantly different metabolites, the concentrations of most identified fatty acids decreased in HE cows. The concentrations of inosine, glutamine, and citric acid were higher in HE-fed cows than in CON-fed cows. Enrichment analysis revealed that linoleic acid metabolism, valine, leucine as well as isoleucine biosynthesis, and glycerophospholipid metabolism were significantly enriched in the two groups.

The selective breeding of beef cattle plays an important role in meeting the growing demand for beef and improving production performance. This study used fattened cattle of the Simmental (S) breed, and two crossbreeds: Simmental × Mongolian (SM) and Simmental × Holstein (SH), which were healthy, of similar age and weight. The results showed that the blood glucose (GLU) levels of the crossbred, genetically improved SM and SH groups were higher than that of the S group. Compared with the S group, there were 49 differentially expressed genes (DEGs) in the SM group, of which 18 genes were up-regulated and 31 genes were down-regulated; and 1,031 DEGs in the SH group, of which 251 genes were up-regulated and 780 genes were down-regulated. We found that crossbreeding may increase GLU levels in the blood by upregulating cytochrome C oxidase subunit 3 (COX3) gene expression and downregulating of PRSS2, providing glycogen to the organism, and therefore enhancing GLU-converting capacity. This study highlighted the differences in feed utilization and energy metabolism among crossbred breeds and provides theoretical support for crossbreeding as a means of selecting breeds and improving beef cattle production. However, the expression of the genes were not validated in the present experiments, and these results need further validation.

Background: In grazing systems, supplementation is an effective way to improve ruminant performance. Little is known regarding how concentrate supplementation affects rumen fermentation and the bacterial community of grazing animals in the grasslands of northern China. Therefore, the objective of this study was to examine the effects of concentrate supplementation on the organic matter intake, rumen fermentation and bacterial community of grazing Simmental heifers. Twenty-four 7-month-old heifers were randomly divided into a supplement group and a control group (n = 12 per group). The control group heifers were grazed on a Leymus chinensis-based pasture without any supplementation (CON), while those in the supplement group (SUP) were grazed on the same grassland but received a concentrate supplement.Results: Compared with the CON heifers, those in the SUP group had a greater (P < 0.05) total organic matter (OM) intake and digestibility. However, heifers from the CON group had a higher (P < 0.05) herbage OM intake than those from the SUP group. The total VFA and NH3-N concentrations were significantly higher in the SUP group than in the CON group; of these, propionate, butyrate, and isobutyrate were also significantly increased in the SUP group. Furthermore, the acetate/propionate ratio was significantly decreased in the SUP group. Compared with the CON heifers, those in the SUP group had a higher bacterial richness. Firmicutes and Bacteroidetes were the two predominant bacteria at the phylum level, representing 54.32% and 38.59% of all sequences, respectively. Compared with the CON animals, the SUP animals showed significant (p < 0.05) increases in the relative abundance of Bacteroidetes and Verrucomicrobia, but supplementation did not affect the relative abundance of other bacteria at the phylum level. At the genus level, different diet treatments had an important effect on the relative abundance of the major genera (Fig. 3C). The relative abundance of the genus Butyrivibrio was greater (p < 0.05) in the SUP group than in the CON group. The relative abundances of the genera Rikenellaceae_RC9_gut_group, Ruminococcaceae_UCG-010 and Ruminococcaceae_UCG-011 were higher (p < 0.05) in the CON group than in the SUP group.Conclusions: In conclusion, providing 1.28 kg of supplement (DM basis) is a nutritional management strategy that can be adopted to improve the rumen fermentation, organic matter intake and digestibility of grazing heifers. Furthermore, supplementation has significant effects on the microbial community in the rumen of heifers, which might contribute to the anatomic development of the rumen, and these findings will contribute to the direction of future research in grazing heifers.

To systematically investigate the metabolic and microbial differences in feed efficiency between Hereford × Simmental (H × S) crossbred and purebred Simmental cattle (S × S), 20 steers (initial weight = 268.80 ± 30.88 kg; initial age = 273.00 ± 14.09 days) were used, which were housed in mixed pens and fed a low-energy diet (0.75 Mcal Neg/kg DM). This study revealed that the level of Hypoglycin B was related to a reduced T3, which could affect growth performance. Metabolomics analysis identified Hypoglycin B, lysoPC, and DHAP as key discriminative metabolites. Pathway enrichment analysis revealed that these metabolites were primarily mapped to glycine, serine, and threonine metabolism; alanine, aspartate, and glutamate metabolism; and pantothenate and CoA biosynthesis. In our study, the relative abundances of Succinivibrio and Clostridium_sensu_stricto_6 were significantly greater in the H × S group than in the S × S group; it may have stronger energy extraction abilities and matches their lower F/G. Romboutsia was positively correlated with Hypoglycin B and negatively correlated with LysoPC (20:2 (11Z,14Z)/0:0), which might be related to changes in blood metabolites. Nevertheless, these explanations remain correlational and require functional validation through targeted interventions.