This experiment was conducted to investigate the effects of astragalus polysaccharides (APS) on serum metabolism of dairy cows under heat stress. Thirty healthy Holstein dairy cows were randomly divided into three groups (10 cows in each group). In the experimental group, 30 mL/d (Treatment I) and 50 mL/d (Treatment II) of APS injection were injected into the neck muscle respectively. Each stage was injected with APS for 4 days (8:00 a.m. every day) and stopped for 3 days. Serum hormone and antioxidant indexes of dairy cows were investigated. Through repeated measurement analysis of variance, the results have shown that cortisol (COR) (F = 6.982, p = 0.026), triiodothyronine (T3) (F = 10.005, p = 0.012) and thyroxine (T4) (F = 22.530, p = 0.002) at different time points were significantly different. COR showed a downward trend, T3 and T4 showed an upward trend. At each time point, different concentrations of APS have significant effects on COR (F = 30.298, p = 0.000 < 0.05), T3 (F = 18.122, p = 0.001), and T4 (F = 44.067, p = 0.000 < 0.05). However, there were no significant differences in serum insulin (INS), glucagon (GC) and heat shock protein 70 (HSP70) between different time points (p > 0.05) and at each time point (p > 0.05). Additionally, the results have also shown that there were also no significant differences in serum Superoxide dismutase (SOD), malondialdehyde (MDA) and lactate dehydrogenase (LDH) between different time points (p > 0.05) and at each time point (p > 0.05). However, the injection of APS had a significant impact on glutathione peroxidase (GSH-Px) (F = 9.421, p = 0.014) at different times, and showed a trend of rising first and then falling. At each time point, APS of different concentrations had no significant effect on GSH-Px (p > 0.05). Furthermore, we used gas chromatography–mass spectrometry (GC-MS) non-targeted metabolomics to determine the potential markers of APS for heat-stressed dairy cows. Twenty metabolites were identified as potential biomarkers for the diagnosis of APS in heat-stressed dairy cows. These substances are involved in protein digestion and absorption, glutathione metabolism, prolactin signaling pathway, aminoacyl-tRNA biosynthesis, pentose and glucuronate interconversions, and so on. Our findings suggest that APS have an effect on the serum hormones of heat-stressed dairy cows, and regulate the metabolism of heat-stressed dairy cows through glucose metabolism and amino acid metabolism pathways.

Heat stress (HS) is directly correlated with mammary gland dysfunction and the hypothalamic-pituitary-mammary gland (HPM) axis is involved in regulating stress responses and lactation in dairy cows. Circular RNAs (circRNAs) play major roles in regulating transcription and post-transcription but their expression in the HPM axis of dairy cows under HS is still unclear. In the present study, we performed RNA sequencing to identify diferentially expressed (DE) circRNAs, DE microRNAs(miRNAs) and DEmRNAs, and performed bioinformatics analysis on those in HPM axis-related tissues of heat-stressed and normal cows. A total of 1680, 1112 and 521 DEcircRNAs, 120, 493 and 108 DEmiRNAs, 274, 6475 and 3134 DEmRNAs were identified in the hypothalamic, pituitary, and mammary gland tissues, respectively. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses indicated that the MAPK signaling pathway is potentially a key pathway. Competitive endogenous RNA (ceRNA) networks related to HS response and lactation regulation were established in three tissues. In conclusion, our results indicate that HS induces differential circRNA expression profiles in HPM axis-related tissues, and the predicted ceRNA network provides a molecular basis for regulating the stress response and lactation regulation in heat-stressed dairy cows.

This experiment was conducted to evaluate the effects of a methionine hydroxy analog (MHA) on in vitro gas production, rumen fermentation parameters, and rumen microbiota. Two different MHA, 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester (HMBi) and the calcium salt of the hydroxy analog of methionine (MHA-Ca), were selected for in vitro experiments. The treatments were the Control group (0% of MHA), HMBi group (2%HMBi), and MHA-Ca group (2%MHA-Ca). Dry matter digestibility was measured after 12 h and 24 h of fermentation, and fermentation parameters and microbial composition were analyzed after 24 h. HMBi and MHA-Ca showed increased (p = 0.001) cumulative gas production in 3 h. The total volatile fatty acids, microbial protein (MCP) concentration, acetate, and acetate to propionate ratio in the HMBi and MHA-Ca groups were significantly higher than those in the Control group (p = 0.006, p = 0.002, p = 0.001, p = 0.004), and the NH₃-N concentrations in the HMBi and MHA-Ca groups were significantly lower than those in the Control group (p = 0.004). The 16S rRNA sequencing revealed that the HMBi group had a higher (p = 0.039, p = 0.001, p = 0.027) relative abundance of Bacteroidetes, Firmicutes, and Synergistetes and a lower relative abundance of Proteobacteria (p = 0.001) than the Control group. At the genus level, Prevotella abundance was higher (p = 0.001), while Ruminobacter abundance was lower (p = 0.001), in the HMBi and MHA-Ca groups than in the Control group. Spearman’s correlation analysis showed that the relative abundance of Prevotella_1, Streptococcus, and Desulfovibrio was positively correlated with dry matter digestibility, MCP, and fermentation parameters. MHA, thus, significantly increased gas production and altered the rumen fermentation parameters and microbiota composition of sheep.

Heat stress (HS) is directly correlated to mammary gland dysfunction in dairy cows, especially in summer. The hypothalamic−pituitary−mammary gland axis (HPM axis) plays an important role in the regulation of stress response and lactation physiology in heat−stressed dairy cows. The aim of this study was to explore the lncRNA profile, and the competitive endogenous RNA (ceRNA) regulatory network in hypothalamus, pituitary, and mammary gland tissues of heat−stressed and normal dairy cows. We performed RNA sequencing (RNA−seq) to identify differentially expressed (DE) lncRNAs, and the ceRNA regulatory network was established in HPM−axis−related tissues. Our results showed that a total of 13, 702 and 202 DE lncRNAs were identified in hypothalamus, pituitary, and mammary glands, respectively. Of lncRNAs, 8, 209 and 45 were up−regulated, and 5, 493 and 157 lncRNAs were down−regulated. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that DE lncRNAs target genes that might play a role in hormone synthesis, secretion and action, apoptosis, mitogen−activated protein kinase (MAPK), AMP−activated protein kinase (AMPK), and mechanistic target of rapamycin (mTOR) signaling pathway. Moreover, the ceRNA regulatory network associated with the MAPK signaling pathway in HPM−axis−related tissues contains 3286 lncRNA–mRNA pairs. Furthermore, the ceRNA regulatory network associated with apoptosis, prolactin, AMPK, and mTOR signaling pathway in the mammary gland contains 772 lncRNA–mRNA pairs. Thus, some lncRNAs may be involved in the regulation of stress response and the physiological process of lactation. The changes in lncRNA expression profiles and ceRNAs (lncRNA–miRNA–mRNA) in HPM−axis−related tissues are the key to affect the stress response and lactation physiology of dairy cows under HS, which provide a theoretical basis for the molecular mechanism in the stress response of HPM−axis−related tissues in dairy cows under HS.

Objective: The aim of the study was to investigate the effect of zinc-bearing palygorskite (Zn-Pal) on rumen fermentation by in vitro gas-production system. Methods: In trial, 90 incubators were evenly divided into five groups: control (0% Zn-Pal), treatment I (0.2% Zn-Pal), treatment II (0.4% Zn-Pal), treatment III (0.6% Zn-Pal), and treatment IV (0.8% Zn-Pal). The contents of zinc for treatments were 0, 49, 98, 147, 196 mg/kg, respectively. The main chemical composition and microstructure of Zn-Pal was investigated by X-ray diffraction. The physicochemical features were evaluated by Zeta potential analysis, cation-exchange capacity, ethylene blue absorption and specific surface area (the Brunauer-Emmett-Teller method). In vitro gas production (GP) was recorded at 3, 6, 9, 12, 18, 24, 36, 48, 60, and 72 h incubation. Incubation was stopped at 0, 6, 12, 24, 48, and 72 h and the inoculants were tested for pH, microbial protein yield (MCP), NH3-N, volatile fatty acids (VFAs), lipopolysaccharide (LPS). Results: The results showed that the GP in the treatment groups was not significantly different from the control groups (p>0.05). Compared to the control group, pH was higher at 24 h, 48 h (p<0.05), and 72 h (p<0.01) (range 6 to 7). The concentration of NH3-N in the three treatment groups was higher than in the control group at 24 h (p<0.01), meanwhile, it was lower at 48 h and 72 h (p<0.01), except in the treatment IV. The concentration of MCP in treatment I group was higher than in the control at 48 h (p<0.01). Compared with control, the LPS concentration in treatment III became lower at 12 h (p<0.05). Total VFAs in treatments were higher than in the control at 24 h, 48 h (p<0.05). Conclusion: These results suggest that the addition of Zn-Pal can improve the rumen fermentation, especially when adding 0.2% Zn-Pal.