Search

Simple Summary: In this study, we analyzed the plasma biochemistry and plasma metabolome of 12-month-old Montbéliard and Holstein backcross and purebred Holstein heifers, with the aim of determining differences in the performance of these two breeds. The findings revealed that the backcrossed heifers are superior to Holsteins with respect to certain antioxidant indices and immune performance. We detected a total of 30 metabolites showing significantly differential levels between the two groups, of which 17 and 13 were significantly up- and down-regulated. Collectively, our findings in this study indicate that compared with 12-month-old purebred Holstein heifers, Montbéliard and Holstein backcross heifers of the same age are characterized by higher antioxidant capacity and immunity. Holstein cattle are the main breed of dairy cattle in China. However, given the high degree of purebred selection of Holstein cattle, Chinese dairy cattle are increasingly being characterized by poor disease resistance, poor quality, and declining fertility. In this study, using Montbéliard × Holstein cattle as females and Montbéliard bulls as males for backcross breeding, we sought to provide a reference for improving the quality and performance of Holstein cattle and enhancing the efficiency of dairy farming. On the basis of similar physiological status and age, we selected 24 Montbéliard and Holstein backcross heifers and 11 Holstein heifers fed the same formula for comparative analyses. Plasma samples collected for plasma biochemical index analyses revealed that the content of ALB and BUN in the Montbéliard and Holstein backcross heifers was 20.83% (31.62 g/L to 26.17 g/L) and 42.36% (6.89 mmol/L to 4.84 mmol/L) higher than in the Holsteins (p < 0.01). The ALB/GLB (0.90 to 0.60, p < 0.05) was significantly higher in Montbéliard and Holstein backcross heifers than in Holstein heifers. Similarly, the activity of CAT in the backcross heifers was 61.28% (4.29 U/mL to 2.66 U/mL) higher than that in the Holstein heifers (p < 0.05). Although the activity of GSH-Px in the backcross heifers also showed an increasing trend, the difference did not reach the level of statistical significance (p = 0.052). Compared with Holstein heifers, the concentrations of IgA, IgG, and IL-4 were elevated by 32.52% (24.90 μg/mL to 18.79 μg/mL, p < 0.01), 13.46% (234.32 μg/mL to 206.53 μg/mL, p < 0.01), and 14.59% (306.27 pg/mL to 267.28 pg/mL, p < 0.05), and the contents of IL-6 and TNF-α were decreased by 15.92% (215.71 pg/mL to 256.55 pg/mL, p < 0.01) and 32.17% (7.17 ng/mL to 10.57 ng/mL, p < 0.01) in the plasma of Montbéliard and Holstein backcross heifers. Among the experimental heifers, five animals from each of the two groups were selected for plasma metabolomic analysis based on untargeted liquid chromatography–mass spectrometry. A comparison of the differential metabolites between the two heifer breeds revealed an up-regulation of d-glucuronic acid, s-glutathionyl-l-cysteine, and oleic acid levels in the backcross cattle compared with those in the Holstein heifers. We speculate that changes in the levels of these metabolites may be associated with an enhancement of the anti-inflammatory, antioxidant, and immune systems in these backcross heifers. Collectively, our findings in this study indicate that compared with 12-month-old purebred Holstein heifers, Montbéliard and Holstein backcross heifers of the same age are characterized by higher antioxidant capacity and immunity. [ABSTRACT FROM AUTHOR]

Heat stress negatively affects lactation performance and rumen microbiota of dairy cows, with different breeds showing varying levels of heat tolerance. This study aimed to compare the lactation performance of Montbéliarde × Holstein (MH, n = 13) and Holstein (H, n = 13) cows under heat stress, and 16S rRNA sequencing and liquid chromatography–mass spectrometry (LC-MS) were used to determine the rumen microbiome and metabolome in experimental cows. The results indicated that during heat stress, milk yield (p = 0.101), milk fat yield, milk protein yield, milk protein, and milk lactose (p < 0.05) in Montbéliarde × Holstein cows were higher than those in Holstein cows, whereas milk yield variation and somatic cell counts (p < 0.05) were lower than those in Holstein cows. The sequencing results indicated that the rumen of Montbéliarde × Holstein cows was significantly enriched with beneficial bacteria, such as Rikenellaceae, Allobaculum, and YRC22 (p < 0.05). In addition, correlations were observed between specific ruminal bacteria and lactation performance. Ruminal metabolites related to antioxidant and anti-inflammatory properties were significantly higher (p < 0.05) in Montbéliarde × Holstein cows than in Holstein cows. Overall, Montbéliarde × Holstein cows showed higher production efficiency under heat stress, which may be related to the different rumen mechanisms of crossbred and Holstein cows in adapting to heat stress. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]