Heat stress negatively affects the transcriptome related to overall metabolism and milk protein synthesis in mammary tissue of midlactating dairy cows

Abstract

Inadequate dry matter intake only partially accounts for the decrease in milk protein synthesis during heat stress (HS) in dairy cows. Our hypothesis is that reduced milk protein synthesis during HS in dairy cows is also caused by biological changes within the mammary gland. The objective of this study was to assess the hypothesis via RNA-Seq analysis of mammary tissue. Herein, four dairy cows were used in a crossover design where HS was induced for 9 days in environmental chambers. There was a 30-day washout between periods. Mammary tissue was collected via biopsy at the end of each environmental period (HS or pair-fed and thermal neutral) for transcriptomic analysis. RNA-Seq analysis revealed HS affected >2,777 genes (false discovery rate-adjusted P value < 0.05) in mammary tissue. Expression of main milk protein-encoding genes and several key genes related to regulation of protein synthesis and amino acid and glucose transport were downregulated by HS. Bioinformatics analysis revealed an overall decrease of mammary tissue metabolic activity by HS (especially carbohydrate and lipid metabolism) and an increase in immune activation and inflammation. Network analysis revealed a major role of TNF, IFNG, S100A8, S100A9, and IGF-1 in inducing/controlling the inflammatory response, with a central role of NF-κB in the process of immunoactivation. The same analysis indicated an overall inhibition of PPARγ. Collectively, these data suggest HS directly controls milk protein synthesis via reducing the transcription of metabolic-related genes and increasing inflammation-related genes.

Surgical castration versus chemical castration in donkeys: response of stress, lipid profile and redox potential biomarkers

“…Alterations in lipid profile is considered as a valid indicator of stress [20,21]. For instance, hypocholesterolemia is an obvious metabolic sign for exposure to stressful situations as cholesterol requirement increases to support the biosynthesis of stress hormones and the production and functions of new cells participate in host defense and tissue repair [22].…”

Food intake dependent and independent effects of heat stress on lactation and mammary gland development

“…Similarly, in the cow, heat stress decreases mRNA expression of genes involved in production of key milk proteins (casein and lactalbumin) and transport of amino acids and glucose (Gao et al, 2019) when compared to that observed in pair-fed cows. In cows, heat exposure also appears to limit the ability of the mammary gland to mobilize fatty acids from triglycerides and catabolize those fatty acid through β-oxidation (Adin et al, 2009; Gao et al, 2019). Accordingly, depressed mammary function appears to be a direct response to heat and may be a result of limited metabolite flux.…”

Hepatic Transcriptome Perturbations in Dairy Cows Fed Different Forage Resources

“…Five cows were randomly selected from each treatment for liver tissue collection. The biopsy was conducted at the end of the 14 weeks as described by Gao et al (2019) and Bu et al (2017) [49,50]. Tissue samples were washed with PBS buffer prepared using RNAase-free water, and then stored in liquid nitrogen immediately until RNA extraction.…”