Heat Tolerance Differences Between Hu Sheep and Hu Crossbred Sheep in Microbial Community Structure and Metabolism

Abstract

Background: The frequent occurrence of extreme temperature events causes significant economic losses to the livestock industry. Therefore, delving into the differences in the physiological and molecular mechanisms of heat stress across different sheep breeds is crucial for developing effective management and breeding strategies.

Methods: This study explores the differences in heat tolerance mechanisms between Hu sheep and Xinggao sheep by comparing their growth performance under normal and heat stress conditions, as well as examining the differences in physiological, biochemical, and antioxidant indicators related to heat tolerance, serum metabolomics, and gut microbiomics in a heat stress environment.

Results: The results indicate that with changes in the temperature-humidity index (THI), Hu sheep exhibit superior stability in respiratory rate (RR) and rectal temperature (RT) fluctuations compared to Xinggao sheep. In terms of biochemical indicators and antioxidant capacity, the levels of creatinine (Cr) and superoxide dismutase (SOD) in Hu sheep serum are significantly higher than those in Xinggao sheep. In comparison, alkaline phosphatase (ALP) and malondialdehyde (MDA) levels are significantly lower. Metabolomic results showed that, compared to Hu sheep, Xinggao sheep exhibited higher cortisol (COR) and dopamine (DA) levels under heat stress conditions, a stronger lipid mobilization capacity, and elevated levels of tricarboxylic acid (TCA) cycle-related metabolites. Furthermore, gut microbiome analysis results indicate that Hu sheep demonstrate stronger cellulose degradation capabilities, as evidenced by significantly higher abundances of microorganisms such as Ruminococcus, Fibrobacter, and Bacteroidales_RF16_group, compared to Xinggao sheep.

Conclusions: In summary, Hu sheep exhibit stronger heat tolerance compared to Xinggao sheep. These findings provide an important theoretical basis for the breeding and selection of heat-tolerant meat sheep varieties and offer strong support for the region's livestock industry in addressing the challenges posed by global warming.

Keywords: gut microbiota; heat stress; meat sheep; metabolome; thermotolerance.

Figure 1

The weather trend before sampling and the measurement of physiological and antioxidant parameters in XL and HL groups during high-temperature conditions. (A) THI changes fifteen days prior to sampling, with −1 indicating the day before sampling, and so forth. Average represents the daily average THI, and the red dotted line marks the heat stress threshold; (B) respiration rates (RR); (C) rectal temperatures (RT); (D) levels of oxidative stress indexes; XL: Xinggao sheep; HL: Hu sheep; * p < 0.05, ** p < 0.01.

Figure 2

(A) Principal component analysis (PCA); (B) partial least squares discriminant analysis (PLS-DA); (C) PLS-DA permutation test plot; (D) volcano plot showing significant differences in metabolites between treatments selected by PLS-DA (VIP > 1, p < 0.05, FC = 1.5 or 1/1.5); (E) biochemical categories of identified differential metabolites are displayed in a pie chart; (F) enrichment pathways of differential serum metabolites in XL and HL groups under heat stress conditions.

Figure 3

The network between different metabolites. Metabolites in brownish red and green represent higher or lower levels, respectively, in the XL group than in the HL group.

Figure 4

(A) Differential analysis of gut microbiota in the XL group and HL group under heat stress conditions. rarefaction of the different samples; (B) differences in principal coordinate analysis (PCoA) of intestinal microbiome XL and HL groups. The red dots represent the samples of the XL group, and the blue dots represent the samples of the HL group. The distance between the two points represents the difference in intestinal microbiota; (C) the taxonomic distribution between XL group and HL group samples (each color represents the relative abundance of a taxonomic bacterium). Between-group at the phylum level (top 14); (D) between-group at the genus level (top 30); (E) heatmap of correlations between gut microbiota and differential metabolites. Red indicates a positive correlation, blue indicates a negative correlation; * p < 0.05, ** p < 0.01.

Figure 5

Verification of specific metabolite concentrations by UHPLC-MRM-MS; * p < 0.05, ** p < 0.01.