Gestational heat stress alters the plasma metabolome of Bos indicus -influenced beef cows and modifies the calf metabolome at birth

Abstract

This 3-year study evaluated the effects of heat stress mitigation during late gestation on the plasma metabolome of Bos indicus-influenced cow-calf pairs. On day 0 of each year (92 ± 19 days prepartum, n = 88/treatment/year), multiparous, pregnant Brangus crossbred cows were stratified by body condition score and body weight and allocated into 16 bahiagrass pastures (8 ha and 11 cows/pasture). Gestational treatments were randomly assigned to pastures and consisted of cows provided with (SH) or without (NSH) access to artificial shade (3.27 m2 per cow) from day 0 to 90. Blood samples were collected from cows on days 0, 30, and 60 (92 ± 19, 62 ± 19, and 32 ± 19 days prepartum, respectively), and from calves at birth, for plasma metabolome determination using liquid chromatography and flow injection analysis coupled with tandem mass spectrometry. Principal component and partial least squares-discriminant analyses were performed within each day to discriminate the treatments using SIMCA 18.0. Single metabolite concentrations were compared between groups using PROC MIXED in SAS, with Benjamini–Hochberg false discovery rate correction applied, and pathway analyses were performed using Ingenuity Pathway Analysis. A clear separation was observed on days 30 (R² = 0.76) and 60 (R² = 0.67) for the plasma metabolome of SH and NSH cows. Effects of treatment (P ≤ 0.05) were detected for 23 metabolites on day 30 and 17 metabolites on day 60. Twelve pathways related to putrescine, glycine, and arginine metabolism were downregulated (P ≤ 0.04), whereas tryptophan degradation X was upregulated (P = 0.02) in SH vs. NSH cows on day 30. On day 60, 23 pathways were upregulated (P ≤ 0.04) and serine biosynthesis and tyrosine degradation I tended to be upregulated (P = 0.05), whereas 4 pathways related to amino acid degradation were downregulated (P ≤ 0.01) in SH vs. NSH cows. At birth, a clear treatment separation was observed (R² = 0.73), with effects detected (P ≤ 0.03) for 10 metabolites and 50 metabolic pathways upregulated in SH vs. NSH calves, predominantly related to amino acid metabolism and antioxidant defense. In conclusion, gestational access to shade was associated with progressive alterations in the maternal lipid and amino acid metabolite profile and with differences in the neonatal metabolome at birth, consistent with a more favorable gestational nutritional environment.