Hepatic thyroid signaling of heat-stressed late pregnant and early lactating cows

Abstract

During the transition between late gestation and early lactation, dairy cows experience severe metabolic stress due to the high energy and nutrient requirements of the fetus and the mammary gland. Additional thermal stress that occurs with rising temperatures during the ongoing climate change has further adverse implications on energy intake, metabolism and welfare. The thyroid hormone (TH)-mediated cellular signaling has a pivotal role in regulation of body temperature, energy intake and metabolic adaptation to heat. To distinguish between energy intake and heat stress-related effects, Holstein cows were first kept at thermoneutrality at 15°C followed by exposure to heat stress (HS) at 28°C or pair-feeding (PF) at 15°C for 6 days, in late pregnancy and again in early lactation. Herein, we focused on hepatic metabolic changes associated with alterations in the hypothalamic–pituitary–thyroid axis in HS and PF animals. T3 and T4 levels dropped with HS or PF; however, in HS animals, this decline was more pronounced. Thyroid-stimulating hormone (TSH) levels remain unaffected, while plasma cholesterol concentrations were lower in HS than PF animals. Hepatic marker genes for TH action (THRA, DIO1 and PPARGC1) decreased after HS and were lower compared to PF cows but only post-partum. Proteomics data revealed reduced hepatic amino acid catabolism ante-partum and a shift toward activated beta-oxidation and gluconeogenesis but declined oxidative stress defense post-partum. Thus, liver metabolism of HS and PF cows adapts differently to diminished energy intake both ante-partum and post-partum, and a different TH sensitivity is involved in the regulation of catabolic processes.

Shading effect on physiological parameters and in vitro embryo production of tropical adapted Nellore heifers in integrated crop-livestock-forest systems

“…Thyroid hormones (TH) are considered “markers” of the body temperature. Weitzel et al ( 2017 ) observed a pronounced decline in T3 and T4 levels in dairy cows submitted to heat stress. We expected changes in T3 and T4 concentrations in response to a better thermal comfort in ICLF.…”

Review: Adaptation of animals to heat stress

“…Elevated temperature induced higher metabolic heat stress in livestock initiates various counter regulatory mechanisms to reduce endogenous heat production. The THR gene regulates the genomic actions of thyroid hormones in animals (Weitzel et al, 2017). The internal metabolic heat production of stressed animals is reduced via hypothyroid activity (Weitzel et al, 2017).…”

“…The THR gene regulates the genomic actions of thyroid hormones in animals (Weitzel et al, 2017). The internal metabolic heat production of stressed animals is reduced via hypothyroid activity (Weitzel et al, 2017). Studies suggest the potential of the bovine blood ATP1A1 gene in ameliorating the effects of heat stress, and the P14 locus within the bovine ATP1A1 gene has been recognized as a DNA marker for bovine heat tolerance in marker-assisted selection (Kashyap et al, 2015).…”

Effect of seasonal thermal stress on oxidative status, immune response and stress hormones of lactating dairy cows

“…In this study, the increased cortisol level and reduced epinephrine level HTHI cows might be explained by an energy imbalance, a consequence of the reduction in DMI, and by organism immune dysfunction under heat stress ( Turk et al., 2015 ). In addition, the thyroid hormone of mammals plays an important thermoregulatory role in maintaining metabolic rates under thermal stress conditions ( Weitzel et al., 2017 ; Hu et al., 2019 ). Thyroxine is the predominated hormone secreted by the thyroid gland and must be deiodinated to triiodothyronine to be biologically active ( Senese et al., 2018 ).…”