Dietary Betaine Impacts Metabolic Responses to Moderate Heat Exposure in Sheep

Abstract

Dietary betaine supplementation can ameliorate physiological responses to heat exposure (HE) in sheep. This experiment measured metabolic responses to glucose (intravenous glucose tolerance, IVGTT), insulin (insulin tolerance test, ITT), and adrenocorticotropic hormone (ACTH) challenges in Merino ewes (n = 36, 39.7 kg) maintained at thermoneutral (TN, 21 °C) or HE (18–43 °C) and supplemented with either 0, 2, or 4 g/day dietary betaine (n = 6 per group). Sheep had ad libitum access to water and were pair-fed such that the intake of the TN sheep mimicked that of the HE sheep. After 21 days of treatment, sheep were fitted with jugular catheters and subjected to consecutive daily challenges (IVGTT, ITT, and ACTH, d 21–23, respectively), followed by skeletal muscle and subcutaneous adipose tissue biopsy collections for gene expression analysis (d 24). The HE-treated sheep had a greater insulin:glucose ratio (p = 0.033), a greater estimated homeostatic model assessment of insulin resistance (HOMAIR; p = 0.029), and a reduced revised quantitative insulin sensitivity check index (RQUICKI; p = 0.015). Sheep fed betaine (2 + 4 g/day) had a greater basal plasma insulin (p = 0.017) and a reduced basal non-esterified fatty acid (NEFA; p = 0.036) concentration, while the RQUICKI was reduced (p = 0.001) in sheep fed betaine. The results suggested that betaine supplementation alters lipid metabolism by potentially improving insulin signaling, although these responses differ between TN and HE conditions. There was no other impact of temperature or dietary treatments on the tissue gene expressions measured. Our results support the notion that betaine, in part, acts to modify lipid metabolism.

A Meta-Analysis of the Effects of Dietary Betaine on Milk Production, Growth Performance, and Carcass Traits of Ruminants

“…This was evident in a study by Zhang et al [12], where the researchers showed that milk yield increased at a dose of 15 g/d during summer, beyond which no effect was observed. These findings are consistent with the findings of DiGiacomo et al [58,59] and DiGiacomo [27] who found that dietary betaine at 2 g/d (0.125 g/LWT0.75) was protective against heat stress in growing sheep. The moderation in response to high doses of betaine during heat stress was speculated to be due to the stimulation of hepatic metabolism and a consequent increase in heat production by the liver, which may offset the decrease in heat production by betaine in the rest of the body [28].…”

Assessment of Betaine as a Feed Additive to Improve the Metabolic Status and Reproductive Performance of Aberdeen Angus Cows in Arid Subtropical Regions

“…Betaine, tri-methylglycine is a recent compound found to ameliorate HS in cows (Kassab et al, 2021;Williams et al, 2021, andKondiba et al, 2023), buffalo (Shankhpal et al, 2019;Deshpande et al, 2020;Shakkarpude et al, 2022, andHussain et al, 2023), goat (Ghoneem and El-Tanany., 2023), sheep (Tsiplakou1 et al,2017, and DiGiacomo et al, 2023, and in poultry (Al Sulaiman et al, 2023, andAl-Garadi et al, 2023).BET has several activities that may reduce the impact of HS on cattle and improve its performance. Initially, BET is a modified amino acid composed of glycine with three methyl groups that acts as a methyl donor in many metabolic pathways (NCBI, 2021).…”