Effects of supplementation of DL-methionine on tissue and plasma antioxidant status during heat-induced oxidative stress in broilers

Abstract

Exposure to high ambient temperature has been shown to impair growth performance and to cause oxidative stress in broilers. This study investigated the hypothesis that supplementation with methionine ( Met ) as DL-Met ( DLM ) more than the National Research Council recommendations improves growth performance and alleviates oxidative stress in broilers exposed to high ambient temperature. One-day-old male Cobb-500 broilers (n = 68) were allotted to 4 groups and phase-fed 3 basal diets during days 1 to 10, 11 to 21, and 22 to 35. One group was kept under thermoneutral temperature conditions and received the basal diets with Met + cysteine ( Cys ) concentrations according to recommendations of NRC. The other 3 groups were kept in a room with an increased ambient temperature from week 3 to 5 and were fed either the basal diet or the basal diets supplemented with 2 levels of DLM in which Met + Cys concentrations exceeded NRC recommendations by around 20% (group DLM1) and 40% (group DLM2), respectively. As expected, the broilers exposed to high ambient temperature showed a lower feed intake, lower body weight gains, a higher feed:gain ratio, and biochemical indications of oxidative stress in comparison to broilers kept under thermoneutral temperature conditions. Supplementation of DLM did not improve the growth performance in broilers exposed to high ambient temperature. However, the broilers supplemented with DLM had increased concentrations of glutathione in liver and breast muscle (groups DLM1 and DLM2), increased concentrations of tocopherols in the liver (group DLM2), and reduced concentrations of 7α-hydroxycholesterol and 7-ketocholesterol in heat-processed thigh muscle (groups DLM1 and DLM2) in comparison to the control group exposed to high ambient temperature. Concentrations of thiobarbituric acid-reactive substances and vitamin C in plasma, liver, and muscle were not different between the 3 groups exposed to heat stress. Nevertheless, the study shows that supplementation of DLM in slight excess of the Met concentration required for maximum growth performance improved the antioxidant status in tissues and reduced the susceptibility of muscle toward oxidation in heat-stressed broilers.

Effect of DL-Methionine Supplementation on Tissue and Plasma Antioxidant Status and Concentrations of Oxidation Products of Cholesterol and Phytosterols in Heat-Processed Thigh Muscle of Broilers

“…We observed that supplementation of DLM led to a reduction of the concentrations of individual and total COPs in heat-processed thigh muscle. This finding agrees with a previous study which has shown that supplementation of DLM reduces the formation of COPs in heat-processed thigh muscle in broilers subjected to heat stress [15]. The inverse correlations between the concentration of GSH and vitamin C in thigh muscle and the concentrations of COPs in heat-processed thigh muscle indicates that the reduced formation of COPs was due to increased concentrations of those antioxidants in the muscle.…”

“…They contained nipple drinkers and automated feeders allowing the birds free access to feed and water. Light intensity and the light:dark regime were in accordance with our recent study [15]. The room temperature decreased from 29.5 • C on day 1, measured at pen height, to 21.0 • C on day 35.…”

“…This observation might be due to the fact that GSH forms a storage pool of readily available Cys, which is increased when Met availability increases [2]. Previous studies have already shown that supplementation of Met increases the formation of GSH in liver and thigh muscle of broilers [4,5,15,[30][31][32]. GSH is one of the major water-soluble antioxidants in the body, and thus an increased GSH concentration could imply that the antioxidant status was improved by DLM supplementation.…”

“…Sample collection and laboratory analyses were largely according to our recent study [15]. On day 35, the birds were killed by bleeding (opening of Vena jugularis and Arteria carotis) after an electrical anesthesia.…”

“…The concentrations of GSH in blood and tissues were determined by HPLC-MS [27,28]. More details of the analytical procedures are described by Zeitz et al [15].…”