Short-term heat stress and vitamin E supplementation affect carcass weight, mucle omega-6 fatty acid and meat quality in lambs

Abstract

The effect of short term-heat stress and -vitamin E supplementation on carcass traits and muscle quality – vitamin E, nutritional value and retail colour of lambs was investigated. Forty-eight lambs (crossbred; 42 ± 2 kg body weight, 7 mo age) were randomly allocated by body weight to one of three groups (n = 16) and fed 3 different doses of Vitamin E and Se. The doses of Vitamin E and Se for control (CON), moderate (MOD), and supranutritional (SUP) diets were 28, 130, 228 mg/kg DM as α-tocopherol acetate and 0.16, 0.66, 1.16 mg Se as SelPlex™ kg/DM, respectively. Lambs were fed for 4 weeks followed by a week of exposure to heat treatment. After 4 weeks feeding in individual pens, including 1 week of adaptation, lambs were moved to metabolism cages for 1 week and allocated to one of 2 heat regimes (8 per feeding group): thermoneutral (TN) (18–21◦C and 40–50% relative humidity) or heat stress (HS) (28–40◦C and 30–40% relative humidity) conditions. Final body weight (P = 0.05, 44.1 vs 46.6 kg) and hot carcass weight (P = 0.01, 21.1 vs 22.5 kg) were significantly affected by diet such that lambs supplemented with SUP levels of antioxidants had a higher FBW and HCW as compared with lambs fed MOD and CON antioxidant diets, respectively. Vitamin E concentration in the longissimus lumborum (LL) muscle tended to be higher in lambs fed moderate or supranutritional levels of antioxidants compared with control lambs and values from all treatments were below the threshold (3.2 mg/kg muscle) for optimal maintenance of retail colour. Vitamin E supplementation also reduced lipid oxidation of aged meat, as assessed by thiobarbituric acid reactive substances (TBARS) formation after 72 h of display. One week of heat stress to lambs significantly increased muscle linoleic acid concentration, which in turn increased total n-6 concentration compared with the control group. Results demonstrate that 4 weeks of vitamin E supplementation or 1 week heat stress might not have been adequate to make significant changes in muscle vitamin E concentration and fatty acid composition, which in turn can influence retail colour stability of meat.