Antioxidants Supplementation on Acid Base Balance During Heat Stress in Goats (Report)
Asian - Australasian Journal of Animal Sciences 2010, Nov, 23, 11
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- 2,99 €
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- 2,99 €
Descripción editorial
INTRODUCTION High environmental temperature challenges the animal's ability to maintain energy, thermal, water, hormonal and mineral balance. Heat stress stimulates excessive production of free radicals (superoxide anion radicals, hydroxyl radical, hydrogen peroxide and singlet oxygen) which are continuously produced in the course of normal aerobic metabolism (Bernabucchi et al., 2002) and these free radicals can in turn damage healthy cells if they are not eliminated. Heat production is directly controlled by the nervous and endocrine systems through modifications of appetite, digestive process and, indirectly, by alterations of the activity of respiratory enzymes and protein synthesis (Yousef, 1985). Exposure of animals to heat stress activates the hypothalamo-pituitary-adrenal axis (Abilay et al., 1975) and hence estimation of concentrations of hormones such as thyroxine, cortisol, and prolactin could be one of the important indicators for assessment of stress in animals. The maintenance of blood pH is high on the list of homeostatic priorities as almost all enzyme systems in the body are influenced by [H.sup.+] concentrations (Fraser, 1991) and it depends primarily on relative concentrations of carbonic acid and base bicarbonate in blood (Coppock et al., 1982). A major strategy to reduce the effect of heat stress on animals is to alter the environment through the use of sheds, fans or evaporative cooling (Bucklin et al., 1991). Such practices are not possible in semi-intensive systems as goats are grazed in the open during most of the day. This necessitates other strategies to counteract the adverse effects of heat stress such as supplementation of antioxidants. Antioxidants such as Vitamin C and E are free radical scavengers, which protect the body defense system against excessively produced free radicals during heat stress and stabilize health status of the animal. Although ruminants can synthesize vitamin C (McDowell, 1989), a large reduction in plasma vitamin C concentration was reported in calves stressed by housing conditions (Cummins and Brunner, 1991) and in heat- stressed cows (Padilla et al., 2006). Dietary vitamin C is extensively degraded in the rumen (Cappa, 1958). Thus, special preparations for ruminants have been developed and some experiments indicated that supplementation with these preparations increased plasma vitamin C concentration in cattle (Hidiroglous, 1999). Ghanem et al. (2008) and Ayo et al. (2006) gave vitamin C to Awassi sheep and goats, respectively, by dissolving ascorbic acid in water and found that this orally supplemented vitamin C was also effective in alleviating stress. Hence we chose the oral route for vitamin C administration.