The Effect of Selenium and Vitamin E on Growth and Energy Linked Biochemical Profile of Damani Goat under Heat Stress

A total of 20 healthy adult goats (10, each of Damani and non-Damani, as experimental and control groups respectively) were randomly selected from livestock department of D.I. Khan where they were properly managed and vaccinated. Experimental group was provided with 50mg vitamin E and 0.3mg Se/kg diet during the hot months of May, June and July.

A blood sample of 5 ml from jugular vein in 15 falcon tube was collected in duplicate from each goat on the 14th and 28th day of each month after administration of combination of vitamin E and Se. Serum was separated by centrifugation at 3000rpm for 10-15 min and used for estimation of total protein, glucose, albumin, T3, T4, TSH and cortisol with the help of commercially available kits (BioCheck, USA).

Mean± S.D. and Euclidean distance statistical tool was used for comparing the difference/distance between experimental and control group for different parameters.

Table I shows the effect of vitamin E and Se on various energy related (total protein, glucose, cholesterol and albumin) and growth related parameters (T3, T4, TSH, cortisol) in the blood sera of Damani goats during the heat season of May, June and July in D.I. Khan division.

It was found that after 14 days treatment, all the biochemical parameters remained unaffected except for cholesterol which showed 160% increase in experimental group compared to control group, and for T3 and T4 which showed 100% and 41.68% increase in control group compared to experimental group. When this treatment was extended to 28 days, all the biochemical parameters linked with energy increased compared to their respective control; protein, glucose, cholesterol and albumin increased 230.67%, 133.72%, 160%, 320% after Se and vitamin E treatment. The growth related parameters showed significant decrease after treatment for 28 days. T3 decreased 100%, T4 decreased 41.68%, TSH decreased 89.90% and cortisol showed 180% decrease.

Cortisol is the general stress hormone and plays a critical role in many physiological, especially thermal regulation, energy productions, lactogenesis and regulation of milk production (Sejian et al., 2012; Ihsanullah et al., 2017; Maraii et al., 2000). The difference in mean values of cortisol in experimental and control breeds were not significant, and this was in contrary with what has previously been reported (Shakirullah et al., 2017). Generally, the release of cortisol is the major indication of the activation of hypothalamic– pituitary–adrenal axis during stressful condition (Rasooli et al., 2004; Kachuee et al., 2013). During heat stress, the level of production of free radicals is higher and beyond the body scope to neutralize them leading to oxidative damage (El-Shahat et al., 2011).

The mean values of metabolic hormones T3, T4 and TSH were significantly higher in control group compared to Damani experimental group. These findings are in disagreement with what was reported earlier (Shakirullah et al., 2017) on the same Damani breed, possibly because of difference in the timings of experiment, the age difference of experimental group, or the metabolic hormones had compensating effect in producing other necessary substances against severe heat stress conditions of the months of May to July. This also showed that the oxidative stress, induced by heat stress may have a negative effect on the availability of Se and thus resulted in reduced production of thyroid hormones.

Significant decrease in total protein concentration in goats has been reported during heat stress (Dangi et al., 2012). Depending upon heat-induced stress conditions,

Table I. Effect of selenium and vitamin E on total protein, glucose, cholesterol, serum albumin, T3, T4, TSH and cortisol in blood seum of both Damani experimental and non-Damani control group on day 14 and day 28 post supplementation. The diet of only experimental group was supplemented.

total plasma protein, albumin and globulin levels have been found to decrease in certain goat varieties (Helal et al., 2010). This low level can be due to augmented plasma volume, mainly because of heat stress. In contrast, heat stress led to production of high amounts of total protein and albumin in goats (Okoruwa, 2014) which might most probably be due to dehydration that takes place as a result of increased respiration rate. During this study, interestingly, in contrast to hormonal profile, the mean concentrations of albumin, glucose, total protein content and cholesterol were found significantly higher on both 14th and 28th day post administration of Se and vitamin E in Damani breed than control breed, showing that Damani breed had comparatively better adaptive capabilities in preparing the internal physiology and metabolic processes in response to heat induced stress conditions.

The present findings showed that combination of Se and vitamin E significantly improved the biochemical processes in Damani goat, making the breed more tolerant to heat stress than non-Damani goat.

The authors have declared no conflict of interest.