MODULATORY EFFECTS OF DIETARY GARLIC (Allium sativum) ON ANTIOXIDANT STATUS, LIVER FUNCTION AND PULSE RATE OF THREE BROILER GENOTYPES EXPOSED TO HEAT-STRESS

This study evaluated graded dietary garlic supplementation on antioxidant enzyme activities, liver enzymes, and pulse rate responses of three heat-stressed broiler strains (Arbor Acres, Cobb 500 and Ross 308). A total of 180 day-old chicks (60 per strain) were assigned to four garlic treatments (0, 1.0, 1.5 and 2.0%, T1-T4) in a 3 × 4 factorial design. From week seven, birds were exposed to 33°C for two hours daily for seven days. Blood was collected from the wing (brachial) vein into plain tubes, and serum was separated by centrifugation and stored for the subsequent determination of Superoxide Dismutase (SOD), Catalase (CAT), and Glutathione Peroxidase (GPx) activities, Malondialdehyde (MDA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) activities. Data were analysed by two-way ANOVA, with means separated using Tukey's test at P<0.05. Garlic increased (P<0.05) SOD, CAT and GPx activities and reduced MDA dose-dependently across all strains. SOD differed among strains (P<0.05), whereas CAT, GPx and MDA did not (P>0.05), and no diet×strain interactions were significant (P>0.05). In Cobb 500, SOD rose from 40.86 to 51.05 U/mg, CAT from 20.81 to 29.40 U/mg, GPx from 12.86 to 22.16 U/mg, and MDA fell from 5.85 to 2.53 nmol/mg; similar trends occurred in Arbor Acres and Ross 308. Serum ALT decreased with garlic (P<0.05) and differed among strains, ranging from 25.05 to 19.20 IU/L (Arbor Acres), 27.90 to 21.80 IU/L (Cobb 500), and 26.20 to 19.60 IU/L (Ross 308), whereas AST and ALP were unaffected (P>0.05). Pulse rate during heat stress exceeded baseline in all strains, and both absolute pulse rate and percentage-increase declined with garlic inclusion, with T1 highest and T4 lowest. Cobb 500 exhibited the highest antioxidant enzyme activity, followed by Ross 308, while Arbor Acres recorded the lowest. It is concluded that dietary garlic, particularly at 2.0%, enhances antioxidant defence, exerts hepatoprotective effects and improves cardiovascular stability in heat-stressed broilers, with benefit magnitude varying by genotype.