Abstract
The study was designed to evaluate the effects of different levels of clove (Syzygium aromaticum) powder in the diet on growth performance and histological changes of the livers and intestines of broiler chickens at 21 and 35 days old. Three hundred and thirty-six one-day-old Ross (308) broilers were allocated to eight treatments, namely: NC: negative control and unvaccinated; PC: positive control and vaccinated; and treatments T1, T2, T3, T4, T5 and T6 supplemented with different levels of clove powder (10, 20, 30, 40, 50 and 60 g clove powder/kg of diet, respectively) and all vaccinated. At 21 and 35 days old, eight birds/treatment were weighed, and samples from the livers and intestines were collected to evaluate morphological and histological changes. The results showed that higher levels of clove powder (T3 to T6) resulted in a gradual decrease in the live body weight of the birds at 21 and 35 days old. Relative liver weight increased in T5 and T6 at 35 days, but not at 21 days. A shorter small intestine was recorded in birds that received 50 and 60 g (T5 and T6) clove powder, while the proportional length of small intestinal parts did not show differences among treatments at 21 and 35 days old. The supplementation in the T3 toT6 groups resulted in a gradual decrease in intestinal weight at 21 days, but was not evident at 35 days. Villus height, villus surface area and villus crypt depth showed a gradual decrease from T1 to T6 at 35 days old. Also, gradual loss was recorded of the intestinal epithelium structure by necrotic enteritis on the wall of villi with an increased level of clove powder (< T2). These results indicated that 10 g clove powder per kg diet could be used to improve the growth rate without affecting the health of the liver and intestines of broilers.