Abstract

Heat exposure is a systemic stressor that adversely influences growth and reproductive performances in cattle. This trial aimed to study the effects of Rosemary (RM) supplementation on reducing the side effect of oxidative stress and its relation with growth performance under heat stress condition. Fifteen male calves were divided into three equal groups, the first was offered the basal diet as a control group, whereas the second and the third groups were fed the same basal diet as in control, in addition to a daily supplement of 3g and 6g dried grinded RM/kg concentrate, respectively, for a period of one month. The results showed that supplement of 3 and 6g dry grinded RM/kg concentrate led to a highly significant (P< 0.01) decrease in oxidant status and an increase in total antioxidant capacity, as well as significant (P< 0.01) declines were noted in the levels of lipids profile, kidney and liver function indicators, and iron concentration. However, RM supplemented groups showed significant (P< 0.01) elevations of feed efficiency and daily weight gain copper and triiodothyronine concentrations. In conclusion, RM improved the calves' growth performance through alleviating oxidative stress side effects under hot summer conditions to improve economic returns.