The investigation aimed to assess the impact of yeast culture (YC) additives on growth performance, blood components, and puberty in cows' heifers. The study involved fifteen cows, heifers six months old, with average body weight 141.84 ± 2.55 kg, divided into three equal groups, with five heifers for each. The control group (C) received basal diet without any additives; while the other two groups (T1 and T2) received basal diet supplemented with 10 g and 20 g of YC per heifer daily, respectively. The experiment took place over 7 months, from July 2023 to January 2024. Throughout this period, changes in body weight were monitored, and blood samples were collected monthly. The findings indicated that the inclusion of YC in the diets led to a significant increase (P < 0.01) in total gain (TG), average daily gain (ADG), body weight changes percentage (BWC%), and a noteworthy improvement in feed conversion ratio (FCR). Moreover, there was a notable rise (P<0.01) in certain blood metabolic parameters; total protein, globulin, and trace elements (iron and zinc) in the yeast groups as compared to the control group. Additionally, the yeast groups exhibited a substantial increase (P<0.01) in the levels of estrogen and progesterone hormones. Consequently, it can be inferred that the addition of
yeast culture enhances the growth performance, blood metabolites in cows' heifers, and could potentially have a positive effect on the early onset of puberty