The effect of feeding zinc-glycine supplement on performance, skeletal growth and fertility parameters in Holstein bull calves

The 15 Holstein bull calves averaging 10.3 months age (± 0.8)and 284.6 kg BW (± 33.2) were allocated in a completely randomized design (5 bull calves per treatment) to investigate the effect of organic zinc supplement(Zn-Gly) on feed intake, growth, blood metabolites and testosterone and testicular development. Three treatments were dietary feeding of 0 (control), 250 or500 mg Zn-Glyper day, respectively. The study lasted 135 days. Feed intake, growth performance, testes development and blood metabolites were determined. The feed intake and growth performance of the animals were not affected by the treatments(p > 0.05).Average scrotal circumference of calves received zinc-Gly supplements was higher compared to the control group(p0.05).With increasing daily feeding of organic Zn, thetestosterone concentration increased, and ALT enzyme decreased. Based on the obtained results, although organic zinc supplementation had no effects on feed intake and growth performance of bull calves, fertility parameters were affected positively through increased testosterone and testicular growth.