Effects of Probiotic and Chromium-Methionine on Thyroid Hormones, Total Protein, Zinc, and Weight Gain in Dairy Holstein Calves During the Weaning Period

BACKGROUND: Many additives have been recommended to calf feed but the effects of each supplement have been under investigation especially during weaning stress. OBJECTIVES: The effects of dietary supplementation of probiotic (Protexin) and chromium-methionine che- late (Cr-Met) on triiodothyronine (T3), thyroxine (T4), total protein, albumin, zinc, and growth body-weight gain in dairy calves during weaning period was investigated. METHODS: A total of 28 dairy Holstein calves were randomly allocated to one of the four experimental treatments (n=7). The study commenced 21 days before weaning (average 70 days).The recommended dosage for both chromium-methionine chelate (Cr-Met) and probiotic (Protexin) is 2 gr/calf daily. Blood samples were collected from the jugular vein, 21 days before weaning and 3, 7 and 21 days after weaning. Serum consen- trations of T3, T4, total protein, albumin, and zinc were measured. Bodyweight (BW) was measured 7 days before, at weaning and 7 days after weaning. RESULTS: No effect of different diets nor interaction was found for body weight gain, total protein, and al- bumin. No effect of different diets was observed for T4 although the interaction was observed between groups and time. An effect of different diets and time was found for T3 and the mean T3 concentration was lowest in group Protexin + Cr-Met. The mean Zinc concentration was at its highest level 21 days after weaning, while different diets did not affect the Zinc concentrations. CONCLUSIONS: There is no benefit associated with the separate or combined feeding of Protexin and Cr- Met on calves’ growth performance according to weight gain, total protein, and thyroid hormones.