Effect of high dietary zinc, copper and manganese concentration and source on ‎plasma progesterone and reproductive performance in repeat breeder cows

We used 263 Holstein repeat breeder dairy cows (193±58 DIM) based on randomized complete design. Animals in control group (no supplementation), groups 2 and 3 supplemented with 2,244 mg of zinc, 295.5 mg copper and 480 mg manganese either inorganic trace minerals (ITM) and chelated (glycinates) trace minerals (CTM) sources, respectively. Supplemental minerals were fed daily as a top dress. All cows were inseminated according to Double-Ovsynch protocol. Super oxide dismutase concentration tended to have higher in CTM and ITM treatments than in control group (P=0.09). Progesterone concentration at day 11 after artificial insemination was higher in CTM and ITM treatments than in control group (P<0.05). Cows in CTM and ITM treatments tended to have greater odds of becoming pregnant at first and cumulative (first and second service) than cows in control group (P=0.1 and P=0.13 respectively). According to the results of this study, diets supplemented above National Research Council (NRC, 2001) requirments for zinc, copper and manganese in repeat breeding cows, improved fertility.