Abstract
A commercial dairy farm with two dairy units (about 3000 cows each), similar management and diets was used to evaluate the effect of a feed additive based on a mix of condense and hydrolysable tannins (ByPro®) on lactating cow services per conception and days open. The experiment was divided in three evaluation periods. Period I, January-March (without-feed additive), Period II, April-September, all cows in one dairy unit received the mix-tannins feed additive at 0.3 % of the total estimated DMI per cow. Period III, October-December (without-feed additive). Services per conception was modeled as a Poisson count using a generalized linear model with log link function. Days open was modeled with a generalized linear model for a gamma variable with log link function. The models included: dairy units (2), periods (3), and their interactions. No significant differences were observed in Period I. During the evaluation Period II, the mix tannins feed additive increased the artificial insemination efficiency, reducing (P < 0.01) the number of services of conception (- 9 %), from 2.20 to 2.02 and days open (P < 0.01) from 92.5 to 87 days (- 6.3 %). Comparable significant effects were observed in Period III without the mix-tannins feed additive that might be related to possible rumen microbiota carried over effects of the cows consuming the mix-tannins for 6 months. Finally, the treatment improved performances on the conception rate and pregnancy rate. The mix of condensed and hydrolysable tannins feed additive (ByPro®) improved reproduction efficiency in lactating cows, by reducing services per conception number and days open.