Al Profesor George Seidel: 13 de julio de 1943-4 de septiembre de 2021

The aim of this study was to evaluate the effect of the use of tail-paint and artificial insemination after estrus detection on the pregnancy rate of lactating Holando Argentino cows subjected to fixed-time artificial insemination (FTAI) programs. Two experiments were conducted in two dairy farms (Farm I: N = 259 and Farm II: N = 252). On day 0, an intravaginal device (IVD) with 1.2 g of progesterone was inserted, and 2 mg of estradiol benzoate were applied to each animal. On day 7, the IVD was removed, and 150 μg of D-cloprostenol, 1 mg of estradiol cypionate and 500 IU of equine chorionic gonadotrophin were applied. At the device removal, cows were randomly assigned to two reproductive managements: 1) With use of tail-paint (WTP): At device removal, the animals were tail-painted, and those with >30% of the tail-paint rubbed off by 60 h after the device removal were inseminated, while those that did not show estrus received a dose of GnRH and were FTAI 72 h after the device removal. 2) Without use of tail-paint (WOTP): 48 h after the device removal, GnRH was administered and the FTAI was performed 60 h after the device removal. In Farm I, the use of tail-paint and artificial insemination after estrus detection during the FTAI program was associated with a numeric but non-significant (P = 0.266) improvement in the pregnancy rate [WTP: 47.2% (59/125), WOTP: 40.3% (54/134)]. However, the improvement was statistically significant (P = 0.001) in Farm II [WTP: 59.4 (76/128), SP: 37.1 (46/124)]. The use of tail-paint and artificial insemination after estrus detection during FTAI programs is in general associated with an increase in the pregnancy rate of Holando Argentino cows. However, the observed differences between dairy farms suggests that there is some other factors that modifies the effect of the reproductive management on the pregnancy rate.