Gestation Rate in Beef Cows with Different Calving Orders Submitted to FTAI Protocol: Effects of Body Condition, Number of Progesterone Intravaginal Device Uses and Bull

The search for better reproductive rates in beef cattle breeding must consider some important issues, such as nutrition, health, animal category, type of reproductive technique, and selection of animals. Thus, the objective of this study was to evaluate the effect of the body condition score (BCS), the number of uses of the intravaginal progesterone device and the effect of the bull on the gestation rate of lactating beef cows, with different calving orders, submitted to a fixed timed artificial insemination (FTAI) protocol. In the study, 623 Aberdeen Angus cows were used, which were categorized into three groups according to the calving order- primiparous cows, second-parity cows, and multiparous cows. On day zero of the FTAI protocol, an evaluation of the BCS of the cows was performed, using progesterone intravaginal devices (IVD) for 9 days, starting from the D0 of the protocol both for used and new IVD. Semen from three different Aberdeen Angus breeders was used. Statistical analysis was made in the NCSS 7.0 software, using the Chi-square test and a significance value of p<0.05. The calving order influenced the pregnancy rate, with the category of primiparous cows having the lowest rates (p<0.05). The BCS and the number of uses of the IVD showed significance only in the primiparous category, in which animals with BCS equal or above 3.5 obtained a higher pregnancy rate, as well as animals with second-use IVD when compared to other groups (p <0.05). Therefore, primiparous cows presented a lower pregnancy rate when compared to the other categories, as well as the BCS and the number of uses of the IVD.