Effect of days postpartum on pregnancy rates in suckling cows with FTAI treatment

Abstract

This work aimed to evaluate the effect of days postpartum at the start of treatment for fixed-time artificial insemination (FTAI) on the pregnancy rate of Bos indicus or crossbreed suckling cows in a grazing system. For this study, 188 cows between 2.5 and 12 years old were used, between 30 and 100 days after calving at the start of the treatments. Animals were located in Upala, Costa Rica, during the last trimester of 2019. The cows were assigned to one of four treatment groups according to the days postpartum. Group 1 (30 to 45 postpartum days; n= 39), Group 2 (46 to 60 postpartum days; n= 40), Group 3 (61 to 75 postpartum days, n= 66), Group 4 (76 to 100 postpartum days; n= 43). Group 1 was subdivided into 3 subgroups of cows for further analysis: Group 1A (30 to 35 days postpartum; n= 11), Group (1B 36 to 40; n= 12), and Group 1C (41 to 45; n= 16). The overall pregnancy rate was 56.9% (107/188). No significant differences were found between the groups: 48.71% (19/39), 70.00% (28/40), 53.03% (35/66), and 58.13% (25/43) for groups 1, 2, 3, and 4, respectively (p= 0.22). The pregnancy percentage in subgroups 1A, 1B, and 1C was 45.45%, 50.00%, and 50.00%, respectively, with no significant differences (p= 0.79) between them. Neither were differences found in the other parameters evaluated, such as ovarian status (p= 0.63), the interaction between ovarian status and postpartum days (p= 0.52), and the effect of the bull (p= 0.42). In conclusion, there is no distinct in the pregnancy rate if hormonal treatment for FTAI starts between 30 and 100 days postpartum.