Autoria: TOMAZI FILHO, J.; PFEIFER, L. F. M.; HOEFLE, C. A.; RODRIGUES, M. F.; FERREIRA, R.

Resumo: The objectives of this study were to determine the effect of calving to timed artificial insemination (C-TAI) interval on fertility of Bos taurus and Bos indicus cows and to determine the best C-TAI interval to include postpartum cows in TAI programs in each genotype (B. taurus and B. indicus). In experiment 1, a retrospective study was per-formed, with data from 2,709 TAI in Bos taurus and Bos indicus cows with different C- TAI intervals. There was a positive linear effect of C-TAI interval on the pregnancy probability (p< .0001). However, there was no effect or interaction with the geno-type. When C-TAI intervals were grouped in classes, pregnancy rate differed in groups (p< .05). Receiver operating characteristic (ROC) analysis was performed, and it was observed that 52 days would be the better C-TAI interval to maximize fertility in beef cows. According to the previous result, we further stratified into two C-TAI interval groups (≤ 52 days or > 52 days). Cows with C-TAI longer than 52 days (C-TAI > 52) had greater pregnancy rate (56%) than cows with short C-TAI (46%; p< .01). In experi-ment 2, 18 postpartum beef cows were subjected to TAI protocol at different C-TAI intervals (n= 6 cows per group): 40, 60 or 80 days postpartum. Cows with 60 days of C- TAI had a greater preovulatory follicle diameter than cows with 80 days postpartum (p< .05). The C-TAI interval did not affect (p> .05) the ovulation rate nor the propor-tion of endometrial polymorphonuclear leucocytes. We conclude that C-TAI interval affects pregnancy rate in both Bos taurus and Bos indicus. We recommend a C-TAI in-terval longer than 52 days to increase fertility of beef cows included in TAI programs.

Ano de publicação: 2022

Tipo de publicação: Artigo de periódico

Unidade: Embrapa Rondônia

Palavras-chave: Endometrial cytology, Pregnancy rate, Reproductive efficiency