Folicular dynamics, endocrine profiles and endometrial gene expression in fertile and subfertile cows.

Context Subfertility has a negative impact on the productivity of beef cow herds; thus, it is relevant to unravel the mechanisms. Aims To study follicular development, body composition, concentrations of progesterone and metabolic hormones and their gene expression in the endometrium during the oestrus cycle. Methods Fertile and subfertile Hereford cows were classified at 25 (n =84) and 60 (n =25) months old, as (1) fertile, pregnant at first insemination at 25months, that became pregnantmore than three of five times at 60months (n =5), or (2) subfertile, i.e. failed to became pregnant during three inseminations at 25months, that became pregnant at fewer than two of the five opportunities at 60months (n =6). Key results Fertile cows had greater concentrations of insuling-like growth factor 1 (IGF-1), leptin and adiponectin (P P P P P Conclusions Differences in progesterone and metabolic hormones in plasma and follicular fluid and their endometrial expression are associated with the success of pregnancy in beef cows. Implications Strategies to improve the follicle and endometrial microenvironments are needed to improve the productivity of beef herds.