Abstract
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 25 months, that became pregnant more than three of five times at 60 months (n = 5), or (2) subfertile, i.e. failed to became pregnant during three inseminations at 25 months, that became pregnant at fewer than two of the five opportunities at 60 months (n = 6). Key results Fertile cows had greater concentrations of insuling-like growth factor 1 (IGF-1), leptin and adiponectin (P < 0.05), associated with differences in body composition. Insulin and progesterone concentrations were lower during the mid–late luteal phase (P < 0.05) in fertile than subfertile cows, with no impact on follicle dynamics. At dissection, healthy follicles from fertile cows tended (P < 0.1) to have more granulosa cells and higher concentrations of IGF-1 in the follicular fluid. Fertile cows had a lower (P < 0.05) endometrial IGF-1 mRNA expression, but tended to have increased (P < 0.1) progesterone and adiponectin 2 receptor expression on Day 7 of the oestrus cycle. 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.
Published Version
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