Previous University of Tennessee research showed that cows with clinical mastitis during early lactation exhibited a prolonged period until first service than cows with no clinical mastitis. Additionally, an increased number of days open and services per conception were observed in cows displaying clinical mastitis between first service and establishment of pregnancy compared to cows not experiencing clinical mastitis or cows with clinical mastitis either before first service or after pregnancy was confirmed.

Continuing research at the University of Tennessee is looking at the mechanisms by which mastitis influences reproductive performance. A recent study, reported at this year's NMC annual meeting, evaluated the effects of experimentally–induced clinical mastitis on release of luteinizing hormone (LH) and prostaglandins (PGFM) during early lactation. Results suggest that experimentally-induced clinical mastitis during early lactation may impair reproductive processes due to LH suppression. Suppression of LH may interfere with several reproductive mechanisms including follicular development and ovulation, thus delaying the postpartum interval. This is consistent with other research which showed that cows that experienced clinical mastitis prior to first service had an extended number of days to first service.

Source: National Mastitis Council 1998 Annual Meeting Proceedings, p. 334