Influence of Subclinical Mastitis During Early Lactation on Reproductive Parameters

Our objective was to determine the effects of mastitis during early lactation on the reproductive performance of Jersey cows. From 1986 to 1997, quarter foremilk samples were collected every 4 to 8 wk during lactation, at drying off, near calving, and when clinical mastitis was diagnosed and were evaluated microbiologically to identify causative bacteria. Services per conception, days open, and days to first service were obtained from DHIA records on 752 cows. Cows were separated by mastitis type (clinical, n=186; subclinical, n=240; control, uninfected or infected after confirmed pregnancy, n=326). Cows were reclassified based on the time of clinical or subclinical mastitis as follows: period 1, before first service (n=374); period 2, between first service and pregnancy (n=52); and period 3, after confirmed pregnancy or uninfected (control; n=326). Milk production did not differ for any group separations. Reproductive performance did not differ between gram-negative or gram-positive mastitis pathogens. Cows with clinical or subclinical mastitis before first service had increased days to first service (77.3±2.7 and 74.8±2.7 d), days open (110.0±6.9 and 107.7±6.9 d), and services per conception (2.1±0.2 and 2.1±0.2) compared with controls (67.8±2.2 d, 85.4±5.8 d, 1.6±0.2; P