Associations among body condition score, body weight, somatic cell count, and clinical mastitis in seasonally calving dairy cattle.

The objective of this study was to determine if an association existed among body condition score (BCS), body weight (BW), and udder health, as indicated by somatic cell score (SCS) and cases of clinical mastitis (CM). The data consisted of 2,635 lactations from Holstein-Friesian (n = 523) and Jersey (n = 374) cows in a seasonal calving pasture-based research herd between the years 1986 and 2000, inclusive. Increased BCS at calving was associated with reduced SCS in first- and second-parity cows, and greater SCS in cows of third parity or greater. This relationship persisted for most BCS traits throughout lactation. Body weight was positively associated with SCS, although the effect was greater in Jersey cows than in Holstein-Friesians. Increased BCS and BW loss in early lactation were associated with lower SCS and a reduced probability of a high test-day SCC. Body condition score was not significantly related to CM with the exception of a curvilinear relationship between the daily rate of BCS change to nadir and CM in early lactation. Several BW variables were positively associated with a greater likelihood of CM. Nevertheless, most associations with udder health lacked biological significance within the ranges of BCS and BW generally observed on-farm. Results are important in assuring the public that modern dairy systems, where cows are subjected to substantial amounts of BCS mobilization in early lactation, do not unduly compromise cow udder health.