CLINICAL MASTITIS IN COWS TREATED WITH SOMETRIBOVE (RECOMBINANT BOVINE SOMATOTROPIN) AND ITS RELATIONSHIP TO MILK-YIELD

Effect of sometribove (methionyl bovine somatotropin) on mastitis in 1 5 full lactation trials (914 cows) in Europe and the US and 70 short-t erm studies (2697 cows) in eight countries was investigated. In full l actation studies, sometribove (500 mg/2 wk) was given for 252 d, comme ncing 60 d postpartum. Although herds varied considerably, incidence o f clinical mastitis within a herd was similar for cows receiving contr ol and sometribove treatments. Relative risk analyses indicated no tre atment effect, and percentage of mastitis during treatment was similar for control and sometribove groups. A positive linear relationship ex isted between peak milk yield and mastitis incidence (percentage of co ws contracting mastitis or cases per 100 cow days); sometribove treatm ent did not alter this relationship. Increases in mastitis related to milk yield increase from sometribove or related to genetic selection w ere similar. When expressed per unit of milk, mastitis incidence decli ned slightly as milk yield increased; this relationship was not altere d by sometribove. No effect on clinical mastitis was observed in 70 co mmercial herds utilizing sometribove for 84 d. However, effects were s ignificant for stage of lactation and milk yield. Overall, studies rep resented a wide range of research and commercial situations demonstrat ing that sometribove had no effect on incidence of clinical mastitis d uring the lactation of treatment. Furthermore, sometribove did not alt er typical relationships between milk yield or herd factors and incide nce of clinical mastitis.