Effect of
sometribove (methionyl bovine
somatotropin) on
mastitis in 15 full lactation trials (914 cows) in Europe and the US and 70 short-term studies (2697 cows) in eight countries was investigated. In full lactation studies,
sometribove (500 mg/2 wk) was given for 252 d, commencing 60 d postpartum. Although herds varied considerably, incidence of clinical
mastitis within a herd was similar for cows receiving control and
sometribove treatments. Relative risk analyses indicated no treatment effect, and percentage of
mastitis during treatment was similar for control and
sometribove groups. A positive linear relationship existed between peak milk yield and
mastitis incidence (percentage of cows contracting
mastitis or cases per 100 cow days);
sometribove treatment did not alter this relationship. Increases in
mastitis related to milk yield increase from
sometribove or related to genetic selection were similar. When expressed per unit of milk,
mastitis incidence declined slightly as milk yield increased; this relationship was not altered by
sometribove. No effect on clinical
mastitis was observed in 70 commercial herds utilizing
sometribove for 84 d. However, effects were significant for stage of lactation and milk yield. Overall, studies represented a wide range of research and commercial situations demonstrating that
sometribove had no effect on incidence of clinical
mastitis during the lactation of treatment. Furthermore,
sometribove did not alter typical relationships between milk yield or herd factors and incidence of clinical
mastitis.