The effects of a sustained-release recombinant bovine somatotropin (somidobove) on udder health for a full lactation.

The lactational effect of somidobove (recombinant bST) injections on dairy cows in a full lactation was measured in 193 primiparous and 159 multiparous Holsteins. Experimental animals, distributed across six study sites, were administered a sustained-release formulation of somidobove by subcutaneous injection every 28 d beginning 36 to 49 DIM. Randomization at each site determined which of the following somidobove treatments cows received: 0 mg (control), 160 mg (primiparous only), 320 mg, 640 mg, or 960 mg (multiparous only). In addition to lactation response, cows on study were monitored for mastitis. Clinical mastitis was detected by examination of quarter foremilk at each milking. Milk from 300 of 352 cows was monitored for new IMI by routine collection and culture of duplicate quarter milk samples. Somatic cell counts were conducted on individual composite milk samples collected weekly throughout the experiment. No evidence existed of an association between somidobove administration and the incidence or duration of clinical mastitis. Furthermore, somidobove administration was not associated with an increase in new IMI or prevalence of infection by common mastitis pathogens or pathogen groups. Somatic cell counts were low in all treatment groups, but a dose-related trend was found for increased SCC in both primiparous and multiparous cows.