Influence of somatotropin and nutrition on bovine oocyte retrieval and in vitro development

The objective of this study was to determine the effects of supplemental bo vine somatotropin (bST) and limit feeding on follicular growth and oocyte c ompetence in yearling beef heifers. Sixteen growing heifers (424 +/- 4 kg) were randomly assigned to 1 of 4 treatments in a 2 x 2 factorial arrangemen t, with main effects of bST (0 or 33 mu g/kg BW/d) and feeding regimen (ad libitum or 0.75 ad libitum intake). Animals were treated for 100 d prior to follicular aspiration, and treatments continued for the 42-d period that f ollicles were aspirated. Follicles were observed ultrasonically then aspira ted, and recovered oocytes were matured, fertilized and developed in vitro. The number of follicles observed ultrasonically was greater with bST treat ment (P<0.01) but was unchanged by plane of nutrition. The number and duali ty of recovered oocytes were similar among treatments, as was the number of oocytes resulting in blastocyst formation. (C) 2000 by Elsevier Science In c.