Immunization against somatotropin release inhibiting factor increases milk yield in ewes

Abstract

Immunization of cross-bred ewes against somatotropin release inhibiting factor significantly increased (P < 0.01) milk yields, relative to yields of similar non-immunized (control) ewes, without affecting milk composition. Feed intakes of immunized ewes tended (P> 0.10) to be lower than those of control ewes and the efficiency of utilization of feed for milk production and digestibility of dry matter were significantly increased (P<0.10) by immunization. No effects of immunization were measured for plasma hormones and metabolites. It appears that the increase in milk production in response to immunization was the result of an increase in the supply of nutrients for milk production caused by a modification of gut function.