The Effect Of Immunization Against Inhibin On The Medium And Large Follicles In Dairy Heifers

Abstract

The study was conductes to investigate the effect of either immunization against recombinant ovine inhibin (r-oINH-a3) or stimulation with PMSG on the number of follicles available for aspiration in dairy heifers. Twenty four Friesian heifers were randomly allocated to 3 treatment groups; placebo (C, n=7), PMSG (P,750 IU per week during the 6 week experimental period; n=7) and inhibin immunization (I,250 ug 4 weeks prior to and 250 ug at the start of the experimental period; n=10). During the experimental period, the total number of follicles=2 mm was not affected by treatment (C=17.0, P=16.0, I=17.6, P>0.05) but the inhibin immunization increased the number of follicles between 5-9 mm (C=4.2,P=4.1, I= 7.1, P<0.001) and = 10 mm (C=1.1, P=1.4, I=4.4, P<0.001) which enable more follicles to be aspirated from the I heifers (C=7.9, P=7.4, I=12.6, P<0.001). As a result, there were fewer follicles 2-4 mm on the ovaries of I heifers (C=11.6, P=10,5, I=6.1, P<0.005). Immunization against inhibin increased the number of medium (5-9mm) and large (=10 mm) follicles through an increased rate of development of follicles =2 mm.