Effect of Passive Immunization Against Testosterone on Postpartum Ovarian Activity in Crossbred Native x Holstein Dairy Cows

Abstract

The objective of this study was to passively immunize against testosterone in crossbred Native x Holstein dairy cows on postpartum ovarian activity. Immunogen was prepared by conjugation between Testosterone-3(O-Carboxymethyl)Oxime and Human Serum Albumin (HSA) to be Testosterone-3-(O-Carboxymethyl)Oxime-HSA (T4-HSA). Experimental animals were derived from three groups. First, crossbred Native x New Zealand White rabbits were used for assessing immunogenicity of the conjugate before administrating to calves. Second, calves from Huay Hong Khrai Royal Development Study Center were employed for producing antibodies against testosterone for passively immunization in cows. Third, were crossbred Native x Holstein dairy cows within the same study center. T4-HSA, which was detected the abilty to stimulate antibody production in the rabbits radioimmunoassay (RIA) technique, was used for immunization to the calves. Positive plasma from the calves that showed antibody titer by RIA were collected for passively immunization to the cows. Experimental design was completely randomized design (CRD) with regiment: control and passively immunization against T4-HSA. The cows were immunized by subcutaneous injection of plasma from intact crossbred milking cows or from the calves which had positive anti-testosterone antibody.  The results of this study were that: the rabbits did react to the T4-HSA and showed ability to produce antibodies that were capable to bind with tritiated testosterone at activities of 1,000 to 3,000 cpm and the calves showed the percentage of binding to the tritiated testosterone at 20-62% throughout 10 weeks of experimental period whilst the control group made only 3-11%. Cows passively immunized by the calves’ antibodies performed normal reproductive cycle and all exhibited pregnancy. These study demonstrated that passively immunization against testosterone trend to improve reproductive performance of the crossbred dairy cows.