EFFECT OF RECOMBINANT PORCINE SOMATOTROPIN AND MONOCLONAL-ANTIBODY DIRECTED TO OVINE SOMATOTROPIC HORMONE ON NITROGEN-RETENTION AND IMMUNE PARAMETERS IN PIGS

Single and combined effects of administration and withdrawal of recombinant porcine somatotropin (rpST) and an enhancing murine anti-ovine growth hormone monoclonal antibody (OA15) on nitrogen retention, and serological and immunological measurements in Pigs were examined in a placebo-controlled experiment. Thirty-six barrows were allotted to one of four treatments: control, rpST, OA15, and OA15+rpST. The trial phase was four balance periods: a preperiod, two periods of treatment, and a postperiod. Weight- and nitrogen gain were higher for the rpST group by 13% (P < .01) and 15% (P < .001), for the OA15 group by 8% (P < .05) and 9% (P < .05), and for the OA15+rpST group by 25% (P < .001) and 20% (P < .001), respectively compared with the control group. During the postperiod, weight gain of the OA15- and the OA15+rpST group was 23% (P < .001) and 22% (P < .001) lower than that of the control group. Nitrogen gain during the postperiod was decreased by 19% (P < .01) for the OA15 group compared with the control group. Single or combined administration of rpST or OA15 did not affect (P > .10) cellular constituents in the blood of all groups during the periods of observation. Animals treated solely with rpST mounted a humoral immune response directed to rpST. This anti-rpST antibody response was, however, decreased (P < .01) in barrows treated with rpST and OA15 simultaneously. Also, a slight anti-rpST antibody response was noticed in barrows solely treated with OA15. Barrows treated with OA15 mounted an anti-mouse immunoglobulin antibody response that correlated with a decrease (P < .001) in gain in the second period of treatment. These titers were lower than those found in pigs treated with a non-relevant mouse immunoglobulin of similar isotype as OA15. The OA15 mimicked effects of rpST. This may have implications for application in pig industry.