IMMUNIZATION OF LAMBS AGAINST SOMATOSTATIN TO IMPROVE GROWTH RATE

Abstract

Weight gain, shoulder height and feed intake responses to immunization against somatostatin (SRIF) were examined in three experiments with a total of 78 lambs. Initial immunizations against SRIF occurred when lambs were 4, 8 and 3 wk old for exps. 1, 2 and 3, respectively, with booster immunizations 2, 4, 6, 8 and 10 wk later. Control lambs were left untreated except in exp. 3 where one group of control lambs was immunized with human serum alpha globulin. Treated lambs were immunized with SRIF conjugated to human serum alpha globulin. Experiments were terminated when lambs reached 45 kg body weight. SRIF immunization did not alter lamb shoulder height or feed conversion efficiency. Rate of gain of ram and wether lambs, but not ewe lambs, was improved by SRIF immunization. Wether lambs in exp. 1 and ram lambs in exp. 2 gained 21 and 15% more, respectively, than their controls by 20 wk of age. In exp. 3, SRIF-treated 3/4 Romanov ram lambs gained 13% more than their controls by 19 wk of age. However, SRIF-treated 7/8 Romanov lambs gained only 3% more than controls during this time. In conclusion, immunizing wether and ram crossbred lambs against somatostatin increased their growth rates sufficiently to reduce the time needed to reach market weight by 2–3 wk. However, feed conversion efficiency was not improved by somatostatin immunization. Key words: Somatostatin, SRIF, immunization, growth rate, lambs