Effects of recombinant ovine placental lactogen and recombinant ovine growth hormone on growth of lambs and milk production of ewes

Abstract

The somatogenic and galactopoietic effects of recombinant ovine placental lactogen (oPL) were compared with the effects of recombinant ovine growth hormone (oGH) in post-weaned growing lambs and in lactating ewes. In two experiments that each lasted 35 days, 2-month-old lambs were given daily subcutaneous injections (0.1 mg/kg live weight) of oPL or oGH, and their daily growth rates were compared with those of non-treated control lambs. Ovine GH and oPL had similar profound ( P<0.01) growth-stimulating effects, enhancing lamb growth by 10 to 25%. In two other experiments, lactating ewes were injected with oGH or oPL (0.1 mg/kg live weight/day) for 14 days in mid-lactation. Treatment with oGH increased ( P<0.001) daily milk production by up to 55% over control ewes. Ovine PL increased ( P<0.01) milk production by up to 25%. In all experiments, treatment of lambs or lactating ewes with oGH, but not with oPL increased ( P<0.05) serum insulin-like growth factor-I concentrations. It is concluded that oPL and oGH have similar somatogenic effects in lambs. Both hormones exhibited galactopoietic effects, but oGH was considerably more potent than oPL.