Effects of recombinant ovine placental lactogen and recombinant ovine growth hormone on growth of lambs and milk production of ewes
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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. 2001 Elsevier Science B.V.