The effect of peripartum administration of ovine prolactin on
lactogenesis in autumn-lambing ewes.
S.W. Peterson, D.D.S. Mackenzie, S.N. McCutcheon, K.R. Lapwood
Department of Animal Science, Massey University, Palmerston North,
New Zealand.
Proceedings of the New Zealand Society of Animal Production 1994,
54: 115-118
Two routes of oPRL supplementation were used to elevate peripheral or
local concentrations of PRL in autumn-lambing ewes which, based on previous
results, were expected to have low plasma PRL concentrations and milk yields
relative to spring-lambing ewes. Administration of 10 mg oPRL directly into
the gland or subcutaneous injection of 0.5 mg/kg oPRL did not increase the
milk yields, or change the composition of milk, compared to controls. These
results suggest that the circulating and intramammary concentrations of PRL in
autumn-lambing ewes are not limiting lactogenesis. However, because the
plasma prolactin concentration in the ewes was unexpectedly high, it was not
possible to reach firm conclusions regarding possible effects of supplementary
oPRL in ewes with naturally low plasma PRL concentrations. Nevertheless,
the results indicate that raising the intramammary concentration of PRL around
the time of parturition, in ewes with circulating PRL concentrations
characteristic of normal spring-lambing ewes, does not enhance lactogenesis.
Keywords: NZSAPAB;
Ovine prolactin; intramammary; lactation; autumn-lambing ewes.
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