Dose-response of injected recombinant porcine prolactin on concentrations of prolactin in lactating sows

Blood profiles of prolactin (PRL) were obtained in sows after receiving a s.c. injection of 0 mg (n = 7), 5 mg (n = 10), or 15 mg (n = 9) of recombinant porcine prolactin (pPRL) on days 6 and 20 of lactation. The 15-mg dose of pPRL increased PRL concentrations (P less than or equal to 0.01) from 15 min to 11 h post-injection at both 6 and 20 d of lactation, whereas a sustained increase in PRL (P less than or equal to 0.05) following the S-mg dose was seen on day 20 only, and lasted from 1 to 7 h post-injection. The results demonstrate that stage of lactation, as well as dose and time since PRL injection affect the PRL response of lactating sows to exogenous pPRL.