PSI-7 Effects of sustained hyperprolactinemia in late gestation on mammary development of gilts

Abstract This project sought to determine the effects of sustained hyperprolactinemia on mammary development in late-pregnant gilts. Gilts were divided into 3 groups on day 90 of gestation to receive i.m. injections of: 1) canola oil (CTL, n = 18) until day 109 of gestation, 2) domperidone (dopamine receptor antagonist) until day 96 (T7, n = 17) or, 3) domperidone until day 109 (T20, n = 17). Treated gilts also received domperidone orally from days 90 to 93. Blood was sampled on days 97 and 110 for prolactin and IGF-1 assays. Mammary glands were collected at necropsy on day 110 for compositional and cell proliferation analyses. The MIXED procedure of SAS was used for statistical analyses. On day 97 of gestation, prolactin concentrations were greater for T20 and T7 than CTL gilts (19.0, 18.9 and 6.0 ± 1.6 ng/mL, respectively, P < 0.001), and were also greater for T20 than T7 and CTL gilts on day 110 (21.7, 8.9 and 10.0 ± 1.5 ng/mL, respectively, P < 0.001). Concentrations of IGF-1 were greater for T7 and T20 than CTL gilts on day 97, and were greater for T20 vs T7 and CTL gilts on day 110 (P < 0.05). There were no effects of treatment (P > 0.1) on parenchymal or extraparenchymal tissue weights, or on cellular proliferation by immunohistochemistry for Ki67. Treatments did not alter concentrations of DM, fat or DNA (P > 0.1) in parenchyma, while concentrations of protein (P < 0.01) and RNA (P < 0.05) as well as total protein, RNA and DNA in parenchyma (P < 0.05) were lower in T20 than T7 or CTL gilts. Increasing prolactin concentrations for 7 or 20 d in late gestation had no beneficial effects on mammary composition, where sustained exposure for 20 d reduced metabolic activity.