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FEED RESTRICTION AND INSULIN TREATMENT DIFFERENTIALLY AFFECT OVIDUCTAL PLASMA STEROIDS AND OVIDUCT PROTEINS IN PIGS.
Foxcroft, George1, Novak, Susan 1, Treacy, Brian1, Almeida, Fernanda1, Mao, Jiude 1, Dixon, Walter 1, 1
ABSTRACT- This experiment was conducted to determine if previous feed restriction and insulin treatment affect the oviductal environment as one mechanism mediating nutritional effects on embryonic survival. In a major collaborative study, littermate trios of cyclic gilts were moderately feed restricted during the first (RH) or second (HR) week of the estrous cycle, with (HR+I) or without (HR) concomitant exogenous insulin treatment. At 12 to 24 h after ovulation, peripheral and oviductal plasma, oviduct flushings and oviduct tissue was harvested under general anesthesia. Plasma estradiol, progesterone, and plasma and oviduct flushing concentrations of insulin-like growth factor (IGF)-I were determined using RIA procedures. Porcine oviductal secretory protein (POSP) mRNA abundance in oviduct tissue, and POSP protein abundance in oviduct flushings were determined using Northern and Western blotting procedures with a cDNA probe and a polyclonal antibody specific for POSP (both obtained from Dr. WC Buhi, University of Florida). Feed restriction during the second week, but not the first week, resulted in a lower E:P ratio and lower estradiol concentrations in oviductal plasma, and reduced total protein concentrations, IGF-I concentration, and POSP abundance and concentration in oviduct flushings. Feed restriction during the second week (HR) also lowered POSP mRNA abundance, and resulted in slower degradation of POSP mRNA with time after ovulation compared to the RH treatment. Insulin treatment differentially affected the oviduct environment by lowering POSP abundance over feed restricted groups. Therefore, previous feed restriction and insulin treatment affect the oviduct environment and may contribute to nutritional effects on embryonic survival.
KEY WORDS: pig, oviduct proteins, nutrition, ovarian steroids