Niblett, Richard T.2021-05-272021-05-272021-05-12http://hdl.handle.net/10919/103530Nutritional feed additives are incorporated into rations to improve reproductive and growth performance in livestock. Dietary supplementation with OmniGen-AF® (OMN; Phibro Animal Health Corporation, Teaneck, NJ, USA) has been studied in dairy and beef cattle to date, but no research has been conducted in swine. This study evaluated the effects of feeding OMN and administration of P.G 600® (400 IU PMSG + 200 IU hCG; Merck Animal Health, Millsboro, DE, USA) on reproductive performance of crossbred gilts. Gilts were randomly assigned to one of four treatment groups: 1. a fortified corn and soybean-meal based control diet, 2. a control diet plus an i.m. injection of P.G. 600, 3. OMN (control diet plus 4 g per 100 kg BW/head/d), 4. OMN plus an i.m. injection of P.G. 600. Gilts were fed appropriate diets for approximately 40 d before breeding, and estrous cycles were synchronized using an orally active progestin (15 mg/d Matrix®; Merck Animal Health) for 14 d, and 24 h after withdrawal received either an injection of P.G. 600, or no P.G. 600. Gilts were bred by post-cervical AI using pooled Duroc semen (Swine Genetics International, Cambridge, IA). Reproductive tracts were harvested at approximately d 50 of gestation. P.G. 600 was effective in reducing the interval to estrus among gilts (P = 0.03), which is consistent with previous studies. P.G. 600 also increased average ovary weight (P = 0.04), and total corpora lutea (P < 0.01) (indicative of ovulation rate), but decreased fetus survival (P < 0.01). Fetus weights were less (P = 0.03) in OMN-supplemented gilts compared with controls. Pregnancy rate decreased after P.G. 600 treatment in OMN-fed gilts, but not in controls (OMN x P.G. 600, P < 0.01). In summary, gilts had typical responses to P.G. 600 and in general, the effects of P.G. 600 were not affected by dietary supplementation with OMN.application/pdfenAttribution-NonCommercial-NoDerivatives 4.0 InternationalMaster's projectreproductionimmunomodulatorfeed additive