47 Influence of Melatonin Supplementation in Pregnant Cattle Consuming Endophyte-Infected Tall Fescue Seed on Offspring Performance

Abstract The objective was to evaluate growth performance and estimates of body composition in offspring dams that consumed diets containing tall fescue seed with (E+) or without (E-) the toxic endophyte melatonin during mid-late gestation. Pregnant heifers (n = 57) artificially inseminated sex-sorted semen (X chromosome-bearing sperm) from a single Angus sire were administered dietary treatments 2 x factorial treatment arrangement (E- melatonin, E-/NM; E- E-/M; E+ E+/NM; E+/M; dose: 100 µg/kg BW) for 70-d period between May July starting at 160 ± 13 days gestation mimic ergot alkaloid concentrations grazing scenario. All contained corn gluten molasses fed using SmartFeed Pro (C-Lock Inc.) controlled feeding units 0900 1400 h daily. Cattle removed 39 19 before calving. Two replicates housed separately an open-air barn, each 1.2-ha paddock. following period, all cattle maintained as group free fescue. Calves weaned 226 d age. Gestation length, calf birth weight, 205-day adjusted weaning weight (205-d WW), carcass ultrasonography measures (ribeye area, REA; REA/CWT; percent intramuscular fat, IMF; rib fat thickness, UFAT; rump URUMP), post-weaning weights (recorded every 28 84 post-weaning), ADG (between post-weaning) evaluated 44). Post-weaning analyzed MIXED procedure SAS specific repeated time fixed effects replicate random. other variables effect random length covariate weight. 205-d WW, decreased (P < 0.04) relative Birth increased 0.02) receiving those WW REA calves born E+/NM E-/NM, E-/M, E+/M 0.03). tended be 0.06). UFAT 0.06) There no treatment, interaction > 0.10). To our knowledge, these preliminary results are first potential therapeutic recover losses pregnant consuming