LAUSR

In utero exposure to toxins can alter fetal development and postnatal performance. The objective of this study was to investigate the effects of in utero exposure of ergot alkaloids via endophyte-infected (EI) fescue diets during gestation on heifer growth, onset of puberty, ovarian characteristics and AI pregnancy rates. Pregnant Angus and SimAngus cows grazed either endophyte-free (EF) or EI pastures on d90-180 of gestation. Assessment of puberty of heifer (n = 40) via measurement of BW, BCS, reproductive tract scores (RTS), pelvic area (PA) and weekly blood sample for progesterone (P4) analysis started at 10 mo of age. At 14 mos of age, all heifers were synchronized using the CoSynch+7d CIDR protocol and inseminated to examine reproductive measurements, follicle mapping and AI pregnancy rate. Data were analyzed using a MIXED procedure of SAS and examined for effects of EI, sire, and age. Statistical significance was determined at P < 0.05 and a tendency at 0.05 < P < 0.10. In utero exposure to EI did not affect ADG, BW, or BCS (P > 0.05) however, there was a sire by treatment interaction for ADG during onset of puberty (P < 0.05). While EI did not affect PA or RTS (P > 0.05), sire significantly influenced RTS and PA (P < 0.05) thus impacting of onset of puberty. Based on P4 concentrations, only 55% of all heifers were cyclic by 14 months of age and there was a sire by treatment interaction for onset of puberty (P < 0.05). No differences were observes in AI pregnancy rate between heifer groups (EF 39.5±7; EI, 43.7±7; P >0.05). While EI did not affect follicle counts or luteal area (P > 0.05), sire significantly influenced the percentage of preselected (2-4mm) and selected (>9mm), but not transitional (5-8mm), ovarian follicles at breeding age (P < 0.05). While consumption of EI fescue during gestation impacts cow performance and onset of puberty in heifers, it has minimal effect on heifer growth and reproductive development and performance.