RESUMEN
Choline is a vital micronutrient that can be utilized in the formation of betaine and multiple phospholipids. In this study, we aimed to confirm, and expand on previous findings, how choline impacts embryos from the first 7 days of development to affect postnatal phenotype. Bos indicus embryos were cultured in a choline-free medium (termed vehicle) or medium supplemented with 1.8 mM choline Blastocyst-stage embryos were transferred into crossbred recipients. Once born, calves were evaluated at birth, 94 d, 178 d and at weaning (average age = 239 d). Following weaning, all calves were enrolled into a feed efficiency trial before being separated by sex, with males being slaughtered at approximately 580 d of age and females followed until their first pregnancy check. Results confirm that exposure of 1.8 mM choline chloride during the first 7 d of development alters postnatal characteristics of the resultant calves. Calves of both sexes from choline-treated embryos were consistently heavier through weaning and males had heavier testes at 3 mo of age. There were sex-dependent alterations in DNA methylation in whole blood caused by choline treatment. After weaning, feed efficiency was affected by an interaction with sex, with choline calves being more efficient for females and less efficient for males. Calves from choline-treated embryos were heavier, or tended to be heavier, than calves from vehicle embryos at all observations after weaning. Carcass weight was heavier for choline calves and the cross-sectional area of the Longissumus thoracis muscle was increased by choline. Few females became pregnant during the experiment although numerically more choline females were pregnant than vehicle females. Results confirm that exposure of the preimplantation embryo to 1.8 mM choline can alter phenotypes of the resultant calves through the first 19 months after birth.
RESUMEN
Consumption of toxic endophyte-infected tall fescue results in poor reproductive performance in domestic livestock. In this study, the objective was to evaluate the effects of ergovaline exposure during mid-gestation (days 93 through 188 of gestation) on dam performance, the growing female fetus, and the subsequent growth and reproductive performance of the gestationally-exposed heifer calves. Pregnant Angus and Simmental-Angus cows were blocked by age (2 - 3, 4 - 7, and > 7 y), body weight (BW), and breed; and then randomly assigned to graze either novel (EN; <5% infection rate; n = 27 Year 1, n = 16 Year 2) or toxic endophyte-infected tall fescue (EI; 99% infection rate; n = 27 Year 1, n = 17 Year 2). Weekly BW, body condition scores (BCS), hair coat scores (HCS), hair shedding scores (HSS), and blood samples for progesterone (P4) analysis were collected from mid-April through July of 2017 (Year 1) and 2018 (Year 2). Gestation length, birth weight, placental characteristics, heifer calf growth, onset of puberty, ovarian characteristics, and artificial insemination (AI) pregnancy rates were measured. Data were analyzed using the MIXED procedure of SAS. Cows grazing EI pastures had reduced ADG, reduced BCS, greater HSS, and decreased P4 concentrations compared to cows on EN pasture (P < 0.01). Birth weights were decreased for heifers whose dams were exposed to EI pastures during their second trimester (P < 0.01). Heifer pregnancy rates were not impacted by EI pasture exposure during gestation for either year of the study. However, a treatment by year effect was seen for pregnancy rate for EI exposed heifers in Year 2; EI exposed heifers in Year 2 had increased pregnancy rates at two of the inseminations. Combined, these data reinforce that consumption of toxic endophyte-infected tall fescue during gestation can negatively impact both dam and offspring performance. More studies are needed to evaluate more parameters in an effort to elucidate the possible life-long impacts of ergovaline exposure during gestation.