Oral administration of rumen-protected choline to ewes during the periconceptional period skews the sex ratio of lambs

Abstract: Feeding rumen-protected choline (RPC) to beef cows during the periconceptional period has been reported to alter embryonic development to reduce weaning weight of the resultant calves. Here, it was tested whether oral administration of RPC to ewes during the periconceptional period programs postnatal development of lambs. In a preliminary experiment, oral administration of 5 g RPC (representing 3 g choline chloride) tended to increase plasma concentrations of the choline metabolite trimethylamine N-oxide, but the treatment did not affect concentrations of any other metabolite, including choline itself. In a subsequent experiment, 183 ewes were treated with oral administration of RPC or a control capsule daily from day -1 to day 7 after anticipated breeding. Rumen-protected choline did not affect pregnancy or lambing rate, plasma concentrations of placenta-associated glycoproteins, or litter size but skewed the sex ratio toward females. Treatment with RPC did not affect lamb weight at birth or through weaning (∼83 days of age) or testis weight at castration (∼50 days of age). For a subset of lambs examined at an average age of 169 days, RPC increased body weight and cross-sectional area and depth of the longissimus thoracis muscle. In summary, maternal supplementation of RPC during the periconceptional period shifted the sex ratio toward females and increased post-weaning body weight and size of the longissimus thoracis muscle area of the resultant lambs. These data provide further evidence for environmental modification of sex ratio in mammals and illustrate the impact that specific nutrients early in development can have on postnatal phenotype. Lay summary: Modification of the mother's environment early in pregnancy has been reported to alter characteristics of the resultant offspring. Here, it was shown that feeding a form of the nutrient choline that escapes destruction in a ewe's stomach influenced the sex ratio of the lambs (increasing the fraction that were female) and increased the cross-sectional area of a major muscle in the lab. Results provide further evidence for environmental modification of sex ratio in mammals and illustrate the impact specific nutrients early in development can have on the characteristics of the offspring after birth.