摘要Background Supplementation of choline chloride in culture medium programs the preimplantation bovine embryo to increase weaning weight of the resultant calf.Here,it was hypothesized that similar programming actions of cho-line can be induced by feeding rumen-protected choline(RPC)to beef cows during the periconceptional period.Results A preliminary experiment was conducted to determine changes in circulating concentrations of choline and its metabolites after RPC supplementation.Suckled beef cows were individually fed 0,30,60,and 90 g of RPC(i.e.,0,8.6,17.3 and 25.9 g choline chloride)and blood samples were collected at random times after feeding.There were no differences in plasma concentrations of choline or its metabolites between groups.In the second experiment,effects of feeding 60 g/d RPC from d-1 to 7 relative to timed artificial insemination were examined for suckled beef cows.Feeding RPC did not affect pregnancy or calving rates,pregnancy losses,plasma concentrations of pregnancy-associated glycoproteins,gestation length or calf birth weight.Calves from RPC fed dams were lighter than control calves at～118 days of age(range 75-150;age included in the statistical model)and at weaning at～248 days of age.There was no effect of treatment on hip height at～118 days of age although there was a trend for RPC calves to be shorter at weaning.Weight/height ratio was lower for RPC than control at both 118 and 248 days of age.Treatment did not affect testis weight at～118 days of age.Conclusions Supplementation of RPC during the periconceptional period programmed development to alter calf phenotype in the postnatal period.The net result,reduced body weight,was the opposite of the phenotype caused by the addition of choline to embryo culture medium.