This is not true. American cattle ARE allowed to cross the border into Canada, but they cannot return once they are in Canada. It is Canadian cattle currently who cannot cross the border into the USA. Like you say, this may change in March for cattle under 30 months. Embryos, semen, and boxed beef under 30 months are allowed currently to cross in both directions. I am from Minnesota and we currently have an American born bull in Ontario, who cannot return until the re-opening of the border.