No, just making sure he/she has a dry, draft-free place should be enough. December - lately - has been really mild if not down right warm. This past Christmas I had the AC on!!!
If it SHOULD turn cold early, I have a foal blanket that should fit.
Real nice bull ! In Cal. beef and sheep ranchers breed to drop calves, lambs in Nov. / Dec./ Jan. to take advantage of new grass groth that starts with the rainy season in late Nov. to mid "Feb. then the grasses mature to produce seeds and after that the grasses go dormant and the grasslands turn a golden brown. So much for grass fed year round ( unless one has irrigated pastures which translates to a very expensive water bill) then an expensive but very tough steak. Nothing tastes better than the advantage of grain + alfalfa fed beef in a feed lot for 90- 120 days.