Underwood E J.Trace elements in human and animal nutrition 4th edi t[M].London:Academic Press Inc.,1977.429.
[2]
Spears J W.Organic trace minerals in ruminants nutrition[J]. An im Feed Sci Tech,1996,58:151-163.
[3]
Spears J W.Zinc methionine for ruminants:relative bioavailability of zinc in lambs and perfomance of growing heifers[J].J Anim Sci,1989,67:835-843.
[4]
McDowell L R.Trace element supplementation in Latin America and t h e potential for organic selenium[A].in “Biotechnology in the Feed Industry”,Proceedi ngs of Alltech''s 13th Annual Symposium[C].Nottingham:Nottingham University Press,1997.389-418