5Schwab C G, Bozak C K, Whitehouse N L, et al. Amino acid limita- tion and flow to duodenum at four stages of lactation. 1. Sequence of lysine and methionine limitation [ J ]. J Dairy Sci, 1992,75 ( 12 ) : 3486 - 3502.
6Pisulewski P M, Rulquin H, Peyraud J L, et al. Lactational and sys- temic responses of dairy cows to postruminal infusions of increasing a- mounts of methionine [ J ]. J Dairy Sci, 1996. 79 ( 10 ) : 1781 - 1791.
7Wittwer F G,Gallardo P,Reyes J,et al. Bulk milk urea concentrations and their and their relationship with cow fertility in grazing dairy herds in southern Chile[J]. Prev Vet Med,1999,38(2/3) : 159 -166.
8Rulquin H, Graulet B, Delaby L, et al. Effect of different forms of me- thionine on lactational performance of dairy cows [ J ]. J Dairy Sci, 2006,89( 11 ) : 4387 -4394.
9Patton R A. Effect of rumen - protected methionine on feed intake, milk production, true milk protein concentration, and true milk protein yield,and the factors that influence these effects: a meta- analysis [J]. J Dairy Sci,2010,93(5) : 2105 -2118.
10krdalan M, Rezayazdi K, Dehghan - Banadaky M. Investigation on he effect of supplementing rumen - protected forms of methionine nd choline on health situation and reproductive performance of Hol- tein dairy cows[J]. Pak J Biol Sci,2009,12(1) : 69 -73.
