5[8]Butler W R,Everett R W.Coppock C E.The relationships between energy balance,milk production and ovulation postapartum Hostein cows[J].J Anim Sci,1981,53:742-748.
6[9]Butler W R,Smith R D.Interrelationships between energy balance and postpartum reproductive function in dairy cattle[J].J Dairy Sci,1989,72:767-783.
7[10]Staples CR,Thatcher W W,Clark J H.Relationship between ovarian activity and energy status during the early postpartum period of high producing dairy cows[J].J Dairy Sci.1990.73:938-947.
8[11]Lucy M C,Staples C R,Thatcher W W,et al.Influence of diet composition,dry matter intake,milk production and energy balance on time of postpartum ovulation and fertility in dairy cows[J].Anim Prod,1992.54:323-331.
9[12]Thatcher W W,Wilcox C J.Postpartum estrus as an indicator of reproductive status in the dairy cow[J].J Dairy Sci.1973.56:608-610.
