4Moran M J. Availability analysis: A guide to efficient energy use[M]. New Jersey: Prentice-Hall Inc, 1982.
5齐长明.奶牛疾病学[M].北京:中国农业科学技术出版社,2006.119.
6Yazwinski T A,Tucker C A. A Sampling of Factors Relative tothe Epidemiology of Gastrointestinal Nematode[J]. The Veter-inary Clinics of North America,2006,22(3) :501-527.
7Geurden T,Somers R,Thanh N T G,et al. Parasitic infectionsin dairy cattle around Hanoi,northern Vietnam[J], VeterinaryParasitology, 2008,153(3-4) :384-388.
