Vanimisetti H B, Greiner S P, Zajac A M, Notter D R
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
J Anim Sci. 2004 Feb;82(2):595-604. doi: 10.2527/2004.822595x.
This study was designed to evaluate breed differences in resistance to Haemonchus contortus in lambs. A total of 181 ewe lambs representing crossbred Dorsets (DO) and Dorpers (DP; out of 1/2-Dorset, 1/4-Rambouillet, 1/4-Finnsheep ewes) and straight-bred Katahdins (KT) were evaluated over 3 yr. An additional 144 DO, DP, KT, and Barbados Blackbelly x St. Croix (HH) wethers were evaluated over 2 yr. Lambs were weaned at 60 to 90 d of age. After deworming at about 4 mo of age, ewe lambs received approximately 10,000 infective larvae and were evaluated for parasite resistance in drylot, whereas wethers were evaluated on pasture under conditions of natural infection. Each sex was analyzed separately. Egg counts per gram of feces (FEC), log-transformed FEC (LFEC), packed cell volumes (%), and body weights (kg) measured at 3, 4, 5, and 6 wk after deworming and reinfection were analyzed. Breed influenced all traits (P < 0.05) except BW in ewe lambs and PCV in wethers. Year and week influenced (P < 0.05) all traits. At most times, DP had the highest FEC, DO had the lowest PCV, and KT and HH had lower FEC and higher PCV than either DO or DP. Clearly, Dorper sheep were not more resistant to parasites than DO, but they were able to cope with infection better by maintaining similar or higher (P < 0.05) PCV and similar BW. Katahdin and HH were more resistant, with lower FEC (P < 0.05) than DO or DP. Breed differences were more apparent when infection levels were higher; DO and DP were less affected when infection levels were low and when animals were on a better plane of nutrition. Caribbean hair sheep originated in hot, humid regions of West Africa. They and the derivative Katahdin breed seem relatively resistant to parasitism. The Dorper, in contrast, was developed in more arid regions and exhibited little parasite resistance.
本研究旨在评估羔羊对捻转血矛线虫抗性的品种差异。在3年的时间里，对总共181只代表杂交多塞特羊（DO）和杜泊羊（DP；来自1/2多塞特、1/4兰布耶、1/4芬兰羊的母羊）以及纯种卡他丁羊（KT）的母羊羔羊进行了评估。在另外2年的时间里，对另外144只DO、DP、KT以及巴巴多斯黑腹羊×圣克罗伊羊（HH）的阉羊进行了评估。羔羊在60至90日龄时断奶。在大约4月龄驱虫后，母羊羔羊接种约10,000条感染性幼虫，并在干燥圈舍中评估其对寄生虫的抗性，而阉羊则在自然感染条件下的牧场中进行评估。对每种性别分别进行分析。分析了驱虫和再感染后3、4、5和6周时每克粪便中的虫卵计数（FEC）、经对数转换的FEC（LFEC）、血细胞压积（%）和体重（kg）。品种对母羊羔羊的所有性状（除BW外）和阉羊的PCV有影响（P < 0.05）。年份和周数对所有性状有影响（P < 0.05）。在大多数时候，DP的FEC最高，DO的PCV最低，KT和HH的FEC低于DO或DP，PCV高于DO或DP。显然，杜泊羊对寄生虫的抗性并不比DO强，但它们能够通过维持相似或更高（P < 0.05）的PCV和相似的BW更好地应对感染。卡他丁羊和HH更具抗性，其FEC低于DO或DP（P < 0.05）。当感染水平较高时，品种差异更明显；当感染水平较低且动物营养状况较好时，DO和DP受影响较小。加勒比毛用羊起源于西非炎热潮湿的地区。它们以及衍生的卡他丁品种似乎对寄生虫感染相对具有抗性。相比之下，杜泊羊是在更干旱的地区培育出来的，对寄生虫几乎没有抗性。
