Amarante A F, Craig T M, Ramsey W S, Davis S K, Bazer F W
Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77843, USA.
Vet Parasitol. 1999 Jan 28;80(4):311-24. doi: 10.1016/s0304-4017(98)00229-5.
This experiment was carried out to compare the worm burden and cellular responses in the abomasal mucosa and blood of Florida Native and Rambouillet lambs and also in animals produced by crosses of these two breeds (generations F1 and F2). Animals were exposed to infection by gastrointestinal nematodes on three different occasions. The first infection was natural, occurring while they were suckling lambs. After weaning, they were kept indoors for 53 days and then were allowed to graze a contaminated pasture for 50 days for a second natural infection. The third infection was an artificial challenge with 6000 Haemonchus contortus infective larvae. The highest mean fecal egg counts (FEC) values were found in Rambouillet lambs followed in decreasing order by F1, F2 and Florida Native lambs. Throughout the trial, most of the high mean packed cell volumes and plasma protein levels were recorded in the F2 lambs; in contrast, most of the low values were found in the Rambouillet lambs. During the natural infection period, the highest percentages of larvae in the fecal cultures of the lambs were Haemonchus. However, high percentages of Trichostrongylus larvae were found particularly in Florida Native lambs. The mean number of blood eosinophils increased after the artificial challenge, reached a peak 21 days after infection and then declined. The highest and lowest blood eosinophil means were recorded in F2 and Florida Native lambs, respectively. The H. contortus burden was significantly higher in Rambouillet and in F1 lambs than in Florida Native and F2 lambs (p < 0.05), while no significant differences were recorded among eosinophil, mast cell and globule leucocyte counts in the abomasal mucosa (p > 0.05). The highest correlation coefficient recorded at the end of this study was between FEC and worm burden (r = 0.7). These two parameters showed a moderate negative correlation with PCV, plasma protein and mast cell counts in the abomasal mucosa. The results obtained in this study indicate that crossbreeding Florida Native and Rambouillet sheep can be a rapid way to combine and improve the characteristics of these two breeds. The parasitological results were promising, however, more studies will be necessary to verify the impact of crossbreeding in other traits.
本实验旨在比较佛罗里达本地羔羊和兰布列羔羊皱胃黏膜及血液中的蠕虫负荷和细胞反应，以及这两个品种杂交产生的动物（F1代和F2代）的相应情况。动物在三种不同情况下暴露于胃肠道线虫感染。第一次感染是自然感染，发生在它们作为哺乳羔羊时。断奶后，它们在室内饲养53天，然后被允许在受污染的牧场放牧50天进行第二次自然感染。第三次感染是用6000条捻转血矛线虫感染性幼虫进行人工攻毒。兰布列羔羊的平均粪蛋计数（FEC）值最高，其次按降序排列为F1代、F2代和佛罗里达本地羔羊。在整个试验过程中，F2代羔羊记录到的平均红细胞压积和血浆蛋白水平大多较高；相反，兰布列羔羊中大多记录到较低值。在自然感染期，羔羊粪便培养物中幼虫比例最高的是血矛线虫。然而，特别是在佛罗里达本地羔羊中发现了高比例的毛圆线虫幼虫。人工攻毒后血液嗜酸性粒细胞的平均数量增加，在感染后21天达到峰值，然后下降。血液嗜酸性粒细胞平均值最高和最低的分别是F2代和佛罗里达本地羔羊。兰布列和F1代羔羊的捻转血矛线虫负荷显著高于佛罗里达本地和F2代羔羊（p < 0.05），而皱胃黏膜中嗜酸性粒细胞、肥大细胞和球样白细胞计数之间无显著差异（p > 0.05）。本研究结束时记录到的最高相关系数是FEC与蠕虫负荷之间的（r = 0.7）。这两个参数与皱胃黏膜中的红细胞压积、血浆蛋白和肥大细胞计数呈中度负相关。本研究获得的结果表明，佛罗里达本地羊与兰布列羊杂交可能是一种快速结合并改善这两个品种特性的方法。寄生虫学结果很有前景，然而，还需要更多研究来验证杂交对其他性状的影响。
