Houdijk J G M, Jackson F, Coop R L, Kyriazakis I
Animal Nutrition and Health Department, Scottish Agricultural College, Kings Buildings, Edinburgh EH9 3JG, UK.
Int J Parasitol. 2006 Feb;36(2):219-27. doi: 10.1016/j.ijpara.2005.09.014. Epub 2005 Oct 25.
Protein supplementation can improve the resistance to parasites of periparturient ewes, as indicated by reduced nematode egg excretion and worm burdens. However, the rate at which this improvement can occur is largely unknown. We investigated the rate of improvement by assessing temporal changes in faecal egg counts after we experimentally reduced nutrient demand. Three groups of nine pregnant ewes each were trickle infected with Teladorsagia circumcincta from day(-70) to day(16) (parturition is day0). Two groups of twin-rearing ewes were fed at 0.8 (L22) or 1.2 (H22) times their assumed metabolizable protein requirements, and a third group was fed the same daily food allowances as L22 ewes, but one of their lambs was removed on day10 (L21). Ewes were slaughtered on day21 to assess worm burdens, in vitro larval establishment on abomasal explants, and mucosal inflammatory cells. Faecal egg counts of L22 ewes were higher than H22 ewes throughout lactation. After the removal of one lamb, faecal egg counts of L21 ewes decreased within 5 days to levels similar to H22 ewes. Relative to L22 ewes, L21 and H22 ewes had lower worm burdens, parasite per capita fecundity and in vitro establishment rates of both T. circumcincta and Haemonchus contortus. Mucosal mast cell and eosinophil counts were similar for all ewes, but H22 ewes had higher globule leukocyte counts than L22 and L21 ewes. The data suggest that a reduction in protein demand can rapidly improve periparturient immunity to T. circumcincta. This may be associated with increased parasite expulsion, reduced fecundity and non-parasite specific reduction of in vitro larval establishment.
蛋白质补充可以提高围产期母羊对寄生虫的抵抗力，这表现为线虫卵排泄量和虫负荷的降低。然而，这种改善能够发生的速度在很大程度上尚不清楚。我们通过在实验性降低营养需求后评估粪便虫卵计数的时间变化来研究改善的速度。三组，每组九只怀孕母羊，从第（-70）天到第16天（分娩为第0天）逐步感染环形泰勒虫。两组双胞胎饲养的母羊分别按其假定的可代谢蛋白质需求量的0.8倍（L22）或1.2倍（H22）进行饲喂，第三组母羊给予与L22母羊相同的每日食物量，但在第10天移除其中一只羔羊（L21）。在第21天宰杀母羊，以评估虫负荷、皱胃外植体上的体外幼虫发育情况以及黏膜炎症细胞。在整个哺乳期，L22母羊的粪便虫卵计数高于H22母羊。移除一只羔羊后，L21母羊的粪便虫卵计数在5天内降至与H22母羊相似的水平。相对于L22母羊，L21和H22母羊的虫负荷、人均寄生虫繁殖力以及环形泰勒虫和捻转血矛线虫的体外发育率较低。所有母羊的黏膜肥大细胞和嗜酸性粒细胞计数相似，但H22母羊的球形白细胞计数高于L22和L21母羊。数据表明，蛋白质需求的降低可迅速提高围产期对环形泰勒虫的免疫力。这可能与寄生虫排出增加、繁殖力降低以及体外幼虫发育的非寄生虫特异性降低有关。
