Houdijk J G M, Kyriazakis I, Jackson F, Huntley J F, Coop R L
Animal Nutrition and Health Department, Scottish Agricultural College, Kings Buildings, EH9 3JG, Edinburgh, UK.
Int J Parasitol. 2003 Mar;33(3):327-38. doi: 10.1016/s0020-7519(02)00284-9.
It has been suggested that the periparturient breakdown of immunity to parasites has a nutritional basis. Our overall hypothesis is that it results from a prioritised scarce nutrient allocation to reproductive functions (e.g. milk production) rather than to immune functions. We tested this hypothesis by offering five levels of dietary metabolisable protein, ranging from 0.65 to 1.25 times their assumed requirements, for 4 weeks post-parturition to twin-rearing Greyface ewes, experimentally infected with Teladorsagia circumcincta. We hypothesised that the initial increments of metabolisable protein supply would increase milk production without affecting the degree of breakdown of immunity whilst later increments would reduce the degree of breakdown of immunity. The first two increments of metabolisable protein supply indeed increased milk production and did not affect final worm burdens, but in contrast to the expectation, reduced faecal egg counts and total egg output. The last two increments of metabolisable protein supply did not further affect milk production and egg output, but resulted in reduced final worm burdens. Metabolisable protein supply did not affect plasma IgG and IgE antibody against somatic L(3) antigen but the first three increments reduced plasma pepsinogen and plasma IgA antibody. The last increment did not further reduce plasma pepsinogen but increased plasma IgA. Metabolisable protein supply did not systematically affect abomasal mucosal mast cell, globule leukocyte and eosinophil counts. Our results support the view that the priority of scarce metabolisable protein allocation to milk production over immune functions may be gradual rather than absolute. The contrast between effects of metabolisable protein supply on faecal egg count and final worm burden points towards the possibility that if different effector responses regulate fecundity and worm expulsion, then they would differ in their sensitivity towards changes in the degree of nutrient scarcity.
有人提出，围产期对寄生虫免疫力的下降有营养方面的基础。我们的总体假设是，这是由于优先将稀缺营养素分配给生殖功能（如产奶）而非免疫功能所致。我们通过在产后4周为双羔饲养的灰脸母羊提供五种水平的日粮可代谢蛋白来检验这一假设，这些水平从其假定需求量的0.65倍到1.25倍不等，这些母羊经实验感染了环形泰勒虫。我们假设，可代谢蛋白供应的最初增加会增加产奶量而不影响免疫下降程度，而随后的增加会降低免疫下降程度。可代谢蛋白供应的前两次增加确实增加了产奶量且未影响最终虫负荷，但与预期相反，降低了粪蛋计数和总产蛋量。可代谢蛋白供应的最后两次增加未进一步影响产奶量和产蛋量，但导致最终虫负荷降低。可代谢蛋白供应未影响针对体细胞L(3)抗原的血浆IgG和IgE抗体，但前三次增加降低了血浆胃蛋白酶原和血浆IgA抗体。最后一次增加未进一步降低血浆胃蛋白酶原，但增加了血浆IgA。可代谢蛋白供应未系统性地影响皱胃黏膜肥大细胞、球形白细胞和嗜酸性粒细胞计数。我们的结果支持这样一种观点，即可代谢蛋白分配优先用于产奶而非免疫功能可能是渐进的而非绝对的。可代谢蛋白供应对粪蛋计数和最终虫负荷的影响之间的差异表明，如果不同的效应反应调节繁殖力和驱虫作用，那么它们对营养稀缺程度变化的敏感性可能会有所不同。
