Houdijk Jos G M, Jackson Frank, Kyriazakis Ilias
Animal Nutrition and Health Department, SAC, Edinburgh EH9 3JG, UK.
Vet Parasitol. 2009 Mar 23;160(3-4):258-66. doi: 10.1016/j.vetpar.2008.11.013. Epub 2008 Nov 19.
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 prioritized scarce metabolizable protein (MP) allocation to reproductive functions (e.g. milk production) rather than to immune functions. We have earlier shown that the relationship between MP supply, milk production and resistance to the abomasal nematode Teladorsagia circumcincta provides support for this hypothesis. Because nutritional sensitivity of resistance to parasites may differ between parasite species, we used the same nutritional protocol to test the overall hypothesis with a different parasite. Thus, five levels of dietary MP, ranging from 0.60 to 1.2 times assumed requirements, were offered for 4 weeks post-parturition to twin-rearing Greyface ewes, experimentally infected with the small intestinal nematode Trichostrongylus colubriformis. We hypothesized that the initial increments of MP supply would increase milk production without affecting the degree of breakdown of immunity whilst later increments would reduce the degree of breakdown of immunity. Indeed, the data suggest that the first two increments of MP supply increased milk production, whilst final worm burdens were reduced from the second increment onwards. MP supply did not affect mucosal mast cell concentration but increased globule leukocyte concentration. These results support the overall hypothesis that scarce MP allocation is prioritized to milk production over immune functions. In addition, the contrast between effects of MP supply on resistance to T. colubriformis and to T. circumcincta supports the view that periparturient immunity to small intestinal nematodes may be less sensitive to nutrient scarcity than periparturient immunity to abomasal nematodes.
有人提出，围产期对寄生虫免疫力的下降有营养方面的原因。我们的总体假设是，这是由于可代谢蛋白质（MP）优先分配给生殖功能（如产奶）而非免疫功能所致。我们之前已经表明，MP供应、产奶量与对皱胃线虫环形泰勒虫的抵抗力之间的关系支持了这一假设。由于对不同寄生虫种类而言，寄生虫抵抗力的营养敏感性可能存在差异，因此我们采用相同的营养方案，用另一种寄生虫来检验这一总体假设。因此，在产后4周内，为双羔饲养的灰脸母羊提供了五种水平的日粮MP，范围从假定需求量的0.60倍到1.2倍，这些母羊经实验感染了小肠线虫蛇形毛圆线虫。我们假设，MP供应的最初增加会提高产奶量，同时不影响免疫功能的下降程度，而随后的增加则会降低免疫功能的下降程度。实际上，数据表明，MP供应的前两次增加提高了产奶量，而从第二次增加开始，最终的蠕虫负荷有所降低。MP供应并未影响黏膜肥大细胞浓度，但增加了球形白细胞浓度。这些结果支持了总体假设，即可利用的MP优先分配给产奶而非免疫功能。此外，MP供应对抵抗蛇形毛圆线虫和环形泰勒虫的效果之间的差异支持了这样一种观点，即围产期对小肠线虫的免疫力可能比对皱胃线虫的围产期免疫力对营养缺乏的敏感性更低。
