Beasley A M, Kahn L P, Windon R G
Australian Sheep Industry CRC, CJ Hawkins Homestead, University of New England, Armidale, NSW 2350, Australia.
Vet Parasitol. 2012 Sep 10;188(3-4):306-24. doi: 10.1016/j.vetpar.2012.03.022. Epub 2012 Mar 28.
A pen experiment was conducted to investigate the interaction of early-weaning and nutrient supply on the periparturient relaxation of immunity to the gastrointestinal nematode (GIN) Trichostrongylus colubriformis in Merino ewes. Mixed-age pregnant and non-pregnant (dry) ewes were infected with 8,000 T. colubriformis L(3)/week, and fed either a high or low quality diet. Following parturition, lambs were either removed from their mothers at 2 days of age or allowed to continue suckling. Systemic immunity began to wane during late pregnancy with circulating eosinophils and plasma total antibody (Ab) levels declining from day -37 (relative to the midpoint of lambing) and day -24, respectively. Pregnant ewes fed the low quality diet exhibited an increasing faecal worm egg count (WEC) from day -24 and had higher intestinal worm burdens on day 13, whereas ewes fed the high quality diet had a delayed transient rise in WEC of lower magnitude. Dry and early-weaned ewes remained highly resistant to T. colubriformis at all times. In the post-lambing/lactation period, ewes fed the high quality diet had higher levels of local total Ab and numbers of goblet cells (GC) in the small intestine on days 13 and 41. Lactating/suckled ewes had a lower anti-parasite local immune response as indicated by reduced titres of total Ab, IgG(1), IgM and IgA and lower numbers of mucosal mast cells (MMC), globule leukocytes (GL) and GC in small intestinal tissue compared to their dry and early-weaned counterparts. Early-weaning resulted in rapid recovery of blood eosinophils and total Ab. On day 13 post-lambing, titres of total Ab, IgG(1), IgM, IgA and IgE, and numbers of MMC and GL were greater than those measured in dry and suckled ewes. When fed the high quality diet, ewes had a higher dry matter (DM) intake, maternal weight, fat score, greater fat depth and eye muscle depth, birthed heavier lambs that had higher growth rates, and produced more milk. The physiological status of pregnancy resulted in a higher DM intake but lower measures of fat depth and eye muscle depth, and suckling led to an increase in DM intake but a reduction in body weight and fat score through mobilisation of fat and muscle reserves. Despite the marked effect of diet quality on production traits, some inconsistencies were observed between body composition and apparent parasite resistance, measured by WEC and worm counts, suggesting that the nutritional influence was not necessarily always mediated through changes in body composition. Although reproductive status affected blood leptin levels, diet had no effect within suckled ewes and therefore it was concluded that leptin has no causative role in maintaining the periparturient relaxation of immunity to T. colubriformis.
进行了一项围栏试验，以研究早期断奶和营养供应对美利奴母羊围产期对胃肠道线虫（GIN）——蛇形毛圆线虫免疫放松的相互作用。不同年龄的怀孕和未怀孕（空怀）母羊每周感染8000条蛇形毛圆线虫L3，并分别饲喂高质量或低质量日粮。分娩后，羔羊在2日龄时要么与母亲分开，要么继续哺乳。在怀孕后期，全身免疫开始减弱，循环嗜酸性粒细胞和血浆总抗体（Ab）水平分别从第-37天（相对于产羔中点）和第-24天开始下降。饲喂低质量日粮的怀孕母羊从第-24天开始粪便虫卵计数（WEC）增加，在第13天时肠道线虫负荷更高，而饲喂高质量日粮的母羊WEC的短暂升高延迟且幅度较小。空怀和早期断奶的母羊在任何时候都对蛇形毛圆线虫保持高度抗性。在产羔/泌乳后期，饲喂高质量日粮的母羊在第13天和第41天时小肠中局部总Ab水平和杯状细胞（GC）数量更高。与空怀和早期断奶的母羊相比，哺乳/ suckled母羊的抗寄生虫局部免疫反应较低，表现为总Ab、IgG(1)、IgM和IgA滴度降低，小肠组织中黏膜肥大细胞（MMC）、球形白细胞（GL）和GC数量减少。早期断奶导致血液嗜酸性粒细胞和总Ab迅速恢复。在产羔后第13天，总Ab、IgG(1)、IgM、IgA和IgE滴度以及MMC和GL数量均高于空怀和哺乳母羊。当饲喂高质量日粮时，母羊干物质（DM）摄入量更高、母体体重、脂肪评分、脂肪深度和眼肌深度更大，所产羔羊更重且生长速度更快，产奶量更多。怀孕的生理状态导致DM摄入量更高，但脂肪深度和眼肌深度指标较低，哺乳导致DM摄入量增加，但通过动员脂肪和肌肉储备导致体重和脂肪评分降低。尽管日粮质量对生产性状有显著影响，但在身体组成与通过WEC和线虫计数测量的表观寄生虫抗性之间观察到一些不一致，这表明营养影响不一定总是通过身体组成的变化来介导。尽管生殖状态影响血液瘦素水平，但日粮对哺乳母羊没有影响，因此得出结论，瘦素在维持围产期对蛇形毛圆线虫免疫放松方面没有因果作用。
