Arrested development of Nematodirus species in grazing lambs

Spring born lambs grazing in initially clean pasture for two successive years acquired low levels of Nematodirus species infection which showed a progressive increase in the level of arrested development, reaching 70 to 90 per cent of the total worm burden in lambs slaughtered in November. Similar levels were recorded in worm free tracer lambs allowed only one month access to contaminated pastures. Results suggested that both seasonal environmental conditions and host age may play an important role in larval inhibition for this genus and that this phenomenon was not density dependent, nor associated with host immunity.     

Interaction between coccidia and Nematodirus battus in lambs on pasture

Five thousand oocysts of each of two species of coccidia, Eimeria crandallis and E ovinoidalis or 30,000 infective larvae of Nematodirus battus, given as single infections to three- to five-week-old lambs, caused only transient diarrhoea and had no effect on growth. Lambs infected first with coccidia and two weeks later with N battus suffered severe diarrhoea, weight loss and some deaths. Simultaneous administration of the coccidia and the nematodes increased the clinical severity of the syndrome and increased the numbers of nematode eggs produced.     

Effect of experimental Ostertagia circumcincta infection on the performance of grazing lambs

Groups of 10 three-and-a-half-month-old Suffolkcross lambs were infected daily, five times a week, for 12 weeks with either zero, 500, 1500, 3000 or 5000 larvae of Ostertagia circumcincta and grazed together on a series of 'clean' paddocks. All the lambs were moved at seven to 10 day intervals to a fresh paddock to prevent autoinfection and were killed after 14 weeks. Another group was killed at the outset as a control for carcase analysis. Mean O circumcincta populations were 34 (grazing control) and 1224, 473, 1092 and 4331 for the groups receiving 500, 1500, 3000 and 5000 larvae per day respectively. The percentage of fourth stage larvae increased with increasing larval intake. Extensive abomasal damage with mucosal hypertrophy and depletion of parietal cells occurred in the lambs receiving 3000 and 5000 O circumcincta larvae per day. Intakes of 1500 larvae per day and above depressed growth rate by 24 to 37 per cent, reduced the deposition of protein in the carcase by 34 to 52 per cent and lowered calcium/phosphorus deposition by 23 to 48 per cent. Plasma pepsinogen concentrations were consistently elevated in lambs receiving 3000 or 5000 larvae per day and may be a useful aid to recognising abomasal damage sufficient to affect productivity.     

Nematodirus battus infection in calves

In studies on the control of parasitic gastroenteritis in calves and sheep, involving an annual rotation of pastures grazed by these host species, it was shown that young cattle could play an important role in the epidemiology of Nematodirus battus, a species usually regarded as a parasite of lambs. Thus, young cattle readily acquired heavy burdens of N battus in spring and the contamination of pastures with eggs from these infections resulted in significant populations of larvae on the herbage, which were infective to both calves and lambs grazed on these pastures in the following year. Although the majority of the N battus eggs hatched in the spring, some hatched in the autumn. The calves developed a strong immunity to N battus during the grazing season as demonstrated by the absence of worms at necropsy in the autumn, despite the presence of infective larvae on the pasture.     

Epidemiology of Nematodirus battus infection in eastern Scotland

A field investigation was carried out from 1981 to 1983 on the prevalence of Nematodirus battus under different systems of lowland sheep management. Pasture larval counts, ewe and lamb worm egg counts, and tracer lamb worm counts were carried out. As expected, contamination was generally greater on permanent pasture than on new leys as measured by pasture larval counts and lamb worm egg counts. However significant contamination was also recorded on young grass fields for which alternate grazing with young calves may have been partly responsible. It is suggested that the 1983 hatch was delayed because of a drop in soil temperature in late March which may have increased subsequent scour problems involving N battus seen in May.     

放牧羔羊矿物质元素消化代谢变化规律的研究

选择健康、体重相近的20只4月龄哈萨克土种公羔羊进行消化试验,试验期为4个月,在试验开始断奶,20只羔羊分为2组。早晨出牧前给试验动物戴粪尿袋,称重后出牧,晚上归牧后称重,每月进行6 d的消化试验。各月龄矿物质元素消化量:钙、锰、镁、锌、铜、铁等6种矿物质元素的消化量的变化规律与体重的变化规律一致的,在整个试验期5月龄和7月龄显著高于其余月龄(P<0.05),而钴的消化量与体重的变化规律不一致,4月龄最高,与其余月龄间差异显著(P<0.05)。代谢量的变化规律与体重的变化规律是一致的,在整个试验期5月龄和7月龄显著高于其余月龄(P<0.05),以尿的形式排泄体外的矿物质元素含量不多,而以粪的形式排泄体外的含量多。     

Demonstration of IgA-containing cells in the small intestine of lambs infected with Nematodirus battus

A peroxidase anti-peroxidase immunohistochemical technique was used to demonstrate IgA-containing cells in the small intestine of lambs infected with Nematodirus battus. These cells were more numerous in the infected lambs than in the uninfected animals. The difference was greatest for the first three sites, 1 to 3 m distal to the pylorus, where the preponderance of the N battus infection is found. It is suggested that future immunohistochemical studies on the relationships between IgA and resistance to N battus should be directed to this area.