Search

Reduced trichostrongylid infection on herbage and in calves was obtained when first-season calves, grazing a common area of pasture, received low-dosage phenothiazine ( ptz ) in two successive years. The average daily dose of ptz was 7·0 or 10–3 mg kg −1 in the first year and, in the second, between 5·0 and 7·0 mg kg −1 . The effect on herbage infection was attributed mainly to ovicidal action. Treatment increased weight gain by 22 and 50 to 60 per cent in the respective seasons. The results suggested a cumulative effect produced by treating calves of successive years. Two calves developed ptz -induced photosensitivity (corneal opacity) in the first season, and two calves in the second season but in the latter, severe bronchopneumonia was believed to be a predisposing factor. To avoid photosensitivity and still maintain adequate drug activity, the daily intake of ptz should probably be restricted to around 6 mg kg −1 .

SUMMARY An experiment is described in which 28 lambs reared under worm-free conditions were fed on a low cobalt diet. When the lambs were approximately nine months of age they were randomly divided into four groups, two of which were supplemented with cobalt. Four weeks later the lambs of one supplemented and of one non-supplemented group were given 70,000 H. contortus infective larvae. Though there was no growth response to cobalt administration, liver cobalt levels of non-supplemented lambs were in the range associated with cobalt deficiency. In the early stages of infestation, cobalt-supplemented lambs showed higher egg counts, more severe anaemia and a 43 per cent mortality compared with lambs whose low cobalt diet was not supplemented and in which there was no mortality. It is concluded that a low level of cobalt in the diet of the host is detrimental to H. contortus.

Extract There are a number of disease entities of sheep, particularly lambs, characterized by some degree of locomotor disturbance. Copper deficiency as a cause of ataxia or posterior paralysis in lambs has received much attention in the scientific literature of different countries, and Cunningham (1946) describes the condition in New Zealand and the circumstances under which it occurs. Hartley (1956), describing the symptoms of focal symmetrical encephalomalacia of lambs, mentions, among other neuorological signs, inability to rise, prostration, and paddling movements of the legs. Muscular dystrophy of lambs has been reported in New Zealand by Hartley (1953) and Dodd (1954), who state that those severely affected are unable to rise, while others may show arched back and stilted gait. Lambs with severe arthritis due to Erysipelothrix rhusiopathiae, though not paralysed, often show marked disinclination to rise, while no obvious heat or swelling may be detected in the affected limb joints (Barry, ...

SUMMARY Forty-four lambs were reared under worm-free conditions and fed on a diet low in cobalt. When their average age was 11 weeks they were randomly divided into four groups, two of which were fed a cobalt-supplemented diet. Five weeks later the lambs of one supplemented and of one non-supplemented group were given 3,000 Trichostrongylus axei infective larvae until a total of 51,000 had been given. Serum vitamin B12 levels were indicative of pronounced cobalt deficiency in non-supplemented lambs. Parasitic infestation did not bring about any fall in serum vitamin BI2 in either cobalt-supplemented or cobalt-deficient lambs. Cobalt deficiency caused a highly significant reduction in growth. Infestation in cobalt-deficient lambs, however, caused no significant depression of live-weight at a time when a similar infestation was causing a highly significant decrease in the weight gain of cobalt-supplemented lambs. This result may mean that either a low cobalt status in the host or general malnutrition as a result of cobalt deficiency had the effect of reducing the pathogenicity of T.axei. Infestation, by causing dehydration and concomitant haemoconcentration tended to mask the anaemia due to cobalt deficiency.

Extract Throughout the Hawkeśs Bay area of the North Island of New Zealand Moniezia expansa, the common tapeworm of sheep, was extremely abundant in lambs at the end of 1955, following a milder and damper winter and earlier spring than is usual. The numbers of tapeworms were such that workers in the meat-freezing works remarked that they had never before seen so many. Examinations of pasture samples from properties where the lambs were severely infested revealed numbers of the oribatid mites, which are the intermediate hosts of Moniezia, far in excess of the numbers usually encountered. Paddocks at the Wallaceville Animal Research Station, from which pasture samples are examined each week throughout the year, were taken as standard.

SUMMARY Two experiments with lambs reared under worm-free conditions and fed on low cobalt diets are described. In the first experiment, a group of cobalt-supplemented lambs harbouring a worm burden consisting of Ostertagia circumcincta superimposed on a long-standing Trichostrongylus axei infestation had significantly lower serum vitamin B 12 levels than cobalt-supplemented lambs some of which were worm-free while others harboured only a recently-acquired O . circumcincta infestation. In the second experiment lambs which were infected with O . circumcincta , and in which cobalt deficiency was kept at a subclinical level, showed higher egg counts, lower haemoglobin concentrations and poorer weight gains than similarly infected lambs receiving adequate cobalt. The results indicated that the effects of low cobalt intake and a mild to moderate O . circumcincta infestation were additive.

SUMMARY The glutamic-pyruvic transaminase and the glutamic-oxaloacetic transaminase activity of fluke tissue has been studied. The GPT activity was 18 times that of an equal weight of sheep liver. Sheep liver, on the other hand, had 10 times more GOT activity than fluke tissue. The possible use of this finding in parasitological research is discussed.

Phenothiazine (PTZ) given indoors to calves artificially infected with Ostertagia ostertagi and Cooperia oncophora showed ovicidal activities of 100, 93, 98 and 85% respectively at daily doses of 9, 8, 7 and 6 mg kg-1. In a grazing study, one group of calves was treated with PTZ via the drinking water, using a "Profel" liquid dispenser. The dispenser was calibrated to add PTZ to the water at a daily dose of 7 mg kg-1, but in practice the dose far exceeded this amount. A dose of 7 mg kg-1 day-1 was given manually to a second group and a third group acted as control, receiving no PTZ. PTZ-induced photosensitivity was widespread in the first group due to over-dosage of medicament by the dispenser and was suspected in one calf in the manually dosed group. PTZ in both treated groups showed marked ovicidal activity and, apparently as a result of this, caused striking reductions in trichostrongylid infection on the pasture and in the calves as evidenced by pasture larval counts, calves' egg counts, pepsinogen levels and live weight gains. Necropsy worm counts showed that the PTZ medication prevented heavy infection by arrested as well as by adult Ostertagia. The reduced infection on the treated calves' pasture was carried over for a second grazing season. Untreated calves grazing the pasture in that season showed lower infection and improved weight gains up to mid-September compared with calves on the control pasture. These effects did not persist for the whole of the second season.

The morantel sustained release bolus was administered at turnout to first-season grazing calves in order to assess its efficacy in the seasonal control of infection by nematode parasites in Ireland. The pastures grazed by control calves showed a marked increase in gastrointestinal trichostrongylid infective larvae by September, while numbers of infective larvae on pasture grazed by bolus-treated calves remained at a low level throughout the grazing season. In consequence, the controls showed significantly higher worm egg counts in late season and significantly higher worm burdens (mainly Ostertagia spp) at necropsy carried out in November on representative number of principal animals selected from each group. These reduced worm burdens were attributed to the suppression of egg output during the early part of the season as a result of treatment with the morantel sustained release bolus at turnout in the spring. Pasture contamination with Dictyocaulus viviparus larvae was present on all treatment pastures. The bolus-treated calves however were subjected to an increase in D. viviparus infection which occurred on their pasture in late season after the active life of the bolus had expired. It was concluded that bolus treatment delayed (rather than prevented) the buildup of D. viviparus infection on the pasture by 60-90 days.