The use of the morantel sustained release bolus under special farm practices (deprime system) in France

The efficacy of the morantel sustained release bolus in controlling gastrointestinal and lungworm parasites when used in first-season grazing animals which followed older animals onto spring pasture (deprime system) was assessed in three trials conducted in Normandy, France. In each trial first-season grazing calves were equally allocated onto two separate but equivalent paddocks where they remained throughout the grazing season. A morantel sustained release bolus was administered to one group of animals at turnout, the other group remained as controls. The effect of the treatment on contamination of pasture (herbage larval counts and tracer worm counts), on faecal worm egg and lungworm larval counts, and on weight gain performance of the principal animals was assessed. In all three trials, worm egg output in the bolus-treated animals was substantially lower throughout the season compared with the control animals. Worm burdens of tracer calves grazing pastures of the treated cattle were also reduced compared with tracer calves grazing control pastures. Clinical parasitic gastroenteritis occurred in the control animals but not in the bolus-treated animals in one trial. Overall the bolus-treated animals outperformed the controls by a mean weight gain advantage of 10.5 kg (P less than 0.01).     

A comparison of the efficacy of four different long-acting boluses to prevent infections with Dictyocaulus viviparus in calves

A field study of calves in their first grazing season tested the efficacy of four long-acting devices--a morantel sustained-release bolus, a levamisole sustained-release bolus, an oxfendazole interval bolus, and an albendazole interval bolus--against Dictyocaulus viviparus. The pasture had been previously contaminated by four calves orally inoculated with infective lungworm larvae. The calves were grazed together with four bolus-treated groups, each comprising four calves. Lungworm infection became patent in the experimentally inoculated calves between 22 and 26 days. Infection in the bolus-treated groups became patent after 54 days. The morantel bolus group excreted the most larvae, followed by the albendazole bolus group, and the levamisole bolus group. The oxfendazole bolus group excreted by far the least larvae. Eosinophil curves and ELISA titres showed that treated groups had essentially the same course of infection. The heavy infection to which the treated calves were exposed produced complete immunity in all groups. Challenge infection of 10,000 larvae at housing did not change any of the test parameters. Post-mortem examination showed only one positive calf with few worms. We concluded that when pastures are heavily infested with lungworm larvae, all boluses prevent severe clinical signs and allow build up of solid immunity, although none completely prevent excretion of larvae.     

Some observations on the use of the morantel sustained-release bolus in first season-grazing calves on a Belgian dairy cattle farm

The efficacy of the morantel sustained-release bolus (MSRB) in controlling gastrointestinal parasites in first-season grazing calves was evaluated on a dairy cattle farm in Belgium. The calves grazed a pasture which had been used by bolus-treated animals in the three previous years. The effect of bolus administration was determined with respect to live weight gain, faecal egg shedding, herbage larval counts, serum pepsinogen levels and ELISA antibody titres. In spite of an incomplete reduction of faecal egg shedding during the first months of the grazing season, bolus administration resulted in the prevention of parasitic gastro-enteritis in the calves. A weight gain advantage of 35,2 kg of the bolus-treated animals over the controls was noted already at two months after turnout. This weight gain advantage was maintained until housing. The usefulness of serum pepsinogen values and ELISA antibody titres as parameters in prevention experiments is stressed. Both serological parameters gave more information concerning infection level than did the faecal egg output and the herbage larval counts.     

Efficacy of the morantel sustained-release bolus in grazing cattle in North America

The efficacy of using a bolus containing morantel in a sustained-release preparation for controlling naturally acquired gastrointestinal parasitic infections in weaned calves and yearling cattle was investigated during the 1982 grazing season at selected sites in the United States and Canada. According to a common trial design under various climatic and management conditions, 10 field trials were conducted with the bolus. At the time of spring turnout, a bolus was administered to each calf or yearling in the treated group. Then, treated and control cattle grazed separate but equal areas of divided pasture(s). The epidemiologic pattern of parasitic gastroenteritis in control animals and the effect of treatment on this pattern was determined in each trial. Safety and practicality of use of the bolus also were established. When compared with untreated cattle (control), those given the bolus deposited significantly (P less than 0.05) fewer worm eggs (89% reduction) during the first 90 days of the grazing season, as well as significantly fewer (P less than 0.05) worm eggs (84% reduction) during the entire grazing season. Consequently, during the second half of the grazing season, larval populations on treated pastures remained significantly (P less than 0.05) lower (66% reduction), compared with numbers of larvae found on control pastures. For pastures grazed by treated and control cattle at trial initiation, mean worm counts recovered from tracer calves were equal, indicating comparable pasture contamination at the beginning of the grazing season.(ABSTRACT TRUNCATED AT 250 WORDS)     

Trichostrongyle larval populations on herbage from grazed and ungrazed cattle pastures in south west Scotland

In the course of studies on the control of bovine parasitic gastroenteritis in south west Scotland using a morantel sustained release bolus the populations of trichostrongyle infective larvae on herbage were monitored over a two-year period. From the results of the herbage analysis and the worm burdens in parasite naive tracer calves introduced at the end of 18 months, it was clear that considerable numbers of infective larvae of Ostertagia ostertagi and Cooperia oncophora survived for at least 18 months on pastures not grazed at all. The results suggest that in south west Scotland after one, or even two, seasons with no further contamination of grazing, permanent cattle pastures cannot be assumed to be helminthologically 'safe' and that this should be taken into consideration when determining prophylactic strategies.     

Efficacy of morantel against nematode populations in calves exposed on a pasture stocked for two years with morantel sustained-release bolus-treated calves

Two groups of 10 parasite-free calves were maintained either for 2 weeks on a pasture grazed by nonmedicated cattle (pasture A) or for 3 weeks on a pasture grazed by morantel sustained-release bolus-treated cattle (pasture B) for the preceding 2 years. After a 4-week holding period to allow for maturation of acquired gastrointestinal nematodes, 5 calves from each group were administered a therapeutic dose (10 mg/kg of body weight) of morantel tartrate. All calves were necropsied 1 week later, and the abomasal and small intestinal nematodes were isolated, identified, and enumerated. A comparison of efficacies between nonmedicated and morantel tartrate-treated calves of each pasture demonstrated that morantel was equally effective against the gastrointestinal nematode infections, regardless of infection source (ie, pasture A vs pasture B). The overall nematode reductions due to morantel tartrate treatment of calves that grazed pastures A and B were 98% and 96%, respectively. It was concluded that the sensitivity of gastrointestinal nematodes to morantel tartrate was not diminished in calves maintained on pasture B, which had been stocked with morantel sustained-release bolus-treated calves for the preceding 2 grazing seasons.     

Efficacy of a morantel sustained-release bolus for the control of gastrointestinal nematodes in Florida dairy heifers

The effectiveness of a morantel sustained-release bolus (MSRB) in controlling gastrointestinal nematode infections was determined in 70 Holstein heifer calves with no prior grazing experience. Calves were allotted to 2 treatment groups and were maintained in Florida during the grazing season on divided pastures of equal area. One MSRB was administered to each calf in 1 group at the time of turnout onto spring pasture, whereas calves in the other group remained as nonmedicated controls. By the end of the grazing season, treatment resulted in significantly (P less than 0.05) lower worm burdens and significantly improved weight gains. The MSRB-treated calves were able to reach breeding weight 2 to 4 weeks earlier than did nonmedicated calves.     

Efficacy of morantel sustained release bolus against gastrointestinal nematodes in first season grazing Holstein calves

The efficacy of the morantel sustained release bolus (MSRB) in reducing gastrointestinal parasitism in first season grazing calves was evaluated during the summer--autumn grazing seasons of 1982 and 1983 in western Oregon. Each of 38 calves (1982) and 40 calves (1983) were randomly assigned to either control or treatment groups which were given MSRB on the day of turnout onto pasture. Mean worm burdens from tracer calves grazed with treated animals in 1982 and 1983 showed overall reductions of 86.4% (P greater than 0.05) and 84.3% (P less than 0.01), respectively, compared to tracers grazed with controls. Ostertagia ostertagi, Cooperia oncophora and Nematodirus helvetianus were the primary nematodes collected at necropsy. Twelve full-season 1982 tracer animals (6 treated and 6 control) indicated an 88.1% (P less than 0.05) overall reduction in mean worm burdens. Mean fecal worm egg per gram (EPG) counts of treated animals reflected a reduction of 69% (P less than 0.05) in 1982 and 90% (P less than 0.05) in 1983. Autumn inhibition of O. ostertagi was observed. In the 1982 trial the control animals showed a slight mean weight gain advantage over the treated group from Day 84 until Day 160 (trial termination) when the mean difference was 7.9 kg. The final mean weight gain advantage of treated animals in 1983 was 13.5 kg (P less than 0.05). These trials demonstrated that the MSRB was an effective anthelmintic for reducing gastrointestinal parasitism in grazing calves and for decreasing pasture larval contamination.     

Evaluation of the morantel sustained release trilaminate in the control of parasitic gastroenteritis in first season grazing cattle

A novel intraruminal bolus developed for the sustained delivery of the anthelmintic morantel tartrate was evaluated in the seasonal control of parasitic gastroenteritis in first season grazing calves. The morantel sustained release trilaminate is a trilaminate sheet consisting of a central lamina of a morantel tartrate/ethylene vinyl acetate matrix coated on both sides with a thin impermeable layer of ethylene vinyl acetate. A symmetrical pattern of circular perforations punched through the device controls the release of morantel. Administration of the trilaminate to calves significantly reduced their faecal egg output compared with untreated controls and thus reduced pasture larval contamination. Clinical parasitic gastroenteritis was prevented in the treated calves and there were significant reductions in their worm burdens compared with the untreated control calves both during and at the end of the grazing season. The control of parasitic gastroenteritis resulted in a significantly greater (P less than 0.0001) weight gain, of 45 kg, by the treated calves.     

Field efficacy of a morantel sustained release bolus for control of gastrointestinal nematodes in yearling steers

The efficacy of a morantel sustained release bolus (MSRB) for control of gastrointestinal nematodes in yearling steers was evaluated over a 6-month grazing period commencing on 26 March 1982. Three groups of 15 steers were allotted to the following treatments: Group 1 -- one MSRB at start of trial; Group 2 -- one therapeutic dose of thiabendazole at start of trial; Group 3 -- untreated control. The treatment groups were grazed separately. Parasite egg counts (EPG), herbage larval counts, pepsinogen levels and weight gains were monitored. Every other month, sets of 2 parasite-free tracer calves were placed in the pasture grazed by each treatment group and allowed to graze for 3 weeks before being subsequently necropsied for worm counts. At the end of the trial, 6 animals from each group were also necropsied for worm counts. The MSRB treatment resulted in significantly lower egg counts, fewer infective larvae on pasture, lower pepsinogen levels and lower worm burdens in tracer calves than was the case for the untreated group, but generally the levels were not significantly different from those associated with the thiabendazole treatment. The mean weight gain for the MSRB treated steers showed a significant advantage (70.9 lb) over the untreated animals, but was not significantly different from those which received thiabendazole. Total worm counts at the end of the trial were not different from any treatment group.     

Evaluation of gastro-intestinal nematode parasite control strategies for first-season grazing cattle in Sweden

A three-year grazing experiment (1998-2000) was conducted with first-season grazing cattle (FSGC) on improved pastures in central-eastern Sweden. Comparison was made between five groups with 10 calves in each group where four of these were set stocked and either (1) untreated, (2) ivermectin bolus treated, (3) subjected to biological control with the nematophagous fungus Duddingtonia flagrans, or (4) treated with a copper wire particle bolus. The fifth treatment was an evasive grazing strategy, whereby untreated calves were turned out onto pasture used by older cattle the previous year and then these calves were moved to silage aftermath in mid-July. To introduce low-levels of parasite infection to the experiment, each animal received a 'priming dose' of approximately 5,000 Ostertagia ostertagi and 5,000 Cooperia oncophora infective third stage larvae immediately prior to the start of the first grazing year of the trial.Results showed that efficient and sustainable parasite control of FSGC was possible to achieve without the use of anthelmintics by using turnout pastures that the previous year had been grazed by older cattle, in combination with a mid-July move to aftermath leys. Biological control also proved beneficial but the efficacy was impaired if high faecal egg counts coincided with rapid dung pat degradation due to heavy rainfall. No indication of parasite control was observed with the copper wire particle bolus. It was also demonstrated that the impact of gastrointestinal (GI) parasitism varied between years and that the level of overwintering contamination is important but likewise, is unpredictable. Although faecal egg counts in 1999 were low, due both to a delayed turnout and drought for the major part of the grazing season, deposited eggs successfully developed to infective larvae and overwintered in large numbers. The population of overwintered infective larvae at the time of turnout in early May played an important role in the course of infection in 2000 and resulted in an average 65 kg advantage of the ivermectin treated calves compared with the untreated calves.Thus, this three-year grazing experiment has emphasised the importance of subclinical gastrointestinal nematode infections in FSGC in Sweden. In addition, the study has shown that adequate parasite control may be achievable without the use of anthelmintics.     

Effects of the fenbendazole SR bolus on Trichostrongylus infections in young calves during two consecutive grazing periods

A two-year study was conducted in northern Germany to investigate the effects of the fenbendazole slow release (SR) bolus on trichostrongyle infections in cattle. Two groups of dairy replacement calves were either given a bolus at their first turncut on pasture or treated with fenbendazole suspension twice in mid-summer and at housing. Bolus-treated and control animals were set stocked on separate pastures during their first grazing season (26 weeks) and grazed together during the second year (24 weeks). During the first season the bolus prevented substantially the output of strongyle eggs for more than four months resulting in a lower infection risk in late summer and autumn as compared to the control group. The plasma pepsinogen concentrations remained low in the bolus-treated cattle during their first grazing period but rose in the controls soon after turnout which indicated increasing trichostrongyle-caused damages of the abomasal mucosa. During the following housing period and the second grazing season the bolus-treated animals showed higher egg counts than the controls. No clinical sign of parasitic gastroenteritis and no patent lungworm infections were observed during the study. The bolus-treated cattle performed better than the control animals during both grazing seasons although the control group had compensated temporarily the group difference in weight gains during the housing period. In conclusion, the use of the fenbendazole SR bolus may impair the development of immunity to trichostrongyle infections to some extent but, under the present conditions, this does not seem of clinical or economic importance.     

Some observations on the use of the morantel sustained‐release bolus in first season‐grazing calves on a Belgian dairy cattle farm

Summary

The efficacy of the morantel sustained‐release bolus (MSRB) in controlling gastrointestinal parasites in first‐season grazing calves was evaluated on a dairy cattle farm in Belgium. The calves grazed a pasture which had been used by bolus‐treated animals in the three previous years. The effect of bolus administration was determined with respect to live weight gain, faecal egg shedding, herbage larval counts, serum pepsinogen levels and ELISA antibody titres.

In spite of an incomplete reduction of faecal egg shedding during the first months of the grazing season, bolus administration resulted in the prevention of parasitic gastro‐enteritis in the calves. A weight gain advantage of 35,2 kg of the bolus‐treated animals over the controls was noted already at two months after turnout. This weight gain advantage was maintained until housing.

The usefulness of serum pepsinogen values and ELISA antibody titres as parameters in prevention experiments is stressed. Both serological parameters gave more information concerning infection level than did the faecal egg output and the herbage larval counts.     

Observations on the epidemiology of Dictyocaulus viviparus in north west England

A five year ley pasture was used as a source of natural infection with Dictyocaulus viviparus for cattle in anthelmintic trials. Pasture larval counts, faecal larval counts of permanently grazing calves and lungworm burdens harboured by tracer calves were monitored in three grazing seasons to assess the pattern of infection. Carrier calves were introduced at the beginning of the grazing season in the first two years of the study but not in the third. In the fourth year the pasture was subdivided into two paddocks where overwintered infection with and without carrier infection were compared. A control paddock exposed to carrier infection but no overwintered infection was also monitored. Pasture larvae survived the winter but carrier infection appeared to make a larger contribution to pasture larval counts and the onset of parasitic bronchitis in susceptible calves. In the absence of grazing cattle at the end of the grazing season the concentration of D viviparus larvae on the herbage fell rapidly to undetectable levels. Discrepancies between contamination of herbage by infective D viviparus larvae and infectivity of pasture for susceptible cattle occurred in all years but were particularly marked on the third year when natural immunity appeared to influence the number of lungworms accumulating in tracer calves. Failure to recover lung worms from tracer calves cannot be regarded as an accurate indication of lungworm free pasture. In the first three years the proportion of the lungworm population which was inhibited in tracer calves was higher early and late in the grazing season and negligible in mid season. This suggests that a predisposition to inhibition in larvae which have overwintered on pasture may influence the time of onset of parasitic bronchitis in the next grazing season, but results from the fourth year did not support this hypothesis.     

Efficacy of a novel sustained release anthelmintic device in preventing parasitic gastroenteritis in first-season calves

The efficacy of the first of a new generation of intraruminal devices for cattle, the morantel sustained release trilaminate, was assessed in two field trials. In each trial the animals were divided into a control group and a treated group. The device was administered to each calf before turn out in the spring and the reduction of gastrointestinal parasitism resulted in a substantial reduction in the level of pasture contamination with infective helminth larvae later in the season. Compared with the control calves the treated calves had a 94 per cent reduction of worm burdens acquired over the entire grazing season in the first trial, despite the controls being treated for clinical disease in September. In the second trial four anthelmintic treatments were administered to the control calves during the grazing season, but nevertheless a 64 per cent reduction of worm burdens in the treated group compared to the control group was recorded. The control of parasitic infection by the sustained-release devices resulted in mean weight gain advantages of 28.3 kg and 34.7 kg by the treated animals in the first and second trials respectively.     

Metabolism and growth in housed calves given a morantel sustained release bolus and exposed to natural trichostrongyle infection

Three groups of calves, previously grazed on permanent pastures contaminated with bovine trichostrongyle (Ostertagia and Cooperia species) infective larvae, were housed from October to May. During the grazing season one group had received fenbendazole at fortnightly intervals to suppress trichostrongyle infections, one received a morantel sustained release bolus before grazing to limit trichostrongyle contamination of the pasture, and the control group was only medicated when heavy infections caused clinical type 1 ostertagiasis. Digestibility of the whole diet was poorer in the control cattle, particularly for dry matter, crude protein and energy fractions. Balance studies conducted throughout the winter housed period showed that both increased faecal and urinary nitrogen outputs in the control animals contributed to a significantly reduced overall nitrogen retention. The effects were most apparent during clinical type 2 ostertagiasis, which occurred in March in the control group.     

Dictyocaulus viviparus in calves: effect of rotational grazing on the development of infections.

A study was made of the possibility of reducing lungworm infections in young grazing calves by rotational grazing for weekly periods on six paddocks. For this purpose three groups of four calves each were grazed on separate pastures in 1989, whereas a fourth group served as a permanently housed control group. Two groups of calves were infected experimentally with six doses of 10 larvae of Dictyocaulus viviparus during the first 3 weeks on pasture. In the third group, low natural infections with overwintered larvae occurred. One of the experimentally infected groups was rotationally grazed for weekly periods on six small plots while both other groups were set-stocked. Faecal larval counts and worm counts in tracer calves demonstrated lower lungworm infections in the rotationally grazed group than in both set-stocked groups. However, the numbers of worms found after challenge infection and subsequent necropsy were relatively high in the rotationally grazed group, indicating that development of immunity was less than in both other groups. Owing to the dry weather conditions in the summer of 1989, no serious clinical signs of husk developed in any of the three groups. These dry conditions, however, did not prevent the build-up of heavy pasture infectivity with gastrointestinal nematodes resulting in heavy worm burdens and serious clinical signs in tracer calves grazing for 4 days in August and September-October, respectively. This implies that rotational grazing did not have a clear effect on build-up of gastrointestinal nematode infections.     

Sequential in vivo measurements of body composition of calves exposed to natural infection with gastrointestinal nematodes

Sequential in vivo measurements of total body water, exchangeable sodium and exchangeable potassium, made by radioisotopic dilution techniques, were used to determine changes in body composition in calves exposed to natural infections with gastrointestinal nematodes during their first grazing season. Two groups of calves were studied, one of which received a sustained release anthelmintic bolus at turn out. Over the grazing season the bolus-treated calves showed a significantly improved pattern of bodyweight gain, compared with the untreated control calves. There were also significant increases in both total body water and exchangeable potassium, as a percentage of the bodyweight, in the bolus calves compared with the controls. These findings indicated that body protein as a percentage of bodyweight was increased in the bolus animals. The bolus-treated calves also had significantly lower serum pepsinogen concentrations, faecal egg counts and worm burdens.     

Control of gastrointestinal strongylids in first year calves: use of Paratect Flex bolus at late pasture turnout]

The efficacy of the Paratect Flex-Bolus for the control of parasitic gastroenteritis in calves was evaluated in a field experiment in the Swiss midland region. The bolus was administered to 9 first year grazing calves at 4 to 5 months of age before turnout on June 26 while 9 calves remained as untreated controls. Both groups were rotated between 8 paddocks that had been pregrazed by older cattle in spring. For a period of 12 weeks the faecal egg output of the treated calves was reduced significantly (p < 0.05) compared to the controls, whereas no significant differences were observed in the mean serum pepsinogen values of both groups. At the end of the experiment (November 14) the bolus-treated calves showed a 4 kg weight gain advantage over the controls which was not significant. The mild infection levels in both groups were probably due to the low pasture contamination with infective larvae throughout the season which most likely resulted from the late turnout of the calves. An outbreak of dictyocaulosis was observed in both groups in October and confirmed that the Paratect Flex-Bolus provides insufficient protection against this infection.     

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.