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1.
The patterns of gastrointestinal and lung helminth infections in grazing calves were studied in two small grazing experiments carried out between May and October in 1985 and 1986, respectively, at Utrecht State University. For lungworm a very rapid translation of infective larvae was seen in both experiments, resulting in a rapid build-up of the worm burdens, and in July the second generation of Dictyocaulus caused husk. After the end of patency for lungworm, in the beginning of August, a rapid decrease in pasture infectivity, measured by pasture larval counts and worm counts of tracer calves, was observed. For the gastrointestinal nematodes the translation of infective larvae was much slower as a distinct 'midsummer increase' of pasture infectivity was not seen before the end of July. The worm counts of the tracer calves and the pasture larval counts showed that these larvae remained on pasture much longer than the lungworm larvae. As in Dictyocaulus, patency stopped in August-September in Nematodirus but not in Ostertagia and Cooperia, indicating a slower rate of development of immunity in both latter genera. In contrast to lungworm, the results indicate a clear and predictable seasonal pattern for gastrointestinal helminth infections. 相似文献
2.
M. Eysker J.H. Boersema J.B.W.J. Cornelissen F.N.J. Kooyman W. A. de Leeuw H. W. Saatkamp 《The Veterinary quarterly》2013,33(1):20-24
Summary An experiment was carried out with three groups of grazing calves and one housed control group to study the effect of rotational grazing for periods of 1 and 2 weeks on the build up of lungworm and gastro‐intestinal nematode infections respectively. The experiment demonstrated that rotational grazing for periods of I week on six plots prevented the build‐up of heavy lungworm infections. A buildup of heavier lungworm infections was observed in a group that was rotationally grazed for periods of 2 weeks on three plots and a group which remained on one plot throughout the grazing season; there was no difference between these two groups. In all three situations, there was an adequate development of immunity against D. viviparus, as measured by worm recovery after challenge infection at the end of the experiment in comparison with worm recovery of the similarly challenged control group. Neither rotational grazing scheme protected the calves against gastrointestinal helminthiasis, because tracer calves, which grazed for 4 days only in August or October, acquired infections which would have resulted in severe illness or even death if necropsy had been postponed for a week. 相似文献
3.
M. Eysker J. H. Boersema F. N. J. Kooyman T. J. G. M. Lam 《Veterinary parasitology》1995,60(3-4):339-348
A grazing study was performed with the main objective of examining the effect of fenbendazole (FBZ) in a ‘dose and move’ system on nematode infections in calves with special emphasis on Dictyocaulus viviparus.
Three groups of six calves were grazed from May to October 1993. One group (DM7) was treated with FBZ and moved to aftermath (pasture which had only been mown) 7 weeks after turnout. The second group (DM9) was similarly treated and moved 9 weeks after turnout and the third group served as untreated pasture control group (PC) and was moved to aftermath 9 weeks after turnout.
FBZ treatment removed adult lungworms from DM7 and DM9. Tracer calves grazed during the first 7 or the first 9 weeks after turnout acquired mean burdens of 18 and 125 lungworms, respectively. In PC faecal larval counts increased until the end of August. Most of the animals in this group were then suffering from lungworm disease and emergency treatment with ivermectin was given. In both FBZ-treated groups, larvae reappeared in the faeces of some of the calves 4–5 weeks after treatment. Subsequent reinfection resulted in higher mean faecal larval counts in both groups 2 months after treatment, although variation in faecal larval counts was high. In DM7 values tended to be higher than in DM9. These higher larval counts were associated with mild signs of parasitic bronchitis in some calves of DM7, whereas no signs were seen in DM9.
At the end of the experiment, all calves, and also a group of six permanently housed non-infected control calves (HC), were infected experimentally with 5000 D. viviparus larvae to evaluate development of immunity. The worm counts at necropsy showed that all calves on pasture had developed immunity. 相似文献
4.
Three groups of calves were put out to graze on separate paddocks within a field known to be infected with Dictyocaulus viviparus and were also given a small initial trickle infection of the parasite. The first group were untreated controls, the second were immunised with live irradiated lungworm vaccine and the third were injected three times with ivermectin; the injections taking place after they had grazed for three, eight and 13 weeks. The subsequent infections of D viviparus were estimated by grazing a series of parasite-free tracer calves in the paddocks used by each group. The first group of such calves grazed from July 17 until August 7, the second from August 22 to September 29. During the first half of the grazing season all the untreated and three of the six immunised calves were observed to excrete D viviparus larvae, in contrast to none of the ivermectin-treated group. As a result all the tracer calves on the areas occupied by the untreated and immunised calves became infected with the parasite whereas only one worm was found in one of the 10 tracer calves grazing the area occupied by the ivermectin-treated calves. 相似文献
5.
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). 相似文献
6.
The efficacy of the oxfendazole pulse release bolus (OPRB) was tested in a grazing experiment at the University of Utrecht. Three groups of four OPRB-treated calves and one group of four untreated control calves were grazed on separate pastures between 18 May and 21 October 1987. Based on faecal egg counts for strongyle-type eggs and Nematodirus eggs, embryonation of Nematodirus eggs and faecal larval counts for lungworm, the first pulse of oxfendazole was released after 28 to 63 days, which was later than the period of approximately three weeks indicated by the manufacturer and others. As far as could be detected, the second to fifth pulses were not as delayed, but generally the three-week period was also exceeded. This delayed release of the pulse resulted in a build-up of pasture infectivity for gastrointestinal nematode larvae and lungworm larvae. Nevertheless, this did not result in clinical gastrointestinal helminthiasis and husk in the treated groups of calves, whereas severe husk and mild gastrointestinal helminthiasis were seen in the control group. 相似文献
7.
G A Oakley 《Research in veterinary science》1982,32(2):163-169
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. 相似文献
8.
E. CLAEREBOUT W. HOLLANDERS H. DE COCK J. VERCRUYSSE H. HIDERSON 《Journal of veterinary pharmacology and therapeutics》1994,17(3):232-236
The effect of an ivermectin sustained-release bolus (I-SRB) on the epidemiology of nematode parasites and on calf productivity was evaluated in a field trial under Northwestern European conditions. Twenty parasite-naive female Friesian calves (principals) aged 5–9 months were used together with six male Friesian tracer calves. Principal calves were allocated by restricted randomization on day 0 body weight to either an untreated control group or a group given one I-SRB, designed to deliver 12 mg ivermectin per day for 135 days, orally on day 0. Each group was grazed on adjacent paddocks, naturally contaminated with parasitic nematode larvae, from 13 May 1991 (day 0) until housing on 30 September (day 140). Body weights of principal calves were recorded and individual blood and faecal samples taken at regular intervals throughout the trial. Pasture nematode contamination was monitored by larval counts on herbage and by worm counts of tracer calves grazed on each paddock from day 126 to day 140. Nematode contamination levels on the control paddock did not rise until the end of the grazing season, as a result of a mid-summer drought period. The period of exposure to a high larval challenge was too short to provoke body weight losses and clinical parasitic gastroenteritis in control calves. Use of the I-SRB resulted in zero faecal egg counts of trichostrongyles during the whole pasture season, thereby preventing a build-up of parasitic gastrointestinal nematodes on pasture. During the second grazing season no signs of parasitic gastroenteritis were detected in any animal, but an outbreak of parasitic bronchitis (PB) was observed in both experimental groups, indicating that PB can occur in older cattle regardless of the control measures taken to prevent clinical parasitism during the first grazing season. 相似文献
9.
J A Hawkins R R Evans T J Newby M H Delivorias T D Tyler 《Veterinary parasitology》1985,17(3):229-238
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. 相似文献
10.
Rolf Jess Jrgensen 《Acta veterinaria Scandinavica》1980,21(4):658
A combined epidemiology and control investigation was performed with parasite-free calves turned out in May on a permanent pasture naturally contaminated with lungworm larvae the previous year. Before the start the field was divided into two plots. One plot was grazed by 12 calves after the first week of May. The other plot was grazed by 12 calves turned out two weeks later. Both groups as well as the plots grazed by them were subdivided six weeks after turning out. Based on a predicted rise in the pasture larval contamination with infective lungworm larvae, one subgroup of each main group was given a tactical anthelmintic treatment six weeks and again eight weeks after their date of turning out. Patent infections from overwintered larvae were detected in both main groups after four weeks of grazing, but not in all individuals of the late turned-out group. The excreted larvae gave rise to pathogenic pasture larval contaminations on the two initial plots five to six weeks after turning out. In the control groups, early turning-out resulted in approx. 10 times higher larval recoveries in faeces and pasture compared to late turning-out. Seven to eight weeks after turning-out critical, severe parasitic bronchitis had developed in the early turned-out control group. In the late turned-out controls, clinical signs were obvious but not critical. Outbreaks were not observed in any of the experimental subgroups, and no larval excretion was observed among them within four to five weeks following treatments. Similarly, no larvae were recovered from their pastures two weeks after treatment and onwards. A third treatment was given to both experimental groups on the same date (August 21) to suppress gastrointestinal parasitism. However, the level of this infection, appeared moderate, probably due to comparatively low precipitation and extensive supplementary feeding given in late summer to compensate for scarcity of grass. 相似文献
11.
G B Mitchell 《The Veterinary record》1987,121(16):377-378
A group of 71 Friesian bullocks, aged six to nine months, vaccinated against lungworm, were randomly allocated on a liveweight basis to two groups of 40 and 31 animals. At turn-out each calf in the group of 40 calves was dosed orally with a pulsed release bolus designed to deliver five doses of oxfendazole at regular intervals during a period of up to 130 days, the first dose being released about 21 days after administration. The group treated with the bolus grazed 2.4 ha and the control group grazed 3.6 ha of permanent pasture for six weeks before having additional access to similar areas of silage aftermath. The control group was treated 99 days after turn-out and when they were housed with fenbendazole (7.5 mg/kg). Faecal worm egg counts, plasma pepsinogen activities, pasture larval counts and liveweights were recorded fortnightly. Significant reductions in worm egg counts and plasma pepsinogen activities were recorded in the calves dosed with the pulsed release bolus together with significant improvements in the liveweight of younger calves compared with control animals. Pasture larval counts were lower in the fields grazed by animals treated with the bolus. 相似文献
12.
Two groups of yearling cattle which had been treated with ivermectin either three and eight, or three, eight and 13 weeks after turn out to trichostrongyle contaminated pasture in their first grazing season were exposed in the following season to natural challenge with helminth parasites. To assess their immunity to this challenge each group shared a pasture with parasite naive first season calves. No anthelmintic treatments were administered at any time during the year. Throughout the grazing period the yearlings showed normal respiratory rates, negative faecal lungworm larval counts, and, relative to the calves, low faecal trichostrongyle egg counts. All the first season calves developed patent lungworm infections and on one occasion the mean respiratory rates of each group of calves were significantly greater than those of the yearling cattle. At the end of the grazing period, from early May until late September or October 1986, the cattle were removed from pasture and together with parasite naive controls challenged with either 10 or 22 third stage larvae of Dictyocaulus viviparus/kg bodyweight and necropsied between 18 and 23 days later. Although the experimental challenge resulted in relatively heavy lungworm infection of the naive controls, none of the yearlings and only three of the 11 calves which had been at pasture were found to be infected. However, large numbers of arrested fourth stage larvae of Ostertagia ostertagi were present in all the naturally infected yearlings and calves. 相似文献
13.
A study was carried out to evaluate the effects of strategic early-season treatments with eprinomectin on first-season grazing calves exposed to strongyle infections on a naturally contaminated pasture. Two groups of first grazing season (FGS) calves were turned out in mid-May on two plots that were similar with respect to size and herbage infectivity. They grazed separately until housing at the end of October. One of these groups was given eprinomectin pour-on at turnout and 8 weeks later, while the other group served as untreated controls. The results showed that the treatments reduced gastrointestinal strongyle infections throughout the season as evidenced by lower faecal egg counts and serum pepsinogen levels compared with the controls. Furthermore, the results of herbage larval counts and postmortem worm counts in tracer animals demonstrated that the treatment had reduced herbage infectivity on the 'treated' plot. Finally, the chemoprophylactically treated calves had a better weight gain over the duration of the study than the untreated controls. 相似文献
14.
Gastro-intestinal helminth of a group of three yearling mare Shetland ponies, which were set-stocked on a small pasture from February until September, were compared with those of a similar group of ponies, which grazed a similar pasture from February to July and subsequently was removed to a pasture which had been grazed by sheep from April to July. In addition both groups were treated with cambendazole when the latter group was removed to the sheep pasture.Pasture larval counts and worm counts demonstrated that the group grazed after the sheep acquired considerably smaller burdens of nematodes of the subfamilies Cyathostominae and Strongylinae, but considerably higher burdens of Trichostrongylus axei than the group which remained on the same pasture. The T. axei infections in the former group caused an increase in the serum pepsinogen levels within two weeks after removal to the sheep pasture followed by a gradual decrease. At necrospy T. axei populations consisted almost exclusively of inhibited early third state larvae. 相似文献
15.
A method of sampling pasture to estimate the numbers of infective nematode larvae to which grazing cattle were exposed was based on the grazing patterns and behavioural activities of two groups of cattle and was compared with other sampling techniques. Each group of cattle consisted of six permanent members, two members fistulated at the oesophagus and one worm-free tracer calf. Grazing time and the area where grazing occurred was not significantly different for tracer calves, fistulated cattle and permanent group members, and there was no relationship between grazing time and the live weight of cattle. Grazing time, the percentage of paddock area grazed intensively and the percentage of the paddock not grazed varied with season. The most intensively grazed areas were always visited between first light and the first rest period during mid-morning, and the plant parts and pasture species eaten could easily be identified by visual examination of these areas of the paddock. Larval recoveries per 100 g pasture ingested were estimated for comparison with the grazing area method using two other manual pasture sampling methods, a sampling method using tracer calves and one using fistulated calves. Correlations between these methods were not consistent but indicated that, given the small number of data sets, all methods were sensitive enough to estimate larval availability on pasture with the exception of the tracer calf method in the overstocked 3.4-ha paddock. 相似文献
16.
An experiment to determine the origin of populations of infective larvae of cattle nematode parasites on pasture during winter was conducted in south-west Western Australia. Six pasture plots were contaminated with worm eggs by grazing worm-infected cattle for periods of a month during summer and autumn. Each plot was contaminated at a different time from the rest. The levels of infective larvae were determined by counting the worm burdens of tracer calves which test-grazed the plots the following winter.Tracer calves which grazed the plots contaminated during summer acquired few worms, whereas those that grazed the plots contaminated during autumn acquired many worms. It was concluded that the hot, dry conditions prevailing during summer and early autumn prevented the development of eggs or survival of larvae in dung pats or free on pasture. In this environment, a programme of worm control which relied on administration of anthelmintic to grazing cattle to prevent autumn contamination of pasture would be most likely to succeed if the first treatment was given in early autumn. 相似文献
17.
R. J. Jrgensen 《Veterinary parasitology》1982,10(4):331-339
Four calves experimentally infected with Dictyocaulus viviparus were made Pilobolus-free by hygienic measures and by feeding them irradiation sterilized feed. Two of the calves were orally administered laboratory cultured Pilobolus sporangia daily. As a result, the faeces from one air contained D. viviparus larvae and Pilobolus spores, and the faeces from the other pair contained D. viviparus larvae, but no Pilobolus spores.
Two identical plots were used for deposition of the two kinds of faeces, and one of them remained free of Pilobolus fructification. Herbage sampling and the use of tracer calves revealed that on this plot the larval contamination and the infectivity of the pasture were greatly reduced. A mean larval count of 1321 near the faecal pats (0–5 cm) in the plot where Pilobolus was observed was reduced to 69 per kg of herbage on the Pilobolus-free plot. At a distance of 100 cm from the pats, a reduction from 99 to 3 larvae per kg herbage was found.
Each plot was grazed by four parasite-free tracer calves for 3 days. During the subsequent stabling period of these calves, the lungworm larval excretion of those from the Pilobolus-free plot was reduced by 90% and the clinical symptoms were milder than those which grazed the plot which contained the fungus. The mean post mortem worm counts after 4 weeks of stabling showed a reduction from 167 to 25 worms.
A more marked effect of Pilobolus fungi on the transmission of D. viviparus infection is to be expected under field conditions where calves are grazing more selectively than in the present study. 相似文献
18.
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. 相似文献
19.
The objective of this study was to examine whether susceptible calves grazing together with second-year resistant heifers are less exposed to trichostrongylid infection than are calves grazing on their own. Two groups of animals representing each age category were turned out onto pasture on 24 May 1997 and grazed at comparable stocking rates. The grazing of calves and heifers together was compared to groups of each age category grazing separately. The results indicated that herbage larval counts were significantly reduced in the second part of the grazing season on the plot grazed by the mixed group compared to the plot grazed by the first-season calves only. The mixed grazing strategy protected the young calves and no clinical signs were observed in this group, while most of the calves that grazed alone exhibited clinical signs. The availability of herbage was reduced towards the end of the season, with subsequent competition for the grass forcing all the animals to graze the tufts around the faecal pats, where the quality of the grass is poor and the numbers of infective larvae are high. The effect of this was visible in the form of increased parasite burdens in the calves that were grazed together with the heifers, confirmed by increased blood serum pepsinogen concentrations and reduced daily weight gains in the second part of the grazing season. The lower numbers of infective larvae on the pasture were probably achieved through the heifers ingesting many of the larvae but subsequently depositing relatively few eggs, since they had acquired some degree of resistance against trichostrongylid infections during their first grazing season. Thus they did not suffer any parasitological ill-effects during mixed grazing with first-season calves. 相似文献
20.
J C Williams J W Knox K S Marbury M D Kimball R E Willis 《American journal of veterinary research》1989,50(12):2108-2116
Four groups of 16 crossbred beef calves were used in evaluating different anthelmintic treatment schedules: group 1 was given ivermectin (IVM) at weaning only (October 31) and grazed on initially safe pasture; group 2 was given IVM at weaning, on January 28, and on April 22, and grazed on contaminated pasture; and group 3 was given IVM at weaning and on April 22, and grazed on contaminated pasture; and group-4 was group treated with fenbendazole (FBZ) at weaning only, with provision for individual salvage treatment, and grazed on contaminated pasture. The investigation was from Oct 31, 1984, to Oct 9, 1985. Initially high fecal egg counts at weaning were more effectively reduced by IVM than by FBZ, and the effect of safe pasture was evident in minimal worm burdens in tracer calves grazed with group-1 cattle during November and least amount of weight loss in group-1 yearlings during winter. Fecal egg counts, pasture larval counts, and plasma pepsinogen concentrations remained low in group 2 after the January treatment. Fecal egg counts of the other groups increased substantially during late winter and spring, but pasture larval counts increased only on group-1 and group-4 pastures. During spring, highest worm burdens were found in group-1 and group-4 tracer calves (grazed in April) and in group-3 and group-4 yearlings (slaughtered in early April). Six cattle of group 4 were salvage treated with FBZ in February and April. Greatest gains were observed from March through June, with group-2 and group-1 cattle gaining the most.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献