A 3-year field evaluation of pasture rotation and supplementary feeding to control parasite infection in first-season grazing cattle: dynamics of pasture infectivity

A 3-year grazing trial (2002-2004) was conducted on a commercial beef cattle farm in south-central Sweden to assess different methods of parasite control. This paper focuses on the dynamics of the free-living larval stages, whereas data on performance and within-host parasitological variables are presented in a complementary paper. Each year in May, 4 groups of 10 first-season grazing (FSG) steers were turned out on to separate 2ha paddocks and subjected to the following strategies: (1) spring turn-out on to pasture which had been grazed the previous year by second-season grazing (SSG) steers (paddock RT), followed by a move to aftermath (paddock AM) after 10 weeks (mid-July), (2) supplementary feeding with concentrate and hay for 4 weeks following turn-out (paddock FD), set stocked, (3) untreated control (paddock UT), set stocked and (4) anthelmintic treated control (paddock DO), set stocked. All paddocks were assigned a new set of FSG cattle each year whereas the treatments remained the same. Pasture infectivity were monitored partly by two tracer calves that grazed each paddock along with the FSG calves for 3 weeks after turn-out and prior to housing, partly by analysis of herbage samples for infective larvae (L3) that were collected from each paddock at monthly intervals between April and October. The predominant genera found were Cooperia and Ostertagia. Tracers grazing paddock RT overall harboured less worms, and in particular less Ostertagia spp., and tracers grazing paddock AM in mid-July harboured insignificant numbers of nematodes compared to tracers on the FD and UT paddocks. Although total worm counts varied between groups, smaller numbers were generally observed early in the grazing-season (May), compared to close to housing (September) when inhibited early L4 larvae were almost exclusively found. Results observed from herbage samples showed high numbers of L3 in spring before the time of turn-out, compared to around housing. In conclusion, the rotation control strategy showed promising results and provided a turn-out pasture that was 'nematode safe' to FSG cattle the following spring, whereas the feeding strategy failed as applied in this experiment.     

Effect of naturally occurring nematode infections on growth performance of first-season grazing calves

Liveweight of calves on 89 dairy farms was measured at the end of the grazing season and related per herd to the level of exposure to nematode infection during the grazing season. There were significant between-herd variations in antibody titres against Ostertagia spp., Cooperia spp. and Dictyocaulus viviparus as well as in pepsinogen values. All but six herds (93.1%) had gastrointestinal nematode infections, as measured by faecal egg counts in September. Faecal samples of 17 herds (19.3%) contained lungworm larvae in September. Liveweight of calves per herd deviated from -68.1 kg to +84.1 kg from the age-adjusted population mean after their first grazing season. Growth performance up to the time of liveweight measurements was significantly correlated negatively with several serological and parasitological parameters. Data could be fitted by means of both linear and segmented curvilinear regression. Antibody titre against Cooperia spp. and gastrointestinal nematode egg output measured in September accounted for 3.1% (P less than 0.10) and 6.7% (P less than 0.05), respectively, of the variation in growth performance among herds. Certain infection parameters, when combined, accounted for 9.2% of this variation; these were antibody titre against Cooperia spp. and larval counts for both gastrointestinal nematodes and lungworm. Adding certain management factors to these infection parameters resulted in a model explaining 27.6% of the observed variation in growth performance among herds. These factors were supplementary feeding, lungworm vaccination, anthelmintic treatment at housing, date of housing and herd age.     

Performance of second-season grazing cattle following different levels of parasite control in their first grazing season

A 3-year grazing trial was performed during 2003-2005 on a commercial steer-producing farm in Sweden to study performance of second-season grazing (SSG) cattle following different levels of parasite exposure during their first grazing season. Initially, groups of 10 first-season grazing (FSG) cattle were each year assigned to four parasite control strategies: (1) turn-out onto pasture that during the previous year was grazed by SSG cattle, followed by a mid-July move to aftermath, (2) supplementation with concentrate and roughage for 4 weeks after turn-out, (3) no treatment, or (4) anthelmintic treatment (injectable doramectin) every fourth week. All animals were set stocked, except for those in group one. Next spring and following housing the cattle were turned out for their second grazing season onto approximately 25 ha communal pasturelands as a common mob. Weighing, faecal sampling and blood collection were performed at turn-out and then every 4 weeks for the 20-week grazing season. Faecal samples were also collected on day 10 after turn-out for detection of coccidian oocysts. Antibodies to Dictyocaulus viviparus were analysed at the time of their second housing period, and when elevated levels were recorded, stored serum samples from seropositive animals were analysed retrospectively. Results showed early-season weight losses of up to 47 kg in the SSG cattle. However, faecal egg counts were generally low and there was no correlation between SSG performance and treatment history as FSG cattle. Still, cumulative egg counts were significantly higher in animals that had been treated with anthelmintic as FSG cattle but serum pepsinogen concentrations showed no significant differences and the output of Eimeria alabamensis oocysts seldom exceeded 10,000 oocysts per gram faeces. Antibodies to D. viviparus were observed from July 2004 and from June 2005 but not in 2003. In 2004 and 2005, 64% and 83% of the animals, respectively, were seropositive for D. viviparus. It is concluded that weight gain penalties resulting from different levels of parasite infections the first grazing season remained during the second grazing season in 2004 and 2005 but no differences in weight gain could be identified in SSG cattle that had experienced different parasite control measures during their first grazing season. This was under conditions where the level of pasture infectivity was low to moderate during the second grazing period. However, D. viviparus was demonstrated in SSG animals during the two last years of the study and was an important confounding factor.     

Evaluation of the effects of nematode parasitism on grazing behaviour, herbage intake and growth in young grazing cattle

Parasitic nematodes, even in the absence of any clinical disease, can cause a reduction in voluntary feed intake in housed ruminants. This trial examined these effects on young cattle grazing pastures. Twenty dairy heifer calves, born in the previous autumn, were blocked according to liveweight and allocated to one of two groups: either untreated or dosed with an IVOMEC((R)) (ivermectin) SR Bolus 10 days prior to turnout on 1 May 1998. The groups grazed separately on two paddocks on predominately ryegrass swards. Liveweights were recorded every 28 days and faecal samples taken for worm egg counts at the same time.In mid-May and mid-July, for two 14-day periods, animals were paired within treatment groups and transferred to one of 10 replicate paddocks of similar sward height and herbage mass. Grazing behaviour and herbage intake were measured during these periods.In mid-May, 2 weeks after turnout, treated and untreated animals showed no difference in grazing behaviour or daily intake of grass. By mid-July, 10 weeks after turnout, the untreated heifers spent on average 105min less per day in grazing time and their daily herbage intake was 0.78kg dry matter (DM) per day lower than that of the treated animals. Residual sward height, mass and composition in the trial paddocks reflected these differences. There were no clinical signs of gastrointestinal parasitism in the untreated group up to this time; in July, the mean worm egg count in this group was 120 eggs per gram (e.p.g.) of faeces. Faecal samples from several untreated animals were positive for lungworm larvae by July, mild clinical signs of bronchitis were observed in two of these animals in mid-July. Over the period from turnout until mid-July, the untreated heifers showed a reduction in mean daily liveweight gain of 150g, compared to the treated animals.     

A 3-year field evaluation of pasture rotation and supplementary feeding to control parasite infection in first-season grazing cattle--effects on animal performance

To evaluate non-chemical strategies to control pasture-borne parasites in first-season grazing (FSG) cattle, a 3-year grazing trial was conducted during 2002-2004 on naturally infected pastures on a commercial beef cattle farm in Sweden. A uniform pasture was divided in 4 equal 2 ha paddocks onto each of which 10, 5-9 months old dairy breed steer calves were allocated at turn-out in May each year. Two strategies were evaluated: (1) turn-out onto pasture which had been grazed the previous year by second-season grazing (SSG) steers, followed by a move to aftermath in mid-July (RT) and (2) supplementation with concentrate and roughage for 4 weeks from turn-out (FD). Comparisons were made with an untreated (UT), and an anthelmintic treated control group (DO). Animal parasitology and performance were monitored monthly throughout the 20 weeks grazing period. Additional sampling occasions were performed on day 9 (for coccidia) and 10 weeks after turn-out (mid-July). Due to clinical parasitic gastro-enteritis (PGE), salvage treatments were performed on all animals in group FD approximately 7 weeks after turn-out in 2003 and of three animals in group UT 5 weeks after turn-out in 2004. In 2003, the geometric mean oocyst excretion 9 days after turn-out was approximately 150,000 opg of mainly Eimeria alabamensis in group FD, and in 2004 approximately 180,000 opg in group UT. Apart from the DO group, geometric mean faecal egg counts (FEC) were between 80 and 400 epg 4 weeks after turn-out. Mean serum pepsinogen concentrations (SPC) of approximately 3.6 U tyrosine were recorded in the FD and UT groups from late August 2002. In 2003 and 2004, mean concentrations in these groups were between 4.1 and 7.2 U tyrosine 8 weeks after turn-out. By the end of the three grazing seasons the average weight gain difference compared to the DO group was for FD -29, -38 and -5 kg and for RT -4, -21 and +14 kg, and compared to the UT group -18, +2 and +22 for FD and +7, +19 and +41 kg for group RT. In conclusion, the rotation control strategy showed promising results, whereas the strategic feeding was poor from a parasite control standpoint.     

Alternate grazing of horses and sheep as control for gastro-intestinal helminthiasis in horses

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.     

A morantel sustained-release bolus for the control of gastro-intestinal nematodes in grazing calves

Prophylactic (summer) and/or therapeutic (autumn) administrations of an intra-ruminal sustained-release bolus (MSRB) containing morantel tartrate were compared for the control of gastro-intestinal nematodes in grazing dairy calves over an 8-month period (December to August). The MSRB was designed to release morantel tartrate at 150 mg/day for 90 days.

Treated and untreated groups of calves grazed separate replicated pastures. Both groups of calves receiving the MSRB at the beginning of summer showed a significant mean liveweight advantage (17.7 kg and 20.7 kg for the summer and summer/autumn treated groups, respectively) at the end of the trial period, when compared with untreated calves. The liveweight advantage of calves receiving the MSRB in autumn only (6.5 kg) was not significantly different from that of the controls.

Both the summer and autumn administrations of the MSRB prevented the accumulation of Pre-Type II burdens of Ostertagia spp.

Retention rates of the MSRB were high and chemical analysis of faecal samples indicated a fairly constant release of the anthelmintic over the predicted 90-day period.

The results indicate that the MSRB is potentially useful for the control of gastro-intestinal nematodes, and particularly for the production of ’safe’ pasture. The MSRB could provide an effective alternative to integrated control based primarily on grazing management.     

Internal parasite control strategies.

To maintain the general health of small ruminants, owners, managers, and clinicians should be familiar with the body condition-scoring [table: see text] methods, general health, and overall appearance of the animals in their care. Any changes in the overall health of individual animals or the flock should be noted immediately, the cause determined, and immediate measures should be taken to correct any problems. Parasite management in small ruminants is a difficult and arduous task. When a program that reduces parasite infestation is discovered, it should be carefully implemented, maintained with vigilance, and constantly "tweaked" to maximize its effectiveness.     

Efficiency of feeding <Emphasis Type="Italic">Duddingtonia flagrans</Emphasis> chlamydospores to control nematode parasites of first-season grazing goats in France

A field trial, conducted over two consecutive years, was aimed at assessing the efficacy of the administration of spores of the nematophagous fungus Duddingtonia flagrans to young goats for the control of nematode parasite infections on a French commercial dairy goat flock. For both years, the first-year grazing kids were divided into two similarly managed groups (fungus and control groups): in 2003 a daily dose rate of 5 × 10⁵ spores/kg body weight was given to the fungus-group animals, while in 2004 a daily dose rate of 10⁶ spores/kg body weight was used; the other half of the kids, acting as control, did not receive the spores. Parameters measured every 3 weeks included nematode egg excretion, larval development in faecal cultures and pasture larval counts. Additionally, at the beginning, the middle and the end of each grazing season, the goats were weighed and blood samples for pepsinogen determination were collected. In 2003, similar results were recorded for all the measured parameters in the control and fungus groups. In contrast, in 2004, the kids receiving the spores showed lower faecal egg counts and pepsinogen levels at the end of the season and higher growth rate compared to kids of the control group.     

The effect of grazing forage containing condensed tannins on gastro-intestinal parasite infection and milk composition in Angora does

The objective of this study was to evaluate effects of the condensed tannin (CT)-containing forage sericea lespedeza (sericea lespedeza (SL); Lespedeza cuneata; 15.2% CT), on fecal egg count (FEC), larval development (larvae/10 g of feces), worm burden and immune response compared with a crabgrass (Digitaria ischaemum)/Kentucky 31 tall fescue (Festuca arundinacea; control forage (CTF)) forage low in CT (0.32% CT) in grazing Angora does and their kids. Fifty worm-free mixed-age does were randomly allocated to three treatments. One treatment (10 does; initial liveweight (LW) = 45+/-1.5 kg) entailed grazing of SL forage from April 25 to July 15, 2002 with a second treatment of CTF (20 does; initial LW = 43+/-1.4 kg) grazing during the same period. Does of the third treatment (20 does; initial LW = 44+/-1.4 kg) grazed a sward of SL for 2 weeks and then one of CTF for 2 weeks followed by alternating between the two pastures every 2-week rotational grazing (ROT). To gauge levels of infective larvae on pasture, three worm-free Angora kids (initial LW = 3.6+/-0.2 kg) were randomly selected as tracers. Tracers grazed for final 60 days and were euthanized for determination of worm burden. The immune response of does was measured by skin thickness reaction after the intradermal injection of 250 microg phytohemagglutinin (PHA). Mean FEC for SL and ROT were substantially lower (P < 0.01) than for CTF does (145, 329 and 894 eggs/g, respectively). The FEC for kids was lower (P < 0.05) for SL than for ROT and CTF (550, 2757 and 3600 eggs/g, respectively). Total fecal egg output (3.3, 6.0 and 26.9 x 10(5) eggs/day, respectively) and larval development (242, 263 and 792 larvae/10 g, respectively) were lower (P < 0.05) for SL and ROT than for CTF. Tracers grazing on SL had lower total worm burdens than ROT and CTF (P < 0.01). The immune response was higher (P < 0.01) for SL (4.9 mm) and ROT (6.0 mm) than for CTF (3.0 mm) at 12 h after injection of PHA. The packed cell volume (PCV) in does was higher (P < 0.01) for SL and ROT than for CTF (27, 26 and 23%, respectively). Does that grazed CT-containing forage had considerably lower milk somatic cell counts (SCC) than does grazing non-CT-containing forage. In summary, grazing CT forages reduced FEC, larval development and worm burden, and also appeared to enhance immune response. The CT-containing forage SL reduced gastro-intestinal parasite infections of Angora does and kids.     

A comparison of nematode control programs for cattle in south western Victoria

Nematodiasis and its subsequent effect on production in Hereford weaner steers in western Victoria was studied during 1983 and 1984. In the first summer, steers were allocated to 2 replicates of 6 treatments--No treatment (Nil); Morantel slow release bolus in March (M1); Morantel bolus in March and June (M2); pour-on levamisole in January, May and July (R3); albendazole in January and July (V2) and albendazole in January, May and July, (V3). In 1984, treatment M2 was discontinued to provide extra replicates for Nil and M1. The replicate paddocks were 5 ha and were stocked with 7 and 8 steers in 1983 and 1984, respectively. Nematode egg counts in faeces, were generally less than 50 epg, indicating low numbers of adult nematodes. Faecal egg counts were highest in autumn and declined during the year. There was a significant (P = 0.02) effect of treatment on mean faecal egg count. Mean egg counts for treatment groups Nil and M1 were 16 and 10 epg above the overall mean (47 epg); those of the other treatments were 6 to 12 epg below the mean. There were no significant (P = 0.8) differences between treatments in the numbers of nematode larvae on pasture, during the experiment. At the end of both years of the experiment most nematodes (92%) were early fourth stage larvae of O. ostertagi. There were no consistent differences in nematode counts between treatments. There were no significant (P = 0.33) differences between treatments in bodyweights at any time during the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Field evaluation of an experimental albendazole pulse release bolus in the control of parasitic gastroenteritis in first-season grazing calves

A field experiment is described which evaluates the use of an experimental albendazole pulse release bolus (E-bolus) on gastrointestinal parasitism. The bolus was administered at turnout to 9 first-season grazing calves and 9 animals were kept as controls on a separate pasture. Dry summer observed. The E-bolus introduced at the start of the grazing season provided moderate control of gastrointestinal parasitism. The beneficial effect of the treatment was demonstrated by lower strongyle egg counts and significant differences in ELISA extinctions for Ostertagia, Cooperia and Dictyocaulus. However pepsinogen values were elevated in the bolus-treated group, probably because of the long interval (31 days) between the pulsed treatments. Although not significant there was a trend for the bolus-treated group to gain more weight than the controls.     

Production responses to internal parasite control in dairy cattle

A significant increase in milk production, averaging 164 litres per cow per lactation (a 4.8% increase), was seen after cows infected with gastrointestinal nematodes, paramphistomes and Fasciola hepatica were treated with broad-spectrum anthelmintics. Three hundred and ninety pairs of cows from eight herds with year-round calving were studied. One cow in each matched pair was given 7.5 mg/kg fenbendazole, 7.5 mg/kg levamisole hydrochloride and 15 mg/kg oxyclozanide in March, May and August of one year; the other cow in the pair received no anthelmintic. The number of nematode and trematode eggs was significantly decreased in the faeces of treated cows.     

Assessment of the effect of gastrointestinal nematode infestation on weight gain in grazing beef cattle

OBJECTIVE: To assess the effect of subclinical, naturally acquired gastrointestinal nematode infestation on weight gain in yearling cattle kept on pasture. DESIGN: Prospective study. ANIMALS: 799 Bos taurus yearlings kept on pasture with 2,805 herd mates in eastern and central South Dakota. PROCEDURE: 11 trials were initiated at 9 sites from 1999 through 2001. For each trial, approximately 10% of cattle in each site's pasture group were identified, weighed, and administered a bolus of ivermectin (sustained-release formulation) prior to turnout. A similar subgroup of nontreated control cattle was identified and weighed prior to turnout. For each trial, treated and control groups remained with the larger pasture group throughout the entire grazing season. At the end of the grazing season, weight measurements and fecal samples were obtained from all treated and control cattle; average daily grazing gain was calculated and compared between these 2 groups. RESULTS: Treatment of grazing cattle with ivermectin increased average daily gain by 0.0459 +/- 0.01 kg/head/d (mean +/- SEM; 0.1 +/- 0.02 lb/head/d), compared with that achieved in control cattle. Control cattle had significantly greater fecal egg counts at grazing season end than treated cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with anthelmintic-treated cattle, yearling cattle with naturally occurring gastrointestinal nematode infestations kept on pasture in the US Northern Plains had a decreased average daily gain equivalent to 6.6 kg (14.5 lb) less gain in a 143-day grazing season. Strategies for control of nematode populations in pastures should be considered to ameliorate this production loss.     

Comparison of three methods for gastrointestinal nematode diagnosis determination in grazing dairy cattle in relation to milk production

Development of resistance to anthelmintic drugs has motivated the search for diagnostic methods to identify animals for targeted selective treatments. We compared three methods for the diagnosis of nematode infection in relation to milk production in a fully grazing dairy herd of 150 cows in the humid Pampa (Argentina). Animals had feces, blood and milk sampled during the first postpartum month for EPG, pepsinogen and anti-Ostertagia antibody determination, respectively. With the results obtained two groups of cows, divided in high and low parasite burden, were conformed for each method, and milk production was then compared between groups. When cows were separated by the EPG method (EPG=0 (N=106) vs. EPG>0 (N=44)) a difference of nearly 800 l of milk per cow per lactation was found (P<0.05). On the other hand, milk production between groups separated by Pepsinogen (mUtyr ≤ 1000 vs. mUtyr > 1000) or by anti-Ostertagia (ODR ≤ 0.5 vs. ODR > 0.5) results did not differ. Interestingly, proportion of cows in each group differed between methods (P<0.0001), and the anti-Ostertagia method yielded significantly more cows in the high index group compared to results using the EPG or Pepsinogen method. No correlations were found between parasite indexes determined by the different methods. High parasite burden estimation found may be ascribed to the production system, fully grazing all year round, and to the sampling time, at the beginning of lactation with cows in negative energy balance and depressed immunity. The fact that the cows were born and reared outside, on pasture with continuous nematode larvae exposure, may also account for the results obtained. In conclusion, EPG counting during the first postpartum month may be a useful tool for the diagnosis of production impairment induced by high nematode burden in adult grazing dairy cows. The anthelmintic treatment of only the EPG-positive recently calved cows would improve milk production, while reducing selective pressure on nematode population for the development of resistance.     

Evaluation of clinicopathological parameters in cattle grazing timber milkvetch.

The purpose of this study was to determine whether hematological and serum biochemical parameters could be used to diagnose poisoning in cattle grazing timber milkvetch (Astragalus miser var. serotinus), a nitropropanol-containing legume. Blood samples were obtained from 20 Hereford cattle on timber milkvetch range in southern British Columbia during 1992 and 1993. Relevant changes in blood parameters were not detected and the parameters could not be used to predict nitropropanol ingestion or intoxication. The same parameters were measured in dosing trials with cattle with rumen fistulas, but relevant changes were not detected. Succinate dehydrogenase is the key target in nitropropanol intoxication and an assay for this enzyme may provide a probe for diagnosis.     

Sero-epidemiological survey of Dictyocaulus viviparus infections in first-season grazing calves in The Netherlands

A sero-epidemiological survey of Dictyocaulus viviparus infections in calves was carried out using an enzyme-linked immunosorbent assay. Infection level with D viviparus was correlated with farm, herd and management characteristics. At least 75 per cent of the herds were infected with D viviparus. Calves on zero-grazing farms were infected at a lower level than calves grazing pasture. No regional differences in infection rate were observed. On 15 per cent of the farms calves had clinical husk while 51 per cent of farms had experienced husk in the past. A higher level of infection was seen when calves were housed later in the autumn. The number of calves grazing together and the stocking rate had a significant positive influence on the level of infection. No significant difference in the occurrence of clinical husk was observed between calves vaccinated against lung-worm disease and calves not vaccinated against the disease.