Effects of residues of deltamethrin in cattle faeces on the development and survival of three species of dungbreeding insect

Objective To assess the toxicity to insects of drug residues excreted in cattle faeces following treatment with deltamethrin.
Design Bioassays were performed on one species of dung-breeding fly ( Musca vetustissima ) and two species of dung beetle ( Onthophagus binodis and Euoniticellus fulvus ).
Animals Cattle on properties near Kangaroo Valley, Canberra and Gundagai were treated with pour-on formulations of deltamethrin. Untreated animals acted as controls.
Procedures Faeces from treated and untreated cattle were inoculated with newly emerged fly larvae or fed to adults of two species of dung beetle. Percentage survival and duration of development provided measures of the toxicity of deltamethrin residues in faeces.
Results Residues of deltamethrin were excreted in concentrations sufficient to inhibit survival of larvae of M vetustissima for 1 to 2 weeks after treatment. Peak concentrations of 0.4mg deltamethrin/kg dry weight of faeces occurred 3 days after treatment and were sufficient to kill adult beetles for at least twice this period. With one of two formulations tested, there was evidence of a reduction in dung beetle fecundity and an increase in the duration of juvenile development. A model of the effect of deltamethrin on the breeding success of dung beetles in the field suggests that a single treatment, applied when most of the population is in a non-parous condition, may cause up to 75% reduction in beetle acitivity by the end of the season. Multiple treatments at 10 or 21 day intervals may drive local populations towards extinction.
Conclusion Depending on the time and frequency of treatment, the effect of deltamethrin on insects in cattle faeces may range from negligible to catastrophic.     

Efficacy of ivermectin in a controlled-release capsule for the control of breech strike in sheep

Objective To investigate the efficacy of ivermectin in an intraruminal controlled-release capsule (CRC) against blowfly strike.
Design Pen and field trials with controls.
Animals Pen studies: Two breech strike trials involving 60 Romney and 60 Merino sheep. One body strike trial using 100 Merino sheep.
Field trials: Eight trials in New Zealand used 1000 Romney and Romney-cross sheep. Fifty Merino lambs in one trial in Australia.
Procedure Pen studies: Sheep were allocated to two equal groups. One was not treated, the other sheep received a CRC that delivered ivermectin at 20 μg/kg/day for 100 days. In the breech strike trials, each animal was given an oral laxative 2 days before exposure to adult Lucilia cuprina . In the body-strike trial, the sheep sheep were kept wet to increase susceptibility prior to the release of blowflies.
Field trials: Fifty or 200 sheep allocated to equal groups of nontreated or treated with the CRC and grazed at pasture exposed to natural blowfly challenge.
Results Pen studies: Breech strikes developed in 24 of 60 controls but in none of 60 CRC-treated sheep. There was a 35% reduction in the number of CRC-treated sheep struck on the body.
Field trials: The average number of breech strikes in CRC-treated sheep was reduced by 86% (P < 0.001). The number of body strikes in the treated groups was a reduced by 27% (P < 0.05).
Conclusion The ivermectin CRC is a useful aid in controlling breech strike, but provides only moderate reduction in the incidence of body strike.     

Efficacy of ivermectin controlled-release capsules for the control and prevention of nasal bot infestations in sheep

Objective To investigate the therapeutic and prophylactic efficacy of an ivermectin controlled-release capsule against nasal bots (Oestrus ovis) in sheep.
Design Trial 1 – A pen study with controls. Trial 2 – A field study with controls.
Animals Trial 1 – Forty Merino wethers with natural infestations of nasal bot were used. Trial 2 – One hundred nasal bot-free wethers were used.
Procedure Trial 1 – Ten randomly selected animals were slaughtered and the heads split and examined to confirm bot infestation. Fifteen animals were allocated to untreated controls and 15 to treatment with a controlled-release capsule delivering ivermectin at ≥ 20 μg/kg/day for 100 days. Twenty-nine days after treatment the sheep were killed and examined for nasal bots. Trial 2 – Nasal bot-free sheep were allocated to two groups of 45 animals. One group was untreated the other sheep were treated with capsules as above. The sheep were grazed as a single group exposed to natural challenge from O ovis . Ninety days after treatment the animals were slaughtered and examined for nasal bot infestation.
Results Trial 1 – Live O ovis larvae were recovered from 60% of control sheep. No live larvae were collected from treated sheep. Trial 2 – Forty-one percent of untreated sheep harbored nasal bot infestations. No live larvae were collected from any treated animal.
Conclusion Treatment with a single ivermectin controlled-release capsule was 100% effective against existing infestations of O ovis and as a prophylactic treatment for this parasite.     

Transmission of Babesia spp by the cattle tick (Boophilus microplus) to cattle treated with injectable or pour-on formulations of ivermectin and moxidectin

OBJECTIVE: To assess the efficacy of ivermectin and moxidectin to prevent transmission of Babesia bovis and Babesia bigemina by Boophilus microplus to cattle under conditions of relatively intense experimental challenge. DESIGN: Naive Bos taurus calves were treated with either pour-on or injectable formulations of either ivermectin or moxidectin and then exposed to larvae of B microplus infected with B bovis or larvae or adults of B microplus infected with B bigemina. One calf was used for each combination of haemoparasite, B microplus life stage, drug and application route. PROCEDURE: Groups of calves were treated with the test drugs in either pour-on or injectable formulation and then infested with B microplus larvae infected with B bovis or B bigemina. B bigemina infected adult male ticks grown on an untreated calf were later transferred to a fourth group of animals. Infections were monitored via peripheral blood smears to determine haemoparasite transmission. RESULTS: Cattle treated with either pour-on or injectable formulations of ivermectin and moxidectin became infected with B bovis after infestation with infected larvae. Similarly, larvae infected with B bigemina survived to the nymphal stage to transmit the haemoparasite to animals treated with each drug preparation. Cattle treated with pour-on formulations of ivermectin and moxidectin then infested with adult male ticks infected with B bigemina did not become infected with B bigemina whereas those treated with the injectable formulations of ivermectin and moxidectin did show a parasitaemia. CONCLUSIONS: Injectable or pour-on formulations of ivermectin and moxidectin do not prevent transmission of Babesia to cattle by B microplus. Use of these drugs can therefore not be recommended as a primary means of protecting susceptible cattle from the risk of Babesia infection.     

Effects of drug residues in the faeces of cattle treated with injectable formulations of ivermectin and moxidectin on larvae of the bush fly, Musca vetustissima and the house fly, Musca domestica

Objective: To assess the toxicity of residues of ivermectin and moxidectin in cattle faeces collected at intervals after treatment.
Design: Replicated bioassays of faeces using larvae of the bush fly, Musca vetustissima and the house fly, Musca domestica .
Animals: Two groups of five Murray Grey x Aberdeen Angus steers were treated with injectable formulations of ivermectin and moxidectin respectively. A third group was used as an untreated control.
Procedure: Newly emerged fly larvae were reared in the dung of treated animals.
Results: Drug residues in faeces collected 3 to 35 days after treatment with an injectable formulation of moxidectin had no significant effect on the survival of larvae of M vetustissima . Similarly, faeces dropped up to seven days after treatment caused no significant reduction in larval survival in M domestica . In day 2 dung, residues of moxidectin delayed development of M vetustissima larvae, but had no effect on their survival. In contrast, ivermectin-treated steers, produced dung that inhibited larval development of both M vetustissima and M domestica for 7 to 14 days after treatment. Significant reductions in survival of M vetustissima larvae occurred in dung collected on days 21 and 28 after treatment, but by day 35 survival did not differ from that in control dung.
Conclusion: Excreted faecal residues of moxidectin are relatively innocuous to larvae of both M vetustissima and M domestica . Those of ivermectin inhibit survival for 7 to 14 days after treatment and are likely to have adverse effects on non-target organisms.     

Comparative effects of abamectin and two formulations of ivermectin on the survival of larvae of a dung-breeding fly

Objectives To compare the survival of larvae of a dung-breeding fly in the faeces of cattle treated either with an injectable formulation of abamectin, or with oral or injectable formulations of ivermectin.
Design Replicated bioassays were conducted on larvae of the bush fly, Musca vetustissima, using faeces collected before and at intervals after drug treatment.
Animals Two cows and their calves were allocated to each of three drug treatments and dosed according to individual weights.
Procedures Differences in the proportions of larvae pupariating were used as measures of the toxicity of drug residues.
Results Development of fly larvae was inhibited in all faeces collected 1 to 4 days after treatment. In cattle treated with oral ivermectin, there was reduced larval survival in faeces collected 8 and 16 days after treatment, but by day 32, survival was equivalent to that recorded in the faeces of untreated cattle. With injectable ivermectin, there was no survival at day 8, limited survival at day 16 and, at day 32, survival was not significantly affected. With injectable abamectin, survival was completely suppressed until day 32, at which time the number of pupariating larvae did not differ significantly from that recorded in faeces from untreated animals.
Conclusion The oral formulation of ivermectin is eliminated more rapidly than the injectable formulation and, as a consequence, is likely to be less harmful to dung-feeding insects. Abamectin and ivermectin appear to equally toxic larvae of M vetustissima.     

Effects of tail amputation and treatment with an albendazole controlled-release capsule on the health and productivity of prime lambs

OBJECTIVE: To assess the effects of tail amputation and treatment with albendazole controlled-release capsule (CRC) on the health and productivity of prime lambs. DESIGN: Field trials on three farms. ANIMALS: About 551 Coopworth-Poll Dorset cross, 588 Border Leicester-Merino-Poll Dorset cross and 575 Corriedale-Poll Dorset cross lambs. PROCEDURE: On three farms, lambs with amputated tails were compared with an equal number of lambs with tails left entire. In both of these groups half the lambs were treated with an albendazole CRC 13 weeks after the start of lambing. Faecal soiling of the breech and flystrike of the breech were recorded. Lambs were weighed and body condition scored at each visit and carcase weights and fat score of each lamb at slaughter. Procedures on the slaughter chain were monitored to determine whether the retention of the tail caused any problems. RESULTS: There were no observed benefits of treatment with an albendazole CRC on the farms in the study. There was no strong evidence that tail amputation had any long-term effect on the growth rate of lambs or carcase traits. No detrimental effects were observed during processing of lambs with long tails in the abattoir. Lambs with entire tails had significantly greater mean dag scores than lambs with amputated tails. On one farm lambs with entire tails were at about twice the risk of requiring crutching and on another farm were at three times the risk of breech strike compared with lambs with amputated tails. CONCLUSION: This study provides evidence that amputating the tail is not an absolute requirement to maintain the health and welfare of prime lambs, but leaving the tail of prime lambs entire is likely to increase chemical usage to control flystrike, and to increase the frequency of crutching.     

Prevention of blowfly strike on coarse and fine woolled sheep with the insect growth regulator dicyclanil

OBJECTIVE: To assess a ready-to-use formulation of dicyclanil to prevent blowfly strike on coarse and fine woolled sheep under New Zealand conditions. DESIGN: Randomized clinical field trials. PROCEDURE: In a first field trial, coarse wooled sheep treated with a ready-to-use, 5% dicyclanil formulation were compared with untreated control sheep for up to 21 weeks. In a second field trial, fine woolled sheep, treated with the same dicyclanil formulation, were compared with untreated sheep for up to 19 weeks. Efficacy was assessed by calculating the aggregated cumulative strike rate. RESULTS: For trial 1 (coarse woolled sheep) the aggregated cumulative strike rate at the end of the trial at week 21 after treatment reached 3.9% and 19.1% for treated and untreated sheep, respectively. For the treated animals the aggregated cumulative strike rate reached the 1% and 2% benchmarks between weeks 11 and 12. For trial 2 (fine woolled sheep) the aggregated cumulative strike rate at the end of the trial at week 19 reached 0.6% and 7.5% for treated and untreated sheep, respectively. Wool length at the time of application did not substantially influence the efficacy of dicyclanil. CONCLUSION: Under New Zealand field conditions, a ready-to-use 5% spray-on formulation of dicyclanil protected coarse woolled sheep for at least 12 weeks and fine woolled sheep for at least 19 weeks.     

The Effect of Anthelmintic Capsules on the Egg Output and Larval Viability of Drug-resistant Parasites

Challenge with an equal mix of drug-resistant and drug-susceptible larvae of Teladorsagia circumcincta resulted in infections in groups of lambs (n = 6) either untreated or given controlled-release capsules, containing either albendazole or ivermectin. Lambs treated with albendazole capsules contained similar numbers of adult worms at necropsy to the other groups but had no detectable faecal egg count. Animals treated with ivermectin capsules had similar worm burdens and faecal egg counts to the control group but the worms had significantly higher numbers of eggs in utero. These results provide evidence for suppression of egg production by both anthelmintic treatments. The observation that albendazole caused a significant reduction in the developmental success of parasite eggs also has implications for the use of faecal egg count as an indicator for pasture contamination with resistant parasites. In two further groups of lambs, either untreated or given albendazole capsules, treatment caused a significant reduction in egg count and adult worm burden of Trichostrongylus colubriformis. No significant effects were observed on in utero egg counts or egg viability and the apparent effect on the number of eggs produced in faeces per adult female was not significant (p = 0.077). There was, therefore, no evidence that albendazole controlled-release capsules caused suppression of egg output in this species.     

A comparison of the development and survival of the dung beetle, Onthophagus taurus (Schreb.) when fed on the faeces of cattle treated with pour-on formulations of eprinomectin or moxidectin

Faeces voided by 1-year old cattle at 3-70 days after treatment with a pour-on formulation of moxidectin had no detectable effects on development or survival of the common dung beetle Onthophagus taurus. In contrast, faeces voided by cattle treated with a pour-on formulation of eprinomectin were associated with high juvenile mortality during the first 1-2 weeks after treatment. Increased mortality also occurred among newly emerged beetles fed on faeces collected 3 days after eprinomectin treatment and there was evidence of suppressed brood production among those that survived. This effect was still apparent even after insects fed for a further 10 days on the faeces of untreated cattle. A model simulating the effects of drug residues on dung beetle populations suggests that in the absence of immigration a single treatment of eprinomectin is capable of reducing beetle activity in the next generation by 25-35%. Effects are likely to be greatest when treatment coincides with emergence of a new generation of beetles.     

The effect of breed, stage of lactation and parity on sheep milk fat CLA content under the same feeding practices

The cis-9, trans-11 C_18:2 (CLA) content in milk fat of four pure sheep breeds (Awassi, Lacaune, Friesland and Chios) was examined. All sheep were kept indoors all year round under the same feeding practices, without any grazing at all. Sheep nutrition was based on alfalfa hay and concentrates. A total of 237 individual milk samples were collected at three sampling times (December, January and March) from sheep of different parity and different days in milk, for CLA determination. The results showed that: (a) there was a large variation in milk fat CLA content among individuals consuming the same diet, (b) the CLA content of milk fat was lower in Friesland breed, compared to the other three breeds but without any significant difference among the four sheep breeds, (c) the CLA content of milk fat was not affected by ewes parity or days in milk, (d) there was a negative but not significant correlation between milk fat and CLA concentration, (e) the CLA content of milk fat was not correlated with milk yield. In conclusion, no others factors, such as breed, parity, days in milk, etc., can affect CLA content in milk fat, which means that the dietary ones remain the sovereign factors explaining the highest proportion of CLA content variability in sheep milk fat.     

The effect of grain species, processing and time of feeding on the efficiency of feed utilization and microbial protein synthesis in sheep

This study investigated the effect of cereal grain species (sorghum, wheat, oats and barley), extent of processing (cracked barley, finely ground barley, and wet whole barley) and time of feeding (barley grain mixed with ryegrass hay or fed 2 h before hay was fed), on whole tract dry matter digestibility (WTDMD), and microbial protein synthesis (MPS), as a supplement to ryegrass hay when fed to rumen-cannulated sheep.Expected dry matter digestibility (EDMD) in mixtures of cereal grain and ryegrass hay was calculated by interpolation between in vitro dry matter digestibility (DMD) of each grain and the ryegrass hay. These were compared with measured actual WTDMD to detect positive or negative associative effects. Among grain species, the percentage difference in digestibility between actual WTDMD and EDMD was negative at − 6.6% units for wheat but positive at + 2.3%, + 4.3% and + 5.7% units for sorghum, oats, cracked or finely ground barley, respectively.As expected, the supplementation of sheep fed ryegrass hay with different sources of carbohydrates increased urinary allantoin output (as an indicator of MPS) when compared to sheep fed ryegrass hay alone. The concentration of urinary allantoin was significantly higher in sheep supplemented with sorghum (1916 mg/sheep/day) than wheat, oats or cracked barley ([mean ± S.E.M.] 1451 ± 24 mg/sheep/day) grain. There was a significantly higher urinary allantoin concentration in sheep fed cracked barley compared to finely ground barley or wet whole barley (1479 vs. 1095 vs. 1031 mg/sheep/day, respectively). There was no significant (P > 0.05) difference in urinary allantoin output, expressed as output/kg DM intake, when cracked barley was mixed and fed with the hay or fed 2 h before hay. However, in terms of total output of allantoin this was significantly higher (P < 0.05) (1479 vs. 1209 mg/sheep/day).In sacco degradability characteristics of organic matter and nitrogen for sorghum, oats, wheat, barley at different levels of processing and for ryegrass hay were also measured in the rumen of cannulated sheep.Among grain species, wheat had the highest effective organic matter degradability in the rumen (78.1%) while sorghum had the lowest. The effective degradability of protein of finely ground barley in the rumen was found to be higher than cracked barley or wet whole barley.Wheat grain, being highly degradable in the rumen, had a negative effect on WTDMD. In contrast, sorghum grain, being more slowly degradable in the rumen, would be expected to provide a substantially increased supply of energy to microbes over time in the rumen for MPS.Both cracked barley and finely ground barley also had a positive associative effect on WTDMD when fed with ryegrass increasing it by 5.7% units. The MPS was significantly higher (P < 0.05) in sheep fed cracked barley compared to finely ground barley or wet whole barley. This supports the hypothesis that slowly degrading carbohydrate sources synchronise more closely with available N from degradation of forage in the rumen.     

The effect of mixed or sequential grazing of cattle and sheep on the faecal egg counts and growth rates of weaned lambs when treated with anthelmintics

An experiment was conducted over two successive years (2002 and 2003) to investigate the effects of grazing improved permanent pasture (mainly perennial ryegrass/white clover) by cattle or sheep, either sequentially or mixed, on the faecal egg counts and growth rates of weaned lambs when treated with anthelmintics. The grazing season was divided into two parts, May-July then July-October, relating to the pre- and post-weaning of the lambs. Four grazing regimes, replicated three times, were compared: (1) sheep only from May to October (SS); (2) cattle May to July followed by lambs until October (C/S); (3) cattle and sheep May to July followed by lambs until October (C+S/S); and (4) cattle and sheep May to July followed by cattle and lambs until October (C+S/C+S). Sward height was maintained at 6 cm using a "put and take" stocking system. At weaning, lambs were weighed and treated with an anthelmintic (0.08% ivermectin drench, Oramec) before being allocated to plots. They were then weighed and drenched every 28 days until the end of the experiment (Day 84). Faecal egg counts (FEC) were measured in all lambs immediately prior to each anthelmintic treatment. In 2002 and 2003, there were differences between the groups in FEC, with the SS lambs having the highest values and C/S lambs the lowest (P<0.01). There were also differences in the rate of liveweight gain of the lambs in each of the study years: for this parameter SS lambs had the lowest growth rate but the fastest growth was in C+S/C+S lambs not C/S lambs (P<0.01), indicating that these differences were due to factors other than parasite infection. Overall, sequential grazing of pastures with cattle then sheep reduced the faecal egg counts in lambs regularly treated with anthelmintics when compared with lambs grazing in mixed systems with cattle and sheep or with sheep only systems, however, the highest growth rates were observed in lambs in the mixed cattle/sheep grazing system throughout.     

The effects of urea‐treated potato pulp (PP) ensiled with beet pulp or wheat bran pellets to reduce moisture of PP and flake density of corn grain supplemented with the PP silage on digestibility and ruminal fermentation in beef steers

The effects of adding beet pulp or wheat bran to urea‐treated potato pulp (PP) in order to reduce moisture of PP silage and flake density of corn grain on digestibility and ruminal fermentation in beef steers were studied in a split‐plot design experiment. The whole‐plot treatments were PP silage mixed with 0% added pellets (CON), 9% (as‐fed basis) beet pulp pellets (BP) or 9% (as‐fed basis) wheat bran pellets (WB) as water‐absorbing materials. The subplot treatments consisted of supplements formulated to contain either high‐density corn (HDC) or low‐density corn (LDC). BP steers consumed more (BP vs WB, P = 0.011) concentrate than did WB steers, whereas hay intake did not differ between the treatments. Dry matter (BP vs WB, P = 0.023) and organic matter (BP vs WB, P = 0.029) digestibility were higher for BP steers than for WB steers. Starch digestibility was higher (P = 0.006) for LDC than for HDC. There were no differences in the concentration of ruminal ammonia nitrogen among the treatments. Molar proportions of ruminal acetate were higher for BP steers than for WB steers (BP vs WB, P = 0.030). Conversely, molar proportions of propionate were lower for BP steers than for WB steers (BP vs WB, P = 0.044). Flake density of corn did not affect ruminal characteristics. In conclusion, from the viewpoint of feed intake and digestibility, BP is superior to WB as a moisture control material for urea‐treated PP silage, and flake density of corn supplemented with urea‐treated PP silage does not alter ruminal fermentation.