The effect of zinc oxide and elemental zinc boluses on the concentrations of Zn in serum and faeces, and on providing protection from natural Pithomyces chartarum challenge in calves.

AIM: To investigate the efficacy of intra-ruminal Zn boluses as aids in providing protection from natural Pithomyces chartarum challenge in calves. METHODS: Sixty-two calves (mean weight 187 (SEM 3.25) kg) were divided into three groups. Commencing on Day 0, they received either a proprietary bolus containing 83% ZnO (ZnO group), a prototype Zn bolus containing 88% elemental Zn (Zn group), or remained untreated (Control group). Concentrations of Zn in serum and faeces were measured weekly between Days 6 and 34, activities of gamma-glutamyl transferase (GGT) in serum on Days -8, 20, 34 and 41, and faecal spore counts between Days 13 and 41. RESULTS: Between Days 6 and 34, mean concentrations of Zn in serum increased in both Zn treatment groups compared with Controls (p<0.001), but were lower in Zn than ZnO animals between Days 6 and 28 (p=0.05). Concentrations of Zn in faeces were increased in both groups following treatment with Zn. Mean concentrations of Zn in faeces in ZnO animals was higher than Zn animals on Days 13 and 20 (p<0.001), but decreased by Day 34, whereas for Zn animals they were still elevated on Day 34. Faecal spore counts were 354,000 and 183,000 on Days 13 and 20, respectively, 610,500 on Day 28, and 115,500 spores/g on Day 34. There were no clinical signs of facial eczema, but based on the activities of GGT on Day 41, 17/20 (85%) Controls were moderately or severely affected (GGT >250 IU/L) compared with 1/21 (5%) ZnO and 3/21 (14%) Zn animals. Mean activities of GGT on Day 41 for ZnO and Zn animals were not different (35 (95% CI=23-54) and 54 (95% CI=32-92) IU/L, respectively; p=0.18), but were below those of the Controls (502 (95% CI=296-850) IU/L), confirming efficacy of both bolus treatments. In both ZnO and Zn animals, there was no significant relationship between concentration of Zn in serum and activity of GGT, but in Zn animals there was a significant relationship between the concentration of Zn in faeces and activity of GGT 21 days later. The regression equation y=2.136-0.002197x (where y is log10GGT activity, and x the concentration of Zn in faeces) provided an estimate of the threshold level of concentration of Zn in faeces. CONCLUSION: The study confirmed efficacy of elemental Zn boluses in providing protection from natural P. chartarum challenge in young cattle.

The effect of zinc oxide and elemental zinc boluses on the concentrations of Zn in serum and faeces, and on providing protection from natural Pithomyces chartarum challenge in sheep.

AIM: To investigate the efficacy of intra-ruminal Zn boluses as aids in providing protection from natural Pithomyces chartarum challenge in sheep. METHODS: Seventy-two adult sheep (mean weight 59 (SEM 0.5) kg) were divided into four groups. Commencing on Day 0, they received either a proprietary bolus containing 67 g ZnO (equivalent to 54 g Zn) (ZnO group), two different levels of elemental Zn (81 and 108 g) delivered in boluses each containing 27 g Zn (Zn81 and Zn108 groups, respectively), or remained untreated (control). Concentrations of Zn in serum, activities of gamma-glutamyl transferase (GGT) in serum, and spore counts on pasture were measured weekly from Day -6, and concentrations of Zn in faeces weekly from Day 21, until Day 77. RESULTS: Mean concentrations of Zn in serum between Days 14 and 42 were significantly higher in ZnO animals (15.4 (SEM 0.70) micromol/L) than the other groups. Mean concentrations in Zn108 animals (11.1 (SEM 0.26) micromol/L) were significantly higher than controls, but there were no differences between Zn81 and the controls (9.9 (SEM 0.20) and 9.4 (SEM 0.26) micromol/L, respectively). Between Days 21 and 49, there was no significant difference in mean concentrations of Zn in faeces between ZnO and Zn81 animals (307 (SEM 28) and 281 (SEM 29) mg/kg fresh weight (FW), respectively), but concentrations were significantly higher in Zn108 animals (500 (SEM 40) mg/kg FW). Spore counts exceeded 70,000/g on Days 14, 28, 49, 56 and 63 but there were no clinical signs of facial eczema. In controls, activities of GGT were unchanged until Day 21, then increased to 637 IU/L at Day 70; for ZnO animals, activities remained <75 IU/L until Day 14, then increased to 200 IU/L at Day 70; for Zn81 and Zn108, they remained <75 IU/L until Day 35, and then increased at Day 70 to 369 IU/L and 293 IU/L, respectively. From Day 56 activities were significantly lower in all treated groups compared with controls, but there was no significant difference between the three Zn bolus treatments. There were significant negative correlations between activities of GGT and concentrations of Zn in serum in Zn108 animals, and with concentrations of Zn in faeces for both Zn81 and Zn108 groups. CONCLUSION: Elemental Zn boluses can reduce activities of GGT associated with elevated spore counts. The association between concentrations of Zn in faeces and activities of GGT suggests that a minimum concentration of Zn in the gastrointestinal tract may be important in providing protection against sporidesmin.

A large-scale clinical field study to evaluate the efficacy and safety of an oral formulation of the amino-acetonitrile derivative ( AAD ), monepantel , in sheep in New Zealand.

AIM: To evaluate the efficacy and safety of an oral formulation of the novel anthelmintic, monepantel (AAD 1566), in sheep, in comparison with some other anthelmintics currently registered in New Zealand. METHODS: A study was conducted on 18 farms located throughout the North and South Islands of New Zealand. On each farm, sheep naturally infected with the target nematodes were randomly assigned to groups, which were then treated with either monepantel, at a minimum dose rate of 2.5 mg/kg, or one of five other anthelmintics encompassing the range of single-entity and combination formulations that are commercially available in New Zealand, or left untreated as controls. Faecal samples were collected from all sheep pre-treatment (1-3 weeks before treatment), at the time of treatment, and approximately 1, 2 and 3 weeks after treatment (Days 7, 14 and 21). Faecal nematode egg counts (FEC) were measured in all samples, and the efficacy of treatments, as indicated by reductions in FEC, calculated. All sheep were inspected at least daily, to check for any adverse effects of treatment. RESULTS: On all 18 farms, on Days 7, 14 and 21 (54 test points), the efficacy of the monepantel solution was >95%. At Days 7 and 14 post-treatment, efficacies>99% were recorded in 15 flocks. At Day 21 post-treatment, efficacies>98% were recorded in 13 flocks. Monepantel was as effective, or more effective, than the registered anthelmintics with which it was compared. Moreover, it was effective against strains of nematodes resistant to one or more of the currently available broad-spectrum anthelmintics. The monepantel solution used in this study was well tolerated by the sheep, and no adverse events could be attributed to its use. CONCLUSIONS AND CLINICAL RELEVANCE: When administered as an oral formulation under field conditions, at a minimum dose rate of 2.5 mg/kg, monepantel appeared to be highly effective against all the major genera of gastrointestinal nematodes of sheep, including Haemonchus, Teladorsagia (=Ostertagia), Trichostrongylus, Cooperia, Nematodirus, Chabertia and Oesophagostomum. This included strains resistant to the currently available broad-spectrum anthelmintics. Monepantel is the first compound from the recently discovered amino-acetonitrile derivative (AAD) class of anthelmintics to be developed for use in sheep.

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.

An evaluation of two cypermethrin-based pour-on formulations on sheep infested with the biting louse, Bovicola ovis.

Two synthetic pyrethroid (cypermethrin) based pour-on insecticide formulations, with high cis/trans isomer ratios (80:20) but differing in their respective active ingredient concentrations and solvent component(s), were applied to sheep infested with the biting-louse, Bovicola ovis. All treated sheep were penned with louse-infested sheep 9,12 and 15 weeks after the insecticide was applied. The 2% cypermethrin formulation achieved a higher level of control than the 1.25% cypermethrin formulation at each challenge interval when applied 12 weeks after shearing. The 2% cypermethrin formulation provided 97-100% control of lice from 4 to 16 weeks after application on sheep shorn 6 or 12 weeks prior to treatment. The 1.25% cypermethrin formulation provided 85% control of lice 4 weeks after application on sheep shorn 12 weeks prior to treatment, the level of control increasing to a maximum of 100% by week 9, and declining thereafter. The 2% cypermethrin formulation may provide a better level of control in long-woolled sheep than 1.25% cypermethrin, by compensating for the diluent effect of lipid.