The efficacy of injectable and pour-on formulations of moxidectin against lice on cattle

SUMMARY The efficacy of one administration of moxidectin against natural infestations of the 3 common species of cattle lice in Australia: Linognathus vitull, Damallnla bovls and Haematoplnus eurysternus, was determined. A high degree of control of L vituli (too long-nosed sucking louse) was achieved with both the cattle Injection (96.7% and 100%) at 0.2 mg/kg and the cattle pour-on formulation (94.6% and 100%) at 0.5 mg/kg on the 2 farms where this louse occurred. An Injection of moxidectin at 0.2 mg/kg did not eliminate D bovis. In these trials efficacy ranged from nll to 85.2%. In contrast the pour-on formulation at 0.5 mg/kg provided consistently high efficacy (83.6 to 100%) against D bovis on 3 farms. Infestations of H eurysternus (the short-nosed sucking louse) were low and no significant difference was recorded between treatment groups In a single trial, however, lice persisted on 3 to 7 cattle In the untreated group at each Inspection, whereas none were found on any animals in the 2 groups treated with moxidectin on Inspection after treatment.     

Detecting benzimidazole resistance with faecal egg count reduction tests and in vitro assays

Composite strains of Trichostrongylus colubriformis and Ostertagia spp consisting of 0, 1, 10, 25, 50, 75, 90, and 100% of known resistant strains were prepared and tested for benzimidazole resistance using faecal egg count reduction tests, in vitro egg hatch assays and tubulin binding assays. All tests detected resistance where the proportion of the resistant strain in the composite was 50% or more, whereas none of the tests unequivocally detected resistance below 25%. Egg count reduction tests were no less sensitive than the in vitro tests in detecting low levels of resistance but the egg hatch and tubulin binding assays provided a better quantitative estimate of moderate to high levels of resistance. Faecal egg count reduction therefore, provides a suitable means of detecting resistance in the field but tests, more sensitive to low levels of resistance are required. Results indicate that the use of post-treatment counts alone provides an adequate indication of anthelmintic efficiency.     

Serological characterisation of Australian isolates of Actinobacillus pleuropneumoniae

SUMMARY: Using hyperimmune rabbit antiserums to 8 reference serovar strains, a total of 51 Australian isolates of Aclinobacillus pleuropneumoniae were serotyped by either a rapid slide agglutination test or a gel diffusion test. The results were: serovar 1 — 24 isolates; serovar 2 — 6 isolates; serovar 3 — 5 isolates; serovar 7 — 15 isolates; nontypable — 1 isolate. The rapid slide agglutination test was suitable for screening field isolates, as 73% of those tested reacted with only 1 of the 8 antiserums and were assigned to a particular serovar of the basis of this test alone.     

Strategic use of crutching and dicyclanil to protect unmulesed sheep against breech strike

Objective   To test strategies for the application of dicyclanil and mid-season crutching to maximise protection of unmulesed sheep against breech strike.
Procedure   Three hundred and eighty unmulesed Merino weaners were randomly allocated to four groups either left untreated or treated by different strategies with 50 g/L dicyclanil. Treatments included breech treatment alone and breech plus body treatment, with two application times, immediately after shearing and 6 weeks after crutching or shearing. To assess protection, larval implants with newly hatched Lucilia cuprina larvae were applied to 10 different sheep from each group at 3, 4, 5 and 6 months after crutching and shearing and assessed for the development of strike at 48 hours. The concentration of dicyclanil was measured in wool samples clipped from the breeches of the test sheep.
Results   All dicyclanil treatments gave significant reduction in strike in comparison to controls up until 4 months after crutching but protection in the sheep treated immediately after shearing had waned at 5 months. Treating at 6 weeks after crutching provided significant reduction ( P < 0.05) in strike for 6 months. Results for strike incidence immediately after shearing and concentration of dicyclanil in the breech wool also suggested improvements in protection by delaying treatment for 6 weeks.
Conclusion   In most environments it should be possible to protect unmulesed sheep against breech strike with a carefully planned integrated control program incorporating strategically timed crutching, shearing and dicyclanil application. Delaying treatment with dicyclanil to at least 6 weeks after shearing or crutching increased the protection provided in comparison to treatment immediately after shearing.     

Dietary Fat Supplementation and the Consequences for Oocyte and Embryo Quality: Hype or Significant Benefit for Dairy Cow Reproduction?

In many countries, fat supplementation in the diet has become common in the dairy industry. There are several ideas as to how dietary fat could influence reproductive performance. Saturated fatty acids, such as palm oil, can increase milk yield but may aggravate negative energy balance and thus may impair fertility when fed during the first week post‐partum. However, priming the lipid oxidation in the liver by feeding saturated fats during the dry period has recently been shown to be a potentially promising strategy to mitigate fat mobilization and liver accumulation post‐partum. Furthermore, polyunsaturated fats (omega‐3 fatty acids and conjugated linoleic acids) are fed to reduce the ‘de novo’ fat synthesis in the udder and thus the milk fat content, which may be of modest benefit for overall energy balance. Furthermore, omega‐6 and omega‐3 polyunsaturated fatty acids are reported to alter follicular growth, steroid synthesis and prostaglandin metabolism in the ovary and endometrium, respectively. Omega‐6 fatty acids are believed to have pro‐inflammatory and thus PGF2α‐stimulating properties rendering them extra value as ‘nutraceutical’ early post‐partum, while omega‐3 fatty acids can weaken this inflammatory potency, leading to a higher chance of survival of the embryo when supplemented during the periconceptual period. Unfortunately, research results rarely provide a consensus in this perspective. The consequences of these fat‐feeding strategies on oocyte and embryo quality remain an intriguing issue for debate. Fat feeding may alter the microenvironment of the growing and maturing oocyte of the early and older embryo and thus may affect reproductive outcome. We recently reported that dietary‐induced hyperlipidaemic conditions can be harmful for embryo development and metabolism. However, to date, research results remain somewhat conflicting most probably due to differences in fat sources used, in diet and duration of supplementation and in experimental set‐up in general.