Simulation modelling as a tool for evaluating surveillance programmes for detection of the Asian honeybee mite (Varroa destructor) in the South Island of New Zealand

AIM: To use a simulation model of the spread of the Asian honeybee mite (Varroa destructor) amongst apiaries, to evaluate a series of detection surveillance programmes for the South Island of New Zealand.

METHODS: Five potential incursion sites into the South Island were selected. A stochastic spatial simulation model, Varroa_sim, was adapted to simulate spread of the mite from these sites as a series of silent-phase propagating epidemics. The study population comprised all apiaries in the South Island registered in the Ministry of Agriculture and Forestry's (MAF's) apiary database in 2003. Six different surveillance programmes were simulated to try and detect the mite. Three of these were the actual multi-stage sampling plans conducted during the autumn (March–May) of 2001, 2002 and 2003, and the other three involved simple random sampling with sampling fractions equivalent to the actual numbers of apiaries tested in each of those years. The relative performances of the different surveillance plans were evaluated in terms of their ability to detect the mite early before it had spread too far and whilst there might still be a chance of eradication.

RESULTS: There were 13,798 registered apiaries in the South Island with valid map coordinates in the apiary database at the time of the study. The model generated 50 epidemics against which the various surveillance programmes were evaluated. The actual surveillance programmes conducted during the autumn of 2001 and 2002 generally performed fairly well in detecting the mite. The programme conducted in autumn 2003 detected the mite reasonably well in high-risk areas, but was very poor in low-risk areas. The simple random sampling strategies performed surprisingly well, and their relative rankings were proportional to the sampling fractions employed.

CONCLUSIONS: This study showed the value in using a spatial simulation model to generate plausible silent-phase epidemics, against which detection surveillance programmes could be evaluated, in ways that would otherwise not be possible.     

Antral Follicle Populations and Embryo Production – In Vitro and In Vivo – of Bos indicus–taurus Donors from Weaning to Yearling Ages

Interest in indicus–taurus cattle has been increasing, as these animals are likely to present the best characteristics of Zebu and European bovine breeds. The aim of this study was to compare the embryo production of indicus–taurus donors with high vs low antral follicle counts obtained by ovum pickup/in vitro production (OPU/IVP) and superovulation (SOV)/embryo collection. Braford females at weaning age (3/8 Nelore × 5/8 Hereford, n = 137, 9 ± 1 month old) were subjected to six serial ovarian ultrasonographs and were assigned to two groups according to the number of antral follicles ≥3 mm as follows: G‐High antral follicular count (AFC, n = 20, mean ≥40 follicles) and G‐Low AFC (n = 20, mean ≤10 follicles). When the females (n = 40) reached 24 months of age, they were subjected to both OPU/IVP and SOV/embryo collection. The average number of follicles remained highly stable throughout all of the ultrasound evaluations (range 0.90–0.92). The mean number of COCs recovered (36.90 ± 13.68 vs 5.80 ± 3.40) was higher (p < 0.05) for females with high AFC, resulting in higher (p < 0.05) numbers of total embryos among females with high vs low AFC (6.10 ± 4.51 vs 0.55 ± 0.83). The mean number of embryos per collection was also higher (p < 0.05) for G‐High vs G‐Low (6.95 ± 5.34 vs 1.9 ± 2.13). We conclude that a single ultrasound performed at pre‐pubertal ages to count antral follicles can be used as a predictor of embryo production following IVP and SOV/embryo collection in indicus–taurus females.     

Oxidative Stress During Pregnancy In The Sheep

During physiological pregnancy, all tissues and, mostly, placenta and foetus require high amounts of oxygen. Reactive oxygen species (ROS), generated both by mother and foetus, are implicated in foetal growth because they promote replication, differentiation and maturation of cells and organs. Nevertheless, ROS excess, if not properly counterbalanced, may lead to an alteration in cell constituents, with harmful effects both on mother and foetus.ROS exert a biphasic effect because adequate ROS concentration is essential for embryo development, implant, foetal defence against uterine infections, steroidogenesis, pregnancy maintainance and partum. On the other hand, an uncontrolled ROS generation, beyond physiological antioxidant defences, may lead to embryo resorption, placental degeneration with subsequent alteration in maternal‐foetal exchanges, delay in foetal growth, pregnancy interruption, stillbirths. This review investigates the mechanisms underlying ROS generation and effects, throughout physiological and pathological pregnancy in sheep, with a look to antioxidants and their importance in such a critical phase of the reproductive cycle of the sheep.     

Comparison of tiletamine-zolazepam-ketamine and tiletamine-zolazepam-ketamine-xylazine anaesthesia in sheep

Summary The anaesthetic effects of intravenous tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg (TK) and tiletamine-zolazepam 6.6 mg/kg-ketamine 6.6 mg/kg-xylazine 0.11 mg/kg (TKX) were evaluated in six wethers. Heart rate, respiration rate, arterial blood pressure, and the electrocardiogram were monitored during anaesthesia. Analgesia was tested by electrical stimulation in the left flank. Atropine (0.03 mg/kg) was given intramuscularly before induction, but after recording of baseline heart rate and respiratory rate. The duration of analgesia was 28.7 ± 6.9 min with TK and 82.8 ± 26.6 min with TKX. Heart rate increased significantly within 5 min after TK or TKX administration. Respiratory rate remained unchanged after TK administration, but increased significantly from 5 to 45 min after TKX administration. Arterial blood pressure decreased significantly at 15 min with TK and 30 min with TKX. Sheep remained recumbent for 201 min with TK and 166 min with TKX. All recovered uneventfully. We conclude that either TK or TKX may be used for anaesthetising sheep.     

Adonis microcarpa (pheasant''s eye) toxicity in pigs fed field pea screenings

Seed of Adonis microcarpa (pheasant's eye) fed at 5.6 g/kg of the diet induced virtually total feed refusal within 3 d in growing and finishing pigs. It also caused vomiting, rapid and shallow breathing and death in a minority. These effects were probably caused by cardiac glycosides whose structure and effects closely resemble those of digoxin. Feed intake and growth recovered within 2 weeks of removal of the seed.