关于加强对肉鸡非典型新城疫和低致病性禽流感防治的建议

随着对鸡传染病防制技术水平的提高和相应的高科技产品的推广运用,加上政府和广大养鸡场（户）对典型新城疫（ND）和高致病性禽流感（HPAIH5亚型）防制工作的重视,成功地控制了这两种疾病的发生。但当前肉鸡业最易忽视、危害又最大的却是非典型新城疫（CND）和低致病力H9亚型禽流感（LPAI）。所谓“重视”是大家都接种了AI和ND疫苗,而忽视的是对AI只接种H5亚型而未接种H9亚型禽流感疫苗;     

Grain,pellet and wax block bait take by the house mouse (Mus musculus) and non‐target species: implications for mouse eradications on coral cay islands

Introduced rodents have been eradicated from large numbers of offshore islands using toxic baits; however, toxic baits have been linked with negative impacts on non‐target species. The present study assessed the bait take of target (house mouse, Mus musculus) and non‐target (buff banded rail, Rallus philippensis) animals on Northwest and Heron Islands in the Great Barrier Reef. Three non‐toxic bait formulations (wax block, pellet and grain) were tested and each was applied at 1 kg ha^?1 in six treatment grids. The tracks of animals visiting the baits were identified using 30 tracking stations per treatment grid. A tracking station consisted of a track‐board placed in the centre of a sand‐pad. Mean bait take differed significantly between the formulations: birds took more grain bait than wax block bait; mice took more wax block than grain bait. Both mice and birds were equally selective of pellet bait. Thus, the findings indicate that wax blocks are the most suitable formulation for future baiting programs to eradicate mice on these and other islands.     

Comparison of efficiency of in vitro cloned sheep embryo production by conventional somatic cell nuclear transfer and handmade cloning technique

Conventional somatic cell nuclear transfer (SCNT) technique of in vitro production of cloned embryos involves use of costly and complicated micromanipulators. Handmade cloning (HMC) technique has been applied as efficient and cost‐effective alternative in many livestock species. The aim of the present study was to compare the efficiency of in vitro production and in vitro development of cloned sheep embryos by the two techniques. Cloned embryos were produced by conventional SCNT using micromanipulator apparatus and by HMC technique. Enucleation efficiency and efficiency of fusion with somatic cell (nucleus donor) were compared. Cleavage percentage was observed on day 2 of in vitro culture (IVC), and morula and blastocyst percentages were calculated on day 7 of IVC. Higher enucleation efficiency (96.98 ± 1.01 vs. 93.62 ± 1.03; p > .05) as well as fusion efficiency was obtained with HMC technique than with conventional SCNT (96.26 ± 1.34 vs. 92.63 ± 0.70, p < .05); 181 cloned sheep embryos were produced in vitro by conventional SCNT and 92 by HMC. Cleavage percentage observed on day 2 of in vitro culture was higher in HMC than SCNT (66.92 ± 3.72 vs. 55.97 ± 2.5, respectively, p < .05). Morula percentage obtained was higher in SCNT than HMC (44.12 ± 2.93 vs. 30.43 ± 6.79, respectively, p < .05), whereas blastocyst percentage obtained by HMC was higher (12.46 ± 4.96) than SCNT (5.31 ± 2.25; p > .05). It was inferred that HMC technique provides a cost‐effective and efficient method of in vitro production of cloned sheep embryos with a comparatively simpler technique with a possibility of automation. Efficiency of cloned embryo production could be improved further by propagating and standardizing this technique.     

Resynchronising returns to service in anoestrous dairy cows in the South Island of New Zealand

AIMS: To investigate the effect of targeted resynchronisation of cows treated for non-observed oestrus before the planned start of mating (PSM), that were not detected in oestrus or pregnant 23 days after treatment (phantom cows), on the proportion pregnant at 42 days after PSM and the end of mating.

METHODS: Farm staff from eight herds in two regions of the South Island of New Zealand identified 1,819 cows not showing oestrus by 10 days before PSM. These cows were treated with intravaginal progesterone for 7 days, and I/M gonadorelin 10 days and 1 day before PSM. Three days before PSM they were injected with cloprostenol and equine chorionic gonadotrophin, with fixed time artificial insemination (FTAI) at PSM. By 23 days after PSM, 1,218 cows had not returned to oestrus. Of these, 161 cows confirmed not pregnant by transrectal ultrasonography were randomly assigned to no treatment (control group; n=74) or were resynchronised 25 days after PSM using the same treatment programme as above, with FTAI 35 days after PSM (n=87). All cows that returned to oestrus were artificially inseminated until 42 days after PSM, when natural mating was used. All cows were examined using transrectal ultrasonography 80 to 90 days after PSM to confirm conception dates.

RESULTS: Of the 1,819 anoestrous cows treated before PSM, 526 (29 (95% CI=23.1–34.0)%) had not been observed in oestrus by 23 days after PSM and had not conceived, so were diagnosed as phantoms cows. For resynchronised cows, 42/87 (48 (95% CI=37.8–58.8)%) were pregnant by 42 days after PSM compared to 21/74 (28 (95% CI=18.1–38.7)%) control cows (p=0.009). At the end of mating 58/87 (67 (95% CI=56.6–76.7)%) cows in the resynchronised group were pregnant and 46/74 (62 (95% CI=50.9–73.2)%) in the control group (p=0.554). The hazard of conception from 21 to 42 days after PSM was 1.9 (95% CI=1.07–3.12) times greater for resynchronised than control cows (p=0.026).

CONCLUSION: In cows not observed in oestrus and treated before PSM, resynchronisation increased the proportion pregnant by 42 days after PSM.

CLINICAL RELEVANCE: The benefit of resynchronisation depends on the number of anoestrous cows before PSM and the number of phantom cows after PSM. However at the herd-level it is likely that providing advice to reduce the known risk factors for cows not being observed in oestrus before the PSM may well be more cost effective than identifying and treating a sub-population of phantom cows.     

Effects of FGF10 on Bovine Oocyte Meiosis Progression,Apoptosis, Embryo Development and Relative Abundance of Developmentally Important Genes In Vitro

Fibroblast growth factor (FGF10) acts at the cumulus oocyte complex, increasing the expression of cumulus cell expansion‐related genes and oocyte competency genes. We tested the hypothesis that addition of FGF10 to the maturation medium improves oocyte maturation, decreases the percentage of apoptotic oocytes and increases development to the blastocyst stage while increasing the relative abundance of developmentally important genes (COX2, CDX2 and PLAC8). In all experiments, oocytes were matured for 22 h in TCM‐199 supplemented with 0, 2.5, 10 or 50 ng/ml FGF10. In Experiment 1, after maturation, oocytes were stained with Hoechst to evaluate meiosis progression (metaphase I, intermediary phases and extrusion of the first polar body) and submitted to the TUNEL assay to evaluate apoptosis. In Experiment 2, oocytes were fertilized and cultured to the blastocyst stage. Blastocysts were frozen for analysis of COX2, CDX2 and PLAC8 relative abundance. In Experiment 1, 2.5 ng/ml FGF10 increased (p < 0.05) the percentage of oocytes with extrusion of the first polar body (35%) compared to 0, 10 and 50 ng/ml FGF10 (21, 14 and 12%, respectively) and FGF10 decreased the percentage of oocytes that were TUNEL positive in all doses studied. In Experiment 2, there was no difference in the percentage of oocytes becoming blastocysts between treatments and control. Real‐time RT‐PCR showed a tendency of 50 ng/ml FGF10 to increase the relative abundance of COX2 and PLAC8 and of 10 ng/ml FGF10 to increase CDX2. In conclusion, the addition of FGF10 to the oocyte maturation medium improves oocyte maturation in vitro, decreases the percentage of apoptotic oocytes and tends to increase the relative abundance of developmentally important genes.     

The effect of elemental Zn boluses on concentrations of Zn in serum and faeces of South American camelids

ABSTRACT

Aims: To monitor the effect of using long-acting Zn boluses on the Zn status of a group of South American camelids, using measurements of concentrations of Zn in faeces and serum.

Methods: As part of a facial eczema (FE) prevention programme, 15 camelids were treated with long-acting Zn boluses designed for preventing FE in sheep. Based on bodyweight, 13 alpacas (Vicugna pacos) received two boluses (26.4?g Zn/bolus) and two llamas (Lama glama) received three boluses. In order to monitor Zn status, measurements were made of concentrations of Zn in serum and faeces immediately prior to bolus treatment (Week 0) and 4, 6, 8 and 10 weeks later. Gamma glutamyl transferase (GGT) activity in serum was measured at Weeks 0 and 8.

Results: Two alpacas regurgitated the boluses; in one case the animal was quickly re-treated but this was not possible in the second animal. Mean concentrations of Zn in faeces were higher at all time points compared to Week 0 (p?<?0.001). Peak concentrations were measured at Week 8, and concentrations >120?mg/kg fresh weight (FW), suggested as being protective in calves, were only measured in all (13/13) treated camelids at Week 6. Mean concentrations of Zn in serum differed between weeks of sampling but changes were not consistent, and concentrations did not exceed 18?μmol/L following treatment. There was no evidence of a natural sporidesmin challenge during the study period and activity of GGT in serum of all animals was <45?IU/L.

Conclusions: Treatment with Zn boluses significantly increased concentrations of Zn in faeces but not in serum, but peak concentrations in faeces were only detected 8 weeks after treatment.

Clinical Relevance: The delay in achieving concentrations of Zn in faeces which were associated with protection against FE in calves, combined with the difficulties of administering boluses to camelids, means that we do not believe that Zn boluses should be used as the primary method for preventing FE in camelids. We recommend that FE prevention in camelids should focus on minimising spore production in pasture through the use of fungicides, grazing management and alternative forages, with boluses only used when it is thought that these methods are unlikely to provide sufficient protection against FE. Such use should always be under the guidance of a veterinarian and monitoring of serum GGT activity should be used to ensure that FE control is being achieved.     

A review of diagnostic tests for diagnosing failure of transfer of passive immunity in dairy calves in New Zealand

ABSTRACT

The aim of this review is to critically assess the test characteristics and practicality of published data on direct and indirect tests for diagnosing failure of transfer of passive immunity (FPT) in dairy calves in New Zealand, to provide recommendations for veterinary practitioners, and to examine the recommended sample size for assessing herd-level prevalence of FPT and the confidence in the results obtained. The definition of FPT is based on measurement of concentrations of IgG in serum of neonatal calves after colostrum intake. The gold standard method for measurement of concentrations of IgG is radial immunodiffusion. However its cost, requirements for laboratory equipment, and the time taken to obtain results have meant that alternative tests have been developed. The turbidimetric immunoassay and ELISA also directly measure concentrations of IgG. Indirect tests include measurement of concentrations of total proteins (TP) in the laboratory or using a refractometer, γ-glutamyl transferase (GGT) activity, and the zinc sulfate turbidity (ZST) test. Of the indirect tests, measurement of concentrations of TP in the laboratory or using a refractometer combine high specificity and sensitivity with a consistent association with concentrations of IgG in calves between 1–7 days of age. Using a refractometer is less accurate than direct measurement in a laboratory, but is still a suitable test if low cost and speed are important. Although GGT activity is strongly associated with concentrations of IgG in serum, the relationship varies with time after birth. Therefore the target thresholds change with time, increasing error compared to the measurement of concentrations of TP in serum. Similarly, factors other than total concentrations of IgG have a significant effect on the association with ZST test, complicating interpretation. Thus, when direct measurement of concentrations of IgG is not feasible, the recommendation is that concentrations of TP in serum should be used as the diagnostic test for diagnosis of FPT, providing calves are not dehydrated. Using a sample size of 12 calves is suitable for estimating whether the herd-level prevalence of FPT is <20% or >20%, if there are no calves or >5 calves diagnosed with FPT, respectively, but is limited in diagnostic confidence when 1–4 calves test positive. Diagnostic interpretation can be significantly improved if tests of FPT are used alongside information on the likely risk of FPT on the tested farm.