The use of electrical stunning followed by electro-immobilization for the humane slaughter of cattle

Sir;- In New Zealand, calves are often electrically stunned before slaughter. However, electrical stunning is not usually used for adult cattle, primarily because the large size of the adult animal makes restraint more difficult, resulting in less reproducible stunning, with potential danger to personnel from animal movement. In addition, the slaughter of cattle may be inhumane if the stunning process does not ensure immediate and permanent insensibility (Newhook and Blackmore 1982b). The use and humaneness of electrical stunning of sheep and cattle have been the subject of our recent research, in which we have addressed and resolved many of these problems. We wish to relate our observations in the context of head-only electrical stunning of cattle followed by electro-immobilization to maintain insensibility and ensure carcass stillness.     

Electrical stunning of cattle--experiences in New Zealand

Ever since the middle of the nineteen-eighties electrical stunning of cattle is used in industrial slaughter plants in New Zealand. Today electrical stun boxes operate in export slaughter plants throughout New Zealand. The reversible stun is utilised on the vast majority of slaughtered cattle. The electrical stunning (head only) immediately followed by bleeding is an alternative to ritual slaughter without prior stunning. Throughout the world's islamic community this alternative is widely accepted as Halal.     

Plasma beta-endorphin increase following electrical stunning in sheep

Plasma concentrations of beta-endorphin were assayed in 10 sheep during the conscious state and in relation to electrical stunning. There was a 2 fold increase after stunning, and a further elevation following recovery. On this basis it is possible that recovery from electrical stunning at slaughter may cause undue distress, and it is suggested that exsanguination must be carried out promptly.     

Distribution of prion protein genotypes in breeds of sheep in New Zealand

AIM: To use an established high through-put genotyping procedure to gain an estimate of the frequency of alleles of the prion protein (PrP) gene in some common sheep breeds in New Zealand. METHODS: Using a genotyping procedure based on matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF), DNA samples from 3,024 sheep from New Zealand, including breeds such as Romney, Texel, Coopworth, Merino and mixed breed, were isolated, genotyped and the results analysed. RESULTS: The 15 scrapie genotypes commonly reported, and derived from the five commonly reported allelic variants (ARR, ARQ, AHQ, ARH and VRQ), were all observed in the samples analysed. The estimates were indicative of the frequencies in the population of alleles present in breeds of sheep in New Zealand. There was a significant difference between the frequencies of alleles between breeds, but the ARQ, followed by the ARR allele, were, except in Carwell sheep, the most common alleles present. CONCLUSION: This study gave an indication of the percentages of PrP gene alleles in sheep in New Zealand, including data previously unreported from breeds in this country. It is of interest because of the relatively large size of the sheep population in New Zealand compared with many countries, and it provides some useful information on the genetic susceptibility or resistance of the sheep population in New Zealand to scrapie. The frequencies of the alleles can be different for an individual breed compared between countries.     

Distribution of prion protein genotypes in breeds of sheep in New Zealand

AIM: To use an established high through-put genotyping procedure to gain an estimate of the frequency of alleles of the prion protein (PrP) gene in some common sheep breeds in New Zealand.

METHODS: Using a genotyping procedure based on matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF), DNA samples from 3,024 sheep from New Zealand, including breeds such as Romney, Texel, Coopworth, Merino and mixedbreed, were isolated, genotyped and the results analysed.

RESULTS: The 15 scrapie genotypes commonly reported, and derived from the five commonly reported allelic variants (ARR, ARQ, AHQ, ARH and VRQ), were all observed in the samples analysed. The estimates were indicative of the frequencies in the population of alleles present in breeds of sheep in New Zealand. There was a significant difference between the frequencies of alleles between breeds, but the ARQ, followed by the ARR allele, were, except in Carwell sheep, the most common alleles present.

CONCLUSION: This study gave an indication of the percentages of PrP gene alleles in sheep in New Zealand, including data previously unreported from breeds in this country. It is of interest because of the relatively large size of the sheep population in New Zealand compared with many countries, and it provides some useful information on the genetic susceptibility or resistance of the sheep population in New Zealand to scrapie. The frequencies of the alleles can be different for an individual breed compared between countries.     

Welfare of farmed deer in New Zealand. 1. Management practices

This review summarises research of management practices that potentially impact on the welfare of farmed deer. The processes of capture and initial domestication of feral deer caused many welfare problems but are now essentially complete in New Zealand. The health and production status of farmed deer, and readily visible indicators of their welfare are generally good, although preventive medicines and optimum management practices have not been universally adopted. Research into social behaviour, effects of yarding, weaning, mating, calving, shelter, shade and nutrition has identified ways of improving the welfare of farmed deer and has provided recommendations for deer industry quality assurance programmes. Research has identified transport design and practices that minimise the impact of transport on deer welfare and reduce carcass wastage caused by bruising during transport. Time in lairage prior to slaughter should be minimised and electrical stunning is a humane method of slaughter. Ongoing research is needed on management practices and farm environments to further improve the welfare of farmed deer, consistent with the goals of the New Zealand deer industry and its proactive approach to date.     

Welfare of farmed deer in New Zealand. 1. Management practices

This review summarises research of management practices that potentially impact on the welfare of farmed deer. The processes of capture and initial domestication of feral deer caused many welfare problems but are now essentially complete in New Zealand. The health and production status of farmed deer, and readily visible indicators of their welfare are generally good, although preventive medicines and optimum management practices have not been universally adopted. Research into social behaviour, effects of yarding, weaning, mating, calving, shelter, shade and nutrition has identified ways of improving the welfare of farmed deer and has provided recommendations for deer industry quality assurance programmes. Research has identified transport design and practices that minimise the impact of transport on deer welfare and reduce carcass wastage caused by bruising during transport. Time in lairage prior to slaughter should be minimised and electrical stunning is a humane method of slaughter. Ongoing research is needed on management practices and farm environments to further improve the welfare of farmed deer, consistent with the goals of the New Zealand deer industry and its proactive approach to date.     

Systemic mycosis in neonatal calves

Extract

It is perhaps surprising that, although the freezing industry has been in existence in New Zealand for as long as export of perishable primary products has been practised, it is only within the last few years that veterinary interest in this aspect has quickened. As far as meat products are concerned, this has come about by pressure from overseas customers for increased direct supervision by professional staff rather than from the inclination of industry or government in this country. None the less, one result has been, and will be in increasing measure, to bring into sharper focus the usefulness of works to agriculturalists in a sense beyond the conversion to cash of one of the major end-products of farming operations.     

Demonstration of polymorphism among Brucella ovis field isolates by pulsed-field gel electrophoresis

Brucella ovis is recognized worldwide as an important pathogen of sheep, and has also been identified in farmed deer in New Zealand. Previously, only one strain type of B. ovis has been identified. The objective of this paper was to perform pulsed-field gel electrophoresis (PFGE) on field isolates of B. ovis to determine whether strain variations exist, whether sheep and deer are affected by the same strains, and to compare the performance of the rare-cutting restriction enzymes XbaI and SwaI. Ten B. ovis isolates from sheep and two from deer in New Zealand, as well as the type strain, were subjected to PFGE analysis using both XbaI and SwaI. PFGE of XbaI restriction fragments produced two banding patterns consisting of 27-28 bands, which were found to be 98% similar by cluster analysis, and were named X1 and X1a. PFGE of SwaI restriction fragments resulted in three banding patterns consisting of 13-15 bands each. Ten of the isolates had identical banding patterns and were named S1. One isolate differed by one band, representing a subtype named S1a. Two isolates differed by six bands, representing a different strain type of B. ovis and this was named S2. Cluster analysis showed S2 to be 78% similar to the S1/S1a cluster. Both strain types were isolated from both sheep and deer. Thus, two distinct strain types of B. ovis were identified in New Zealand, which is the first report of more than one strain type being identified worldwide. Neither strain was species-specific for sheep or deer. The restriction endonuclease SwaI was found to be more discriminatory than the enzyme XbaI, which has been used in previous studies.     

Breeding sheep in New Zealand that are less reliant on anthelmintics to maintain health and productivity

Breeding sheep that are less reliant on the use of anthelmintics to maintain acceptable health and productivity is one of several options that may assist farmers to manage the growing anthelmintic-resistance problem in New Zealand and meet consumer demands to minimise drug usage in livestock. Although it has been known for many years that genetic factors contribute to the ability of sheep to cope with roundworm challenge, attempts to selectively breed for such factors have occurred only recently. Two host traits, 'resistance' and 'resilience', are thought to be involved in limiting the deleterious effects of roundworms on the health and productivity of sheep, and the associated need for treatment with anthelmintics. Over the last decade, considerable advances have been made in our understanding of the feasibility and implications of breeding for these traits under practical conditions. The experimental breeding lines developed as part of this research are now proving to be a valuable resource for further work directed at identifying genes and/or genetic markers associated with host resistance and understanding the mechanisms of host immunity to nematode parasites in ruminants. This review provides an up-to-date summary of the results of research in this field, with particular reference to dual-purpose sheep in New Zealand, and describes how this information is being applied in practical breeding programmes.     

Quantification of historical livestock importation into New Zealand 1860–1979

AIMS: To quantify the numbers of live cattle, sheep and poultry imported into New Zealand and, where possible, their country of origin from 1860 to 1979.

METHODS: Information on the origin and number of live animal importations into New Zealand was collected for cattle, sheep and poultry for the period 1868–1979 from the annual reports compiled by the New Zealand Registrar General's Office, Government Statistician's Office, Census and Statistics Office, Census and Statistics Department, Customs Department and Department of Statistics. Census data from 1851 to 1871 were also used to estimate the livestock population during this period. The number of animals imported and the mean population for each species in a decade were determined, and the major countries of origin were identified.

RESULTS: A large number of cattle (53,384) and sheep (604,525) were imported in the 1860s, and then there was a marked reduction in importations. Live poultry were imported in relatively small numbers (20,701) from 1880 to 1939, then 1,564,330 live poultry were imported between 1960 and 1979. Australia was the predominant country of origin for sheep between 1868 and 1959 (51,347/60,918; 84.3%) and of cattle between 1868 and 1979 (10,080/15,157; 66.5%). Only 6,712 (11.0%) sheep and 3,909 (25.8%) cattle were imported from the United Kingdom over the same periods, and even fewer from other countries.

CONCLUSIONS: The collated data and historical reports show that from 1860 to 1979 Australia has been the main source of livestock introduced into New Zealand. The pattern of importation showed that large numbers of cattle and sheep were initially imported in the 1860s, probably in response to rapid agricultural expansion. Thereafter importations continued at much reduced numbers. In contrast, relatively small numbers of poultry were introduced until the 1960s when large numbers were imported as part of the development of a modern high-production industry. The overall pattern for both cattle and sheep was of a bottleneck event, as initially a relatively limited number of animals arrived from outside populations, followed by population expansion with ongoing but limited immigration (admixture). Investigation into the genetic population structure of New Zealand's cattle and sheep, as well as their host-associated microorganisms, could reflect the impact of these early historical events.     

Evaluation of an enzyme-linked immunosorbent assay for the serological diagnosis of Neospora caninum infection in sheep and determination of the apparent prevalence of infection in New Zealand

Neospora caninum has recently been shown to be a cause of abortions of sheep in New Zealand. A commercially available enzyme-linked immunosorbent assay (ELISA) was validated for use in sheep with sera from experimentally infected sheep. A cut-off threshold was established that demonstrated sero-conversion between 7 and 14 days post-infection. Higher inocula led to earlier sero-conversion. This ELISA was applied to 640 sera collected from rams across New Zealand and 0.625% (+/-0.61%) (4/640) were shown to be serologically positive. The four positive sera were also demonstrated to be positive by indirect fluorescent antibody test (IFAT). The ELISA evaluated here lends itself more readily to large-scale investigations than IFAT. The low background of N. caninum infection in the New Zealand sheep population suggests that N. caninum abortions could be more easily diagnosed by serological means than in populations with higher background sero-prevalence.     

Reflexes and loss of sensibility following head-to-back electrical stunning in sheep

The effects of head-to-back electrical stunning on the incidence of post-stunning reflex activity and cortical evoked responses were investigated in sheep. The stuns were effective in terms of inducing epileptiform activity and they resulted in cardiac fibrillation which ensured that there was no recovery of consciousness. Even though the corneal reflex and respiratory gasps were present, in 10 out of 12 sheep there were no concomitant visual and somatosensory evoked responses following a stun. In the remaining two, the responses were rudimentary and it would be unwise to conclude that the animals were conscious. It is suggested that brain stem reflexes following this stunning method should not be relied on as indices of recovery. The results support the view that an electrical stunning method which induces cardiac fibrillation results in improved animal welfare.     

Registration of generic alternatives to praziquantel for the control of Taenia ovis

Extract

Taenia ovis is a parasite which infects dogs (the definitive host) and sheep and goats (intermediate hosts). It has been the subject of a control programme in New Zealand based largely on the 6-weekly dosing of rural dogs with praziquantel. Since the patent for praziquantel has expired, various generic formulations have become available, including the formulation tested here. It is debatable whether such products should be tested for bioequivalence and biological activity against the target parasite or for bioequivalence only. In this instance, although the drug had been registered on the basis of blood levels of praziquantel achieved, it was felt that a biological test would be beneficial if the generic drug, mixed with other anthelmintics, was to be used on a wide scale to control Taenia ovis in New Zealand.     

Development of a simple typing method for the ovine Toll-like receptor 4 gene

Toll-like receptor 4 (TLR4) recognizes lipopolysaccharide (LPS) from Gram-negative bacteria, as well as a number of other ligands. Genetic variation in the TLR gene has been associated with altered immune responses to pathogens and results in variation in disease susceptibility. The objective of this work was to develop a simple and rapid genotyping system for ovine TLR4 and of a sensitivity that would allow detection of allelic variation in this gene. While variation in exon 3 of the ovine TLR4 gene has been described previously, we describe here an improved genotyping method. This method could not only reveal the four alleles that have been reported previously, but also revealed a further three new alleles of this gene in a population of 1670 New Zealand sheep. This improved genotyping method will be useful in understanding innate immune responses in individual sheep and could also be a useful tool for large-scale immune studies in sheep production systems.     

The distribution of Nematodirus spp. occurring in sheep in New Zealand

Extract

Most outbreaks of parasitic gastro-enteritis in sheep in New Zealand have been ascribed to the presence of nematodes of the family Trichostrongylidae, and in particular the genera, Haemonchus, Ostertagia, and Trichostrongylus. However, during the period 1956–58, a number of outbreaks of disease occurred in lambs and the condition was associated with heavy Neniatodirus infestation. Although Neinatodirus spp. are commonly foundin sheep in this country, only moderate numbers of worms are usually present in any individual and the worm has been regarded as non-pathogenic. Similar views were held in the British Isles until about 1951, when an acute disease condition of lambs, associated with heavy Neniatodirus burdens, caused serious losses.     

Management of gastrointestinal nematode parasites on sheep farms in New Zealand

AIM: To report current farmer opinions and farming practices relating to control of gastrointestinal nematodes and anthelmintic resistance on sheep farms in New Zealand. METHODS: An interview-based cross-sectional study of grazing management and anthelmintic usage was conducted by veterinarians on 80 randomly selected sheep farms in New Zealand. RESULTS: Useable data were returned by 74/80 (92%) farmers who participated in the study. However, despite contacting 400 farmers the target sample size of 100 farms was not reached. The results indicated that only 31% of farms had previously tested for drench resistance, that effective quarantine-drenching of imported stock was not always carried out, and that farmers were more likely to integrate cattle than ewes into their grazing management of lambs. Furthermore, the number of drenches given to lambs had changed little in 25 years. The use of faecal egg counting by farmers has increased. CONCLUSIONS: Dependence on anthelmintics continues to be high on sheep farms in New Zealand. Whilst the number of drench treatments has changed little, there is more widespread use of persistent or long-acting treatments. Farmers need to be encouraged to monitor the resistance status of nematode populations on their farms and use this information to develop strategies aimed at maintaining susceptible alleles within the parasite populations and conserving the efficacy of existing drug families.     

Resistance to moxidectin and abamectin in naturally acquired Ostertagia circumcincta infections in sheep

AIM: To investigate the occurrence of resistance to macrocyclic lactone (ML) anthelmintics by Ostertagia circumcincta in lambs on a sheep and cattle property in the North Island of New Zealand. METHODS: Thirty lambs were randomly allocated to one of five equal-sized groups, consisting of an untreated control and four treatment groups. The treatments, which were administered at the manufacturer's recommended dose rates, included oral moxidectin, oral abamectin (both at 0.2 mg/kg), an albendazole-levamisole combination, and an albendazole-levamisole-ivermectin combination. Post mortem worm counts were undertaken 7 days after treatment to determine the efficacy of each anthelmintic. RESULTS: The albendazole-levamisole and albendazole-levamisole-ivermectin combinations both reduced O. circumcincta burdens to zero whereas for moxidectin and abamectin efficacies of only 72% and 29%, respectively, were recorded. CONCLUSIONS: These results clearly demonstrated the occurrence of resistance to MLs by O. circumcincta. Although this is not the first occasion where resistance to this anthelmintic family has been detected in this parasite in sheep in New Zealand, it is the first instance that resistance to either moxidectin or abamectin has been reported.     

Can sheep become infected by grazing pasture contaminated by cattle with Johne's disease?

Extract

Madam:- Transmission of Johne's disease (JD) under natural conditions from sheep to cattle has been demonstrated in iceland⁽²⁾ but not in New Zealand.⁽¹⁾ The reverse, sheep becoming infected with Mycobacterium paratuberculosis of bovine origin, has been shown experimentally with large inocula (c. 5 × 10⁹organisms/lamb),⁽³⁾ but not under natural conditions. It could be important in New Zealand where sheep may be used to “clean up” pasture grazed by paratuberculous cattle.     

The use of pestivirus antigen ELISA currently available for the detection of hairy shaker disease/border disease virus in sheep

AIMS: To estimate the number of cases of scrapie that would occur in sheep of different prion protein (PrP) genotypes if scrapie was to become established in New Zealand, and to compare the performance of two commercially available, rapid ELISA kits using ovine retro-pharyngeal lymph nodes (RLN) from non-infected and infected sheep of different PrP genotypes.

METHODS: Using published data on the distribution of PrP genotypes within the New Zealand sheep flock and the prevalence of cases of scrapie in these genotypes in the United Kingdom, the annual expected number of cases of scrapie per genotype was estimated, should scrapie become established in New Zealand, assuming a total population of 28 million sheep. A non-infected panel of RLN was collected from 737 sheep from New Zealand that had been culled, found in extremis or died. Brain stem samples were also collected from 131 of these sheep. A second panel of infected samples comprised 218 and 117 RLN from confirmed scrapie cases that had originated in Europe and the United States of America, respectively. All samples were screened using two commercial, rapid, transmissible spongiform encephalopathy ELISA kits: Bio-Rad TeSeE ELISA (ELISA-BR), and IDEXX HerdChek BSE-Scrapie AG Test (ELISA-ID).

RESULTS: If scrapie became established in New Zealand, an estimated 596 cases would occur per year; of these 234 (39%) and 271 (46%) would be in sheep carrying ARQ/ARQ and ARQ/VRQ PrP genotypes, respectively. For the non-infected samples from New Zealand the diagnostic specificity of both ELISA kits was 100%. When considering all infected samples, the diagnostic sensitivity was 70.4 (95% CI=65.3–75.3)% for ELISA-BR and 91.6 (95% CI=88.2–94.4)% for ELISA-ID. For the ARQ/ARQ genotype (n=195), sensitivity was 66.2% for ELISA-BR and 90.8% for ELISA-ID, and for the ARQ/VRQ genotype (n=107), sensitivity was 81.3% for ELISA-BR and 98.1% for ELISA-ID.

CONCLUSIONS: In this study, the ELISA-ID kit demonstrated a higher diagnostic sensitivity for detecting scrapie in samples of RLN from sheep carrying scrapie-susceptible PrP genotypes than the ELISA-BR kit at comparable diagnostic specificity.

CLINICAL RELEVANCE: The diagnostic performance of the ELISA-ID kit using ovine RLN merits the consideration of including this assay in the national scrapie surveillance programme in New Zealand.