Breeding for resistance to footrot--the use of hoof lesion scoring to quantify footrot in sheep.

So that genetic studies can be undertaken on footrot in sheep, it is necessary that a reliable and repeatable method to categorise the phenotype is available. This paper summarises the methods used and results obtained from 1600 hoof lesion scores of 100 mixed-age ewes independently scored twice by two trained operators. Using a 5-pont scale describing the severity of foot lesions, residual correlations were used to assess agreement between scorers and scoring occasions. Data were analysed using both zero-1 and continuous data methods. The average prevalence of any score >0 was 15%, and of scores >1 was 12%. The residual correlation between scorers for SUM_FR was 0.87 and between scoring occasions it was also 0.87, indicating high repeatability or agreement both within and between scorers. No significant differences were detected between scorers or between scoring occasions for any of the traits analysed, or different analytical methods used.

Randomised, controlled field trial of two new techniques for the castration and tail docking of lambs less than two days of age.

Two methods to reduce the pain associated with the castration and tail docking of lambs with rubber rings were tested by 10 shepherds, each using 60 housed lambs. In 20 of the lambs the innervation to the scrotum, testes and tail was crushed with a 'Big Nipper' bloodless castrator, and in 20 local anaesthetic (2 per cent lignocaine with adrenaline) was injected with a newly developed high-pressure jet injector under the rubber rings after they had been applied; 10 lambs were given a placebo treatment and 10 were treated by the shepherds' routine elastrator ring procedure. Both new methods significantly decreased the incidence of limb and tail movement by 78 per cent and the time spent by the lambs in abnormal postures, when compared with either the shepherds' routine treatment or the placebo treatment. An experienced observer and most of the shepherds also assessed that the lambs suffered signficantly less pain when treated by the two new methods than when they were treated with rubber rings alone. No detrimental long-term effects of the two new methods were observed. On average the new methods took 68 seconds to apply, compared with 29 seconds for the rubber rings; of the two new methods most shepherds preferred using the pressure jet injector.

Effects of acute pain reduction methods on the chronic inflammatory lesions and behaviour of lambs castrated and tail docked with rubber rings at less than two days of age.

Lesions were produced by castration and tail docking of two-day-old Dorset-cross lambs with elastrator rings with (RRla) and without (RR) local anaesthetic or after destruction of the innervation by crushing close to the ring (Brr). The lesions were monitored twice weekly for six weeks and the behaviour of handled controls (H), RR and RRla lambs was recorded for two 3 h periods 10, 20, 31 and 41 days after treatment. There was no significant effect of castration and tail docking, with or without pain reduction methods, on daily liveweight gain. In the Brr lambs, the dead tails were cast 10 days earlier than from RR and RRla lambs. The time taken for the scrotal lesion to reach maximum severity was halved in Brr and RRla lambs, although the maximum severity of the lesion was unaffected by the methods of pain reduction. During the four 6 h behavioural observation periods, RR lambs showed a significant increase in the mean (+/- sd) frequency of foot stamping (RR13 +/- 13; H2 +/- 2.5), tail wagging (61 +/- 26; 15 +/- 6), head turning to the scrotum and inside hind-leg (12 +/- 10; 1 +/- 1). Less abnormal behaviour was found after RRla than after RR treatment. This unexpected finding may be evidence of long-lasting increases in pain sensitivity after an episode of intense acute pain in young animals.

PCR-based detection of the polymorphism at codon 136 in the ovine prion protein gene.

In many breeds of sheep, a polymorphism at codon 136 of the prion protein gene has been shown to be strongly associated with the risk of developing scrapie. A single-step procedure for detecting this allelic variation is described here. When performed on a series of animals, the test was in complete agreement with their genotypes as had been previously determined by sequencing. The test is potentially easier and quicker to perform than any of the variety of methods that are currently used for this purpose.

Reduction in pain suffered by lambs at castration.

The acute pain produced by bloodless castrators was studied by comparing the behavioural and plasma cortisol changes in groups (n=8) of 3-week-old Dorset cross lambs after castration with a 22 cm (9") Burdizzo, a new power assisted castrator and by a combined method using a Burdizzo and elastrator ring. The time spent in abnormal postures (52-58 min) and the peak cortisol response (110-120 mmol l(-1)) were similar for the three methods, although the powered castrator produced a more sustained response. The Burdizzo method halved the incidence of active behaviours compared with the powered castrator and combined methods (16 versus 30, 32 counts). Intratesticular local anaesthetic administered 2 min before the Burdizzo castrator and combined method, or intramuscular injection of the non-steroidal anti-inflammatory drug diclofenac, 20 min before the application of a Burdizzo, significantly reduced the peak plasma cortisol response to 80 nmol l(-1). Diclofenac also significantly reduced the time spent trembling or in abnormal postures.

Association between natural scrapie and PrP genotype in a flock of Suffolk sheep in Scotland.

The incidence of natural scrapie in sheep is associated with polymorphisms of the PrP gene, particularly those at codons 136, 154 and 171. In many breeds, the PrP allele encoding valine at codon 136 confers an extremely high risk of scrapie, but in Suffolk sheep this allele is vanishingly rare. In this study of a single closed flock of Suffolk sheep in Scotland, scrapie occurred primarily in animals which were homozygous for glutamine at codon 171, a genotype which was significantly less frequent in healthy flockmates. However, the apparent linkage between glutamine at codon 171 and scrapie was not completely recessive because two of 64 scrapie cases were heterozygous glutamine/arginine. These results suggest that breeding for increased resistance to scrapie in Suffolks by the selection of animals according to their PrP genotype is a feasible option.

Bloodless castration of lambs: results of a questionnaire.

Interviews of nine flockmasters who used bloodless castrators to castrate lambs revealed wide variation in the size of castrator used and the techniques employed. Eight flockmasters used inappropriately sized instruments which were cumbersome to operate and probably applied excessive crushing pressures over an unnecessarily large area of the lambs' scrotums. The methods of restraining lambs were often inefficient in terms of labour requirement. In 11 of 15 flocks, some lambs were not properly castrated and in six flocks, instances of injury and death attributed to castration were reported. Evaluation of bloodless castrators showed that the crushing pressure applied by castrators even those of the same size could vary by over 100%. The requirement for further research into bloodless methods of castration is highlighted as is the urgent need for training for operators.

Role of oxytetracycline dihydrate in the treatment of mycoplasma-associated ovine keratoconjunctivitis in lambs.

Thirty-six lambs were placed in two groups of 10 each, one group of 11 and one group of five. The first three groups were challenged with a field strain of Mycoplasma conjunctivae and the group of five lambs with an inactivated culture. One group of lambs was treated with oxytetracycline dihydrate as conjunctivitis developed at 1 day post-inoculation (dpi) and the other group was treated when the conjunctivitis was at its most severe (3 dpi). A rapid response to treatment was observed with a complete recovery obtained after 2 and 4 days, respectively. However, the treatment did not eliminate the M. conjunctivae infection. Conjunctivitis did not develop in the five lambs challenged with the inactivated culture.

Comparison of a complement fixation test, a gel diffusion test and two absorbed and unabsorbed ELISAs for the diagnosis of paratuberculosis in sheep.

A complement fixation test for paratuberculosis, a gel diffusion test and two enzyme-linked immunosorbent assays (ELISA) were evaluated using sera from Mycobacterium paratuberculosis infected and non-infected sheep. Gross pathology and histopathology were used as parameters of infection. The two ELISAs, one of which is commercially available for testing cattle, were used before and after sera had been absorbed with a soluble sonicate of Mycobacterium phlei. Differences between the various tests and between ELISAs before and after absorption were non-significant (P > 0.05) in non-infected sheep or in animals with gross or histopathological lesions. The specificity of all the tests was at least 97%. Sensitivity in histopathologically positive sheep was at least 98%. Sheep from infected flocks but without histopathological lesions showed serological results which were poorly correlated between the various tests.

Nutritional factors associated with vaginal prolapse in ewes.

Serum calcium, magnesium and phosphate values of ewes recently affected by vaginal prolapse were compared with unaffected ewes in four flocks. Subclinical hypocalcaemia was demonstrated in some affected and unaffected ewes in three flocks. Magnesium and phosphate values were normal. In two flocks the body condition of ewes recently affected by vaginal prolapse was variable and reflected the variation in condition found in the flock. In a third flock affected ewes had significantly lower body condition scores than unaffected ewes (P less than 0.001). Analysis of the fourth flock was not possible. Oestrogenic mycotoxins were not detected in any of the feed samples taken from these flocks. The following year the management, nutrition and energy, and the protein and calcium status of ewes in 12 flocks of greyface/mule ewes with a history of a regular high (greater than 3 per cent) or low (less than 1 per cent) prevalence of vaginal prolapse were compared. A high prevalence was not associated with any particular feedstuff. A high or intermediate (1 to 3 per cent) prevalence of vaginal prolapse was found in three of the four flocks managed as a single group and these three flocks were fed on an unrestricted basis. Body condition scoring and beta-hydroxybutyrate estimation confirmed that ewes in these flocks were overfed. The prevalence of vaginal prolapse in the flocks was not related to the serum albumin, calcium or urea of the ewes. Therefore subclinical hypocalcaemia was probably a consequence of vaginal prolapse rather than a cause.