The knowledge is out there... - Veterinary Practice
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InFocus

The knowledge is out there…

Vetinary Practice reports on the breeding debate at the recent BVA AWF meeting

FISH farmers could face the same serious welfare problems that have arisen through breeding for commercial characteristics in other sectors of the livestock industry, according to a leading fish veterinarian.

Speaking at a BVA Animal Welfare Foundation symposium in London, Peter Southgate, a director of the Inverness-based Fish Vet Group, warned that the emphasis on breeding for rapid weight gain was spawning significant health problems in farmed Atlantic salmon.

The consequences of laying down muscle at the expense of other tissues are similar to those which caused the high incidence of leg deformities in broiler chickens and the fish industry needs to learn from the way that the poultry sector has dealt with the problem.

Dr Southgate said farmed salmon now put on weight twice as fast as they did 20 years ago and at four times the rate of wild fish. The result was a growing incidence of fish with growth defects such as a truncated spinal column. Also, with the shallow gene pool the industry is increasingly reliant on, there is little margin for error in coping with other health problems.

During the periods of rapid growth that accompany warmer weather, there is the risk of disease caused by shortages of rate limiting nutrients, such as cataracts due to histidine deficiency.

Heart defects

In comparison with wild fish, a remarkably high proportion of farmed salmon survive into adulthood. While this may appear to be an indication of successful husbandry, it also produces problems. Many of the larval salmon will be carrying, for example, congenital heart defects which much later may cause them to expire with the stress of being handled and graded.

Some defects are a result of the hot shock process that is used to create the fast growing and sterile triploid fish that are used extensively in the farmed salmon industry.

Another source of problems is a result of there being three sets of chromosomes in the nucleated erythrocytes that are found in fish. With an enlarged nucleus there is a reduced haemoglobin carrying capacity and so the fish are effectively anaemic and extremely vulnerable to oxygen stress, he said.

Although these welfare issues are currently confined to salmon, it is quite probable that there will be similar developments in other species that are kept in the increasingly important global fish farming industry. In any species, growth defects are likely to become even more prevalent if genetic modification is used to boost production rates, as is currently occurring in the North American salmon industry.

However, Dr Southgate is optimistic that the farmed sector will avoid the worst of the welfare problems that arose in other sectors. It can count on high standards of stockmanship within the industry and the increasing involvement of veterinary practitioners who can apply the lessons learned in conventional agriculture.

“The knowledge is out there, we just need to be able to translate it to our own industry,” he said.

Unwise strategies

Fish farming is not the only area where the small but growing veterinary presence can help to tackle the consequences of unwise breeding strategies. London practitioner William Wildgoose described very similar welfare issues, including congenital spinal and other defects, resulting from breeding for the sort of characteristics required by breeders of ornamental carp.

Where selective breeding has failed, these enthusiasts are willing to use artificial colouring to produce the same effects.

Indeed, this process has developed even further in some East Asia states where they tattoo pale-skinned fish to produce decorative features such as a company logo. While it is illegal to decorate fish in this way in the UK, they can still be imported from overseas suppliers, he pointed out.

Of course, the key difference between welfare issues in these two sectors is that those problems affecting ornamental fish are a product of human vanity rather than purely economic considerations.

Lively debate

The veterinary profession’s role in treating such fashion victims across all domestic species was the subject of lively debate at the meeting.

Veterinary ophthalmologist Pip Boydell reckoned that 96% of his caseload in pedigree dogs was a direct result of breeding. He jokingly suggested that the welfare of veterinary practitioners could be enhanced by persuading breeders to only produce puppies with defects that can be treated – rather than problems like degenerative diseases of the retina, which vets are powerless do anything with.

More seriously, he suggested that breed problems could be reduced by the Kennel Club refusing to register any dog with a confirmed genetic disease or puppies with a co-efficient of inbreeding greater than some defined maximum. However, he doubted that any measures intended to limit the supply of defective puppies would be a solution to the problem.

Reduce demand

He felt that efforts should be directed towards reducing the demand, and the significant costs of veterinary treatment might eventually help to limit the public’s appetite for dogs with some of the worst welfare problems.

It was proposed from the floor that breeders of valuable pedigree animals should be required to provide evidence that the animal was healthy and had been checked by a veterinary surgeon before the sale.

Herefordshire veterinary surgeon (a former BVA president and incoming RCVS president) Peter Jinman noted that this was accepted practice in the equine world, even for transactions at the lower end of the market.

Mr Boydell agreed that concept was sound but the problem would be in enforcement – introducing the home information packs scheme (HIPS) for property house sales was supposed to guarantee the interests of purchasers but in 40% of relevant transactions last year the process was ignored.

Cornish practitioner and current BVA president Nicky Paull warned that the choices made by pet owners were not necessarily logical ones. She described long-standing clients of the practice who had bought several generations of dogs of a particular pedigree breed and took perverse pleasure from the cost of the veterinary treatment. As well as trying to educate the owners, vets must also try and understand their point of view, she said.

The technical director of the Veterinary Defence Society, Fred McKeating, also tried to dampen down enthusiasm for the concept of pre-sale vetting of pedigree dogs. He noted the difficulties in providing a meaningful and accurate certificate for a litter of puppies.

If something goes wrong and the buyer is unhappy about his or her choice of puppy, it is likely to be the veterinary practitioner who will pay the penalty, he said.

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