tabled a motion in January 2019 asking for legislation to end breeding for higher numbers born and increased number of teats. That was rejected. The same party tabled another two motions asking the government to define a five-year plan to reduce pre-weaning mortality to be lower than 10%. This was approved. Yet another motion was tabled in December 2019 to forbid the breeding of sows with litter sizes larger than 12. This was rejected.


2. Back fat and pork flavour The heritability (h2) of back fat on ad libitum fed pigs has an


average value of 0.49 (range 0.12–0.74). As a result, it has been relatively easy to slim down the pig carcass with tradi- tional quantitative selection. Other techniques, such as the inclusion of the very lean Pietrain breed as a terminal sire ei- ther pure bred, or part of the make-up of a synthetic terminal sire line, has contributed to the production of very lean pigs. At the same time, the heritability of various meat quality traits such as tenderness, drip loss, pH, colour, flavour and juiciness has been calculated by the meat scientists. In gener- al terms, there is a strong negative correlation between all eating quality traits and carcass leanness. Modern pig carcasses in the weight range of 90–105kg with a P2 back fat cover of 11–13mm will nearly always have a lean, tough and almost tasteless pork. Modern chefs are always looking at ways to make pork more interesting because it de- veloping a reputation for being tasteless. The Duroc breed is rapidly gaining in popularity as a terminal sire, as its progeny will high a higher level of intramuscular fat or marbling, which helps to improve the flavour of the pork. In spite of all the bad press about pork flavour, selection pressure is still being applied to backfat.


3. The cost of lameness The old English equine expression, “no foot, no horse”, could


quite equally be applied to boars standing at AI studs. In a study of 44 North American studs, 81% of the studs rated feet and legs as a primary reason for culling. Terminal boars in traditional AI systems will potentially sire some 15,000 slaughter generation pigs. Recently it was re- ported that in the USA lameness is a cause of over 9% of the mortality in finishing barns, and prevalence can be as high as 34%. A GP boar will sire some 3,000 breeding gilts, who will in turn produce 150,000 slaughter generation pigs. Yet, how often are boars considered acceptable with less than optimal foot conformation, because of availability or because the ge- netic supplier insists on the boar’s superior genetic merit? A higher reject rate on foot and leg quality of the boars, while they are still in quarantine, will send a clear message to the genetic supplier as well as reducing the costly problem of lameness in the finishing herd. In 1988, Max F. Rothschild of Iowa State University showed significant (p<0.01) improvement in just five generations of


A hernia umbilicalis in a piglet – a common genetic defect.


selection for front leg structure in Duroc, with a scoring pro- cedure involving 3,598 pigs. He noted heritability (h2) of 0.29.


4. Hernias and other genetic defects Back in the early 1980s, when a litter was born with any ge-


netic defect (hernia, splay leg, etc.), the whole litter was iden- tified, not put onto performance test at 30kg and sold as weaner pigs. This drastic method ensured that there was no transmission of undesirable genes. Today, things have changed (for the worse). All genetic com- panies are obsessed with the highest possible test numbers to improve their famous “immature-to-total” (I/T) ratio, a measure of genetic progress. They feel that discarding a whole litter will potentially lose them their good ratio. The result is that it is very common to encounter levels of 2–3% of hernias in the slaughter generation stock. These in- evitably end up as early culls. From a welfare point of view, in the EU, pigs with hernias that have a diameter of more than 20cm cannot be transported to a slaughterhouse. That means even more on-farm euthanasia, which is an unpleasant job for farm staff and involves extra costs for carcass disposal. In recent years, nighttime illegal incursions into integrated company farms in Spain, where pigs with hernias were pho- tographed, resulted in TV exposure that caused serious dam- age to the company’s sales of pig meat and product recalls from the supermarkets. All breeding companies need to try to address that growing problem.


References available on request. ▶PIG PROGRESS | Volume 36, No. 6, 2020 27


PHOTO: ROBIN BRITSTRA


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