Further reading from the Universities Federation for Animal WelfareScience in the Service of Animal Welfare:
Brachycephalic Airway Obstruction Syndrome (BAOS)
1. Brief description
Brachycephalic Airway Obstruction Syndrome (BAOS) or Brachycephalic Obstructive Airway Syndrome (BOAS) .occurs in all dog breeds with brachycephaly Brachycephaly is characterised by greatly shortened upper jaws and noses, but the soft tissues of the nose and throat remain unchanged, thus these tissues are squeezed into a substantially smaller space. This leads to narrowing and increased resistance in the upper respiratory tract. BAOS describes the clinical signs seen due to these effects. The main congenital abnormalities (abnormalities present from birth) seen are stenotic nares (abnormally narrowed nostrils), excessively long soft palate in relation to head shape and tracheal hypoplasia (abnormally narrowed windpipe). The permanent narrowing and obstruction of the airways makes breathing harder. The constantly increased respiratory effort leads to secondary changes which further narrow the air passages, including collapse of the larynx (the voice box, the opening to the windpipe). BAOS leads to snoring, respiratory noise, mouth breathing, respiratory distress with rapid breathing and struggling for breath, and can lead to collapse and death. Dogs with BAOS are unable to take even moderate amounts of exercise, are very prone to heat stroke and have constantly disrupted sleep.
2. Intensity of welfare impact
This is a major welfare problem and affected dogs are at risk of bouts of severe respiratory distress, and these crises can be life-threatening eg they are especially at risk when exercising in hot weather. Even mildly affected dogs are likely to suffer disrupted sleep and are prevented from carrying out normal canine behaviours such as running and exercising due to their respiratory compromise. It seems unacceptable that this condition, even in its mildest form, could be considered normal.
3. Duration of welfare impact
It is a progressive, life-long condition. BAOS can affect immature dogs under 6 months of age.
4. Number of animals affected
To an extent, all French Bulldogs may be affected in some way by this condition, because of their severe brachycephalic conformation, but the severity of clinical signs may vary.
Vets would suspect BAOS in any French bulldog showing the typical signs, as it is so common in the breed. However, specific diagnosis of most of the abnormalities, that together form the syndrome, requires examination under anaesthetic, plus radiographs (x-rays) and possibly endoscopy (examination with a fibre optic tube inside the dog). These procedures have to be performed under anaesthesia, which creates a dilemma as dogs with BAOS have a substantially increased risk of dying under anaesthesia because of their respiratory compromise.
BAOS is caused by brachycephaly. This inherited defect is a consequence of the appearance and breed standards of all brachycephalic breeds.
7. How do you know if an animal is a carrier or likely to become affected?
Probably all French Bulldogs are affected with BAOS to a greater or lesser extent, but the clinical signs will vary from mild to severe. Examination of any puppy prior to purchase is essential, along with its dam and sire. To avoid the risk of perpetuating the welfare problems associated with this condition, dogs showing any signs of BAOS, or whose parents have any signs or have had surgical procedures to alleviate the condition should not be purchased.
8. Methods and prospects for elimination of the problem
As BAOS is due to the brachycephalic head shape, it seems unlikely that it will be possible to eliminate the condition from French bulldogs without changing the conformation (and the breed standard). As all French bulldogs have this condition, to a greater or lesser extent, this would mean out-crossing to non-brachycephalic breeds. Opinions differ as to whether it is ethically acceptable to breed animals whose welfare is likely to be compromised.