EXERTIONAL MYOPATHY AND OSTEOCHONDROSIS O F PIGS AS A RESULT OF BREEDING FOR GROWTH-RATE

Selective breeding programmes for pigs to maximise growth rate and a h igh meat content of carcases has been recognised as a direct cause of osteochondrosis and exertional myopathy for 25 years. The immature ske leton suffers a weight gain of approximately one kg per day at the age of three to five months. In breeding and fattening pigs, in Northern Gel-many, the incidence of osteochondrosis in limb joints and vertebra te in between 0,3 and 1.6%. The disease is characterised by degenerati on of cartilage and epiphisiolysis with proliferative reaction of the bone. Pain-avoiding body postures and advene disturbances of movement follow requiring premature slaughter of pigs. The genetic antagonism b etween stress susceptibility and the proportion of large white muscle fibres in the hams and back muscle results in a contrary selection whi ch favours the more economically attractive characteristics. Increased stress susceptibility resulted fi-om the aim of increasing the lean m eat content of carcases. Sudden death as a result of lactacidosis and cardiac shock and poor meat quality due to PSE are signs of exertional myopathy. Stress susceptibility and poor meat were reduced and almost eliminated in some neighbouring countries, such as Switzerland and De nmark by altering the selection by the use of CK and MHS or meat quali ty parameters. It is desirable that pig breeders and veterinarians wor k together to improve the quality of products and resistance to diseas e and against arty commercial interests. Mortality in pigs, with one m illion deaths per year in Germany as a result of poor breeding does no t conform to the idea of protection of animals against cruelty.