8.1.6 Suitability of animals for breeding
Animals with congenital heart disease should not be passed as suitable for breeding purposes because it is possible that these conditions have a hereditary element. At present, there is no evidence that acquired valvular or myocardial disease has a hereditary' basis in the horse, although this is sometimes true in other species.
Horses with congestive heart failure may be maintained on suitable treatment to allow them to be used for breeding. Some stallions with severe cardiac disease only show clinical signs when covering mares. However, it would be difficult to recommend a stallion with moderate or severe valvular heart disease for use as a breeding animal. Mares with moderate or severe heart disease may be clinically unaffected in early pregnancy, but often show clinical signs towards the end of pregnancy. These signs may be controllable, with drug treatment if necessary, but further pregnancies cannot be recommended. It would therefore be unwise to recommend the purchase of a mare with moderate to severe volume overload for breeding purposes. Horses with AF but no underlying heart disease may remain useful for breeding for many years.
An echocardiographic examination is advisable before the purchase of breeding animals with valvular heart disease or AF because there is a risk that the breeding life of the animal would be curtailed compared with a normal animal. A full evaluation may show that there is little volume overload and that myocardial function is normal. Under these circumstances, an animal may be a suitable purchase for some owners. Insurance may be problematic for the purchasers of valuable breeding animals with cardiac disease. Specialist examination and an echocardiographic examination may be required before an underwriter will take on such cases, and it is worthwhile investigating this problem before the purchase of a valuable animal.
The significance of cardiac disease detected at a pre-purchase is summarised in Table 8.2.