Epidemiology and genetic basis of ketosis in Finnish Ayrshire cattle

The epidemiology and genetic variability of ketosis in Finnish Ayrshire cattle were examined. In the spring of 1982, a new health recording system was started on all dairy farms in Finland. Ketosis data collected during the first year were analyzed. Seven percent of 8201 Finnish Ayrshire cows which were daughters of 80 randomly selected bulls were treated for ketosis. Eighty-nine percent of cases occurred within 8 weeks after parturition, with the highest occurrence 3–5 weeks after calving. When cases were categorized by month of calving the risk of ketosis was higher during indoor feeding (September-May) than during outdoor feeding (June-August). Ketosis occurrence increased with parity, but was not associated with milk yield. Problems in estimating the correlation between ketosis and milk yield were discussed. The incidence rate among bull-daughter groups varied from 0 to 26 percent. The heritability estimate of 2.3% for ketosis on the binomial scale was not significant, even though it corresponded 81% on the normal scale. Research is needed on new statistical methods for threshold characters in order that breeding programs can be designed to accoint for possible inherited susceptibility to metabolic diseases.