A registry-based study of declined foaling rates in Finnhorses

In Finland, the seasonal foaling rates of trotters began declining at the beginning of the 2000s. This retrospective study aimed to elaborate factors behind the declining foaling rates in Finnhorses using multivariable logit models. The mating records from years 1998 to 2000 (period 1, n = 5967) and 2002 to 2004 (period 2, n = 5373) originated from the Finnish trotting and breeding association. The over-all foaling rate was 66.6% during period 1 and 62.4% during period 2 (p < 0.0001). Foaling rate for on-site artificial insemination decreased from 70.2% to 64.8% (p = 0.003). The proportion of the most fertile mare groups, 2–9-year-olds and foaled mares, decreased by 8.2 and 7.1 percentage points, respectively. Differences in foaling rates between young and middle-aged mares, and maiden and foaled mares changed from non-significant to significant (p<0.0001) due to the foaling rate decline in middle-aged (p = 0.001) and maiden mares (p = 0.01). The decline in foaling rate was also significant for barren and rested mares (p < 0.05), natural mating (p = 0.01), and book size >68 (p < 0.0001). It was concluded that multiple factors were responsible for the foaling rate decline.