Twinning in thoroughbred mares in Poland

Of the thoroughbred population bred in Poland from 1952 to 1976, an average of 3.3% twinnings were registered. Of these averages 73% resulted in abortion, 11% in still births, and 16% in the live birth of one or both of the foals. Twins were not any more valuable for racing or breeding than normal. Mares mated in June had a twinning coefficient of 6.6% and those mated from February to May had one from 3.0% to 3.6%. The twinning coefficient was higher for mares which had not lactated during the previous year (6.0%, p