Investigations on oestrous interval in cattle with reference to early embryonic death
Vet.-med. Dissertation, Tierarztl. Hochsch, Hanover., 54
561 oestrous intervals were determined by external signs of heat in 373 Black Pied Lowland cows in 37 herds. 276 intervals were followed by natural mating or A.I., and the remainder were not. 63.4% of all intervals were considered normal (18-24 days), there being no difference in percentage between cows in naturally mated and A.I. herds. The percentage of intervals of 39-46 days was 6.7% and 8.9% resp. in these 2 types of herd, the difference being non-significant.