Breed, parity, and cycle season effects on life-time reproduction in bitches: a retrospective study

The aim of this retrospective study was to evaluate the effects of breed, parity, and season on the reproductive parameters in bitches reared under a temperate climate. Breeding and pregnancy statuses, proestrus, estrus, and pregnancy durations, litter size, and cycle interval were recorded from German shepherds (GS, n = 34), Labrador retrievers (LA, n = 23), Belgian Malinois dogs (BM, n = 13), and Pointers (PO, n = 9) up to 10th parities. The mean age at first breeding (464.8 +/- 26.2 days, mean +/- SD) and the pregnancy rate (74.6%) were not different among breeds. The pregnancy duration was shortened as the number of puppies born increased in each whelping (P < 0.008). The cycle interval varied by breed (208.2, 215.1, 208.6, and 237.0 days for GS, LA, BM, and PO, respectively, P < 0.01) and decreased linearly from 241.1 to 202.0 days as parity increased from 1 to 10 (P < 0.04). The season did not affect the cycle interval, proestrus, and estrus length (P > 0.05). Reproductive parameters varied among the GS, LA, BM, and PO bitches reared in Turkey. The effect of seasonal variation was negligible.