Abstract
A
retrospective analysis was performed to determine the effects of age,
breed, parity, and litter size on the duration of gestation in the
bitch. Bitches at two locations were monitored from breeding to
whelping. A total of 764 litters whelped from 308 bitches (36 large
hounds, 34 Golden Retrievers, 23 German Shepherd Dogs (GSD), and 215
Labrador Retrievers). By breed, the number of whelpings was 152, 72, 58,
and 482 for the hounds, Golden Retrievers, German Shepherd Dogs, and
Labrador Retrievers, respectively. Whelping was predicted to be 57 d
from the first day of cytologic diestrus in the hounds or 65 d from the
initial progesterone rise in the other breeds. The average gestation
duration (calculated as 8 d prior to Day 1 of cytologic diestrus in
hounds or measured from the initial progesterone rise in other breeds)
by breed (days ± S.D.) was 66.0 ± 2.8, 64.7 ± 1.5, 63.6 ± 2.1, and
62.9 ± 1.3 for the hounds, Golden Retrievers, German Shepherd Dogs, and
Labrador Retrievers, respectively. The relationship of age, breed,
parity, and litter size with the difference in gestation duration was
evaluated using log linear modeling. Age or parity had no effect on
gestation duration. Compared to Labrador Retrievers, the German Shepherd
Dogs, Golden Retrievers and hounds were more likely to have a longer
gestation duration; three, four and nearly eight times as likely,
respectively. Bitches whelping four or fewer pups were significantly
more likely to have a longer gestation duration than those whelping five
or more pups; the prolongation averaging 1 d.
