724 
ON THE GESTATION OF COWS. 
From the inspection of this table it will be seen that the shortest 
period of gestation when a live calf was produced was 220 days, 
and the longest 313 days, but I have not been able to rear any calf 
produced at an earlier period than 242 days. Any calf produced 
at an earlier period than 260 days must be considered decidedly 
premature, and any period of gestation exceeding 300 days must 
also be considered irregular, but in this latter case the health of 
the produce is not affected. It will also be seen that 314 cows 
calved before the 284th day, and 310 calved after the 285th ; so 
that the probable period of gestation ought to be considered 284 
or 285 days, and not 270, as stated in the book upon Cattle pub- 
lished under the superintendence of the Society for the Diffusion 
of Useful Knowledge*. 
It appears, also, that the number of breeding females is less con- 
siderably than the number of males, and to the number of males 
ought generally to be added as animals that will not breed, the 
females who are twins with males. I have heard and believe, that, 
in some cases, a cow-calf, twin with a bull, will breed ; but in no 
instance in which I have bred twins of different sexes has the 
female been a breeding heifer. The number of breeding heifers 
from these 764 cows was 354 ; the number of bull-calves 422 ; and 
the number of heifers, twin with bulls, usually called freemartins, 
11 . 
There is a prevalent belief among farming men, and, I believe, 
farmers, that when the time of gestation of a cow is longer than 
usual, the produce is generally a male calf. I must confess that I 
did not believe this to be the case, but this table shews that there 
is some foundation for the opinion. In order fairly to try this, the 
cows who calved before the 260th day, and those who calved after 
the 300th, ought to be omitted as being anomalous cases, as well as 
the cases in which twins were produced ; and it will then appear that, 
from the cows whose period of gestation did not exceed 286 days, 
the number of cow-calves produced was 233, and the number of 
bull-calves 234 ; while from those whose period exceeded 286 
* In another work, however, entitled “ British Husbandry,” published under 
the superintendence of the Society for the Diffusion of Useful Knowledge, 
the experiments of M. Tessier, of Paris, on the gestation of cows, are recorded 
to have given the following results : — 
“21 calved between the 240th and 270th day, the mean term being 259£ 
544 do 270th . . .. 299th 282 
10 do 299th . . .. 321st 303 
In most oases, therefore, between nine and ten months may be assumed 
as the usual period ; although, with a bull-calf, she has been generally ob- 
served to go about forty-one weeks, and a few days less with a female.” Vol. 
ii, p. 438. — F. Burke. 
