score:7
Apparently the rule did exist. John Dundas Cochrane clarified its origin in his Narrative of a pedestrian journey through Russia and Siberian Tartary, from the frontiers of China to the Frozen sea and Kamtchatka; performed during the years 1820, 1821, 1822, and 1823:
Much benefit has been derived to the colony from the exertions of the present Chief, Captain Rikord. The rule of never allowing a cow to be killed until she is past calving, is in itself excellent, but the stock on hand is so small that a century would elapse before what can be termed herds of cattle could be seen wandering and feasting upon the almost unhounded pastures of the Peninsula.