The IRS assigns assets a useful life. While there is not one for dogs specifically, both livestock and racehorses have useful lives anywhere from 3 years for horses and hogs to 7 years for breeding animals. If your dog, as an asset, was entered into service and taken out of service out of service in the same year, depreciation is not allowed.
The better way is to include them as inventory. As each dog comes in, you record the purchase price in Cost of Goods Sold. As that animal leaves, you remove them. You record the sales price as gross income. The COGs will act as your basis for the sale.
