Tricky question. You can deduct all "ordinary and necessary" expenses for your business. These words mean typical, helpful, appropriate, useful. At first glance chickens don't seem to meet this test. However, if you incorporate chickens into the learning curriculum of your business, then the cost of feed would be deductible. You would need to show this by having written records of what you taught children about chickens, how the children interacted with the chickens, photos of children with chickens, etc.