Bernard Keane did well to summarise the recent Productivity Commission "Regulation of Agriculture" report's chapter on animal welfare. It's 61 pages in an 800-page report, but there were a few more relevant chapters that are crucial to understanding how agriculture is and isn't regulated in Australia. Probably the most important is that on biosecurity, and it demonstrates how easily the Productivity Commission can be led astray.
Keane notes that the commission brings animal welfare within its remit by putting numbers on the costs and benefits to the community of changing the way factories treat animals. I use the word "factories" because well over half of the meat eaten here comes from animals you'd never see in any drive through the Australian bush, except perhaps on the back of trucks. But to economists, animal suffering is of no consequence unless consumers put a monetary value on it.