There is soo many answers to this question, however, I will focus on just one. The health of large animals such as cattle, horses and pigs matters to human health because their organs are used in our bodies. Did you know this? There are several heart procedures that replace our human 'valves' and replace them with cattle or big valves because they are so close in size, matter & function as ours.
Another approach you could take on this is we eat these large animals. Would you like to eat an unhealthy animal? Probably not.
*hope this helps - good luck*