It just depends. For a county fair it probally isn't necessary unless it is very competitive. It might come in handy at a bigger show but you have to be careful. You don't want to shrink him so much he looks out of place and you also want to make sure you have enough time to make him look fresh again. There is a reason a lot of the big shows are now hip height. It won't hurt the animal unless done to extremes, frequently. When a calf weighs1300, in the big picture it is no problem for their weight to vary 50 pounds either way just by the amount they eat or don't eat at a given feeding. It wouldn't be a stretch to shrink a calf 50 pounds just by limiting water and hoping they poop and pee right before they get on the scale. Make sure you know what weight your calf will look its best at. You don't want to shrink it so much he looks out of place. I have seen the whole shrink thing done wrong and calves that could have won shows at the right weight get third in class because they are to big.