When experiencing dry times, the first supplement we feed out is copra meal, which is the white meat from inside the coconut shell, dried and ground to a powder. It is very high in protein and a good source of energy.  If the dry continues, the stock are given a small ration of grain for energy, which would always constitute less than 5% of their total dry-matter intake (as per the Australian Certified Organic specification). In severe and prolonged dry periods, hay is fed out (we have only ever had to do this once), but in this situation, the option to send the cattle on assignment (if there is any certified country available) is always taken.
The only other time the cattle feed is supplemented is when sale cattle are just about to be trucked.  We feed them copra meal (as described above) from daylight on the day they are trucked (being when they are yarded) which provides both a boost of energy and protein for the following 24 hours they are off feed and in yards. This also helps ‘dry’ the existing feed in their stomachs, which slows down their process rate, and helps maintain ‘gut-fill’ and muscle glucose levels for longer.