Thank you for your query,

In this instance I would recommend NRM Evolve. Older horses can be fed feeds formulated for young horses as they have many of the same requirements.  As horses get older they benefit from the higher protein feeds that are formulated for young horses as well as the yeast cultures etc that are often incorporated into feeds. The higher calorie level of the feed can also help the condition on the older horse. NRM Evolve also contains a KER premix which means when fed at the recommended rate no further vitamin and mineral supplementation will be required other than salt.  

I hope you find this information useful