Free choice hay in a ration

Question
Hi,

I'm recalculating my horse's ration to include a grain change at the barn. I have been a terrible person and had not changed the rations when they went to free-choice round bales and realize I guess now is the time. I would take a sample of the hay to get tested but how do I figure out what my gelding eats of hay in a day when he's in a herd? How did you manage to figure rations for outdoor boarded horses?

Thanks

Answer
Hi Ali,

Thank you for your question.  When I formulate a ration, I always start by estimating a horse's dry matter intake based on their workload (incl. age, sex, etc). I'm always looking for a forage based diet, and so calculate the horse's entire diet in hay first.  If the ration does not balance, I then add in grain and remove the equivalent dry matter in hay.  

For example, if I have a 1000 pound adult horse doing light to moderate work, I assume he will consume 2% of his body weight in dry matter...or 20 pounds of hay on a dry matter basis (assuming the hay is 85% DM, equates to 23.5 pounds as fed). If you then take your forage analysis and find that his nutrient requirements are not met by eating those 23.5 pounds of hay you have to sub in some grain to meet requirements.

Of course if you design a diet around a set amount of grain (not my preferred approach) then you subtract the amount of grain you feed from your horse's estimated dry matter intake, and what you have left is how much hay the horse will eat in a day.

For example, if you feed 5 pounds of grain on an as fed basis (4.5 pounds dry matter), then that same 1000 pound horse is going to eat 15.5 pounds of hay in dry matter, or about 18.2 pounds of hay as fed (assuming hay is 85% dry matter).

Hope that helps.

Thanks, Corlena