It was suggested to me by two equine nutritionists to add calcium carbonate to my horse’s (two seniors) diet due to my orchard grass hay being so low - Calcium 0.43 and Phosphorus 0.28. I purchased food grade ground limestone and feed 1 tablespoon once a day. Curious to hear if anyone else adds calcium to their horse’s diet?
How much do they weigh, and how many pounds are they eating?
I wouldn’t say those numbers are low at all.
22lb of that hay provides 42gm Ca and 27gm P.
An 1100lb horse needs around 30gm and 18gm respectively if in light work, up to 40gm and 29gm if in very heavy exercise (very few horses, think racing).
Thanks JB.
One weighs 1,200 and the other 1,000. They share 35 lbs hay plus 1 hour pasture time each day. One horse is 100% retired, the other is in light work right now.
So an average of only 1.6% of their combined weight in hay a day? Is that all they’ll eat, or are they restricted due to weight issues?
If 1200lb guy is eating 20lb, then still, .43% Ca is providing 39gm of Ca, and 25gm P which is more than he needs for light work (or retired, whichever he is). The ratio of ca:phos is 1.56:1 which is perfect
If 1000lb guy is eating 15lb, then it’s 29gm Ca and 19gm P which is juuuuuust borderline low on C if he’s in light work and is MORE than the needed 20gm if he’s retired. It’s juuuust borderline enough on P if he’s in light work (18gm needed) and plenty if he’s retired (14gm). The ratio is 1.52 which is perfect
So what, exactly, did the nutritionist give as the reason for needing more Ca, and just as importantly, why not more P?
Both are easy keepers, one being IR. Both nutritionist said to boost the Ca, and felt it was too low. No mention of more P.
“felt” doesn’t have any bearing on numbers 
You can see the math above.
