I have a 14 year old Swedish WB mare who is currently 8 1/2 months pregnant with her second foal. She is 16.1 and easily 1,350 lb (while not pregnant). She is a VERY easy keeper and I want to avoid sugars and starches in her diet as much as possible.

Currently she is fed 10 lb grass hay, 10lbs alfalfa, 1 lb of haystack, and 1 lb of oats per day. I’m looking for a supplement that will meet all of her nutritional requirements for her third trimester without adding any additional grain to her diet (although I may need to increase her haystack over the next few months).

What supplement do you recommend for her and in what quantity as she reaches her final phase of gestation?

Answer by Ph.D. Equine Nutritionist, Kelsey Johnson Nonella:

One very important nutritional aspect in a pregnant and nursing mare’s is calcium: phosphorous ratio, which should be 2:1. By feeding your mare half grass, half alfalfa you are good on the Ca:P ratio.

One thing that is very important to added as soon as possible is organic selenium. At her weight she need 4.5 mg of organic selenium. She will receive this from 1 1/2 scoops (3 oz) of Horse Guard. At such a low dose, it won’t add any substantial amount of calories to her diet. I would recommend keeping her on the supplement on the time, but especially during nursing and if you are going to breed her again. Mares that are selenium deficient have greater chance of retained placenta and complications with birth, and foal health problems. It takes a selenium deficient horse approximately 8 months to reach adequate levels.

Horse Guard


About Dr. Kelsey J. Nonella Ph.D., P.A.S.

Kelsey J. Nonella, Ph.D. is an equine nutritionist who was riding horses before she could walk. Her love for horses drives her to help educate people on what their horses’ needs in order to have happy, healthy horses. Kelsey went to Cal Poly receiving a Bachelor’s of Science in Animal Science and then onto West Texas A&M, where she got her Masters and eventually her Doctorates in Equine Science. At A&M, Dr. Nonella did extensive research on Selenium within horses. Click here to view her research. Kelsey’s colleagues have mentioned her as an one of the United States equine Selenium experts.
View all posts by Dr. Kelsey J. Nonella Ph.D., P.A.S.

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