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RE: [RC] [RC] OT (slightly) Pregnant older mares and calcium/phosphorus - Eleanor KellonThe feeding recommendations for pregnant mares have changed. HIgher protein and slightly higher calorie intake is recommended even in early pregnancy, mineral needs start to rise significantly after the sixth month. Not sure how any charting would format on the other end, but for comparison this is what you're looking at for targets for an 880 pound mare (ideal nonpregnant bodyweight), where NP = nonpregnant, 7M = 7th month, 11M = 11th month, L = lactation:
Protein: NP = 432 g; 7M = 583 g; 11M = 714 g; L = 1228 g
Calcium: NP = 16 g; 7M = 22.4 g; 11M = 28.8 g; L = 67.8 g
Phosphorus: NP = 11.2 g; 7M = 16 g; 11M = 21 g; L = 30.6 g
Common sense alone tells you need for other minerals increase also but since these aren't as well studied the recommendations are kinda just hanging there. Mineral ratios are also important.
Having seen several hundred analyses of grass hays from around the country, I can tell you that "grass hay" means nothing when it comes to predicting mineral levels. They can range from hays that have calcium levels almost as high as alfalfa, to hays which have an inverted Ca:P ratio (more phosphorus than calcium).
If we use a high Coastal Bermuda as an example that usually has a good Ca:P ratio, the breakdown is: protein about 10%, calcium 0.49%, phosphorus 0.27% (magnesium OK, copper and zinc low) so as a starting point, 22 pounds of this hay (2.5% of bodyweight) would provide 1000 g of protein, calcium 46 g, phosphorus 27 grams so she's set for these until you hit lactation. Trace minerals would be deficient though and you'll need to know for sure exactly how much they are actually eating. The only way to know if your particular hay is adequate is to have it analyzed.
Many mares don't gain any weight at all in the last 3 months of pregnancy because they simply can't eat enough with the space the uterus is taking up. Using stored body fat to support the foal's growth in late pregnancy is no problem. Breaking down their own muscle and bone to meet protein and mineral needs isn't an ideal situation though and you can avoid that by feed a high protein vitamin and mineral concentrate. Because of the gut fill problems in late pregnancy, you really want to try to make sure these mares have a little extra fat before they get to that point. If your hay is adequately meeting protein and mineral needs, you won't have to buy an expensive commercial feed. A mixture of 3 parts beet pulp to 1 part rice bran, by weight, has a balanced Ca:P ratio, 11 to 12% protein and a calorie density equivalent to a grain mix.
The second mare is old enough that I would seriously consider having her tested for Cushing's, even if she doesn't have any other outward signs than poor immunity (rain rot) and wasting. The classical coat changes only appear fairly late in this condition. If she has Cushing's, she's at higher risk for laminitis with pregnancy and you'll have to be even more careful how you feed her.
Eleanor
-- Eleanor M. Kellon, V.M.D. Equine Nutritional Solutions 58 Maple Farm Road Ephrata, PA 17522
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