The issue of milk production has been a question for many years. The mare has never been selected on the basis of the milk she produces, and there appears to be a great variation in the quantity of milk produced. The question might be posed as to the slow – growing foal - - is it small because of genetics or because of a lack of milk? Mares that lose weight during lactation usually produce large growthy foals, whereas mares that gain weight usually have small foals which would indicate that the size of foal at weaning is related to milk production.

Mares peak in milk production at about four to six weeks after foaling. After this point, the foal does not seem to grow as well until he begins to eat supplement feed.

In addition to the fact that production of milk begins to drop after six weeks, the quantity of milk also begins to decrease, the fat level drops from about 1.5% to 6% or less and the protein level decreases from 4.17% to about 2% or less. It is for these reasons that foals should be introduced to a good grain ration early so that they can be weaned at three to four months of age without suffering a setback. Mare’s milk calcium level is estimated at 03% to .04% with phosphorus at .014% to .015%. (Cow’s milk has ten times the calcium and phosphorus of mare’s milk.) The composition of mare’s milk actually is very similar to human milk. The milk is virtually devoid of copper, iron and zinc. Increasing these minerals in the diet of the mare will not change concentration in the milk.

If a mare is fed an adequate ration of 14 – 16% crude protein and enough energy to maintain weight, there are no supplements that will increase milk production or change the milk composition. Composition of dairy cows’ milk has been enriched over the years, but only by selective breeding, and by doing so, the fat content of cow’s milk has been increased.

Mares can tolerate relatively wide ratios of calcium to phosphorus because of an apparent ability of mature horses to excrete calcium through the urine. The young animal does not seem to have this ability. The blood level of calcium is controlled by two hormones, parathormone, and calcitonin, which appear to work in opposition to each other. When serum calcium is low, parathormone is secreted and increases absorption of both calcium and phosphorus from the intestine and renal reabsorption of calcium. At the same time, the production of 1.25 dihydroxycholecalciferol ( 1.25 DHCC ), an active form of vitamin D is stimulated. This increases calcium absorption and mobilizes calcium from the bone. On the other hand, when serum calcium is elevated (hypercalcemia), calcitonin is secreted, which indirectly prevents bone calcium from being mobilized into the serum and probably acts on the kidney and intestine to block utilization. At times this can be seen visibly as milky white colored urine. The ration of calcium to phosphorus is more critical for the young horse and should be no wider than 2 parts calcium to 1 part phosphorus. Under no circumstances should phosphorus be greater than calcium.

The fact of the matter is that no matter what the diet is composed of , milk cannot be changed. There have been suggestions made that feeding high levels of protein will increase protein levels and make milk “too rich” for foals. Available data does not substantiate this claim. The amount of milk produced will increase with better nutrition, but the composition remains. The levels of fat and protein decrease with time, and milk sugar, calcium and phosphorus increases slightly, but the increase in these components does not overcome the total consumption because of the decrease in milk quantity.

Have a question for Dr. Tyznik ? Dr. Tyznik is in the Tizwhiz office every Tuesday and Wednesday mornings from 8:00 to 11:30. You can call him by using the following phone numbers. (937) 462-8105 or 1-800-860-6789 ext. #11. Or, you can e-mail your questions to kimj@tizwhizfeeds.com.