Like all mammals, a mare builds a foal from her own reserves. If nutrition is inadequate she will draw calcium from her own bones, minerals from her own organs and amino acids from her own muscles. While she is able to produce a foal this way, it will leave her depleted for the task of feeding that foal at foot.
In late pregnancy, calorie requirements increase around 30% but protein requirements increase by 100% and minerals by 80%.
You can easily add calories by increasing the pre-pregnancy feed, but this will not necessarily meet protein and mineral requirements. High protein feeds include alfalfa (lucerne) hay and soybean meal.
“We have underappreciated the value of alfalfa as a protein source,” said Dan Undersander, emeritus forage agronomist with the University of Wisconsin. “Although alfalfa adds fiber to the ration, has a high rate of passage, and is palatable, it really brings value from a protein perspective. Whereas average corn silage is about 7.5% to 8.5% crude protein, alfalfa is 18% to 22%,” he explained during a recent Alfalfa U webinar presentation.
Alfalfa leaves contain about 25% to 30% crude protein while the stems have only 6% to 10%. Generally, tall or stemmy alfalfa is lower in protein than shorter alfalfa. “Alfalfa grown with limited water that is shorter tends to be higher in crude protein than alfalfa with adequate water and normal height,” Undersander noted.
Choose leafier lucerne hay if it's available. Lucerne is also one of the higher sources of calcium for horses and is particularly useful for horses grazing on oxalate pastures like kikuyu and setaria.
Soybean meal is an excellent source of protein, especially for the young growing horse. It contains the highest level of lysine (Table 12.2) of the plant protein concentrates used in horse feeding. It is even higher in lysine than dried skim milk, which itself is an excellent source of protein for the young foal. Soybean meal contains either approximately 44% or 48% protein; the 48% soybean meal is prepared by removing the hulls. Soybean meal is the most widely used protein supplement in horse feeding with excellent results. In practice, however, it is usually fed in combination with other protein sources. Properly processed soybean meal by the hydraulic, expeller, or solvent method has about the same feeding value. Overheating soybean meal destroys lysine whereas underheating soybean meal makes its methionine less available. For maximum nutritional value, therefore, soybean meal needs to be properly heat treated and processed.
Soybean meal is available in most produce stores as Pryde's Protein Pak. Here at Sound Advice we feed soy bean meal to horses generally to improve topline, particularly for older horses.
Evaluating condition in a mare later in pregnancy is different from non-pregnant horses, as it's common for them to have ribs showing. A better visual clue is the condition of the neck, rump and thighs.
Sound Advice Trace Mix will supply sufficient amounts of copper, zinc and iodine. The foal develops rapidly from the midway point. You can increase the dose from mid-pregnancy, particularly if you a breeding a larger horse. We can also add selenium to this mix.
Supply adequate salt - around 50 grams per day, or 2 tablespoons. You can offer a salt lick, but it is difficult to determine which horse and/or how much salt they are consuming. It is highly palatable, so easier to supply directly in the feed bin.
As always, these are general comments and every horse is different. We are happy to provide you with specific recommendations for your horse. Our consults can be done in person in the Hunter Valley or by email.
Let ALfalfa Soften Your Protein Bill Mike Rankin
Hay and Forage Grower March 2021
Salt consumption and the effect of salt on mineral metabolism in horses
Cornell Vet April 1987
Value of Feed for Horses
Physiological development of the equine fetus during late gestation
Equine Veterinary Journal November 2019
Prenatal establishment of the foal gut microbiota: a critique of the in utero colonisation hypothesis
Kirsty L. Mols AC , Gry B. Boe-Hansen B , Deirdre Mikkelsen A , Wayne L. Bryden A and A. Judy Cawdell-Smith A
Animal Production Science November 2020