Question
I have an orphan foal, and I am trying to decide whether to use milk replacer or goat’s milk to nourish it. We have goats on the farm, so I am tempted to use a foster nanny. Is goat’s milk a suitable milk replacer for a foal, or is there a downside to using it for my orphan?
Answer
Goat’s milk has been used as milk replacer for foals for centuries, particularly when a nurse mare was not available. Techniques for grafting foals onto goats can be found in numerous older publications. Designs for ramp and platform setups that position the goat so the foal can reach the teats easily are available, although foals do learn to get down on their knees to nurse goats. If the foal can be adapted to drinking instead of suckling, the milk can be offered in a bucket.
Goat’s milk is similar to mare’s milk, and probably more so than milk from other species. Foals generally accept goat’s milk more readily than milk replacer. The milk supply of one goat may not be enough to meet the total needs of an orphan if it is not receiving other supplementation, and a second goat may be necessary. Goats can provide companionship to an orphan as well, so the orphan learns some social behavior from another animal.
That said, goat’s milk is not a perfect match for mare’s milk, and there are differences that can result in suboptimal growth of the foal. Nutrients in highest demand in milk are water and energy, followed by protein, calcium, and phosphorus. There are subtle differences in the energy and nutrient content in milk from goats and mares. The water content is very similar between the two (11% solids in mare; 13% solids in goat), and is not enough to warrant dilution of goat’s milk.
The energy content is higher in goat’s milk (690 kcal/l in goat; 550 kcal/l in mare), largely because it is higher in fat. In fact, the fat content in goat’s milk is nearly double that in mare’s milk (40 g/l for goat; 21 g/l for mare). In contrast, the calories in mare’s milk come mostly from carbohydrate and are higher by 25% in mare’s milk. The form of carbohydrate found principally in both milks is lactose, which causes no problems in foals. In contrast, commercial milk replacers sometimes add maltodextrin, corn syrups, oligosaccharides, and glucose polymers that may cause excessive gas production or osmotic diarrhea in young foals. Their immature digestive tracts have difficulty handling these types of carbohydrates. Calcium and phosphorus levels in both milks are similar, and there are very minor differences in the other minerals and vitamins.
Protein content is 24% higher in goat’s milk than mare’s milk. The quantity of protein is similar but the amino acid composition is not. There is a distinct difference in the quantity of the amino acid arginine, as it is twice as high in mare’s milk. At this time nutritionists are not sure how important this one amino acid is for growth, but the lack of arginine in goat’s milk and most commercial milk replacers may be related to suboptimal growth of orphan foals.
Perhaps the proportions of whey to casein found in goat’s milk make it more suitable for the foal than milk from other livestock such as cows. The whey to casein ratio in goat’s milk is 86:14 and is reversed from cow’s milk, which is 16:82. This ratio in mare’s milk is 85:15 immediately after parturition and normalizes to approximately 50:50 during the first 28 days of lactation.
Goat’s milk may be a suitable substitute for mare’s milk in many cases, but a research study done in 1990 found that the complications can be poor weight gain and a possibility of metabolic acidosis. These can be attributed to the differences in composition of milk.
The economics of using goat’s milk in your case may be the deciding factor since you already have the animals on the farm. If it came down to buying goat’s milk, it would not be as economical as buying milk replacer.
