# Mare Milk and Foal Plasma Fatty Acid Composition in Foals Born to Mares Fed Either Flax or Fish Oil During Late Gestation

## TL;DR

Feeding mares fish oil during late pregnancy increases DHA levels in newborn foals, but not in mare milk or blood.

## Contribution

Fish oil supplementation in late-gestation mares boosts neonatal foal DHA at birth more effectively than flaxseed or no supplementation.

## Key findings

- Foals born to fish oil-fed mares had higher DHA levels at birth compared to control mares.
- Foal plasma DHA levels were highest at birth before nursing and decreased by days 5 and 30.
- Mare plasma and milk DHA levels were not significantly affected by the treatment.

## Abstract

Fish oil provides animals with eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, omega-3 fatty acids that have many important roles in animal health. In comparison, terrestrial plants provide the omega-3 fatty acid alpha-linolenic acid, a fatty acid that grazing animals can metabolize into EPA and DHA. The current study supplemented late-gestation mares with one of three treatments: fish oil, flaxseed, or unsupplemented controls. This was carried out to compare the effects and benefits of these fatty acid sources on their blood and milk fatty acid compositions. The mares received treatments beginning on day 310 of gestation and continued through day 5 post-parturition. Blood and milk samples were collected from the mares, and blood samples were collected from the foals. The plasma, harvested from the blood samples, and milk were analyzed for their fatty acid compositions using gas chromatography. Foals born to mares provided with fish oil exhibited increased plasma DHA levels at birth. Regardless of the treatment, the plasma DHA content was higher in foals prior to nursing than on days 5 and 30. No treatment differences were observed in the mares’ plasma or milk fatty acid composition. The most efficient avenue for increasing neonatal foal DHA levels may be through maternal supplementation with fish oils during late gestation.

Maternal supplementation with omega-3 fatty acids during late gestation has been shown to have a variety of benefits for neonates. The current study utilized 13 mares and their foals, assigned to one of three dietary treatments: an unsupplemented control diet (CON; n = 5), or the addition of either fish oil-derived omega-3 (FO; n = 5) or a flaxseed (FLAX; n = 3) supplement. The mares received treatments beginning on day 310 of gestation through day 5 post-parturition. Samples of plasma were collected from the mares prior to beginning supplementation, on days 0, 5, and 30 post-partum. Milk samples were collected from the mares 12 h post-partum. Plasma samples were collected from the foals at birth and at 5 and 30 d post-partum. The fatty acid compositions of the mare plasma, mare milk, and foal plasma were determined using gas chromatography. The data were analyzed using repeated-measures ANOVA. Foals born to FO mares exhibited increased plasma docosahexaenoic acid (DHA) levels at birth compared with those born to CON mares. Across the treatments, the plasma from foals at birth prior to nursing had the highest DHA content compared with on d 5 and 30. No treatment differences were observed in the mare plasma or milk fatty acid composition for DHA levels. FLAX mares had higher 20:3 n6 plasma proportions than FO or CON mares. Beginning supplementation with fish oil on day 310 of gestation may be sufficient to elevate neonatal foal DHA concentrations.