Effects of oral supplementation with β-carotene on concentrations of β-carotene, vitamin A and α-tocopherol in plasma, colostrum and milk of mares and plasma of their foals and on fertility in mares.
Authors: Kuhl J, Aurich J E, Wulf M, Hurtienne A, Schweigert F J, Aurich C
Journal: Journal of animal physiology and animal nutrition
Summary
# Editorial Summary: β-carotene Supplementation in Mares — Passive Transfer Works, But Fertility Benefits Remain Unclear Researchers investigated whether supplementing mares with 1000 mg daily β-carotene from two weeks before foaling through six weeks post-partum would enhance antioxidant status in dams and neonates whilst improving reproductive outcomes. Using 30 mares (15 supplemented, 15 control), they measured β-carotene, vitamin A and α-tocopherol across plasma, colostrum and milk samples, monitored foal plasma concentrations, and tracked return to oestrus and pregnancy rates following first post-partum breeding. Supplementation successfully increased β-carotene in maternal plasma and colostrum (p < 0.05), with foals from supplemented dams showing substantially higher plasma β-carotene by day one (0.048 μg/ml versus 0.008 μg/ml), demonstrating effective passive transfer through colostrum; however, vitamin A and α-tocopherol concentrations were unaffected by treatment, and both groups showed normal oestrous cyclicity post-partum. Surprisingly, pregnancy rates following first post-partum oestrus actually favoured control mares (7/7 versus 5/12 in the supplemented group, p < 0.05), suggesting that β-carotene supplementation at this dose may not confer reproductive advantages and warrants further investigation into potential trade-offs with other physiological processes during early lactation.
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Practical Takeaways
- •While β-carotene supplementation effectively transfers to foals via colostrum, this does not translate to improved mare fertility post-partum, so supplementation decisions should not be based on fertility benefits
- •If supplementing mares peripartum for other reasons, expect increased β-carotene in milk and colostrum but monitor fertility outcomes independently
- •The unexpected finding that control mares had better fertility outcomes warrants further investigation before routine supplementation in breeding programs
Key Findings
- •Oral β-carotene supplementation (1000 mg/day) significantly increased β-carotene concentrations in plasma and colostrum of supplemented mares compared to controls (p < 0.05)
- •β-carotene concentrations in foals were substantially higher when born to supplemented mares (0.048 ± 0.018 µg/ml on day 1 vs 0.008 ± 0.0023 µg/ml in controls)
- •β-carotene supplementation did not improve fertility rates; control group showed higher pregnancy rates after first postpartum estrus (7/7 vs 5/12, p < 0.05)
- •Vitamin A and α-tocopherol concentrations did not differ between supplemented and control groups despite higher levels in colostrum than milk