Does dietary supplementation of pregnant mares with a commercial stud feed balancer improve the transfer of passive immunity in their foals? A controlled field trial.
Authors: Stoneham S J, Tyler N, Holmes M A, Archer D C
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Failure of passive transfer (FPT) remains a significant health risk for foals, yet opportunities to optimise maternal immunity transfer through late-pregnancy nutrition have received limited research attention. Stoneham and colleagues conducted a controlled field trial on 68 mare–foal pairs to evaluate whether supplementing pregnant mares with a commercial stud feed balancer during the final 64–224 days of gestation could improve colostral antibody content and reduce FPT incidence (defined as foal serum IgG <8 g/l within 12–36 hours of first suckle). Foals born to mares receiving the commercial balancer showed significantly lower rates of FPT compared to controls fed the farm's standard concentrate mix; moreover, supplemented mares produced colostrum meeting quality thresholds (Brix ≥23.0) more consistently. In multivariable analysis, only the intervention itself and foal sex remained significant predictors of FPT status, suggesting the dietary supplement's effect was robust and independent of other commonly implicated risk factors. For stud farms and practitioners managing pregnant mares, these findings support the use of targeted mineral and micronutrient-balanced feeds in late gestation as a practical, non-invasive measure to strengthen neonatal immunity and reduce the incidence of FPT—a condition that carries substantial treatment costs and welfare implications.
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Practical Takeaways
- •Consider supplementing pregnant mares with a commercial stud feed balancer in late pregnancy (64-224 days prepartum) to reduce the risk of FPT in foals
- •This dietary intervention appears to improve colostral quality, which is a practical proxy indicator for improved passive immunity transfer
- •Sex of foal should be considered as a risk factor when assessing FPT risk, in addition to mare supplementation status
Key Findings
- •Foals of mares supplemented with commercial stud feed balancer were significantly less likely to develop FPT (IgG <8g/l) compared to control group
- •Colostral quality (Brix ≥23.0) was significantly greater in the intervention group versus control group
- •Group assignment (intervention vs. control) and foal sex were the only variables significantly associated with FPT in multivariable analysis