By S.J. Stoneham, N. Tyler, M.A. Holmes, D.C. Archer
Graphics: © The Authors
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.
Equine neonates are born immunocompetent but immunologically naïve due to the epitheliochorial structure of the equine placenta that precludes the transfer of immunoglobulins in utero.
1. Introduction
Transfer of maternal antibodies is therefore reliant on absorption of colostral IgG and other immune factors by endocytosis via specialised, short-lived cells in the newborn foal’s small intestine that are operational during the first 12-18 hours after birth. In clinical practice, foals with IgG concentrations of <8g/l at 18-36 hours of age are defined as having failure of transfer of passively derived colostral immunity (FPT) [1,2]. FPT is a well-documented risk factor for neonatal sepsis [1,3,4,5,6,7] and increases the risk of neonatal mortality [8,9] and morbidities [10]. The reported prevalence of FPT in foals varies widely between different populations, ranging from 5.5-44.7% [3,5,11,12,13,14,15,16,17]. Factors such as breed, management and IgG assay methods are likely to contribute to these differences. In foals >12 hrs of age, intravenous administration of plasma (transfusion) is currently the only treatment option for FPT, with additional associated costs of veterinary care and risks to the foal [5]. Although plasma provides the foal with additional immunoglobulins, colostrum contains many other factors that may positively support the neonate’s innate immune system including the cytokines TNF-alpha, IL-6, IFN gamma, IL-8, IL-4, growth factors, lactoferrin and maternal lymphocytes [18,19,20].
Efficacy of transfer of passive immunity is dependent not only on early ingestion and efficient enteric absorption of colostrum by the foal, but also on the quality and quantity of colostrum produced by the mare [11,21,22,23]. The latter has been shown to be associated with maternal factors including breed, mare age, and gestational length [23]. In pigs, maternal nutrition has been shown to affect colostral IgG concentration and volume, and the efficiency of IgG absorption [25,26,27]. The role of maternal nutrition in late pregnancy in the efficacy of transfer of passive immunity to their offspring is a current area of ongoing research in food animals. However, current evidence for the broodmare is lacking.
The objective of this controlled field trial was to evaluate the effect of dietary supplementation of a commercial Stud Feed Balancer (FB) in a population of pregnant sports horse mares on the efficacy of transfer of passive immunity to their foals. We hypothesised that broodmares that received a Stud Feed Balancer, specifically designed to balance a forage-based diet during pregnancy, would produce higher quality colostrum and that the incidence of FPT in their foals would be reduced, compared to non-supplemented mares and their foals.
2. Materials and methods
2.1. Ethical approval: Ethical approval was granted by The University of Cambridge Ethical Review Panel (CR 636) and informed consent was obtained from the owners of the mares for participation in the study and use of anonymized data. Client confidentiality has been maintained throughout this study... To read the complete article you need to be a subscriber
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