Practical Approach to Nutritional Support of the Dysphagic Foal

Coordinating suckle-swallow and breathing activities requires a complex integration of motor and sensory signaling. This ability is only partly perfected in the newborn, and disease can disrupt this process easily, resulting in hypophagia or dysphagia. Nutritional support is an important component in the treatment of the sick foal, whether the animal is an orphan or accompanied by its dam. Indwelling feeding tubes designed for use in the equine neonate facilitate the delivery of enteral nutrition to foals that have developed dysphagia due to a variety of diseases. Providing nutrition through the enteral route is a relatively safe and inexpensive method of supporting the dysphagic neonate through its disease process. Careful management of the feeding tube and diet is essential to prevent complications such as enteritis or aspiration pneumonia in the foal.

1. Introduction

The average neonatal foal has a strong suckle-swallow reflex that is apparent at birth and allows the foal to ingest its first milk meal within 2 hours or less of parturition. Since foals are born with minimal energy reserves, the ability to suckle-swallow is closely coupled with survival. The coordinated suckle-swallow reflex is a complex task that requires precise integration of muscle and nerve activity. In addition, the suckle-swallow reflex must be synchronized with the expiratory phase of respiration and is accompanied by a moment of apnea to minimize the risk of particulate inhalation. In foals, dysphagia results from compromised ability to swallow and/or suckle, and sick neonates of many species often demonstrate a concurrent loss of suckle and swallow as their disease state progresses. A dysphagic foal that presents for treatment accompanied by its lactating dam will require the same nutritional support as an orphan foal due to its inability to suckle and meet its nutritional needs. Dysphagia results from a variety of causes including structural abnormalities such as cleft palate or physiological dysfunction such as muscle weakness, stupor, or loss of neurogenic control. Regardless of the cause, treatment requires rapid intervention either in the form of enteral or parenteral nutrition. Enteral supplementation is the most practical and economic approach to providing nutritional support but depends on gut function and appropriate delivery to prevent complications associated with aspiration, gastrointestinal ileus, or infection. Additionally, administering long-term parenteral nutrition is not practical in a field environment, but simple formulations can be used to bridge the gap between the foal’s initial presentation and stabilization of the foal’s condition to the point where it can tolerate enteral support. Providing adequate nutrition is often as important a treatment modality as administration of antibiotics, and the goal of this presentation is to offer the audience options for management of the dysphagic foal outside of the neonatal intensive care unit.

2. The Development and Control of a Coordinated Suckle-Swallow-Breathing Reflex

Understanding the development and complexity of the normal suckle-swallow-breathing (SSB) reflex provides a foundation for recognizing dysphagia in compromised neonates. Mammals are born with the ability to suckle and swallow, but the development of oral-motor skills is far from complete. Learning these skills continues after birth, and the rate of development is dependent on exposure to food of different textures. This progressive developmental pattern is observed in all species that are transitional feeders (progress from milk to semisolid and solid food) in which the development of eating skills has been examined.¹ As compared with human children, foals develop the full range of oral-motor skills at a much earlier and less variable age. Most foals begin creep feeding by 2 weeks old and can tolerate weaning as early as 4 weeks of age. In contrast, human children require at least 1 year to establish a full range of oral-motor skills, and the rate of development varies by 6 months or more from child to child.¹

Although suckling and swallowing are considered unique functions, the mechanics of these activities overlap significantly. Suckling requires the foal to search and identify the teat; latch onto and remain attached to the teat; form a curl with the tongue to surround the teat; pool milk in the rostral aspect of the mouth; and elevate the tongue in a wave-like fashion to move milk from a rostral to caudal position and against the soft palate; lift, shorten, and widen the soft palate; propel food (milk) into the pharynx; and elevate the larynx as the bolus enters the pharynx.² Execution of the suckle-swallow reflex requires orchestration of approximately 20 muscle groups and culminates in bolus transport, suspension of respiration, and airway protection. The whole pattern is completed in about 1 second in humans.^1,3  [...]