Liquid Diets for Horses
In equids with decreased appetite or complete anorexia, enteral diet choices are limited to those that can be administered through a nasogastric tube. Types of liquid enteral diets include
■ TABLE 50.4
Nutritional Content of Selected Liquid Diets
| Vital HNa | Osmolitea | Critical Care Meals/Packet | |
| Cal/L | 1000 | 1008 | 1066 |
| Protein | 41.7 g/dL | 40 g/dL | 12% |
| Fat | 10.8 g/dL | 34 g/dL | 1% |
| Carbohydrate | 185 g/L | 135.6 g/L | 73% |
aProduct formulated for human use.
slurry diets composed primarily of normal feedstuffs (Table 50.2), commercial equine enteral diets, liquid component diets that allow the clinician to tailor the feeding regimen adding fiber, vitamins, minerals, and amino acids separately (Table 50.3), and commercially available liquid diets for humans (Table 50.4).
Complete pelleted feeds offer several advantages—they are relatively inexpensive, meet the maintenance nutrient requirements, and contain sources of fiber. Fiber is beneficial in increasing colonic blood flow, enzymatic activity, and ruminal and colonic mucosal cell growth and absorption.41
Both human and equine liquid formulations are available and have been used as enteral nutrition support in horses.42-45 The use of human products (Osmolite and Vital HN) in the mature horse can be expensive and has been associated with diarrhea and laminitis (though cause and effect are not clear); consequently they are rarely used and not currently recommended, having been largely replaced by equine-specific formulations.46,47 WellSolve Well Gel (Purina Mills, LLC, St.
Louis, Mo.) and Enteral Immunonutrition Formula (Platinum Performance, Inc. Buellton, Calif.) are two diets currently available for use. The major disadvantage of these products over complete pelleted diets is their cost.Component diets have been described for use in equids.47 Corn oil may be added to the diet to increase the caloric content but should be added gradually (increasing the intake by ¼ cup or 60 mL daily not to exceed 2 cups or 600 mL total daily intake) to prevent diarrhea.
Liquid diets can be given by continuous flow through an indwelling small-bore (18-French) nasogastric feeding tube (Mila International Erlanger, Ken.) or via periodic passage of a nasogastric tube and administration of larger meals. When using pelleted diets in equids, the authors recommend that 1 kg of a pelleted complete feed be soaked in approximately 4 L of water. Once this water has been absorbed, an additional 2 L of water are added to form a slurry that can be administered via a large-bore (external diameter 305 cm) nasogastric tube. Slurry diets made from complete pelleted feeds may not pass through a nasogastric tube using gravity alone. Instead, the slurry can be administered by use of a marine supply bilge pump. If a bilge pump is not available or a large-bore tube cannot be passed, pulverizing the pellets before adding water may improve gravity flow. The horse should be checked for the presence of gastric reflux before administration, and the slurry should be pumped slowly with attention paid to the animal's attitude and reaction. As the stomach volume of a mature, 450-kg horse is approximately 9 to 11 L, the volume of each feeding should not exceed 6 to 8 L per feeding. The volume fed should be adjusted for smaller horses. Long-term placement of nasogastric tubes in horses is not without the risk of complications.47 Small-bore, 18-French, softer (polyurethane) tubes (Mila International, Erlanger, Ken.) are recommended if intubation is prolonged, as they are better tolerated by the patient but generally preclude the use of slurry diets.
Alternatively, intermittent placement of a nasogastric tube is effective in decreasing complications but can be difficult, and at times traumatic, for the patient. When instituting enteral feeding, particularly in a patient with prolonged anorexia, it is best to start gradually increasing the amount fed over several days (Table 50.5). A maximum of 50% of calculated requirements should be fed in the first 24 hours; if the patient tolerates this level of supplementation, the amount can be increased over the next few days until the target feeding rate is achieved. Rapid changes in feed amount such as feeding 100% of required intake the first day in an animal that has not eaten for 3 to 5 days can be associated with colic, regurgitation, or diarrhea, particularly with liquid diets made for humans or high-fat diets.Creation of an esophagotomy should be considered when prolonged enteral nutritional support is likely to be required or when medical or surgical conditions prevent passage of a nasogastric tube. Esophagotomy can be performed in a standing, sedated animal and, once in place, allows frequent intubation and feeding while avoiding the trauma and discomfort associated with repetitive nasogastric intubation. Once the animal has recovered and its appetite has returned, tube feeding can be discontinued to allow the esophagotomy incision to heal by second intention.