Developed by Rob Costello
The importance of administering electrolytes to scouring calves is well recognized. Most calf facilities include electrolytes as a standard item in their arsenal of diarrhea medications and treatments. It is interesting that even though electrolytes are widely used, the method of administration, the amount given, timing, frequency, expected outcomes and actual results are quite variable. That’s not surprising considering the misunderstanding, confusion and disagreement surrounding the basic principles of electrolyte and water balance in the body. The information presented in this publication is not unique to baby calves, and is applicable to electrolyte and water movement in other animal species.
Chapter 1: Digestion, Absorption & Water Movement
This section describes how water moves into and out of the small intestine as it facilitates digestion and absorption of nutrients. An overview of intestinal mucosa structure and function is provided. The role of sodium in water movement and its relationship to amino acid and glucose absorption are also discussed. These are key concepts necessary for understanding electrolyte function, water loss, rehydration therapy and electrolyte formulation.
Chapter 2: Electrolyte and Acid-Base Balance
This section describes how individual cells, the kidneys and the lungs regulate the body’s electrolytes and water. The kidneys and lungs work in concert to regulate the chemical composition of blood, providing primary control over electrolytes, water and acid-base balance. This elementary exploration of the physical chemistry of biological solutions is one of the more technical discussions in this publication. Although an understanding of this material is not required before reading each of the remaining sections, these discussions provide a good foundation for understanding electrolyte and water balance, dehydration, and electrolyte formulation.
Chapter 3: Water Loss Mechanisms & Diarrhea
Pathogens, feed characteristics and management influence digestive function and can result in water loss through the digestive tract. There are four basic types of digestive water loss. Each is described in this section. A diarrheic animal may actually suffer from more than one type of water loss at the same time. The process of dehydration and the clinical signs associated with progressive water loss in calves are also discussed
Chapter 4: Oral Rehydration Therapy
The amount and timing of electrolyte replacement therapy is critical for rapid recovery from dehydration. This section describes the relationship between the degree of water loss and the amount of electrolyte solution required to offset the loss. An overview of the effect of different pathogens on water loss and rehydration therapy, regulation of voluntary intake and effects of tube-feeding are presented. The importance of regular milk replacer feedings on the hydration status of the animal and in maintaining nutrient intake is also explored.
Chapter 5: Components of Electrolyte Solutions
Electrolyte solutions should be formulated for their ability to enhance water absorption and water retention, to restore electrolyte levels and to reduce acidosis. Since diarrhea can have a serious effect on bacterial populations in the digestive tract, inclusion of specific direct-fed microbials favors conditions for growth of beneficial bacteria and reestablishment of a normal intestinal environment. Organisms that cause diarrhea often damage the intestinal lining and impair gut function. Electrolytes may also contain ingredients that can help repair damage and improve function. This chapter reviews the nature and function of the major ingredients found in electrolyte products.
Chapter 6: Electrolyte Formulation and Function
This chapter draws upon the concepts and discussions presented in previous chapters, fusing them into a practical approach to evaluating electrolytes. Osmolarity, the relationship between strong ions and water, and their effects on acid-base chemistry are reviewed and applied to electrolyte formulation. The purpose is to enhance understanding of electrolyte formulation and its effects, not to provide instruction on how to formulate an electrolyte product. Acidosis, and the correction of this condition, is of special interest. A considerable portion of this chapter explores this metabolic condition, with special focus on the processes of alkalinization, alkalinizing compounds and their mode of action. Acid-base variables can be categorized as either independent, where changes in their concentrations affect acid-base balance, or they are categorized as dependent variables whose concentrations do not affect other variables nor do they affect acid-base mechanisms. This final discussion has profound implications.
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