What Should an Oral Rehydration Solution Contain?
What Should an Oral
Rehydration Solution Contain?
Important ingredients in an electrolyte for treating scouring calves.
· Water
· Sodium
· Energy
· Glycine
· Alkalinizing agents
· Potassium
· Chloride
First, an important distinction needs to be made between oral rehydration solutions used for treatment of scouring calves and those used for electrolyte supplementation.
The latter are used to supplement extra electrolytes to older, usually weaned calves or cattle during times of stress from transport, weather and other situations that can cause loss of fluids and electrolytes.
It is easy to mistake one type for another; however, if the directions require small amounts of powder being mixed into many litres of water, this indicates that the solution is only supplemental and should not be used for treatment of scours in pre-weaned calves.
One of the most important components of oral rehydration solutions is water. Water is the essential ingredient to a rehydration solution.
Sodium should be included in the solution at 70 to 145 mmol/L. Sodium is tightly regulated by the body and although low amounts of sodium in the body can cause problems (from diarrhea, for example), high amounts can also cause problems. If the sodium offered is too high, calves will need to drink more water to dilute these amounts; this extra water may not be available in the pen or they may be too weak to reach it. Sodium should also be at an average ratio of one to one with glucose to be absorbed efficiently.
Another important ingredient is an energy source such as glucose (dextrose may also be listed but it is only a different name for glucose). Glucose is transported into the intestine on a one to one ratio with sodium and thus helps sodium absorption. However, no more than 200 mmol/L should be included because this may change the osmolarity of the solution.
A solution with high osmolarity will draw water out of the intestine instead of into the intestine. When the amount of solutes is high on one side of a semi-permeable membrane, this causes water from the side with a low concentration to be drawn to dilute the contents of the side with a higher concentration.
The same happens in the intestine. If the solution in the lumen of the small intestine is too high in solutes, water will come out of the body into the lumen to dilute the contents and end up being excreted instead of absorbed.
Glycine is a non-essential amino acid that is commonly added to oral rehydration solutions and has been shown to enhance absorption of glucose. To calculate the amount that should be included in the oral rehydration solution, the level of glycine should be added to the sodium level and the total should not exceed 145 mmol/L. The total of glycine and sodium should also equal a one to one ratio with glucose.
Alkalinizing agents are added to decrease metabolic acidosis and may also provide some energy. These are usually attached to sodium and include bicarbonate, citrate, lactate, acetate or propionate.
One of the most common alkalinizing additions is bicarbonate, which should not be fed directly or within a few hours of whole milk. Bicarbonate and citrate inhibit the formation of the casein curd in the abomasum. If feeding an oral rehydration solution with bicarbonate or citrate, it should be fed about 4 hours after milk feeding. Acetate is the most easily metabolized. Alkalinizing agents should be included at 50 to 80 mmol/L.
Oral rehydration solutions will also contain other electrolytes, especially potassium and chloride, as well as many minerals. Potassium and chloride are needed to maintain pH of the blood and for muscle contractions, especially in the heart.
Although little research has concentrated on evaluating amounts of potassium and chloride needed to replenish electrolytes in scouring calves, the range of potassium found in most solutions is 20 to 30 mmol/L and chloride is 50 to 100 mmol/L.
Other additions can include gelling agents such as guar gum, pectin and others. Oral rehydration solutions containing gelling agents reduce diarrhoea within hours of feeding and may coat inflamed intestinal mucosa. Slowing down the passage rate of the rehydration solution also may allow the intestine to absorb more nutrients. More research is needed to determine the advantages and disadvantages of gelling agents.
Many rehydration solutions are also adding direct-fed microbials. These are bacteria that re-establish the correct ratios of gut microflora. Usually these probiotics consist of lactobacillus and Bifidobacterium species, both of which work against E. coli and are beneficial to the intestinal environment.
Reference: Penn State University. College of Agricultural Sciences. https://extension.psu.edu
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