Oral
Electrolyte Therapy in Dairy Calves
By Robert Corbett, DVM, PAS, DIPL. ACAN, Dairy Health
Consultant
The most common calfhood disease
that results in the highest economic loss to the dairyman is diarrhea.
Dehydration and acidosis are the most important issues that have to be
corrected in the majority of diarrhea cases. Most individuals responsible for
treating sick calves understand the importance of rehydrating the calf and are
generally familiar with the use of oral electrolyte solutions.
However,
choosing which oral electrolyte to use, unfortunately, is often based on price,
or the recommendation of the animal health route person that visits the calf
operation. The dairy industry has been suffering from low milk prices for the
past several years, so the emphasis on using less expensive products has been a
high priority on most operations. It is common for the larger operations to
purchase their oral electrolyte product in bulk to reduce the cost per
treatment. Even though the bulk products usually contain a scoop that is
supposed to deliver the exact dose needed for 1 treatment, this is often
increased by a heaping scoop or perhaps more than one scoop on the premise that
if a little bit is good, a lot would be better.
When
choosing which product to use, it is generally assumed by those purchasing the
electrolyte that they are all created equal, so price is the major factor in
determining which product to buy. Another factor often considered is how well
the calf will drink the oral electrolyte solution so that administering it by
stomach tube will be less frequent. When looking at the labels, it is very
difficult to compare one product to another. The ingredients in electrolyte are
often expressed in different ways such as percentage, grams, milliequivalents
per liter, etc., making it next to impossible for those who are purchasing the
product to determine which product is the best as far as its ability to
rehydrate the calf. In addition to this, there hasn’t been much information
provided to the dairyman as far as what concentrations of the individual
ingredients are optimum to rapidly restore the normal physiological state of
electrolyte balance and hydration. Dr. Geoff Smith from the University of North
Carolina has published several articles on this complicated topic for
veterinarians, to help them better understand the physiology of rehydrating the
calf and correcting acidosis, and thus be able to better advise their clients
on this topic. The majority of the information on electrolyte formulation in
this article is taken from a chapter written by Dr. Geoff Smith from Veterinary
Clinics of North America 2008.
Diarrhea
results in rapid loss of the extracellular fluid volume (ECF) with a slight
increase in intracellular fluid (ICF). As stated by Dr. Smith “Sodium is the
osmotic skeleton of the ECF and therefore of plasma”. Since sodium is the main
determinant of the ECF, it must be included in a well-formulated electrolyte
product in sufficient amounts to rapidly reestablish a normal state of
hydration. There is not an exact amount of sodium that is recommended, but
rather a range which was determined by the various research articles that have
been published on the topic. Dr. Smith recommends that the sodium concentration
be between 90 and 130 mmol/L (millimoles per liter).
Even
though calves do lose some chloride with diarrhea, it is not lost in near the
amounts that sodium is. Dr. Smith recommends that the chloride concentration be
between 40and 80 mEq/L (milliequivalents per liter) with concentrations toward
the lower end of the scale probably being better.
Potassium
is also lost in the feces of calves with diarrhea. All calves with diarrhea
will have a total body deficit of potassium. However, some calves with acute
severe diarrhea may actually have a level of potassium that is higher than
normal at the same time. When a calf becomes dehydrated, it releases a hormone
called aldosterone from the pituitary gland which tries to conserve sodium and
water in the kidneys, but at the expense of potassium. Dr. Smith recommends a
potassium concentration of 10 to 30 mmol/L in oral electrolyte formulations.
The
absorption of sodium in the small intestine is a passive process. There must be
some other substance that is actively absorbed in the product in order to
facilitate the absorption of sodium. The most common ingredient added to an
electrolyte product to enhance sodium absorption is glucose. Glucose is also an
important energy source in the diarrheic calf since most calves are in a state
of negative energy balance during the episode of diarrhea. Neutral amino acids
such as glycine, alanine and glutamine have been shown to increase sodium
absorption. Glycine is the most common one added to oral electrolyte solutions.
It is generally assumed that including both glucose and a neutral amino acid
will further improve sodium absorption above that of glucose alone. Volatile
fatty acids such as acetate or propionate have also been shown to enhance
sodium absorption. It is also thought that adding a volatile fatty acid to the
electrolyte will further enhance sodium absorption as well.
Osmalality
is defined as the concentration of a solution expressed as the total number of
solute particles per liter. The osmolality of the oral electrolyte solution is
extremely important since it has a direct effect on how fast and complete the
electrolyte solution is absorbed across the intestinal epithelium into the
bloodstream of the calf. Osmalality is quite a complex subject, so only the
basic information needed to determine which product would be recommended on
farm will be provided. The osmolality of the various electrolyte products
varies tremendously. Electrolyte products that are considered to be isotonic
(the same osmolality as that of the ECF of the calf) would be in the range of
280-300 mOsm/L (milliosmoles per liter). Those that are extremely hypertonic
(much more concentrated) may have an osmolality as high as 700-800 mOsm/L. If
the osmolality of the electrolyte solution is significantly higher than the ECF
the absorption of the electrolyte is greatly decreased, and could also result
in the flow of fluids into the lumen of the intestine, causing the diarrhea to
become more severe.
The
main factor in determining the osmolality of an electrolyte solution is the amount
of glucose in the product. The other ingredients also add to the osmolality. As
mentioned previously, glucose not only enhances sodium absorption, but is an
important energy source as well. The osmolality at the tip of the intestinal
villus is approximately 600 mOsm/L. Therefore, the extremely hypertonic
electrolyte solutions could actually result in fluid loss. Since there is
already an excess secretion of fluids across the gut membrane, these extremely
hypertonic solutions have the potential to increase fluid loss.
The
amount of glucose in the electrolyte solution is important as an energy source,
but also has a major influence on the osmolality of the product. The general
recommendation is that there is between 2 and 3 grams of glucose per kg of body
weight of the calf. When choosing which product to use, both the osmolality and
the total amount of glucose in the electrolyte must be considered together. The
extremely hypertonic electrolyte solutions often result in a slowing down of
the abomasal emptying, often resulting in abomasal bloat and/or abomasitis. Dr.
Smith recommends that the osmolality of an electrolyte solution be no more than
500 mOsm/L. The osmolality of the oral electrolyte solution is absolutely
critical in how fast it is absorbed. For this reason, the dairyman should know
what the osmolality is of the product they are using, and each company selling
an oral electrolyte should know what the osmolality is. The osmolality is more
important than having a high level of glucose in the product.
Almost
all calves that have diarrhea will develop acidemia and metabolic acidosis.
Correcting this acidosis is an important function of a well formulated oral
electrolyte solution. Calves can be rehydrated but still suffer from metabolic
acidosis. For this reason, it is important that an alkalinizing agent be added
to the electrolyte formulation. This would include bicarbonate, acetate, and
propionate. Bicarbonate is effective as an alkalinizing agent in its original
state. Both acetate and propionate have to be metabolized in the liver to be
effective as an alkalinizing agent. Even though this process is somewhat
slower, it does not appear that there is any major difference between these two
types of products as far as correcting metabolic acidosis in the calf.
Bicarbonate
will lower the pH of the abomasum. If feeding whole milk, this will interfere
with the normal clotting of the milk. Most milk replacers use whey protein as
the protein source and these proteins do not form a clot in the abomasum, so bicarbonate
will not have an effect on these types of milk replacers. Another important
point is that a low pH in the abomasum is an important deterrent to bacterial
pathogens such as E. coli and Salmonella. These pathogens are
susceptible to a low pH and the majority of them are prevented from passing on
into the small intestine if a low abomasal pH is maintained.
Acetate
and propionate do not lower the abomasal pH. They also facilitate the
absorption of sodium as previously mentioned. When metabolized in the liver,
these volatile fatty acids are also an energy source, which bicarbonate is not.
They will not interfere with the normal milk clotting process of whole milk.
Some
electrolyte formulas contain Psyllium or some other gelling factor. This will
slow down gastric emptying as well as absorb fluid from the intestine. However,
this does not have an effect on rectifying dehydration since the fluid is still
in the intestinal lumen and not in the ECF. It is generally not recommended to
use these types of agents for this reason. These products will often result in
less volume of diarrhea, giving the caretaker a false impression that the calf
is improving, when in fact the process of improving hydration is not
progressing.
Ideally,
administration of oral electrolyte solutions should be spaced evenly between
milk feedings to gain the maximum benefit of rehydration. This is often
difficult to implement from a management aspect. Milk feedings are rarely
spaced evenly apart. If feeding two times a day, it is common that the two
feedings are actually spaced less than 8 hours apart so that one shift of
employees can handle both feedings. This results in periods of more than 16
hours before the next morning feeding. The electrolyte feeding should be
administered midway between the two milk feedings. The ideal situation would be
to feed two feedings of oral electrolyte solution per day, one between the two
feedings and the other after the last feeding, as far apart as possible.
However, this rarely happens without having at least two shifts of employees
working in the calf operation.
It is
also advisable not to mix the oral electrolyte solution with milk or milk
replacer. Milk products also have an osmolality, and when mixed with an oral
electrolyte solution, this will increase the osmolality of the combination,
likely resulting in an extremely hypertonic solution that could exacerbate the
diarrhea problem. If the electrolyte solution has to be fed close to the milk
feeding, it might also be advantageous to feed the milk replacer at a level of
12 to 12.5% solids.
Many
dairies are feeding an increased level of solids which is beneficial for
increasing growth and average daily gain. If currently feeding an increased
level of solids, it would be beneficial to reduce the solids to 12 to 12.5% if
it is necessary to feed the oral electrolyte solution close to the milk
feeding.
There
are some common mistakes that are made in the treatment of calf diarrhea. One
is discontinuing the feeding of milk during treatment. The milk is the major source of nutrients for
the calf and also its immune system. If treated correctly, most calves should
be able to maintain a positive weight gain during a bout with diarrhea. Another
is the use of oral antibiotics to treat all cases of diarrhea. In general,
unless the calf has an elevated temperature, oral and systemic antibiotics are
contraindicated. This will have a significant negative effect on the microbiota
of the gastrointestinal tract which is important in maintaining the mucin layer
of the gut lining, maintaining the gut-associated immune system, competitive
inhibition of pathogens, and digestion of nutrients passing into the small
intestine.
Following
is a summary of the general recommendations of a well-formulated oral
electrolyte solution:
·
Sodium Concentration 90-130 mmol/L
·
Chloride 40-80 mEq/L
·
Potassium 10-30 mmol/L
·
Osmalality less than 500 mOsm/L
·
Strong Ion Difference at least 50 mEq/L
·
Contain one or more alkalizing agents:
Bicarbonate, acetate, propionate
·
Glucose 2-3 grams per kg body of the calf
·
Contain glucose, neutral amino acids, and
volatile fatty acids to facilitate sodium absorption
In his
chapter in VCNA, Dr. Smith has an excellent summary statement to veterinarians:
“Practitioners should focus on selecting oral electrolytes solutions that
satisfy the following four requirements: (1) supply sufficient sodium to
normalize the ECF volume, (2) provide agents that facilitate absorption of
sodium and water from the intestine, (3) correct the metabolic acidosis usually
present in calves with diarrhea, and (4) provide energy. Additionally, the oral
electrolyte should not cause any deleterious effects (such as abomasal bloat).
Because veterinarians are often not directly involved with the administration
of oral electrolytes to calves, it is important that they examine the
electrolyte product being used in their clients’ herds and make recommendations
when appropriate.”
It is
important that the dairy or calf ranch is familiar with these general
recommendations of the levels of ingredients in a well-formulated oral
electrolyte solution so they can choose the best electrolyte product possible
that is available to them. Proper administration of a high-quality product is
necessary to correct dehydration and metabolic acidosis, resulting in a more
rapid correction of these issues and a decreased morbidity and mortality rate
in young calves. Every dairy should be able to obtain the goal <1% death
loss in the milk fed calves if a good nutrition program exists along with good
management, hygiene and cleanliness of the environment. This should result in a
lower incidence of calfhood diarrhea as well. Implementing the proper use of a
high-quality oral electrolyte solution should also be part of a well-managed
calf raising operation.
Dr. Robert Corbett, DVM, PAS, DIPL. ACAN earned his B.S. and D.V.M. degrees from Washington State University. He has worked in dairy practices in Idaho, Texas and Utah, including consulting work in 13 states and several countries worldwide. He has published over 160 articles, taught over 500 seminars, and continues to consult with five major companies worldwide involved in providing supplements and additives in dairy cattle rations. This article is reprinted with permission from the March-April 2020 issue of Dairy World, published by IBA, Inc.
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