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Nutritional strategies to recover diarrheic calves

Juliette Wilms and Michael Steele for Progressive Dairyman Published on 28 February 2019

Complications associated with dairy calf diarrhea are the leading cause of calf mortality in our industry. Successful recovery from diarrhea relies on the implementation of appropriate nutritional strategies in the early stages of the disease.

Regardless of the diarrhea cause, diarrheic calves undergo extensive fecal electrolyte and water losses. Consequently, calves with diarrhea often get dehydrated.

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Metabolic acidosis (blood pH less than 7.36 in calves) is also a common condition in diarrheic calves and occurs as the result of fecal bicarbonate losses, strong ion imbalances in blood, fermentation of unabsorbed nutrients and renal dysfunction.

It is therefore not the diarrhea itself but rather its complications (dehydration and metabolic acidosis) which lead to death in acute cases.

How to feed calves with diarrhea

Diarrhea is often associated with severe intestinal villus damage, which reduces the nutrient absorptive capacity of the calf. Consequently, calves are not able to absorb all the nutrients present in their meal.

Unabsorbed nutrients further pull water into the gut lumen and further increase the severity of metabolic acidosis. A common practice to avoid additional digestive disturbances associated with milk feeding is to withdraw milk until diarrhea has stopped.

However, several research studies show withholding milk exacerbates weight loss and dehydration and prolongs the calf’s recovery from diarrhea. A better nutritional choice is to reduce meal size and increase feeding frequency to facilitate digestion.

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How to support recovery of diarrheic calves

A main goal of diarrhea treatment is to mitigate dehydration and metabolic acidosis, which involves the administration of oral electrolyte solutions (OES). OES contain sodium and glucose to facilitate water absorption and replenish diarrheal losses.

Additionally, OES contain alkalinizing agents to increase blood pH by supplying bicarbonate or bicarbonate precursors to the animal.

Finally, OES should have an adequate mineral composition in sodium, potassium and chloride to correct mineral imbalances in blood due to diarrhea. Considerable variability exists in the composition of OES for calves.

See Table 1 for OES composition recommendations.

Recommendation for OES composition for calves

OES for calves often contain high concentrations of glucose (greater than 150 mmol per litre) as an attempt to correct for the negative energy balance occurring during diarrhea.

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Osmolality, which is a measure of the concentration of particles in water, is often as high as 400 to 600 mOsm per kilogram in commercially available OES. However, the amount of energy present in OES represents less than 10 percent of the energy requirements of a 45-kilogram calf.

Consequently, it is important to rely on milk when considering energy supply. Thus, OES with moderate glucose concentration and moderate osmolality (250 to 350 mOsm per kilogram) might be more appropriate for diarrheic calves that have a reduced absorptive capacity.

When and how to feed OES

Recent research shows offering OES alongside usual milk allowance maximizes recovery from diarrhea. A practical approach is then to feed OES in between milk meals through a teat bucket or a bottle (Table 2).

Example of feeding scheme for diarrheic calves

A diarrheic calf can easily lose over 5 kilograms of feces (mostly water) within 24 hours compared to 100 grams for a healthy calf.

It is therefore important to provide at least an equivalent (or higher) volume of water through milk feedings (for energy supply and regeneration of the gut), OES (for rehydration and correction of metabolic acidosis) and clean water (for regulation of blood minerals and blood metabolites).

Ideally, it is best to provide OES when calves exhibit signs of dehydration (Table 3) and have a depressed appetite rather than when they have wet feces.

Evaluation of hydration status of a calf

Rehydration solutions support recovery from diarrhea but do not prevent the diarrhea itself. Rehydration solutions do not act at the pathogen level but rather treat symptoms (dehydration and metabolic acidosis).

In cases of doubt, OES can be offered at the early stages of diarrhea to avoid complications. When a dehydrated calf refuses to drink milk and OES, then OES can be drenched once, or maximum of twice, a day.

Drenching should be restricted to severe cases, and the volume of a single drenching should not exceed 2 litres. Rehydration solutions can be applied for a standard length of three days. In cases of relapse, a veterinarian should be consulted.

For acute dehydration (greater than 8 percent bodyweight), OES can be fed in conjunction with intravenous saline solutions to further correct blood pH and rehydrate calves. Milk feeding should be resumed as soon as possible.

Can I mix OES into whole milk or milk replacer?

Administration of sugar and mineral powder in whole milk and milk replacer is a common practice, as it reduces the labour associated with the treatment of diarrheic calves. However, the risks associated with such practices have to be clearly evaluated and understood.

Most OES products contain high concentrations of sodium and glucose. Whole milk, and especially milk replacers, already contain high concentrations of lactose and sodium.

While mixing OES into milk, the osmolality of the solution can rise above 600 mOsm per kilogram, with sodium concentrations above 100 mmol per litre.

As a reference, normal osmolality for blood and whole milk is close to 300 mOsm per kilogram, and a solution is called hypertonic when its osmolality is superior to 300 mOsm per kilogram.

Feeding very hypertonic solutions to calves may result in osmotic diarrhea, which will further increase diarrhea severity by pulling water into the lumen of the gut.

Additionally, very hypertonic milk meals slow down abomasal emptying rates, which may increase incidence of gastrointestinal disorders such as abomasal bloat.

Finally, when OES are mixed into milk, water access is mandatory in order to allow the animal to balance its blood sodium and chloride concentrations.

Feeding of OES in milk, and especially milk replacer, without access to water over two to four days consistently results in sodium chloride intoxication (hypernatremia), which can lead to central nervous dysfunction and death.

Access to water should also be available even when OES are mixed into water because some OES products can have excessively high sodium concentrations in water (greater than 130 mmol per litre).

Therefore, mixing OES into whole milk or milk replacer represents a dangerous practice and should be avoided.  end mark

Michael Steele is an assistant professor at the University of Alberta.

Juliette Wilms
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