August 2011

Are Your Calves Dehydrated?

While scours may seem like a regular part of calf raising, the hot summer months put calves at increased risk for severe dehydration and death. Scouring is typically associated with >60% of calf deaths, representing the number one cause of death in pre-weaned calves.

Think about what the incidence of pre-weaning mortality and scours is on your farm:

• Are half of your losses due to scours?
• Are your calves also suffering growth losses – are they doubling their body weight by 8 weeks?
• What about your treatment and labour costs?

Are Scours 'Normal'?

Even if you are experiencing the 'average' incidence of scours, calf diarrhea still represents something going wrong in the calf. Normally, liquids are transported by:

• Fluid passing from blood to the intestines (secretion)
• Fluid going from the intestines back to the blood (absorption)

These processes transport ~100L of water a day in a healthy 45kg calf. Any change to this fluid movement will increase the amount of fluid in the intestines, resulting in scours.

Different pathogens cause different effects to fluid transfer:

• Parasites such as Cryptosporidium and coccidia cause water transported from the blood to become stuck in the intestines, resulting in more fluid feces
• Some bacteria, such as E. coli, produce endotoxins; the intestines increase secretion to flush out the toxins.

Differentiate nutritional from infectious scours, and keep in mind that nutritional scours are temporary since there has been no intestinal damage, and will go away once the stress (often due to changes in the amount or type of milk fed, such as a change from whole milk to replacer) is removed or overcome. However, prolonged nutritional scours can require treatment if excessive water loss occurs. Keep in mind that scours can stem from antibiotic use as well.

Dehydration

Treatment for scours can be successful and of minimal cost when caught early, but calves can be 5-6% dehydrated and not exhibit any signs. To know how dehydrated your calves are, try the skin tent test (pinching a fold of skin on the neck and counting how long it takes to flatten):

• 2 sec: normally hydrated
• 2-6 sec: 8% dehydrated (may need IV fluid therapy)
  
• 6 sec: over 10% dehydrated

Gums should be pink and damp; if white and dry, the calf is likely 8-10% dehydrated. Other signs to look for include general lethargy, a dull coat, gaunt abdomen, wet hindquarters, sunken eyes, dry nose, droopy ears, or an increased rate of breathing. Signs of severe dehydration include cold extremities and the inability to stand, suck or blink.

Treating the Symptoms

Death typically results from the loss of water and electrolytes, so it is important to focus treatment on the symptoms by correcting the fluid loss. Free choice water should always be available to calves to avoid dehydration. However, significant water loss causes an electrolyte imbalance, requiring further intervention. Oral electrolyte solutions supply salts, increasing the absorption of water by the intestine. Water fed alone can pass through the calf with little absorption. For treatment, consider the following:

• Match fluid intake to fluid losses; ie. a 45kg calf that is 8% dehydrated requires an additional 3.6L (45kg x 0.08 = 3.6L)
• Feed fluids in addition to milk; never withhold milk from the calf as it requires energy and protein to fight disease
• Mix electrolytes in warm water, as per package recommendations, and feed at least 1-2hr after regular milk feedings
• Assess calves daily, as they can lose 6-12% of its body fluids in 8-12 hours. While the summer is a busy time, leaving the calf to see how it looks tomorrow can be the difference
• Treat calves early and often!

Prevention

Keep in mind that antibiotics do not work against viruses and parasites. Consider fecal culturing to determine the pathogens present in your herd and develop the best intervention strategy along with your veterinarian. Record-keeping of your calves can provide powerful insight as to your true disease and mortality rates. Consider at what age disease is most prevalent in your calves:

• Scouring in the first 5 days is usually due to maternity pen pathogens
• Scouring after 7 days is often associated with pathogens from the calf pen

Disease is ultimately determined by the overall pathogen exposure and immune system strength of the calf, with scours often being a result of more than one cause. Good hygiene and proper colostrum management are still the best defense for calves, and will protect against multiple pathogens.

For more information on this and other calf health and management topics, visit www.calfcare.ca

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