Dehydration in calves

By Andy Sears – Director of Product Innovation 

Dehydration, loss of electrolytes and decrease in blood pH are the three biggest challenges for calves facing intestinal challenges. Dehydration, in level of percentages is best explained as the percent of water loss relative to total body weight. Rehydrating those calves is therefore critical. Rehydrating means supportive administration with fluid and electrolytes. This is vital, regardless of the cause of the intestinal challenges.

When a calf is 5% dehydrated, the effect can start to become visible. The calf is dull —not as strong and perky. If you pinch the upper eyelid or the neck [skin tenting], and see how fast it sinks back into place, this gives a clue. If the calf is less than 5% dehydrated, it falls back into place quickly. This is referred to as skin elasticity, or turgor. At 5% or more, the skin stays tented for a few seconds. The more dehydrated the calf, the longer the skin stays tented. 

The eyeball of a dehydrated calf looks like it is sinking back into the head. This is caused by tissues around the eye are also dehydrated. The more sunken the eyes look, the more dehydrated the calf is. If you roll down the lower lid and see a big space there, this indicates dehydration. 

Ideally, you want to give fluids orally —while the calf still has a functional gut. When it gets severely dehydrated, fluids just sit in the stomach and cannot be absorbed because the gastrointestinal tract has shut down. If the calf can still stand and walk — even if it is slightly weak and wobbly — it may still benefit from oral electrolytes. 

At about 12% dehydration, the calf is at a high risk. There is a small window of time between 5% [when you can tell it is dehydrated], to 10% or 12%, when the calf is severely challenged. Intervention needs to be as soon as possible, while the calf is still strong and can restore quickly. Chart 1 provides insight into how dehydration levels can be measured and what the best recommended way is to support the calf. 

Chart 1 : Determination of calf’s dehydration %. Demeanour is a description of the calf’s appearance and reaction to feeding and stimulation. Calves start to lose energy, become lethargic, and show signs of a non-optimal well-being at 8% dehydration. Oral administrations refer to providing electrolytes in the morning in addition to their meal. Also, leave a bottle in between feedings and feed another bottle at night in addition to their meal. When it comes down to providing an IV administration –when a calf is 8-10% dehydrated, and has a poor or no suckling reflex, fluids are provided subcutaneous instead or intravenous. The veterinarian is consulted at this stage. 

Effectively addressing rehydration 

People are surprised by the volume of fluids that a dehydrated calf will need. If the calf is 5% or more dehydrated, you can estimate the amount of fluid needed by estimating how much the calf weighs. This can be done using chart 1. The equation: weight x dehydration percentage equals the approximate amount of electrolyte solution needed. In case of oral solutions, provide the calf with the goal to rehydrate multiple times a day while still feeding milk. It is especially important is to be mentioned that energy provided by electrolyte administration is insufficient to maintain a calf for any period, hence the continuous milk feedings. The reason for calculating the amount of fluid needed based on the calf’s weight, is that three things are considered. The normal maintenance need of the calf, the degree of dehydration, and the estimated loss from the challenges in the intestines.  

Note that, the younger the calf, the more quickly it will dehydrate from intestinal challenges. A small young calf has no body reserves; it is more important to give fluids often and fast. When a young calf gets severe intestinal challenges the only way you can turn it around is to give fluids every six to eight hours or even more frequently, depending on the situation. 

Importance of continuous milk feeding 

As previously mentioned, continuation of milk feeding is essential to provide the energy required for gut regeneration, recovery, and growth. Calves with early onset of mild intestinal challenges will, by themselves, increase their water intake, helping replace lost fluid. Therefore, clean, fresh water should be available to all calves from birth and it often surprising how much water a new-born calf will consume if it is readily accessible. Electrolyte administration in the form of oral rehydration solutions actively replaces the fluid lost with intestinal challenges. Commercially available electrolyte gels and pastes will not actively provide water and rely on voluntary ingestion which can be compromised in calves with moderate to severe intestinal challenges or… when water is not made available. The importance of using a good electrolyte solution cannot be underestimated. Calf Managers may think that products are equally suitable, but this is not always the case. To reverse electrolyte imbalances, the right products must be used. These should contain salts that provide electrolytes; sodium, potassium and chloride, an energy source like glucose, and optionally amino acids like glycine or alanine. The glucose and amino acids aid in absorption of electrolytes [especially sodium, which in turn helps the gut absorb fluids]. Most commercially available oral electrolyte solutions typically do contain these components. Since these calves are acidotic [due to dehydration causing electrolyte imbalance], commercial electrolytes may also contain some kind of buffer. There are several options for buffers, including bicarbonate, acetate, citrate, to name a few. All of them have various advantages, depending on the calf’s situation.  

Would you like to know more about this topic and how AHV can support you and your herd? Please fill in the form below or contact your local farm advisor directly.