Under normal circumstances, calves can maintain a proper hydration status simply by drinking. If changes in cellular volume and concentration of osmolytes occur, they cause thirst and drive the animal to drink. If an animal cannot, or does not drink, the normal pathway to hydrate is obstructed and different control systems will be set in motion to prioritize important body functions. This has an effect on other body systems. These effects result in signs that allow for recognition of a dehydrated calf: poor skin turgor, sunken eyes and a dry muzzle.
In cases where dehydration in calves is not due to disease, making good quality water available will correct the hydration status. In those cases it is important to make sure animals start drinking as soon as possible.
When calves are dehydrated as a result of calf diarrhoea, there is an urgent need to stabilize the water and electrolyte balance. In a response to deal with the dehydration a lot of sodium is lost. Next to that, calf diarrhoea results in metabolic acidosis. Therefore, it is important to make sure animals drink water that contains the right amounts of sodium and buffering agents.
The differentiation of aforementioned types of dehydration becomes even more important when you consider the difference between calves and older animals. When the calf matures, the ratio of water stored as extracellular fluid (blood, interstitial fluids) and intracellular water (all fluids inside cells) changes. Calves have a much larger extra-cellular fluid pool.
Extracellular fluids are being less protected are lost much quicker compared to intracellular fluids. To replenish the extracellular fluid pool, water and sodium are needed – preferably a combination of both. For the intracellular fluid pool, rehydration requires mainly potassium, not sodium. Depending on the cause of dehydration, it is either the extra-cellular or the intra-cellular fluid pool in which water is lost. Therefore specific causes of dehydration result in a need for specific electrolytes.
Adding to that: adult cows also have a large reservoir of water in the form of their rumen, whereas calves do not. In other words, a young calf suffering from calf scours requires a more rapid intervention, compared to an older animal dehydrted as a result of transport. If we understand these differences, we can support any dehydrated animal much better!
