Newborn calves naturally dispose of only scant energy reserves (glycogen, fat) and, owing to their large body surface area relative to their weight, they possess a very high rate of metabolism. They accordingly need energy-rich as soon as possible after they are born. What is important to calves of normal health will be vital to young animals that, for example, contracted a diarrheic disease. The digestive processes disturbed by diarrhea will very soon result in consumption of the diseased animals. Particularly the immune system of animals affected has to achieve peak performances and requires the best possible supply of energy for this purpose.
Neither is a sufficient supply of vitamins guaranteed in many cases, which would be especially important in stressful situations and immediately after birth. Vitamin deficiency results in a poor constitution and hence poor growth. Particularly at the beginning will poor growth oftentimes lead to a persistent poor development and later to poor feed conversion efficiency, poor milk yields and breeding performances.
In Germany, the losses of calves range at about 15 percent, three-fourths of which can be accounted to diarrheic diseases. Normally, treatment with nothing but electrolyte drinks is not sufficient. They only compensate the loss of fluid and electrolytes, but do not attack the pathogens, hence the actual cause. An additional attempt to control noxious microbes with antibiotics, however, invariably harbors the risk of developing resistances.
Why are calves so susceptible to pathogens causing diarrhea?
Owing to a variant structure of the placenta as compared to humans, the calf is not supplied with antibodies as long as it remains in the womb. Accordingly, it depends on the administration of colostral immunoglobulins as early as possible. However, this passive protection derived from the beestings is only intended to be an immunological jump start. The calf will have to build up its own active immunity as soon as possible. Even if everything proceeds quite regularly, there will be two immunity gaps in the calf, one immediately after birth, i.e. before the initial uptake of colostrum, and one after approximately 4-6 weeks when passive protection (colostrum) recedes, while the animal’s own, active protection has not yet been fully established. If the immune system is now additionally burdened by stress (reallocation to other pens, weaning, change of feed), bad housing conditions (high occupancy, bad stable climate), or imbalanced feed (lacking minerals, vitamins), the causative agents of diarrhea will encounter ideal conditions for colonization. In this context, important pathogens are: