Energy Balance & Immune Competence
All components of the immune system are present when the foal is born but it is naïve and response is low until foal is 4-6 months old.
Immunity is not passed from the dam to the foetus in utero.
For early protection against diseases, foals rely upon passive acquired immunoglobulins obtained from colostrum.
Any of the factors below may reduce the animal’s ability to fight new disease challenges.
- Their vitality in the first 24hrs (colostrum quality and quantity, timing and hygiene)
- Duration and nature of any transfer to rearing unit. (climatic stresses, deprivation of milk and water, handling, noise, transportation)
- Changes in environmental conditions (mixing, high infection risk, change in housing system, climate, feeding level and composition etc.)
The period of 2 to 3 weeks after birth is considered the critical phase in the young foal’s survival. The priority during this period is to optimize growth plus control and minimize the occurrence of health disorders.
After birth or orphaning, feed intake may be low. The importance of feeding a high energy and protein quality milk replacer is paramount in maintaining thermo-neutrality, optimizing growth and the immune system. These young animals can easily fall into negative energy balance.
If low levels of feed are offered and the energy requirement for maintenance is not met, then the young animal will become increasingly dependent upon the mobilization of body energy reserves to meet energy requirements. This will be reflected in low or negative growth rates. Heat production is an important criterion of survival at this young age.
Heat production decreases with time during the first 2-week period and is affected by feeding level and ambient temperature, (i.e.) at low feeding levels, animals are less tolerant to cold temperatures.
Nutrition
- Restricted feeding can impair the immune system. (Kelly, 1980)
- Stress can affect the apparent digestibility of energy and thus utilization of feed ME (Schrama, 1993).
- If feed is restricted, digested dietary protein is used as an energy source (Mcdonald et al, 1981). This will negatively affect protein gains and will increase the production of urea and energy loss via urine. This is not an efficient use of feed supplied.
Conclusion
Energy shortage (by low feeding levels or inappropriate ration) in young foals is undesirable since it may be a predisposing factor for health disorders.
Newborn/orphan animals should be fed an adequate level of a high quality balanced milk replacer to overcome stress challenges and provide for optimum growth.
