Which animals are at Risk of Impaired Immune Function?
Animals Experiencing Rapid Body Weight Loss
Research has indicated that immune responsiveness decreases for many cows during the transition period.
This decrease in immune function has been linked to inflammation which is in turn associated with diseases such as mastitis and metritis.
Elevated levels of fatty acids due to body weight loss—both pre- and postcalving—can lead to a decrease in liver function. This can be monitored by measuring NEFA (non-esterified fatty acid) levels in the
blood during the transition phase.
Animals Experiencing Heat Stress or Acidosis
Heat stressed animals experience a decrease in DMI and a decrease in rumen pH. This will lead to the increased production of free radicals and an oxidative imbalance.
Heat stress and acidosis can both lead to liver inflammation and a subsequent decrease in immune function. Heat stress and acidosis are linked with similar physiological reactions.
A similar reaction will occur with animals that experience acidosis and sub-acute acidosis (SARA). In the acidotic cow, abnormal rumen bacterial fermentation can lead to the production of gram-negative toxins which can depress the normal cellular function of the immune system.
Animals Consuming mycotoxins
Research has demonstrated that the presence of toxins (especially DON, T-2) will lead to a depression in immune function. An immune system that is depressed by the consumption of mycotoxins can be further compromised by stress (example: the Transition Dairy Cow – pre- and post-calving stress).