Lactate
Lactate (from Latin for lactic acid) is produced by bacteria. In horses, it is relevant both in digestion and in performance metabolism:
- Digestion
Lactate-forming bacteria live in the large intestine. With a horse-appropriate diet rich in crude fibre, they exist in small numbers and in good association with other microbes, e.g. cellulose-splitting bacteria and lactate-utilising microbes. Only when easily fermentable carbohydrates flood into the large intestine does a sharp drop in pH occur, along with excessive proliferation of acid-tolerant lactate-forming bacteria. This leads to an accumulation of lactate in the gut and to even greater acidification.
The result is damage to the intestinal mucosa, lactate entering the bloodstream, and the organism being flooded with lipopolysaccharides (endotoxins), which can lead to diseases such as laminitis.
See also Laminitis - Performance metabolism
As a flight animal, the horse is evolutionarily adapted to fast, short sprints. When the horse needs to flee, immediate energy is supplied to the muscle via anaerobic (without oxygen) metabolic pathways (lactate fermentation). However, this form of energy supply is not very efficient, and the muscles involved fatigue quickly.
During sustained exertion, the muscle normally switches to efficient aerobic (with oxygen) energy production. However, this is only possible if the horse is able to inhale sufficient oxygen while doing so. Depending on the horse’s training condition, the muscle can sustain higher or lower speeds aerobically. At excessive speeds, it must (depending on fitness) increasingly switch back to anaerobic metabolic pathways, resulting in increased lactate production in the muscle. Excessive lactate is therefore also used as a marker for (excessive) muscular exertion.