Acidifiers are mainly designed for weaned piglets as feed additive to compensate for lack of gastric acid in stomach. The research of acidifiers has a history of over 40 years. In 1960, people in feed industry found that piglet diarrhea can be relieved by organic acid. After that, simple acidifiers were used to lower pH value in feed and promote pig growth. Not until 1990 were acidifiers widely used in animal breeding. The purpose of research has transferred from preventing diarrhea only to improving feed efficiency and promoting growth. Acidifiers then are gradually used in animal nutrients and feed preservatives. Many studies have shown that acidifiers can improve the production of animals, improve feed efficiency and enhance body immunity.

1. Organic Acidifiers
Formic acid and its salts like calcium formate can be used as organic acidifiers to improve feed palatability, sterilize feed, provide energy to body and take part in nutrient metabolism. But the cost is higher. Large quantities of studies have confirmed that adding organic acidifiers in piglet daily diet can improve pig production. Formic acid has strong causticity, bad palatability, but it is most effective in lowering feed pH, killing bacteria like Escherichia coli and Salmonella, improving growth and feed efficiency. The antimicrobial activity mainly aims at saccharomycetes and other bacteria, but no effect on lactic acid bacteria and fungi.
Researchers have conducted experiments on adding different kinds of organic acidifiers into fodders for piglet and growing-finishing pig, which show that formic acid as acidifier can significantly improve daily gain for both piglet and growing-finishing pig and reduce the feed conversion ratio, thus proving that formic acid and its salts are most effective as organic acidifiers. Apparent digestibility of crude protein can be effected by adding calcium formate into daily diet of piglets. Studies have also proved that by adding 0.6%~1.8% of calcium formate into piglet daily diet, feed consumption, daily gain and feed efficiency can be improved. The best effect can be obtained by adding 0.6%~1.2% of calcium formate into daily diet of piglet.

2. The mechanism of feed acidifiers
Decrease the dietary buffer capacity and pH value in gastrointestinal tract, and improve the activity of digestive enzyme

Breast milk is the main food source for piglets before weaning, which contains much lactose. Lactose can be decomposed into lactic acid under the influence of lactobacillus. Thus the pH value in stomach can be maintained around 4.0, which is appropriate environment for digesting lactoprotein. In the early period after weaning, the gastric acid and digestive enzymes secretion are insufficient due to un-developed digestive system and immune organs. Besides, the food resources become solid feed instead of liquid milk, which results in lack of lactose produced in stomach. Solid feed has higher dietary buffer capacity than breast milk. All these factors can cause pH value higher than 5.5, while the best pH range for pepsase is 2.0~3.5. When pH becomes higher than 4.0, the activity of pepsase weakens and even lose activity totally. The high pH condition after weaning can lead to digestive ability of protein decreases. In this case, adding acidifiers into piglet daily feed can decrease the dietary buffer capacity and pH value in gastrointestinal tract, and improve the activity of digestive enzyme, the digestion of protein and feed consumption can increase accordingly. By adding acidifiers into daily diet for weaned piglets, the acidization can activate propepsin and stimulate secretion of pepsase, thus improving the digestive rate of protein.

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