Feed water activity (Aw for short) refers to the ratio of the water vapor pressure of feed to the vapor pressure of pure water in a closed container at the same temperature

Aw=P/P0=ERH／100；

In the formula, Aw represents water activity;

P represents the vapor pressure generated by the moisture content of the substrate (feed) at a certain temperature;

Po represents the vapor pressure of pure water at the same temperature as P;

ERH represents the relative humidity of the substrate (feed).

Water activity is a very important concept in the feed industry and is one of the main factors determining feed quality and safety. Water activity can affect the reproduction, metabolism, resistance, and survival of microorganisms in feed, and is an important indicator in the feed quality control system.

In the aquaculture industry, feed is an essential input, and feed water activity is one of the important indicators to measure its quality. Water activity not only affects the stability of feed and microbial growth, but also has important impacts on feed cost, quality, storage, transportation, and other aspects. This article will explore and study the impact of feed water activity on cost, quality, and economy, providing scientific basis for breeders on feed water activity.

Under certain conditions, both grain seeds and processed compound feed and premix have a certain water activity. The growth and reproduction of various microorganisms, as well as various chemical and biochemical reactions, also require a certain level of water activity to occur.

The water activity has an impact on the enzyme activity in feed. All chemical or biochemical reactions occur in aquatic environments, and water is the fundamental medium for chemical reactions and necessary for enzymes to maintain their activity. However, when the water content exceeds a certain amount, enzyme particles will aggregate into clusters. In feed production, in order to compensate for the deficiency of endogenous enzymes, enzyme preparations are often added to feed to improve digestion and utilization efficiency. The biological materials used in feed processing contain many different types of enzymes, which play important roles in the growth, maturation, processing, and storage of raw materials.

Specifically:

Feed with high water activity is prone to oxidation and deterioration, leading to a decrease in nutritional value. Especially nutrients such as vitamins and amino acids are prone to lose their activity in high temperature and high humidity environments.

The high water activity of feed may affect its palatability. For example, excessively wet feed can cause digestive problems and diarrhea in poultry, affecting their growth and health.

Feed with low water activity is more stable and less prone to oxidation and spoilage. Feed with high water activity is prone to spoilage during storage and transportation, which affects its quality.