SUMMARY
  • It is important to prevent oxidation in animal feed stuffs by using antioxidants to ensure good product quality.
  • Oxidation occurs in vitamins, pigments, fats and oils, with lipids being the most susceptible, reducing quality and quantity of expensive ingredients.
  • Oxidation changes the chemical structure and affects the nutrient value and palatability of finished feed.
  • Oxigard, Oxigard Free, Oxihold and Oxistat are antioxidant blends developed by Anpario.

 

BACKGROUND
  • Many organic materials, such as oils, vitamins and pigments are used in animal feed and readily undergo oxidation, even when bagged, due to air already present in the packaging.
  • The oxidation reaction is irreversible and results in chemical changes leading to loss of nutrients and quality, poor palatability and reduced shelf life.
  • Oxidation manifests itself in different ways according to the nature of the feed material.
  • Unless steps are taken to protect the material by arresting the oxidation process, toxic aldehyde and ketone compounds can be produced and are subsequently unable to be removed.

 

Table 1. Results of Oxidation on Feed Material

Feed material Result of oxidation
Vitamins Loss of active levels (IU)
Pigments Loss of active levels (ppm)
Fats and Oils

Reduction in energy value (MJ/kg)

Rancidity

Palatability problems

Digestive disturbances

Taints in meat, milk, egg cellular dysfunction

STAGES OF OXIDATION
  • The reactions of oxidation are complex, but the stages are common to all: Initiation → propagation → termination

lipid peroxidation pathway

Figure 1. Lipid peroxidation pathway

PEROXIDE VALUE
  • The process of oxidation can be monitored by measuring peroxide values over a period of time.
  • When displayed graphically, this produces a characteristic curve as shown below:

Relationship between stages of lipid oxidation and peroxide value

Figure 2. Relationship between stages of lipid oxidation and peroxide value (Finley & deMan, 2018). 

  • Once the induction point has been reached, oxidation will proceed at an ever-increasing rate and cannot usually be stopped. Prevention, or slowing, of the oxidation process can only be done effectively before or during the propagation stage.

 

PREVENTING OXIDATION
  • In order to prevent oxidation of susceptible materials, antioxidants are used.
  • The concept behind such products is that they provide hydrogen atoms, which react with free radicals (oxygen atoms) to reduce the likelihood of free radicals damaging the valuable nutrients in the feed.
  • Oxygen from the environment, alongside relative humidity increases the risk of oxidation. Therefore expelling air and storing feed/ingredients in cool, dry environments is recommended.
  • The antioxidant itself forms a second free radical, which is far less reactive than the original lipid radical.
  • The principle products used in this way are Butylated Hydroxanisole (BHA), Butylated Hydroxytoluene (BHT) and Ethoxyquin. Certain antioxidants have been found to have a synergistic effect when used in combination, forming an antioxidant blend.

 

IMPORTANT CONSIDERATIONS
  • An effective antioxidant must be correctly formulated and applied early enough to afford the best protection.
  • Applications to materials already undergoing considerable oxidation may have little or no effect.
  • By virtue of its mode of action, an antioxidant will gradually become consumed and therefore inactivated, at this point oxidation can proceed unchecked.
  • The inclusion of antioxidant must be targeted to the level of risk from the material and the environmental conditions.

 

For recommended inclusion levels, see the product data sheet and for more information please contact your Anpario representative.