Mold Infestation and its Control in Feed Raw Materials

Mold infestation in animal feed material is a usual occurrence till date as there is no completely safe mechanism which can prevent it. It starts from field plant cultivation and prevails at storage, contaminating further animal feed and human food.

For a feed miller or any farmer; be it dairy, poultry or swine farmer, mold control in their feed raw material is a consistent and persistent challenge.  Mold contamination not only affects the nutritive profile of the feed raw materials but also have an adverse health impact on both animals as well as human being. Animals fed on high mold-contaminated feed results in its mycotoxin traceability in animal secretions like urine, faeces, and milk.

The biggest challenge in effective mold control at Feed Mill or Livestock Farm is that it does not get contamination at the facility but already persists in either its direct presence or in form of fungal spores in the feed material from its place of cultivation.

Molds and mycotoxins in the African region specifically have much prevalence of Aspergillus contaminating the dead and decaying plant materials, which causes rotting of maize ears in the field. It produces powdery spores in abundance on cobs, both pre and post-harvest. The effective control of the prevailing fungi is to combine timely harvest and drying of cobs before the storage.

Feed Millers and farmers do have awareness about molds and mycotoxins, but still, its safety limits and the mechanism to control it in feed raw materials seems to be an area of improvement. There is always a consistent confusion on fungal contamination linked to their own storage process and adoption of ways to tackle the complex situation of the mold and mycotoxin management at their facilities. On the basis of certain traceability studies, we were able to get occurrence of the molds starting from the field.

Before understanding about the mold contamination and its control in the feed raw material, it is quite important to understand mold’s broad classification in terms of field fungi and storage fungi. Field fungi infect the crop throughout the vegetative stage of plants and exist till storage. At storage, their infestation intensity though relatively reduces but in many cases under ideal thriving conditions, field fungi also contaminate plants and grains under storage condition. The distinction between field fungi and storage fungi is not only based on its taxonomic classification but also about their life cycle, prevalence, infestation, and ability to persist in the feed material.

Few field fungi can contaminate feed grains even under storage condition as they contaminate grains post-harvest if grains outer shell is cracked due to mechanical reasons or eaten by insects, leaving the inner core exposed for further fungal contamination.

Multiple pieces of research demonstrate that the important factors influencing the prevalence of mold in plants and grains under field and storage conditions are, temperature, moisture, and pH of the feed material. Under high humidity and high temperature, plants are usually stressed and it is perfect condition for mold or its spores to infest the stressed plant.

Fungi under field condition require high moisture that helps spores to grow and flourish on the plant and maturing seeds.  Few fungi are pathogenic to the plant and many coexist on the plant and contaminate grains post-harvest.  Drying of grains and keeping under good storage condition having low moisture and proper ventilation or provision of hot air in the silo to keep grain under the dried condition, will limit the prevalence of fungi under storage condition.

Field fungi usually persist on plant and maturing seeds, even under dried condition. These also continue to inhabit on the seed under storage condition, but not necessarily impact the quality of the seeds. Field fungi invade usually maturing seed in cereal plants at 22% moisture with a relative humidity of 95%. Common field fungi invading the seeds are Alternaria, Cladosporium, Fusarium, and Helminthosporium. Comparatively less prevailing fungi are Curvularia, Epicoccum, Nigrospora, and Stemphylium. The major effect of storage fungi on the stored grain is grain’s discoloration, mustiness, and heating of the grain.

Once fungi contaminate the feed raw materials, there would be an impact on the nutrient quality of the raw material. There is a loss of metabolizable energy in tune of 5%-25% depending upon the level of contamination. Impact on protein content can only be quantified in the advanced stage of deterioration. The reduction in Amino acid mainly cysteine, lysine, and arginine were more in comparison to other Amino acids. Major impact on Vitamin utilization by the mold for its own growth has been suggested to be more on Vitamin A, D3, E., K B12, Thiamine, Riboflavin, Pantothenic acid, Pyridoxine, and Biotin. Further to it, the toxic metabolites of molds also influence the nutrient quality of ingredients and its availability thereafter.

Some important reasons which contribute to the growth of molds in feed raw materials and Animal Feeds are:

  1. On intact grain, mold grows slowly as it needs nitrogen and energy to grow, which is trapped inside the grain.
  2. Right temperature and moisture are required for molds to grow. In a tropical climate, where temperature and humidity remain high, Aspergillus and Penicillium sp. grow more whereas Fusarium sp. grows better in the colder climate.
  3. Molds being obligate aerobic organisms need oxygen to grow and proliferate. Their proliferation and growth can, therefore, be controlled by maintaining an anaerobic environment.
  4. Water activity (aw-value) is an indicator of the amount of free water, depicted by Aw value.  Aw-values greater than 0.6 indicates an increased risk of mold growth.

At Feed mill, consideration of following steps can to a certain extent help to prevent and control the risk of mold proliferation in the feed raw materials.

  1. Be an active contributor in assisting efforts of technical institutes and government agencies to enhance awareness among the agriculturists about the adoption of better post-harvest measures.
  2. Extend analytical measures of the feed raw material to their QC labs; any possible mold contamination is linked with the ingredient and nutrient loss of the stored material.
  3. To ascertain that, adequate measures and preservation technique should be deployed by their vendors in terms of maintaining good quality grain resulting in the procurement of good feed raw material by their organization.
  4. Awareness and conscious efforts to be taken by the feed millers and while procuring the feed raw materials.
  5. Adoption of good quality control norms by the feed millers.
  6. Screening of Feed raw materials on arrivals helps feed millers to ascertain adoption of the method as per the quality of raw materials and determining the acceptance, rejection.
  7. Give raw material storage area a prime importance as any loss of nutrients in stored ingredients is a major economic loss.
  8. Avoid procurement of high moisture ingredients as there will be more expensive to be incurred in term of keeping them in the right condition, especially if intended to be stored for a longer time.
  9. Have FIFO (First in First Out) and batch system strictly in place, so no old material remains in the storage area, increasing the chances of contamination.
  10. Build comprehensive mechanism for pest, insect and mold control management of feed raw materials by the adoption of the global standard practices.
  11. Periodical internal and external audits will give chance to the feed millers to know about the ground realities and accordingly place a plan to improve their own quality systems.
  12. Adoption of modern feed moisture optimization programs which not only help them to ascertain the right moisture and Aw activity in the end product but also properly use mold inhibitors in the animal feed to improve quality and shelf life of the feed product.
  13. In terms of right choice of the mold inhibitors, usage of a blend of buffered organic acids especially with activated propionates and surfactants gives good preservation results.
  14. As storage fungi keep on contaminating stored raw materials in the storage area, a good quality toxin binder should be used in order to cover any further risk of mycotoxin in end product.
  15. Routine scheduled maintenance of the feed mill to review HACCP compliance, so all critical area in the feed mill is being examined and fixed if necessary.

Dairy Farmers, those who make their own corn or grass silage should also consider that simply harvesting and packing fodder in silage pit may not be efficient to prevent mold growth and mycotoxin contamination in silage. Knowledge about the pre-harvest and post-harvest mold contamination especially in case of own fodder cultivation will help the dairy farmer to cut down carry over the risk of the molds proliferation from a field to silage pit. Incorporation of right silage preservatives and proper packing of silage pit is always beneficial in terms of getting the mold and mycotoxin free silage.

Managing procurement of mold-free raw materials will be always a challenge for livestock farmer due to lack of the analytical facilities and volume purchase by them. In such a situation, a random check of the raw materials or getting themselves associated with the reputed feed production units is a good option.

Overall, managing risk of molds in feed raw material needs to be viewed holistically as its challenge to the feed and food Industry is enormous, both in terms of economic as well animal and human health. As mold contaminate plants and produce secondary metabolites i.e. mycotoxins which have their clear traceability in the human food directly through cereal grains and oils seeds and indirectly through animal food chain especially milk, meat, and eggs so it is important to be aware of molds occurrence and prevalence in feed raw materials.