Example 2: Maize-based Animal Feed - South East Asia

Introduction

This HACCP plan follows on directly from Example 1 and considers utilisation of the yellow maize kernels in a feed mill in Southeast Asia. The mill will usually offer contracts to Secondary Traders for the supply of maize of a specified quality, but may also buy from visiting traders, especially if stocks are low.

Task 1 - The HACCP team

An appropriate HACCP team will include: the plant manager or his deputy, the quality control manager, the procurement manager, the senior engineer, and the quality control laboratory manager.

Tasks 2 and 3. - Table 5: Product Description and Intended Use

Target limit = in the range 5 to 50 µg/kg, depending on animal

Tasks 4 and 5 - The Commodity Flow Diagram (CFD), Verified

The CFD was established and verified and an outline summary is shown in Figure. 9.

Fig. 9. HACCP Flow-diagram: Maize-based feed in Southeast Asia

Tasks 6: Mycotoxin hazard analysis and identification of possible control measures.

Hazard Analysis

a) Identification of mycotoxin hazard

Maize is susceptible to a number of mycotoxins including: zearalenone, one or more of the trichothecenes, ochratoxin A and fumonisin B₁, in addition to the aflatoxins. Maize can be contaminated with more than one mycotoxin, and sometimes contains a cocktail of five or six. These mycotoxins can significantly reduce animal production, and there is a possibility of carry-over to the human food chain. Few countries have set regulatory limits for mycotoxins other than aflatoxin, so for this example the HACCP team has identified aflatoxin as the major mycotoxin hazard.

b) Identification of steps in the Commodity Flow Diagram (CFD) where mycotoxin contamination is most likely to occur.

Step 1: Procurement and storage

Most of the aflatoxin, and indeed other mycotoxins, found in feeds are usually present in the incoming raw materials.

Step 2: Milling

Aflatoxin contamination is unlikely at this stage, provided that normal cleaning is carried out, as would be expected under Good Manufacturing Practice (GMP)

Step 3: Storage of milled maize.

Aflatoxin contamination is unlikely at this step, provided that moisture content is controlled at Step 1.

Step 4: Mixing of feed ingredients.

This step and needs to be performed correctly to ensure that the aflatoxin content of the mixed-feed is within the target level.

Step 5: Pelleting

Aflatoxin contamination can occur at this step as a result of adding too much water during pelleting, or perhaps after pelleting, in order to maximise the moisture content.

Steps 6: Packaging

Aflatoxin contamination is unlikely at this step, and indeed correct packaging can provide protection from subsequent contamination.

Step 7: Labelling

Correct labelling is very important to ensure safety of the feed.

Step 8: Storage of mixed feed

Feed mills rarely store mixed feed for long, and indeed feed is usually despatched and used by farmers within two or three weeks. There is little risk of aflatoxin contamination at this step.

Step 9: Transportation

Animal feed is usually distributed by truck, but sometimes it may be shipped between islands. There is little risk of aflatoxin contamination during transportation.

Step 10: Retailing

Aflatoxin contamination of feed is unlikely at this step.

Step 11: Farm storage and use

Poor on-farm storage and feeding practices can result in aflatoxin contamination of feed.

c) Possible Mycotoxin Control Measures

The most important control measure is to procure maize, and other feed ingredients, which have only a low, acceptable risk of containing unacceptable levels of mycotoxin. This can either be achieved by buying maize with reliable certification, or by segregating acceptable from unacceptable batches on procurement.

Prevention of mycotoxin in the feed mill is best controlled by ensuring that the procured maize is at a 'safe' moisture content on procurement, and that the moisture content remains too low to support mould growth during all subsequent steps.

Selection of appropriate formulations to produce feed within the aflatoxin specification for each type of feed is essential.

Tasks 7 to 10: Development of a HACCP Plan

A worksheet summarising the HACCP Plan for the production of maize-based mixed feeds is given in Table 6. The development of the plan at each step in the CFD is given below.

Step 1: Procurement and storage, CCP1

It is essential to either purchase maize that has reliable mycotoxin certification, or to segregate acceptable from unacceptable batches on procurement. This control measure will prevent unacceptable levels of mycotoxin entering the feed mill.

The critical limit will be 50 µg/kg aflatoxin B₁ in this example, but critical limits for other mycotoxins can also be set if required. The critical limit is monitored by collecting representative samples, ideally in the form of a pre-loading sample collected from the suppliers warehouse. Failing this, representative samples taken from individual trucks, or groups of trucks can be collected for testing. The samples are then analysed by a rapid mini-column or test kit method, and only those batches containing an acceptable level of mycotoxin are accepted.

It is also very important to procure feed ingredients which have a moisture content at or below the 'safe' level corresponding to an water activity (a_w) of 0.70.. This control measure will prevent aflatoxin, and other mycotoxins, being produced within the feed mill.

The critical limit for maize is an average moisture content of 14%, but it is most important that no bags should contain >15% moisture, so spot samples are required as well as representative samples. The critical limit is monitored by measuring the moisture content of representative and 'spot' samples from each batch, using a regularly calibrated moisture meter.

Aflatoxin levels would not be expected to rise during storage, provided that the moisture content requirements mentioned above have been met. Normal Good Storage Practice (GSP), such as storage on pallets, a clean store, first in first out, and a sound roof will suffice. When mills store raw materials for extended periods, to ensure supply or to buy when prices are low, then insect and rodent control become important. However, these procedures are still covered by GSP.

Step 2: Milling of maize, GMP

Cleaning to prevent a build-up of dust within the mill, which might become a source of mould and contamination, is required.

If the mill conditions maize by adding water prior to milling, then this process would need to be controlled, and the step would become a CCP.

Step 3: Storage of milled maize, GSP

It is uncommon to store milled maize for longer than a few days. Good storage practice will prevent significant increase in moisture content and subsequent mould contamination.

Step 4: Mixing of feed ingredients, GMP

Selection of appropriate batches of feed ingredient, and dietary formulations, to produce feed within the aflatoxin specification for each type of feed is essential. A good estimate of the level of aflatoxin in each of the ingredients of the formulation must be known and the level of aflatoxin in the mixed feed can then be calculated. The batches of ingredient used have to be carefully selected, especially for low-aflatoxin feeds. Sometimes it might be necessary to change the formulation to meet aflatoxin criteria.

This step might be considered to be a CCP, but is covered by GMP if the controls at Step 1 are in place.

Step 5: Pelleting of feed, CCP2

Moisture is added to feed in the form of dry steam during the pelleting process. It is critical to cool the pellets to ambient temperature using sufficient aeration to effect drying to a 'safe' moisture content.

A critical limit of moisture content is set at 13% for pellets just prior to packaging. This critical limit is monitored by the collection of a representative sample from each batch. The moisture content of each of these samples is then measured using an appropriate, calibrated moisture meter.

The addition of dry steam at 110°C during pelleting will sterilise the feed. Mould spores present in the feed will be killed and this will reduce the likelihood of any subsequent mould contamination.

Step 6: Packaging of feed, GMP

Correct packaging, such as use of moisture barrier bags, will prevent re-wetting of the feed and subsequent mycotoxin contamination.

Step 7: Labelling of feed, GMP

Correct labelling is very important, for instance the mis-labelling of a bag containing beef cattle feed (at, say, 49 µg/kg aflatoxin B₁) as a dairy feed (target level £ 5 µg/kg) would have serious implications. However, control of this procedure is covered by GMP.

Include certification that the feed meets aflatoxin regulations.

Step 8: Storage of feed, GSP

Feed is rarely stored for more than a few days at a feed mill, and no special storage practices are required.

Step 9: Transportation, GMP

Water barrier packaging will protect the feed during transportation.

Step 10: Retailing, GSP

The retailer should not stock feed that has passed the sell-by date and should not store opened or damaged bags of feed.

Step 11: Farm storage and use, GSP/GAP

Farm storage must be adequate to prevent wetting of the feed.

Farmers should not use feed that has passed its use-by date. Feed dispensers must be cleaned daily to prevent the growth of mould on left-over feed.

Task 11: Establish verification procedures

Validation procedures are required for each of the CCPs and overall verification of the HACCP Plan is provided by aflatoxin results on representative samples of batches of feed leaving the feed mill.

Complaints from farmers or traders would be logged and followed-up, especially if a pattern developed which was consistent with an outbreak of aflatoxicosis. This could indicate that the HACCP plan has failed and needs to be amended.

The HACCP Plan would be audited quarterly and amended as necessary.

Task 12: Establish documentation and record keeping

The HACCP Plan is fully documented, and records kept of the CCP monitoring data, deviations and corrective actions.

Table 6. HACCP Plan Worksheet - Maize-based animal feed - South East Asia