Volume 13: Industry Processes and Controls
7. Animal feed manufacture
Processes involved in animal feed manufacture in 1986
Manufacturing process
Labelling
Cross-contamination of feed

Manufacturing process ¹

Intake

7.34 Ingredients were purchased by the manufacturers against a forward demand requirement, which could be for the next day's consumption only or, for some raw materials, for a full year's requirement. ²

7.35 All products were delivered to them by road. The material was sampled before being tipped into an intake pit from which conveyors and elevators transferred the load to bulk silos.

Raw material storage

7.36 Deliveries were stored in raw material holding bins. Low volume items (minerals, vitamins, etc) were stored in smaller bulk containers. Some were stored in bags and handled manually.

Weighing, mixing and grinding

7.37 In automated mills, ingredients were automatically weighed out of storage, according to the formulation being used for that batch.

7.38 A smaller feedmill would usually have a simple weighing, mixing and production system. More typical of larger, more automated mills was a complex blending and mixing system with several production units.

7.39 In a simple system, one batch of about a tonne was mixed at a time. A few of the main cereal ingredients, held ready-ground in bulk bins, were drawn onto a conveyor and into the mixer. Any medicinal additives were incorporated at this stage (for more on medicinal additives, see the section below on cross-contamination). If the feed was to be sold as a meal, it would now be diverted to storage. Otherwise, steam was added to the meal mixture to raise its temperature (a procedure known as 'conditioning') before the material was forced through a ring roll press to form 'pellets', which varied in diameter from 2.5 to 20 mm. The moist, hot pellets were then passed through a cooler to reduce their temperature, also causing them to harden. If some of the production was to be sold in bulk, the sieved pellets or mixed meal went to holding bins. However, in small mills of this type it was not usual for much of the feed to be delivered in bulk, in which case it was bagged.

7.40 In a more complex mixing system, typical of a high-volume mill, there were groups of bins for cereals, proteins and possibly minerals. These bins discharged their contents in discrete batches of one to four tonnes through separate, computerised weighers to a collecting and elevating system. The material then passed through a hammer mill, which reduced the particles to a size which allowed them to pass through a screen from which they were conveyed to the batch mixer. This was usually a 'three-tier' mixer consisting of:

1. holding bin above the mixer;
2. the mixer itself; and
3. a discharge/holding bin below the mixer.

7.41 At this stage the vitamins, trace materials and other low inclusion ingredients (such as medicinal additives) were normally added in a premix directly into the mixer. Some oils and other liquid materials could also be added at this stage. After a mixing period of three to four minutes, the batch was transferred as a meal to bulk storage ready for bagging or bulk delivery, or to conditioning and conversion into pellets. A high-capacity mill of this type probably produced a large proportion of its output as pellets or cubes, and as much as 90 per cent of its output was delivered in bulk.

Storage, loading and bagging

7.42 The finished product was stored in bulk bins prior to loading or bagging. Bulk quantities of feed were loaded into bulk tanker lorries. In most mills, the vehicles stood on a weighbridge while being loaded. Smaller quantities were siphoned into bags of 25 kilograms.

Delivery

7.43 Lorries were divided into compartments and often visited several farms to deliver feed into bulk bins. Bagged feed was delivered on a flat lorry, the pallets being loaded by forklift.

7.44 As mentioned above, most compound feed, about 70 per cent, was sold from the mill directly to farmers. The other 30 per cent was sold through the agricultural merchant trade. ³ As Mr Ian Smith of Midland Shires Farmers (MSF - an agricultural cooperative) said in oral evidence:

MSF certainly would have a number of merchants, particularly in Wales, who would in effect be the selling agent for the product. We might well deliver it. He might indeed collect it from the mill. But the actual contact between the customer and the seller would be with the merchant. He may or may not have been supported by an MSF technical adviser and that would be common throughout the industry.

Clearly, if it moved in a bulk lorry, it tended to go from the mill to the farm regardless of the invoicing arrangements. If it was produced in bags, clearly then it could have gone through a store or, in MSF's case, since we have about 23 shops, it could have gone through the shop and been bought by the customer from the shop. ⁴

7.45 If sales to feed merchants were in bulk, then, depending on the particular merchant's storage facilities, different types of feed might have been stored in common facilities, or feed from different batches might have been intermingled.

7.46 The use of compound animal feed on farms is considered in detail in vol. 12: Livestock Farming.

Labelling

7.47 The legislation governing the labelling of compound animal feed is described in detail in vol. 14: Responsibilities for Human and Animal Health. In effect, it obliged the seller of prescribed feedstuffs to supply the buyer with a statutory statement (in the form of a label on the container or, for bulk deliveries, a document) containing certain particulars. The statement provided by a seller of feed for ruminant animals had to specify the amount of protein and, if any, the amounts of oil and fibre. ⁵ The statement was not required to specify the source or nature of the protein (for example, to specify that the protein was MBM). The seller could, but was not obliged to, list the specific ingredients in the statement. ⁶

7.48 Owing to both the technical difficulties in providing an accurate list of ingredients, and the fear of compromising commercial secrets, most compounders did not publish ingredient lists. ⁷

Cross-contamination of feed

7.49 Cross-contamination of animal feed in the mill was a serious concern for the industry, even before the BSE period. In the late 1980s, most feedmills produced feed for different classes of stock in the same plant. ⁸ A number of possible opportunities for the occurrence of low-level cross-contamination existed, not only during compounding of the feed, but also during manufacture and delivery of the raw materials, and during delivery of the finished product. For example, cross-contamination might occur:

• at an ingredient importer's store;
• during manufacture of a processed ingredient, or as a result of a batch of blended feed or raw material picking up traces of feed or raw material left behind by the previous batch;
• from raw material having built up on the sides of bins, conveyors or manufacturing machinery, and falling into the stream of material of a later batch;
• as a result of errors in the computer software controlling the manufacturing processes; or
• as a result of human error (eg, mistakes by formulators, consignment of raw material to the wrong bin leading to an unplanned mixture of raw materials, or consignment of feed to the wrong truck compartment resulting in delivery of the feed to the wrong farm). ⁹

7.50 In fact, there were so many opportunities that some degree of cross-contamination was considered unavoidable where different types of feed were manufactured by the same equipment. ¹⁰

7.51 Before BSE, this low-level cross-contamination was of primary concern when medicinal additives were used in the production of compound feed. ¹¹ The problem here was that medicinal additives beneficial to one species could harm other species, or different species could tolerate different levels of additive. An example of this was the use of copper additives to promote growth:

In the case of pig food it is used at 100, 150 parts per million; whereas in other ruminants it is used at 30 to 40 parts per million. That level in sheep is too much to accept. ¹²

7.52 The UKASTA 'Code of Practice for Cross Contamination in Animal Feedingstuffs Manufacture' was first published in 1982. The Inquiry was provided with the amended version of this document, which was published in June 1984. The Code divided medicinal additives into:

• Group I medicinal additives, which could be used without veterinary supervision. They were routinely included in feeds made for many classes of stock, to control disease or improve growth or performance. When the Code of Practice was published, about a third of the annual production of compounds included medicinal additives from Group I; and
• Group II medicinal additives, which could only be used under veterinary supervision. They were usually for the treatment of disease, and were used in less than 5 per cent of total feeds manufactured. ¹³

7.53 The Code of Practice covered a number of areas of concern, including:

• design of new plant or modification of existing plant, which should take account of the possibility of cross-contamination;
• training of staff, which should make clear the principles and implications of the medicinal additives being used, and the potential hazards of their misuse;
• storage and handling of medicinal additives, including issues such as security, labelling and record-keeping;
• manufacturing, with attention to scheduling of production and plant operation (see below), and management and disposal of discarded material containing medicinal additives; and
• packaging and delivery, which required clean equipment and bulk vehicles, and clear identification of medicated feed. ¹⁴

7.54 In respect of production scheduling, the Code of Practice required each mill to draft rules based on the needs of that particular mill. The rules were to be divided into:

(i) General programme rules based on the following:

Plan for the longest runs possible with minimal changes.

A medicated feed should be followed only by a feed for a species for which the medicament is licensed.

As a qualification to the above, particular care should be taken with breeder feeds.

Where feeds are made containing different concentrations of a medicinal additive, related to the age of stock within a species, feeds should be manufactured in descending order of concentration.

(ii) Particular exclusions, for example:

All feeds with high levels of added copper never to be followed by a feed for sheep.

All feeds containing monensin never to be followed by feed for horses. ¹⁵

7.55 In respect of plant operation, the Code of Practice required the following:

(i) Monitoring of plant performance

Regular assessment of plant performance should be made to ensure that the assessed potential for minimising cross-contamination is being fully realised.

(ii) Nature of premix

Addition of concentrated medicinal additives should be avoided by suitable dilution.

(iii) Point of addition

The medicinal additive should preferably be added directly to the mixer; otherwise it should be added as near to the mixer as possible. Due consideration should be paid to accuracy and reliability of 'in-mill' communication. The point of addition should be of a type enabling clean injection of the medicinal additives to be made.

(iv) Time of addition

The medicinal additive should be added to the main flow of ingredients and not at the beginning or end, both of which increase the likelihood of medicinal additives remaining in the system.

(v) Flushing and cleaning

This should be done by taking off the first 50 kg of the succeeding batch, except in the case where the same medicinal additive is being used at a lower concentration.

N.B. If 50 kg is considered inadequate in relation to a particular plant and products, then the amount should be increased accordingly.

(vi) Extruded feeds

Particular attention must be paid to the avoidance of an unacceptable level of recirculating feed in the subsequent batch. The level of this residue should be laid down for each production unit.

(vii) Extra provision for Group II medicinal additives

In addition, it is essential that dead spaces, such as elevator boot pockets and other accessible parts of the manufacturing plant, be physically cleaned out after production of a batch containing Group II medicinal additives. This must not be done beforehand. ¹⁶

7.56 As noted above, many farmers preferred to mix their own feed on the farm, from ingredients purchased from the feed manufacturers or merchants (including protein concentrates and MBM), rather than relying on feed compounded in a mill. The Feeding Stuffs Regulations 1991 later applied some controls to feed produced on farms, but did not subject it to the full labelling and compositional requirements for other feedstuffs. In 1992, the Lamming Committee found that some farmers were not well informed about their responsibilities under the Regulations. The Committee recommended that farm-mixed feeds be sampled and inspected to ensure they complied with the statutory limits for undesirable substances and additives in feedstuffs. It also recommended that on-farm mixers be provided with a Code of Practice of their own to encourage good manufacturing practice and to explain farmers' obligations under the Feeding Stuff Regulations. ¹⁷