2.3.4. Quality Control

The enormous variation in the composition of raw materials requires quality control

- on receipt of raw materials;
- on manufacture of the feed.

Quality control of raw materials received

Quality control of materials is necessary in order to calculate precisely the properties of the feed which must satisfy the nutritional requirements of the stock to ensure optimum productivity. Such control is effected by means of a laboratory with the appropriate equipment and reagents for analysis. The latter is conducted in accordance with internationally recognised methods so that the results of one laboratory may, if necessary (for instance in the event of a dispute), be checked by another; this would make no sense if the methods used were not strictly identical. There are EU regulations covering methods of analysis for animal feedstuffs.

Analytic procedures may be divided into four categories:

- Routine analysis: humidity crude protein fats, cellulose, mineral substances, insoluble in HCl.

- Conventional analysis: calcium, phosphorous, chlorides.

- Special analysis: magnesium, sodium, potassium, oxidation of fats, cell-wall components, trace elements (iron, copper, cobalt, zinc, manganese, iodine), aflatoxins, gossypol, cyanides, available lysine, etc.

- Investigation tests: amino acids, fatty acids, vitamins, toxins, etc.

These are in fact chemical tests requiring specific techniques in which the complexity of the equipment and the necessary skill level increase as one moves from routine to investigation tests.

This is why, in practice, a regional or sub-regional laboratory which can legitimately conduct quality control through routine analysis is a very important first step in improving feed quality. Near infra-red spectrometry is a recent technique which enables the composition of raw materials and finished products to be determined precisely in a few minutes.

As the analysis is conducted only on a sample of a few dozen grams, the latter must be representative of the lot from which it comes. This is why sampling must be conducted with care. One should preferably use a probe to take samples from various places in the lot; these will then be mixed together roughly and a sample taken for the laboratory.

The laboratory results will be sent to the nutritionist responsible for formulation, who will use them to establish the various formulas to be manufactured. Software is currently available to calculate feed formulas, bearing in mind the individual characteristics of each of the raw materials and their cost, as well as the nutritional constraints imposed by the nutritionist.

It goes without saying that this most valuable and efficient tool will not provide useful solutions unless the information provided is itself reliable, hence the necessity for continuous verification of the data used in calculating the formulas.

Quality control of manufactured feed

The manufactured feed is checked to ensure that its properties are in accordance with those calculated by the nutritionist. Manufacturing errors can thus be detected if there are inadmissible discrepancies. The manufacturer will have a record of the analyses of the manufactured feed which he can go through in the event of a dispute.

It is worth pointing out that while chemical analysis is a precious aid in manufacturing quality feed, it is no less true that it is not sufficient in itself. The appearance of the raw material also plays an important part in appreciating quality.

Sometimes, a simple visual, olfactory or organoleptic examination suffices to assess the sanitary status of a raw material (presence of weevils, cockroaches, worms, putrid or fetid smells, musty, sulphurous or rancid smells, abnormal colouring and so on are all indicators which might lead to a suspicion of defective quality).

The preliminary examinations can then be confirmed by microscopic, bacteriological or even chemical examination by a specialist external laboratory.