In many parts of the world attention is being focused again on a concept known as "Step Grinding" What is "Step Grinding", why is there such interest returning, and is this a concept that may hold benefit for you?
Step grinding in the simplest terms, is size reduction accomplished in steps or stages, usually incorporating two grinding machines (hammermills, roller mills, pulverizers, or some combination thereof). The primary objective of step grinding is to reduce the cost to produce a ton of fine ground finished product. Additional benefits may include improved control of the particle size distribution (more uniform grind with less oversize and fewer fines), reduced product heating and subsequent moisture loss, a reduction in the maintenance cost per ton of ground material, finer finished products, and greater flexibility in the grinding circuit.
The basic premise for manufacturing formula feeds is that by "least cost" formulation of ma ingredients, and additive feeds may be manufactured that provide optimum nutrition and health to animals, poultry and fish. It is assumed that feed must be mixed so that each serving or at least each day's consumption of feed should provide nutrients and additives at formulated levels.
The "level of scrutiny" is thereby critical, as a cow may consume 10 kilos of feed a day and a shri less than 1 gram. Even if the mixing of feeds is validated by analyzing for one or many nutrients or additives as tracers for all other ingredients, mixing may not be adequate if the particle sizes of specific ingredients or additives are not fine enough to provide a uniform dispersion at the "level of scrutiny¡ã An example would be adding a powdered vitamin that clumps on the end wall of a mixer. When it falls off the wall, it will be present in the feed as formulated but it will not be adequately dispersed even if other ingredients are.
There have been a number of recent enquiries about pellet quality and the influence of "fines" on bird performance. The article on "Fines", which was published over 20 years ago, seemed to answer many of the questions asked and thus it was decided to reproduce it.
Work reported in relatively recent years, from the Agricultural Research Station in Kentville, shows that the percentage of fines in a ration has to get to a level beyond 25% to significantly alter the performance of broilers and probably even higher before turkey performance is affected.
The daily ration of nutrients that an animal receives from a feed may vary from time to time due to a number of reasons. The sources of variation will probably cause variation in the day-to-day level of nutrition received by an individual animal. Certain nutrients are guaranteed to be present at minimum levels and regulatory officials will be concerned, if guarantees are not met. Certain ingredients may be toxic at very high levels.
The nutrient variation in feeds is most likely to occur for the following reasons (Wilcox and Balding, 1976):
While it is true that the main factors influencing the nutritive value of a diet are the ingredients employed and their chemical composition, there are many other factors that can have a marked influence on the feeding value of a diet. Unfortunately since many of these are routine steps in feed manufacturing, often a minimum amount of effort is put into making sure that they are optimized so as to maximize diet efficiency.