March 2016: Particular about particles

Pig diets can tick all the right boxes, but still not perform quite as well as they should. The nutritionist should have taken age and phase of production into account for the sow, weaner or growing herd. And he or she will have considered the type and quality of the raw materials on offer in coming up with the best balanced diet to maximise performance at optimum cost. But have they considered how these raw materials have been processed?

It’s an area that’s often not questioned, and producers assume that the processing of the raw materials is adequate for optimal performance. But it’s a critical area in the feed supply chain. More focus on particle size of your cereal and soya fractions can pay real dividends.

With feed representing by far the largest cost in pig production, it’s important to get the absolute maximum from each raw material entering the mill.

Reducing particle size has a great impact on feed efficiency. By increasing the surface area of the grain, there’s greater interaction of the feed with digestive enzymes, thus improving the digestibility of nutrients.  But, excessive grinding will increase the milling energy costs and lead to feed management problems such as increased dust levels and bridging in the feeder and bulk bin. The incidence of gastric ulceration can also increase significantly when feed is ground excessively. This demonstrates very simply why optimum diet particle size shouldn’t be ignored. A decision must be made between pig performance and milling efficiencies.

Current information suggests that the optimum particle size for growing pigs is 650 to 800 microns (0.65 to 0.80mm). Particularly important is the distribution of particle size within a material and a narrow distribution in size is the ideal. Large percentages of dust, with particles smaller than 150 microns, and very coarse particles greater than 1,200 microns should be minimised.

Research from the US has indicated that, for maize based diets ranging in particle size from 1,200 to 400 microns, there’s a 1.0 to 1.5% improvement in feed efficiency for every 100 micron reduction in average particle size. In monetary terms, this is a saving of £0.40/pig per 100 microns.

Further work carried out in the US showed that the digestibility of essential amino acids in soyabean meal increased from 91% to 92.4% as particle size was decreased by grinding from an average of 900, 600, 300 or 150 microns. A particle size of 600 microns showed the largest improvement in digestibility when compared against the 900-micron treatment.

Particle size checks using a sieve test on ground grain, soya and complete feeds is relatively inexpensive, and should be a carried out regularly as part of the home-milling operation. Results are then used to make adjustments to the milling equipment.

Preparation of raw materials, and in particular particle size, is an important part in feed management and ration performance. It might be worth checking that this isn’t a weak link in your system, compromising return on investment of your on-farm milling facility.

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About The Author

Barry Hoare is Cargill's pig nutritionist for the UK and Ireland. Based in southern Ireland, he graduated from University College Dublin with a masters degree in pig nutrition in 2001