Precision nutrition: weighing feed ingredients correctly

The ability to mix a quality feed is often equated to the quality of the mi xer; the ability to weigh ingredients correctly has received little attenti on. To assess how accurately feed mills weigh their ingredients, 14 feed mi lls specialising in swine diets were surveyed, which yielded 8432 data poin ts (for 229 ingredients and 11-44 batch records per ingredient within mills ). Amounts actually weighed (according to scale readings) were compared to calls, and differences were analysed statistically. Feed mills overdosed in gredients by 1.5+/-16.3%: between mills, overdosing ranged from -0.7 to 13. 0%. Within ingredients, weighing variation ranged from 0.6 to 11.1% between mills and averaged 5.2%. Some of the weighing problems observed were attri buted to discrepancies between the cab size and the scale resolution. For e xample, weighing 11.3 units (pounds) on a scale with a 2 unit resolution le ads to a minimum error of 6%. Such problems occurred for 8.7% of the calls and resulted in a minimum error ranging from 0.01 to 20%, averaging 1.95%. Poor choice of scales was the major source of errors in weighing, and the r elationship weighing variation = 10(Lambda)[1.56-0.50 log (call/scale resol ution)] explained 40% of the variation observed (p < 0.05). Weighing ingred ients in the right scale would thus not only benefit feed quality but also reduce diet cost, as it would reduce the overdosing of ingredients. (C) 200 1 Society of Chemical Industry.