title: Variability in mixing efficiency and laboratory analyses of a common diet mixed at 25 experiment stations.
abstract: An experiment involving 25 experiment stations in the North Central and Southern regions (NCR-42 and S-288, respectively) was conducted to assess the degree of uniformity of diet mixing among stations and to assess the variability among station laboratories in chemical analysis of mixed diets. A fortified corn-soybean meal diet was mixed at each station using a common diet formula (except for vitamin and trace-mineral additions). The diet was calculated to contain 14% crude protein (CP), 0.65% Ca, 0.50% P, and 125 ppm Zn (based on 100 ppm added Zn). After mixing, samples were collected from the initial 5% of feed discharged from the mixer, after 25, 50, and 75% was discharged, and from the final 5% of discharged feed. The five samples were sent to the University of Kentucky, finely ground, and divided into subsamples. Each set of five subsamples from each station was distributed to three randomly selected stations for analysis of CP, Ca, P, and Zn (i.e., each station analyzed five diet sub-samples from three other stations). In addition, two commercial and two station laboratories analyzed composites of the five subsamples from each of the 25 mixed diets. Based on the laboratories that analyzed all diets, means were 13.5, 0.65, and 0.52%, and 115 ppm for CP, Ca, P, and Zn, respectively. Ranges of 11.8 to 14.6% CP, 0.52 to 0.85% Ca, 0.47 to 0.58% P, and 71 to 182 ppm of Zn were found among the 25 diet mixes. The coefficients of variation among the 25 diet samples for CP, Ca, P, and Zn were 4.3, 9.3, 4.1, and 17.4%, and among the 25 laboratories were 3.6, 12.5, 10.7, and 11.1%, respectively. Overall analyses of the five sub samples were, respectively, CP: 13.4, 13.6, 13.4, 13.5, and 13.4% (P < 0.06); Ca: 0.66, 0.67, 0.67, 0.66, and 0.67%; P: 0.50,0.51,0.51,0.50, and 0.50%; and Zn: 115, 116, 112, 113, and 120 ppm (P < 0.001). Diets were not uniformly mixed at all stations (station x sample No. was P < 0.08 for Ca and P < 0.01 for CP, P, and Zn). Among stations, the range of the five samples, expressed as a percentage of the mean and averaged for CP, Ca, P, and Zn, varied from +/- 1.1% (i.e., 98.9 to 101.0%) to +/- 12.9% (84.6 to 110.4%), with an overall average of +/- 5.2%. Neither type nor volume of mixers was related to mixing uniformity. The results suggest that uniformity of diet mixes varies among experiment stations, that some stations miss their targeted levels of nutrients (especially Zn), and that the variability among experiment station laboratories in analysis of dietary Ca, P, and Zn in mixed diets is quite large.
authors.affiliation: Dept. of Animal Sciences, University of Kentucky, Lexington 40546, USA. gcromwel@uky.edu
authors.forename: G L
authors.initials: GL
authors.lastname: Cromwell
authors.forename: J H
authors.initials: JH
authors.lastname: Brendemuhl
authors.forename: L I
authors.initials: LI
authors.lastname: Chiba
authors.forename: T R
authors.initials: TR
authors.lastname: Cline
authors.forename: T D
authors.initials: TD
authors.lastname: Crenshaw
authors.forename: C R
authors.initials: CR
authors.lastname: Dove
authors.forename: R A
authors.initials: RA
authors.lastname: Easter
authors.forename: R C
authors.initials: RC
authors.lastname: Ewan
authors.forename: K C
authors.initials: KC
authors.lastname: Ferrell
authors.forename: C R
authors.initials: CR
authors.lastname: Hamilton
authors.forename: G M
authors.initials: GM
authors.lastname: Hill
authors.forename: J D
authors.initials: JD
authors.lastname: Hitchcock
authors.forename: D A
authors.initials: DA
authors.lastname: Knabe
authors.forename: E T
authors.initials: ET
authors.lastname: Kornegay
authors.forename: A J
authors.initials: AJ
authors.lastname: Lewis
authors.forename: G W
authors.initials: GW
authors.lastname: Libal
authors.forename: M D
authors.initials: MD
authors.lastname: Lindemann
authors.forename: D C
authors.initials: DC
authors.lastname: Mahan
authors.forename: C V
authors.initials: CV
authors.lastname: Maxwell
authors.forename: J C
authors.initials: JC
authors.lastname: McConnell
authors.forename: J L
authors.initials: JL
authors.lastname: Nelssen
authors.forename: J E
authors.initials: JE
authors.lastname: Pettigrew
authors.forename: L L
authors.initials: LL
authors.lastname: Southern
authors.forename: T L
authors.initials: TL
authors.lastname: Veum
authors.forename: J T
authors.initials: JT
authors.lastname: Yen
mesh_terms: D000821:Animal Feed / Q000032:analysis / Q000592:standards*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002136:Calcium, Dietary / Q000032:analysis; D004044:Dietary Proteins / Q000032:analysis; D005504:Food Analysis; D005525:Food-Processing Industry / Q000592:standards*; D007753:Laboratories / Q000592:standards; D016226:Phosphorus, Dietary / Q000032:analysis; D013552:Swine; D015032:Zinc / Q000032:analysis
chemical_list: D002136:Calcium, Dietary; D004044:Dietary Proteins; D016226:Phosphorus, Dietary; D015032:Zinc