Shrink, weighing accuracy, and weighing precision of mineral supplement in five commercial dairies in the Western United States

Abstract

Shrink, accuracy, and precision of ingredient weighing are critical factors of effi ciency in TMR-fed dairy systems. Those factors have been evaluated for major feeds; however, we are not aware of any reports for mineral sup plement. Farms commonly mix mineral sup plement with other low-inclusion ingredients into a premix which is used later as a single in gredient for TMR formulation. Our objectives were to evaluate shrink, weighing accuracy, and weighing precision of mineral supplement dur ing premix formulation, and variation in concen tration of minerals in mineral supplement and TMR, in five large dairies in the Western United States. We used the automated weight-tracking system at each farm to account for all the min eral supplement loaded into the mixing-wagon and collected samples of mineral supplement and TMR from time of mineral supplement de livery at the farm until 100% of it was consumed. Mean, standard deviation and coefficient of variation (CV) for each variable were calculated with SAS 9.4. Average shrink was estimated at 2.0% for mineral supplement during storage and loading, ranging from 0.37% to 3.25%. Mineral supplement weighing deviation from the targeted amount was 1.54% on average for the five dairies with a 95% CV. Mineral composition of mineral supplements averaged 11.3%, 0.27%, and 3.16% for Ca, P, and Mg, and 215, 881, and 1533 ppm for Cu, Mn, and Zn, respectively. Mineral com positions in TMR averaged 0.84%, 0.41%, and 0.37% for Ca, P, and Mg, respectively; and 15.1, 71, and 94.5 ppm for Cu, Mn, and Zn, respect ively. The CV of all minerals except Ca, were larger for mineral supplement than TMR, and with the exception of P in mineral supplement, CV of trace minerals were larger than CV values for macro minerals. Our shrink estimates for mineral supplement represent an initial approxi mation to this issue. Results of our weighing deviation analysis suggest some room for im provement on the precision of weighing mineral supplement at the time when premix is prepared at the farm, which could improve consistency in chemical composition of the premix and conse quently reduce the variation (CV values) of min eral concentrations in TMR