Evaluation of macromineral meters to detect cation- anion difference concentration and uniformity in a total mixed ration

Objectives: Our objectives were to evaluate predic-tion of macromineral concentrations in a TMR by various meters compared with laboratory macromineral analyses, to determine whether these meters could estimate DCAD in the TMR for close-up and lactating-cow pens, and to determine whether meters could estimate uniformity of TMR.Materials and Methods: Meters used were Cl (Oak-ton SaltTestr, Oakton Instruments, Vernon Hills, IL), K (Laqua Twin K Meter, Horiba Scientific, Kyoto, Japan), S (Hanna Instruments Smithfield, RI), and Ca and Mg (Hanna Instruments Ca/Mg Photometer, Smithfield, RI). The TMR samples were collected from close-up and lactat-ing-cow pens in 10 dairies. Ten subsamples of TMR were collected per pen at the time of feeding and sent to Analab (Agri-King Inc., Fulton, IL) for analysis, and another 10 were used to measure mineral concentrations with the me-ters. Mineral concentrations analyzed by the laboratory were regressed on meter mineral concentrations. Results and Discussion: Prediction of Cl and K con-centrations in TMR were best (R2 = 0.53 and R2 = 0.66, respectively). The combination of K and Cl meter con-centrations was able to predict TMR DCAD (R2 = 0.72). The Cl meter was also able to predict TMR coefficient of variation (R2 = 0.57) to evaluate TMR uniformity.Implications and Applications: Chloride and K me-ters can aid in identifying the source of TMR DCAD fail-ure and can predict overall TMR uniformity delivered by the mixer