Animal Industry Report

Extension Number

ASL R2201



Summary and Implications

Hypocalcemia (clinical and subclinical) create a major economic loss in early postpartum dairy cows. Ration formulation for dairy cows just prior to parturition must control the diet cation-anion difference (DCAD) if hypocalcemia and milk fever are to be avoided. The purpose of this research was to evaluate the use of specific fertilizer regimes for forages and evaluate their impact on mineral and DCAD levels in hays, as well as forage yields. The experimental design involved four different species of hay (alfalfa, bromegrass, orchardgrass, and reed canarygrass) fertilized with either CaCl2 or K2CO3 (designated K2O) alone or a combination (designated KCl) of both.

In the plots not receiving K fertilization (Control and CaCl2) the K content of the plants regardless of species was lower relative to those receiving K (K2O and KCl). With regards to plant Cl content, the plots fertilized with CaCl2 alone or in combination with K2O resulted in substantial and at least a 2 fold elevations in tissue chloride in all the hays tested. DCAD was also significantly reduced with CaCl2 treatment alone and was reduced 50-75% in the Orchardgrass, Reed Canarygrass and Orchardgrass hays. The combination of K2O and CaCl2 resulted in an attenuation of this effect. CaCl2 treatment alone had no detrimental effect on yield when compared to Control plots. However, those plots fertilized with K (with or without Cl) had higher numerical yields than those not receiving K.

These data suggest that withholding K fertilization in combination with Cl fertilization may be an effective means of increasing the Cl and ultimately decreasing the DCAD content of several species of hay without sacrificing yield. We will continue to monitor the effects of K and Cl fertilization on plant parameters during the FY05 and FY06 growing seasons. The effect of Cl fertilization on hay quality and palatability is currently under investigation.

Copyright Holder

Iowa State University