Urea, Calcium, Potassium and Sulfur Impregnation of Whole Corn—Development and In Vitro Evaluation

Abstract

A method of impregnating whole corn grain to meet the nitrogen and mineral requirements of growing-finishing lambs was developed. Several compounds were compared as calcium (Ca), potassium (K) and sulfur (S) sources based on solubility in a urea solution. A laboratory study was used to evaluate two urea-mineral solutions containing urea, calcium chloride, potassium acetate and sodium thiosulfate. The ratio of these compounds to whole corn was based on a final product containing 12% crude protein, .37% Ca, .50% K and a 10:1 N (from urea) to S ratio (dry matter basis). Dry stored corn and high moisture corn were mixed on a horizontal rolling device with either 11 or 6.5 ml solution/100 g corn dry matter. Both solutions provided the same quantity of salts; only water addition varied. The impregnated corn was then dried by either ambient laboratory air for 24 h or heat (95 C) for 1 h to 88% or higher dry matter content. A washing procedure was used to determine the relative amounts of added nutrients absorbed by, or adhered to, corn kernels. Neither corn source, stored or high moisture, nor drying method had any affect on N, Ca or K retention with the exception of more (P<.01) retained Ca in stored corn. The reduced volume of added water resulted in increased (P<.01) Ca retention as well. Although washing reduced (P<.01) the amounts of N, Ca and K in impregnated corn, 79, 70 and 59% of the added N, Ca and K, respectively, remained associated with the kernels. In an in vitro ammonia-N release study, ammonia-N concentration in the incubation medium was lowered (P<.05) during several of the first 6 h of a 24-h incubation when impregnated corn was compared with liquid urea-supplemented corn.