DEGRADATION BY FICIN OF PROTEIN FROM ALFALFA HAY CONSERVED AS CONVENTIONAL AND LABORATORY-SCALE BALES

Ficin was utilized in a 2-h in vitro incubation procedure to characterize the partitioning of N into fractions based on resistance of alfalfa (Medicago sativa L.) proteins to enzymatic degradation. Objectives included evaluation of the following treatment effects on N partitioning: (i) moisture content; (ii) laboratory bale density; (iii) laboratory baling without heating during storage; (iv) spontaneous heating in laboratory bales; and (v) conventional baling. Alfalfa at three moisture levels (268, 229, and 185 g kg(-1)) was conserved in the following bale types: (i) conventional bales; (ii) laboratory bales made at 1.0, 1.3, 1.7, and 2.0 times the density of conventional bales and incubated in two environments (straw stacks or insulated boxes); or (iii) a prestorage control, Significant (P less than or equal to 0.05) moisture x bale type interactions were observed for most N fractions, indicating N partitioning among bale types was greatly changed in high-moisture hay, but remained relatively stable in dry hay, Except for the Pool-C N fraction, which includes Maillard reaction products, laboratory-bale density generally had little effect on N partitioning. At the medium and low moisture levels, prestorage controls had more Pool-A N (greater buffer solubility) than did nonheated laboratory bales. Heating in laboratory bales facilitated additional significant change in N fractions, relative to nonheated laboratory bales. While Maillard reaction products increased in response to laboratory bale density, large increases in the portion of potentially available N most resistant to enzymatic degradation (B-2 subfraction), appeared dependent on large heat increments incurred specifically in conventional bales.