CHEMICAL AND PROTEIN-QUALITY PARAMETERS OF HEAT-PROCESSED SUNFLOWER OILCAKE FOR DAIRY-CATTLE

The effect of heat processing on chemical and protein quality paramete rs of sunflower oilcake (SFOC) was evaluated. SFOC was processed in a drum roaster at six temperature settings and five time intervals. Chem ical analysis included: N-solubility (N-sol.), percent pepsin insolubl e nitrogen (% PIN), percent acid detergent insoluble nitrogen (% ADIN) . These methods were used as screening tests to select six processed a nd one control sample for in situ evaluation. The in situ polyester ba g and mobile bag techniques were used to determine the effective rumen protein degradability and undegradable protein (UDP) digestibility, r espectively. Heat processing significantly influenced UDP digestibilit y. The relationship between total tract crude protein (CP) disappearan ce and % ADIN (R(2) = 0.88), and between digestibility of UDP and % AD IN (R(2) = 0.88) was linear (P < 0.05), indicating the potential of % ADIN to indicate heat damage. Optimum heat processing was assumed to o ccur at 12 to 15% of total N as ADIN. Heat processing, decreased the c oncentrations (P < 0.05) of the amino acids (AA) Arg, His, Lys and Ser in the unincubated samples. The AA Arg, His, Lys, Met, Ala, Ser and T yr were (P < 0.05) less resistant to microbial degradation compared wi th the control, whereas Lys, Asp, Gly and Ser were less absorbable (P < 0.05). The largest amount of AA from UDP theoretically available in the small intestine (SI) occurred at 150 degrees C/30 min, which agree d with the optimum level of ADIN. Results demonstrated the usefulness of ADIN as an indicator of heat damage for SFOC.