Prof Christopher Ramsey

Abstract:

We describe the operation of a commercial system as modified for preparation of CO2 for the CO2 source. AMS samples are automatically combusted in a CHN analyzer, and stable isotope measurements are made on line. We describe the performance of this equipment, with reference to yield, sample contamination, memory effect, accuracy of isotope measurement, convenience and cost. We discuss the current status of dating using the CO2 source. This is the only source in operation at Oxford, and has been in routine dating since September 1989. We assess the practicalities of operation, including the latest measurements on background, memory, sample-size requirements and operating schedules. We also describe modifications to the sputter beam optics and to the gas handling systems.

Abstract:

Three experienced persons evaluated 158 carcasses 24 h postmortem for USDA yield grade (YG) and quality grade factors, nine subcutaneous (SC) fat indicators, and four intermuscular (IM) fat indicators. Forty sides (YG 1.1 to 3.8) were selected for determination of chemical composition, two measures of cutability, and total IM fat from the round, loin, rib, and chuck. The IM fat estimates at the 12th rib, rib-plate juncture, and 5th rib were correlated with percentage of chemical fat (r = -.72, -.70, and -.55, respectively). Simultaneous consideration of YG factors accounted for 61% of the variation in chemical fat. Substituting the IM fat estimate at the 12th rib for adjusted fat thickness (AFT) in the equation explained 60% of the variation in percentage of chemical fat. An equation containing two IM fat estimates, marbling score and longissimus muscle area explained 68% of the variation in chemical fat. Simultaneous consideration of the YG factors accounted for 59% of the variation in boneless, closely trimmed (6 mm SC fat and no IM fat) retail cuts from the round, loin, rib, and chuck. Substituting the IM fat estimate at the 12th rib for AFT in the equation accounted for 65% of the variation. These data from a fairly uniform set of steer carcasses show that percentage of chemical fat and cutability can be reliably predicted from IM fat estimates and other traits that can be visually estimated on hot-fat trimmed carcasses.