Development and validation of equations utilizing lamb vision system output to predict lamb carcass fabrication yields.

This study was performed to validate previous equations and to develop and evaluate new regression equations for predicting lamb carcass fabrication yields using outputs from a lamb vision system-hot carcass component (LVS-HCC) and the lamb vision system-chilled carcass LM imaging component (LVS-CCC). Lamb carcasses (n = 149) were selected after slaughter, imaged hot using the LVS-HCC, and chilled for 24 to 48 h at -3 to 1 degrees C. Chilled carcasses yield grades (YG) were assigned on-line by USDA graders and by expert USDA grading supervisors with unlimited time and access to the carcasses. Before fabrication, carcasses were ribbed between the 12th and 13th ribs and imaged using the LVS-CCC. Carcasses were fabricated into bone-in subprimal/primal cuts. Yields calculated included 1) saleable meat yield (SMY); 2) subprimal yield (SPY); and 3) fat yield (FY). On-line (whole-number) USDA YG accounted for 59, 58, and 64%; expert (whole-number) USDA YG explained 59, 59, and 65%; and expert (nearest-tenth) USDA YG accounted for 60, 60, and 67% of the observed variation in SMY, SPY, and FY, respectively. The best prediction equation developed in this trial using LVS-HCC output and hot carcass weight as independent variables explained 68, 62, and 74% of the variation in SMY, SPY, and FY, respectively. Addition of output from LVS-CCC improved predictive accuracy of the equations; the combined output equations explained 72 and 66% of the variability in SMY and SPY, respectively. Accuracy and repeatability of measurement of LM area made with the LVS-CCC also was assessed, and results suggested that use of LVS-CCC provided reasonably accurate (R2 = 0.59) and highly repeatable (repeatability = 0.98) measurements of LM area. Compared with USDA YG, use of the dual-component lamb vision system to predict cut yields of lamb carcasses improved accuracy and precision, suggesting that this system could have an application as an objective means for pricing carcasses in a value-based marketing system.

An evaluation of the lamb vision system as a predictor of lamb carcass red meat yield percentage.

An objective method for predicting red meat yield in lamb carcasses is needed to accurately assess true carcass value. This study was performed to evaluate the ability of the lamb vision system (LVS; Research Management Systems USA, Fort Collins, CO) to predict fabrication yields of lamb carcasses. Lamb carcasses (n = 246) were evaluated using LVS and hot carcass weight (HCW), as well as by USDA expert and on-line graders, before fabrication of carcass sides to either bone-in or boneless cuts. On-line whole number, expert whole-number, and expert nearest-tenth USDA yield grades and LVS + HCW estimates accounted for 53, 52, 58, and 60%, respectively, of the observed variability in boneless, saleable meat yields, and accounted for 56, 57, 62, and 62%, respectively, of the variation in bone-in, saleable meat yields. The LVS + HCW system predicted 77, 65, 70, and 87% of the variation in weights of boneless shoulders, racks, loins, and legs, respectively, and 85, 72, 75, and 86% of the variation in weights of bone-in shoulders, racks, loins, and legs, respectively. Addition of longissimus muscle area (REA), adjusted fat thickness (AFT), or both REA and AFT to LVS + HCW models resulted in improved prediction of boneless saleable meat yields by 5, 3, and 5 percentage points, respectively. Bone-in, saleable meat yield estimations were improved in predictive accuracy by 7.7, 6.6, and 10.1 percentage points, and in precision, when REA alone, AFT alone, or both REA and AFT, respectively, were added to the LVS + HCW output models. Use of LVS + HCW to predict boneless red meat yields of lamb carcasses was more accurate than use of current on-line whole-number, expert whole-number, or expert nearest-tenth USDA yield grades. Thus, LVS + HCW output, when used alone or in combination with AFT and/or REA, improved on-line estimation of boneless cut yields from lamb carcasses. The ability of LVS + HCW to predict yields of wholesale cuts suggests that LVS could be used as an objective means for pricing carcasses in a value-based marketing system.

Microbial contamination occurring on lamb carcasses processed in the United States.

Lamb carcasses (n = 5,042) were sampled from six major lamb packing facilities in the United States over 3 days during each of two visits (fall or winter, October through February; spring, March through June) in order to develop a microbiological baseline for the incidence (presence or absence) of Salmonella spp. and for populations of Escherichia coli after 24 h of chilling following slaughter. Samples also were analyzed for aerobic plate counts (APC) and total coliform counts (TCC). Additionally, incidence (presence or absence) of Campylobacter jejuni/coli on lamb carcasses (n = 2,226) was, determined during the slaughtering process and in the cooler. All samples were obtained by sponge-sampling the muscle-adipose tissue surface of the flank, breast, and leg of lamb carcasses (100 cm2 per site; 300 cm2 total). Incidence of Salmonella spp. in samples collected from chilled carcasses was 1.5% for both seasons combined, with 1.9% and 1.2% of fall or winter and spring samples being positive, respectively. Mean (log CFU/cm2) APC, TCC, and E. coli counts (ECC) on chilled lamb carcasses across both seasons were 4.42, 1.18, and 0.70, respectively. APC were lower (P < 0.05) in samples collected in the spring versus fall or winter, while TCC were higher in samples collected in the spring. There was no difference (P > 0.05) between ECC from samples collected in the spring versus winter. Only 7 out of 2,226 total samples (0.3%) tested positive for C. jejuni/coli, across all sampling sites. These results should be useful to the lamb industry and regulatory authorities as new regulatory requirements for meat inspection become effective.

Relationship of visual assessments of feeder lamb muscularity to differences in carcass yield traits.

We examined the relationship between visual differences in muscle thickness among feeder lambs and subsequent differences in carcass composition. Medium-framed, crossbred feeder lambs (n = 120) were selected at two commercial feedlots to exhibit distinct phenotypic differences in muscularity. The lambs were assigned scores (ranging from 1 to 9; 1 = extremely thin, 5 = average, 9 = extremely thick) for muscle thickness and were sampled serially on d 0, 14, 28, and 42 of the trial. After recording yield grades, one side of each carcass was deboned, and the soft tissues from the entire side were ground, sampled, and analyzed for lipid and moisture content. The opposite side was fabricated into boneless, closely trimmed (.25 cm maximum fat depth) subprimal cuts. When lambs of the same frame size were compared at the same live weight, greater muscle thickness was associated with greater (P < .05) fat-free muscle mass. Correspondingly, thickly muscled lambs produced carcasses of a given weight that had a higher (P < .05) composite yield of lean meat and a lower (P < .05) proportion of trimmable fat compared with carcasses of thinly muscled lambs. When comparisons were made at the same percentage of extractable fat in the carcass, greater muscle thickness was associated with heavier (P < .05) live and carcass weights, increased (P < .05) fat-free muscle mass, and increased (P < .05) weights of trimmed, boneless subprimal cuts. Results suggest that visual assessments of muscle thickness in feeder lambs, as applied in this study, are indicative of commercially important differences in carcass yields of lean meat.

Relationship of feeder lamb frame size to feedlot gain and carcass yield and quality grades.

Small-(S), medium-(M), and large-(L) framed feeder lambs (n = 243 S, 247 M, and 245 L) were finished on five diets differing in amount of concentrate (C) and crude protein (CP): 1) 30% C, 12.5% CP; 2) 55% C, 12.5% CP; 3) 55% C, 14.5% CP; 4) 80% C, 12.5% CP; and 5) 80% C, 14.5% CP. Lambs were sampled over a wide weight range to establish relationships of frame size to daily gain and live weight at specific carcass grade end points. Increased frame size (F) was associated with more rapid gains during finishing, although differences in daily gain among L, M, and S lambs were not expressed consistently across all dietary treatments (D), as reflected by a significant F x D interaction for ADG. The rate at which external fat thickness increased as the lambs became heavier was not affected by frame size, sex, or diet. However, increased frame size was associated with lower (P < .05) values for fat thickness (FT), body wall thickness (BWT), yield grade (YG), and quality grade (QG) when comparisons were made at a constant slaughter weight. Similarly, later-maturing wether lambs were leaner and had lower YG and QG than ewes of the same weight. Dietary treatment had no effect on FT, BWT, and YG when treatment groups were compared at a constant live weight. Subclass regressions of YG on live weight were used to project the weights at which lambs of various frame sizes would be expected to produce YG-2 carcasses. Projected final weights for wethers were less than 50 kg for S, 50 to 55 kg for M, and greater than 55 kg for L. Projected final weights for ewe lambs were approximately 2.5 kg lower. Dietary treatment did not affect relationships among frame size, live weight, and YG. A grading/classification system for feeder lambs based on frame size could be developed to predict carcass grade end point.

Effect of water temperature, pressure and chemical solution on removal of fecal material and bacteria from lamb adipose tissue by spray-washing.

The objectives of this study were to determine the efficacy of various water temperatures, pressures and chemical solutions of spray-washing on the removal of fecal and bacterial contamination from lamb carcass samples taken from the breast area (< 15 min post mortem) and inoculated (6.50 cm(2) area) with an ovine fecal paste containing Escherichia coli (ATCC 11370). Inoculated samples were held for 15 min and then knife-trimmed and/or spraywashed with varying water temperatures (16, 35 or 74 °C), pressures (2.76, 13.79, 20.68 or 27.58 bar) and chemical solutions (12% trisodium phosphate, 2% acetic acid, 5% hydrogen peroxide or 0.003% available chlorine) for 18 s. After the respective treatments, samples were evaluated visually for presence of fecal material and microbiologically for aerobic plate counts (APC). Knife-trimming reduced (p < 0.05) APC of inoculated samples, while subsequent spray-washing of knife-trimmed samples reduced APC (p < 0.05), even compared to uninoculated control samples. Spray-washing with any temperature and pressure combination reduced (p < 0.05) visible fecal contamination on the samples. Bacterial reductions ranged from 1.48 to 3.83 log colony forming units (CFU/cm(2)) at the inoculation site. Use of 74 °C water was more effective (p < 0.05) in decreasing APC than either 16 or 35 °C water, while water pressure effects were similar. Use of 2% acetic acid reduced the APC more than the use of any other chemical solution tested. APC for the areas surrounding the inoculation site were similar to APC at the inoculation site; thus indicating that either there was no major spread of bacterial contamination to areas above or below the inoculation site or that contamination was diluted to levels lower than initial contamination. Overall, acetic acid and water temperature were the most important factors in reducing APC and fecal contamination on lamb adipose tissue.