The objective of this study was to evaluate the effects of crude glycerin on performance and carcass characteristics in finishing wether lambs. Thirty black-faced, Suffolk-cross wether lambs (44.1 +/- 5.6 kg initial BW) were stratified and blocked by BW to 1 of 5 individually fed, isocaloric, isonitrogenous dietary treatments containing 0, 5, 10, 15, or 20% crude glycerin (88% pure) on a DM basis. Diets were fed once daily for ad libitum consumption and contained 15% chopped hay, approximately 25% dried distillers grains with solubles, and the specified treatment combination of cracked corn replaced with increasing amounts of crude glycerin. Wethers were weighed on 14-d intervals and were selected for slaughter when they reached an approximate 12th-rib fat depth of 0.51 cm (28 to 84 d on trial). Carcass characteristics were collected after a 48-h chill. Dry matter intake (linear, P = 0.004) and ADG (quadratic, P = 0.05) increased with increasing concentrations of glycerin in the diet during the first 14 d of the feeding period. Similarly, G:F tended to increase quadratically (P = 0.06) with increasing concentrations of crude glycerin in the diet during the first 14 d. However, there were no differences among treatments for final BW, days on feed, or cumulative DMI, cumulative ADG, and cumulative G:F (P >or= 0.11). Body wall thickness, dressing percent, HCW, LM area, flank streaking, leg score, conformation score, quality grade, yield grade, and percent boneless, closely trimmed retail cuts did not differ (P >or= 0.21). Adding up to 15% crude glycerin to finishing wether diets improved feedlot performance, particularly during the first 14 d, without any concomitant effect on carcass characteristics.
Market weight lambs, average weight 52.5 kg (+/-6.1), were used to evaluate nontraditional live animal measurements as predictors of carcass composition. The sample population (n = 106) represented U.S. market lambs and transcended geographic location, breed, carcass weight, yield grade, and production system. Realtime ultrasonic (RU) measurements and bioelectrical impedance analysis (BIA) were used for development and evaluation of prediction equations for % boneless, closely trimmed primal cuts (BCTPC), weight or % of dissected lean tissue (TDL), and chemically derived weight or % fat-free lean (FFL). Longitudinal ultrasonic images were obtained parallel to the longissimus thoracis et lumborum (LTL), positioning the last costae in the center of the transducer head. Images were saved and fat and LTL depths were derived from printed images of the ultrasonic scans. Bioelectrical impedance analysis was administered via a four-terminal impedance plethysmograph operating at 800 microA at 50 kHz. Impedance measurements of whole-body resistance and reactance were recorded. Prediction equations including common linear measurements of live weight, heart girth, hindsaddle length, and shoulder height were also evaluated. All measurements were taken just before slaughter. Bioelectrical impedance measurements (as compared to RU and linear measurements) provided equations for %BCTPC, TDL, %TDL, FFL and %FFL with the highest R2 and lowest root mean square error. Even though BIA provided the best equations of the three methodologies tested, prediction of proportional yield (%BCTPC, %TDL, and %FFL) was marginal (R2 = .296, .551, and .551, respectively). Equations combining BIA, RU, and linear measurements greatly improved equations for prediction of proportional lean yield.
Accurate price signals are essential for producers of American lamb to ensure production of uniformly lean animals. Development of carcass merit-pricing systems will require the use of objective technology for assessing carcass composition or lean distribution. The objective of this study was to evaluate electronic technologies for accurate determination of lamb carcass composition. Lambs (n = 106) were selected as a representation of U.S. market lambs that transcended geographic location, sex, breed, carcass weight, yield grade, and production system. The independent variables used to predict lamb composition varied with the technology. The electronic technologies tested included realtime ultrasound, optical reflectance probe, bioelectrical impedance analysis, and electromagnetic scanning (TOBEC). All technologies, except realtime ultrasound, were tested on warm (prerigor) carcasses and repeated after a 24-h chill. Longitudinal ultrasonic scans of fat and muscle tissue depth and grading probe fat depths were marginal predictors of proportional carcass yield. The TOBEC measurements often accounted for more variability associated with kilograms of dissected lean and percentage of carcass lean than did carcass weight. Equations from TOBEC measurements were the most accurate predictors of weight and percentage of dissected and fat-free lean. Bioelectrical impedance measurements of resistance and reactance combined with carcass weight were also good predictors of carcass composition. Prediction of carcass lean distribution by measures of TOBEC were the most accurate for prediction of leg lean. The implications of usefulness of these technologies will depend on the commitment of the U. S. sheep industry in development of a lamb price discovery system based on carcass composition.
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