Prediction of suckling lamb carcass composition from objective and subjective carcass measurements.

Correlations and regression between fatness and carcass conformation measurements and carcass tissue composition has been studied for both sexes in suckling lambs, with slaughter weights between 9 and 15 kg. Objective fat measurements showed higher correlations than subjective fat measurements, mainly with carcass fat. Conformation measurements presented greater correlations with tissues weight than with tissues proportion (r⩽0.50). CCW was highly correlated with total muscle in the carcass (R(2)=0.961). Two fatness measurements (KKCF proportion and dorsal fat thickness) were included for the prediction of the muscle proportion. Furthermore, the model included other measurements, such as fore cannon bone weight and internal carcass length although they displayed very low correlation coefficients. This equation explained 64.1% of the variation of carcass muscle proportion (r.s.d.=1.532). CCW was included in the prediction equations of tissue weights, although in the fat tissue equation it appeared in the form of the carcass compactness index (CCW/L). CCW was a good predictor of the weight of carcass tissues in suckling lambs, especially for muscle. Prediction equations for tissue composition in grams were more accurate (R(2)⩾0.91) than those for tissue proportion. When gender was included in all models it did not improve either accuracy or precision of the prediction.

Carcass and meat quality of light lambs using principal component analysis.

Eighty-six male light lambs of Manchego breed were used in this study. Principal component (PC) analysis was performed to study the relationship between carcass quality variables (n=22) and between meat quality measures (n=21). The carcass quality was assessed using objective and subjective measurements of conformation and fatness besides the joints proportion and tissues proportion of the leg. The measurements used to evaluate meat quality were pH in longissimus dorsi and semitendinosus muscles, the colour, moisture, water holding capacity, cooking losses, texture and sensorial analysis on longissimus dorsi. The five first PCs explained about 77% of the total variability for carcass measures whereas for meat quality the 74% of the total variability was explained for the eight first PCs. All the carcass measurements showed similar weight to define the first PC, whereas the muscle and bone proportion as well as muscle:bone ratio of the leg were useful to define the second PC. The meat quality measures that were more effective to define the first PC were the meat colour measurements, whereas the sensorial variables defined the second PC. The projection of the carcass quality data in the first two PCs allowed to distinguish clearly between heavier carcasses (higher than 6.5 kg) and lighter carcasses (lower than 5.5 kg). The carcasses with a weight higher than 6.5 kg were on the left side of the figure, where the variables of conformation and fatness lie. The group of medium carcass weight were placed between the two previous groups. The projection of the meat quality data in the first two PCs did not differ between hot carcass weights, although there was a trend, the lighter carcasses lay on the left side of the graph, which implies small differences between meat quality in this range of carcass weight.

Carcass classification in suckling lambs. II. Comparison among subjective carcass classification methods: fatness scales and conformation scales with 0.25 point-intervals.

Forty-nine Manchega breed suckling lambs were used. Carcass weight was less than 13 kg, and lambs were slaughtered at 10, 12 and 14 kg liveweight. Carcasses were classified by three assessors on colour photographs, by several classification methods: the European Union scale for light lambs carcasses (EU), Colomer-Rocher methods for fatness (CF) and conformation (CC), and the new scale for suckling lambs (SL) developed by our research group. Carcasses were also assessed using these scales divided into 0.25 point-intervals (EU-25, CF-25, CC-25 and SL-25). A correlation analysis was made between assessors score and tissue composition in the carcass and in three joints (leg, best end of neck and loin, and shoulder). For all the methods studied 0.25 point scales were best correlated to tissue composition than 1.0 points-interval scales. When 1.0 point-interval scales were used the SL scale was best correlated to tissue composition. When 0.25 point-scales were used, the EU scale gave the best correlations. Conformation scale (CC) was useful to predict carcass composition, specially kidney knob and channel fat content.

Carcass classification in suckling lambs. Discrimination ability of the European Union scale.

Forty-nine Manchega suckling lambs were used in this trial. Lambs were slaughtered at 10, 12 and 14 kg liveweight (cold carcass weight lower than 13 kg). The degree of fatness was assessed by three assessors on colour photographs of the carcasses, using the European Union scale for light lambs (EU), and another new scale developed in our laboratory (Suckling Lamb scale, SL). Carcass degree of fatness was reassessed using the same scales divided into 0.25 point-intervals (EUI, SLI). Carcasses were allocated into four groups by means of a tree classification algorithm (cluster analysis), according to 27 variates, namely muscle percentage, whole fat percentage, subcutaneous fat, intermuscular fat, kidney knob and channel fat percentage and muscle percentage, both in the carcass and in three joints (leg, best end neck plus loin, and shoulder). SL scale groups showed a higher number of variates well correlated to assessors' scoring than EU scale groups. Nevertheless, the EU scale showed significant between-groups differences in a higher number of variates (P<0.01). Using 0.25-points interval scales, EUI scale scoring was the best correlated to tissue composition. However, most variates were better correlated to dorsal fat thickness measurement (4 cm back from last rib and 4 cm from the carcass midline) than to assessors' scoring. All four groups in the tree classification were statistically different from one another, but assessors only were able to detect differences between whole fat percentage in group 1 and the rest. These results suggest that it is possible to improve the photographic standards of the EU method by using a 0.25 points interval scale. In abattoir conditions, the new SL method (1.0 point intervals) proved to be better. Measure of dorsal fat thickness proved to be a very good predictor of carcass tissue composition, but it is a more expensive measure.

Changes in meat quality characteristics of bovine meat during the first 6 days post mortem.

The development of some quality parameters in bovine meat during the first 6 days of post mortem ageing was studied in two commercial groups (heifer and bull). In the first day bull meat is harder and springier. Meat pH falls during the first 24 h post mortem in both groups, reaching values around 5.5, and it did not change during the next 5 days. Water-holding capacity (expressed as percentage of expelled water) increased in heifer meat. Instrumental texture measures (texture profile analysis, TPA) showed a decrease in hardness, springiness and chewiness in bull raw meat. Sensory analysis showed that assessors perceived a decrease in hardness and in springiness in bull meat and a decrease in juiciness and in chewiness (number of chewings before swallowing) in heifer meat. Ageing showed no effect on assessors' pleasantness either in heifers' or in bulls' meat. During the first 3 days, heifer meat was juicier. Heifers' meat produced a greater pleasantness on the sixth day. Both meats were not very different for most quality parameters studied in this work.