Virgínia Santos

Carcass composition and meat quality of equally mature kids and lambs.

The interaction between sarcomere length and postmortem proteolysis as related to meat tenderness is not clear. The extent of thick and thin filament overlap alters actomyosin binding and may alter substrate availability during aging-induced tenderization. The objective of this study was to determine the influence of sarcomere length on proteolytic degradation in beef. Strips from bovine semitendinosus were either stretched 40% and restrained or allowed to shorten unrestrained in an ice bath. After rigor completion, 0.6-cm cross sections were fabricated and were randomly assigned to 2, 4, 7, or 10 d of aging treatments. Myofibrils were isolated for sarcomere length determination. Samples were collected and frozen for shear force analysis, and muscle proteins were extracted for SDS-PAGE and Western blotting analyses to determine troponin T (TnT) proteolysis. Sarcomere length was greater (P < 0.01) in stretched muscle samples compared with shortened samples (2.57 vs. 1.43 microm, respectively). Correspondingly, shear force values were greater (P < 0.05) in shortened samples than stretched samples. Western blots revealed the presence of 3 major intact TnT bands that diminished with time postmortem and 4 bands (TnT degradation products) that accumulated during postmortem storage. Quantification of intact TnT showed increased (P < 0.05) proteolysis at 4 and 7 d postmortem in samples with long sarcomeres. By 10 d, only traces of the greatest molecular weight intact TnT band were evident in both shortened and stretched samples, suggesting this TnT band may be more susceptible to proteolysis than other intact TnT bands. Degradation products of TnT appeared earlier postmortem in samples with long sarcomeres. The 30-kDa TnT fragment appeared after 7 d of postmortem storage in samples with long sarcomeres but not until 10 d in muscle containing short sarcomeres. Collectively, these data show that postmortem TnT proteolysis is sarcomere length-dependent and suggest that thick and thin filament overlap may influence the postmortem aging process in beef.

Sheep carcass composition estimated from Longissimus thoracis et lumborum muscle volume measured by in vivo real-time ultrasonography

The use of Longissimus thoracis et lumborum muscle (LM) volume measured in vivo by real-time ultrasonography (RTU) to estimate carcass composition was evaluated in 47 female sheep. Animals were scanned over six sites (7th, 9th, 11th and 13th thoracic vertebrae and 2nd and 4th lumbar vertebrae). After slaughter carcass weight (CW) and composition by dissection were determined. RTU volume measurements were calculated by multiplying the LM area at each site by the vertebra lengths. Equivalent measurements to those taken in vivo were obtained on the carcass using a digital camera and image analysis. The correlation between LM volume measured by RTU and in the carcass was high for all scans. LM volume was better in predicting carcass muscle than carcass fat. Lower determination coefficients were obtained between LM volume and carcass tissues expressed in % of CW. The best estimates of carcass tissues weights and proportions were obtained using the LM volume between the 2nd and the 4th lumbar vertebrae for all tissues. Multiple regression equations were fitted using live weight (LW) and LM volume to predict carcass composition. For all tissues, the best fit was obtained with two, three or four independent variables and the stepwise procedure was consistent in selecting LW to establish the prediction equations. Weights and proportions of muscle, subcutaneous fat, intermuscular fat and total fat were accurately predicted. These results indicate that Longissimus thoracis et lumborum muscle volume measured in vivo by RTU can be used to predict sheep carcass composition (muscle and fat).

Modeling lactation curves of "Barrosã" beef cattle with Wood's model

This study aimed to investigate the lactation curve properties of primiparous and multiparous Barrosã cows, using two different milking systems. A data set with 2518 daily milk yields of 15 primiparous (107 test day records by lactation) and 11 multiparous (83 test day records by lactation) cows was individually fitted with the Wood’s model by the application of a non linear procedure. Milk yield measurements were recorded using a weigh-suckle-weigh technique in half of the cows and the remaining cows were handmilked. Average daily milk yield of primiparous and multiparous suckled cows were 4.9 and 5.2 kg, respectively, while correspondent scores on milked cows were lower (2.4 and 3.0 kg). All 26 fitted lactations followed the typical curve shape with high goodness of fit. Analysis performed on Wood’s parameters indicated that milked cows have a peak yield of 3.5 and 4.6 kg reached at lactation day 23 and 16, for primiparous and multiparous, respectively. On the other hand, suckled cows reached later (56–63 d) their peak of lactation and the peak yield (5.3–5.7 kg) was greater than milked cows. The absence of the calf and the cow’s difficulty in adapting to the handmilking can explain differences between milked and suckled cows. Barrosã cows, in their traditional production system, have lactation yields of 805 and 843 kg in parities 1 and 2, respectively.

Estimation of carcase composition of goat kids from joint dissection and conformation measurements

Abstract The aim of this study was to develop equations to estimate percentages and carcase tissue weights of suckling goat kids by using cold carcase weight (CCW), carcase conformation measurements and joints tissue as independent variables. Carcases dissection data from 55 goat kids were used for regression analysis. Leg and shoulder muscle weight showed the highest positive correlations with carcase muscle weight (r = .98). Shoulder tissue weight showed the highest correlation with carcase bone weight (r = .97), carcase subcutaneous fat weight (r = .95) and carcase intermuscular fat weight (r = .95). Also, shoulder tissue percentage showed the highest correlation with carcase muscle percentage (r = .93) and carcase subcutaneous fat percentage (r = .90). CCW explained 95.9% of muscle weight carcase variability. The percentage of the variation explained in other tissues (bone, subcutaneous and intermuscular fat) was lower, but not negligible (89.6%, 60.7% and 48.7%, respectively). Chest circumference and carcase compactness presented the highest correlation with weight of carcase tissues, especially with muscle weight (r = .93), bone weight (r = .93 and .89, respectively), subcutaneous fat (r = .71 and .79) and intermuscular fat weight (r = .68 and .67). The results of this study support the conclusion that the shoulder tissue composition allows accurate estimation of the carcase composition. Also, CCW, chest circumference and carcase compactness measurements were good predictors of the weight of carcase tissues in goat kids, with the advantage to be non-destructive and easy to obtain.