| Serum was collected immediately after exsanguination from cattle (n = 286) randomly selected from commercial packing plants in Nebraska and Texas with the purpose of determining if serum chemistry profiles can be used as an on-line predictor of tenderness for classifying beef carcasses into "tender" or "tough" palatability groups. Serum was analyzed for the following constituents: albumin, alkaline phosphatase, amylase, aspartate, aminotransferase (AAT), beta-hydroxy butyric acid, calcium (Ca), chloride, cortisol (CORT), creatinine, creatinine phosphokinase, gamma-glutamyltransferase, globulin, glucagon, glucose, magnesium, non-esterified fatty acids (NEFA), phosphorus (P), potassium (K), sodium (Na), total bilirubin, and total protein. After a 24 h chill, carcass traits were measured and one longissimus steak from the strip loin was collected from each side of each carcass and used for 2-d and 14-d slice shear force (SSF 14) determination. "Tender" carcasses (SSF14 < 20.0 kg) had higher (P < 0.05) hot carcass weights, USDA Quality Grades, and a* values and lower (P < 0.05) dark cutting discount, pH, and 2-d slice shear force values than tough carcasses. Tender carcasses also had lower (P < 0.05) AAT, Ca, NEFA, P, K, and Na levels and higher (P < 0.05) CORT levels than tough carcasses. Logistic regression models were developed to sort carcasses into either a "certified tender" or "tough" groups with threshold value of 20 kg for SSF14. The model utilizing only USDA Quality Grades resulted in a 61.5% certification of carcasses with an 8.0% error rate (occurrence of tough steaks in certified tender group). In terms of ease of application and minimizing error rates, the best overall model using serum profiles utilized CORT, NEFA, and K and resulted in a certification rate of 65.4% and a 5.3% error rate. This study found that blood chemistry displays some usefulness in predicting tenderness. |
