EFFECT OF CATTLE BREED, AGE AND TRANSPORTATION STRESS ON GROWTH, MEAT YIELD AND QUALITY, AND BLOOD BIOCHEMICAL PARAMETERS

Abstract

The study was conducted to evaluate the physiological bases for tenderness, level of stress, carcass and beef characteristics from Arsi, Borana, Harar and Holstein Frisian crosses finished on the same feeding system. A total of 24 bulls with age categories of 2-3 and 4-5 yeas were used in complete block design for the experiment. A total mixed ration with roughage (60%) which contain grass hay and wheat straw, and concentrate (40%) which contained wheat bran, noug (gucia abysica) cake, maize grain, limestone, salt and ruminant premix was provided at 3% of their body weight during experimental periods. Simple linear regression models were used to explore the relationship between live body weight change and change in Body condition score as well as seven linear body measurement for all age groups were evaluated. The result of the study revealed that the average daily weight gain of the four breeds range from 0.49 to 0.71 kg. Feed conversion efficiency also ranges from 0.11 – 0.15. An average change for a unite of body condition score was equivalent to 20.3, 20.61, 22.42 and 27.78kg for Borana, Arsi, Harar and HF-crossbred bulls respectively. BCS was significantly (P<0.01) influenced by breeds. There was a significant and positive strong association between change in BW, change in BCS , total topline, neck length, heart girth, flank circumference and rump length with correlation coefficient (r) ranging from 0.57 to 0.97. Partial budget analysis revealed that higher (P<0.01) net profit of 7,380.47 ETB per bull was obtained for Borana bulls followed by Harar, Arsi and HF Crossbred bulls with net profit of 5,406.86, 5193.29 and 3,384.98 ETB, respectively. The average slaughter weight, hot carcass weight, cold carcass weight, shrink loss, commercial dressing and true dressing percentage were 179.1kg, 86.8kg, 82.7kg 4.7%, 48.8% and 78.3%, respectively. Total edible and nonedible offal were significantly (P<0.01) influenced by breed and age. Pelvic fat was significantly (P<0.01) influenced by breeds. Meat yield percentages of Arsi, Boran, Harar and crossbreed were 78.1%, 77%, 72.8% and 77.2% respectively. Arsi bulls attain the highest (78%) meat yield at an early age but decrease by 0.713 rates as age advanced whereas the meat yield from other breeds showed an increment in meat yield percentage with the rate of 1.98, 1.1 and 0.1 for HF cross, Borana and Harar bulls, respectively. Yield from fore shank, sirloin, top and bottom sirloin primal cuts were affected by breeds. Arsi breed has higher meat to bone ration over HF crossbreed. Retailed meat yield was significantly (P<0.001) predicted from rib area and subcutaneous fat thickness (P<0.001) with a coefficient of determination 61%, coefficient of determination had increased when live animal trait and primal cuts were included in the model by89.56% and 94.78%, respectively. Myoglobin analysis revealed that meat from Harar bulls has a higher (P<0.05) Mb xviii concentration, red in color and chroma than meat from Borana, Arsi and crossbred bulls. The meat from the older age group recorded higher (P<0.05) Mb concentration, pHu, TBARS, redness (a*) and chroma values than younger age group. The extent of lipid oxidation was significantly influenced (P<0.001) by length of days stored in the refrigerator with 0.185, 0.310 and 0.688 mg/kg for the third, sixth and the tenth day of storage, respectively. Evaluation of meat color revealed meat from Harar bulls had higher (P<0.01) redness (a*) and chroma value. Beef from Borana and HF-cross bulls had significantly longer (P<0.01) sarcomere lengths than Arsi bulls. The sarcomere length was significantly (P<0.01) decreased as the age of animals increased. Meat proximate composition was significantly (P<0.001) influenced by age and breeds of bulls. Beef from HF-crossbred and Arsi bulls contained lower fat and higher protein percentage compared to beef from Borana and Harar bulls. Beef from younger (2-3 years) bulls contained higher protein and lower fat percentage compared bulls 4-5 years of age. Instrumental and sensory tenderness were significantly (P<0.01) influenced by breed and age. All experimental bulls produced very tender beef with Borana bulls recording lower instrumental value over beef from Harar and Arsi bulls. Beef from bulls 2-3 years of age had exhibited lower instrumental value over beef from bulls 4-5 years of age. Water holding capacity and thawing loss were significantly (P<0.05) influenced by breed. Moreover, thawing loss was a significantly (P<0.05) influenced by interaction of breed and age. The experimental bulls were in moderate tolerance towards transportation weight loss and good resilience in weight recovered after transportation. Serum glucose, protein, LDH and cortisol were significantly (P<0.05) influenced by cattle breeds both before loading from their respective local markets and after unloading at experimental site at Haramay University. Glucose and cortisol concentration was significantly (P<0.05) elevated after transportation of experimental bulls. There was a significant (P<0.05) difference between breeds on the value of CK and LDH evaluated during experimental period on the farm while the value of glucose, protein, and cortisol were not significantly different. CK was significantly (P<0.05) elevated in all experimental bulls due to transportation stress. Harar breed bulls show more resistance in serum glucose and cortisol change due to transportation stress. All blood biochemicals did not significantly influenced by cattle age. The experimental bulls were in moderate tolerance towards transportation weight loss and good resilience in recovering from transportation stress. Generally, it was concluded that all experimental bulls in the current study produced high quality beef that can be competent in the world meat market interms of its very tender beef, stable meat color and oxidative rancidity. Fattening HF-crossbred bulls was advantageous in beef production. It was recommended that the effect of higher concentrate supplement on growth of HF-Crossbred bulls need to be investigated. Moreover, the contribution of muscle fiber type, collagen concentration and endogenous proteins to the quality of beef form local and crossbreed cattle need to be further investigated in future studies.