Effect of dietary energy levels and phase feeding by protein levels on growth performance, blood profiles and carcass characteristics in growing-finishing pigs
Carcass characteristics
At the end of experiment, 3 pigs from each treatment group were selected and slaughtered for the carcass analysis. Pork samples were collected from nearby 10th rib on right side of carcass. Because of chilling procedure, 30 min after slaughter was regarded as initial time. The pH was measured at 0, 3, 6, 12 and 24 h and meat color of longissimus muscle was determined at initial time and 24 h after initial time. The pH was measured using a pH meter (Model 720, Thermo Orion, U.S.A.) and pork color was determined by CIE color L*, a*, and b* values using a CR300 (Minolta Camera Co., Japan). Chemical analysis of pork samples were conducted by the method of AOAC [1]. Water holding capacity of pork was measured by centrifuge method. Three samples of longissimus muscles were ground and sampled in filter tube, than heated in water bath at 80 °C for 20 min and centrifuged for 10 min at 2,000 rpm at 10 °C (Eppendorf centrifuge 5810R, Germany). To calculate the cooking loss, longissimus muscles were packed with polyethylene bag and heated in water bath until core temperature reached 72 °C and weighed before and after cooking. After heated, samples are cored (0.5 in. in diameter) parallel to muscle fiber and the cores were used to measure the shear force using a salter (Warner Barzler Shear, USA). Water holding capacity, shear force and cooking loss of pork were analyzed in Foundation of Agri. Tech. Commercialization Transfer. The amino acid contents in loin meat were determined by ion-exchange chromatography (Amino Acid Analyzer L-8900, Hitachi, Tokyo, Japan) with post-column derivatization with ninhydrin. Performic acid was used in oxidizing amino acids and neutralized with sodium citrate dihydrate, and then hydrolyzed with 6 N HCl for 22 h at 110 °C to be liberated from the protein. Amino acids were quantified with the internal standard method (amino acid mixture standard solution Type H, Wako Chemical, Osaka, Japan; L-cysteic acid, Tockyo Chemical Industry, Tokyo, Japan; DL-methionine sulfone, Sigma, Missouri, US) by measuring the absorption of reaction products with ninhydrin at 570 nm.
Backfat thickness at P2 position (mean value from both sides of the last rib and 65 mm away from the backbone) of finishing pigs was measured using ultrasound device (Lean-meter, Renco Corp., Minneapolis, US) at the end of feeding trial (13 week).