BODY-COMPOSITION AND PROTEIN AND FAT ACCRETION IN VARIOUS BODY COMPONENTS IN GROWING GILTS FED DIETS WITH DIFFERENT PROTEIN-LEVELS BUT ESTIMATED TO CONTAIN SIMILAR LEVELS OF IDEAL PROTEIN

A comparative slaughter technique was used to determine the effect of dietary protein levels on body composition and protein and fat accreti on in various body components in Yorkshire gilts. Diets were formulate d to contain similar levels of ideal protein. Eight gilts were slaught ered at 20 kg BW to determine initial body composition. Twenty-four gi lts were assigned to each of three dietary treatments (16.6, 15.0, and 13.0% CP) during the growing period (20 to 55 kg BW). During the fini shing period (55 to 100 kg BW), dietary CP levels were reduced by appr oximately two percentage units. Eight gilts per treatment were slaught ered at 55 kg BW, and the remaining pigs were slaughtered at 100 kg BW . At slaughter, the pigs were divided into three components: carcass, empty gastrointestinal tract, and other non-carcass parts. Half of the carcass was further dissected into retail cuts. None of the carcass r etail cuts was affected (P > .10) by the dietary CP levels, except tri mmed ham was smaller (P < .05) in gilts fed the 13% CP growing and 11% CP finishing diets. Fat content in the empty body (P = .12) and in th e carcass (P = .06) was highest and the empty body water accretion rat e was lowest (P = .05) in gilts fed the 13% CP growing and 11% CP fini shing diets. Other aspects of chemical body composition, protein and f at accretion rates, and estimated lean yields were not affected by die tary CP level (P > .10).