The Impact of Feeding Diets of High or Low Energy Concentration on Carcass Measurements and the Weight of Primal and Subprimal Lean Cuts

Pigs from four sire lines were allocated to a series of low energy (LE, 3.15 to 3.21 Mcal ME/kg) corn-soybean meal-based diets with 16% wheat midds or high energy diets (HE, 3.41 to 3.45 Mcal ME/kg) with 4.5 to 4.95% choice white grease. All diets contained 6% DDGS. The HE and LE diets of each of the four phases were formulated to have equal lysine:Mcal ME ratios. Barrows (N = 2,178) and gilts (N = 2,274) were fed either high energy (HE) or low energy (LE) diets from 27 kg BW to target BWs of 118, 127, 131.5 and 140.6 kg. Carcass primal and subprimal cut weights were collected. The cut weights and carcass measurements were fitted to allometric functions (Y = A $CW^B$) of carcass weight. The significance of diet, sex or sire line with A and B was evaluated by linearizing the equations by log to log transformation. The effect of diet on A and B did not interact with sex or sire line. Thus, the final model was cut weight = (1+$b_D$(Diet)) A($CW^B$) where Diet = -0.5 for the LE and 0.5 for HE diets and A and B are sire line-sex specific parameters. Diet had no affect on loin, Boston butt, picnic, baby back rib, or sparerib weights (p>0.10, $b_D$ = -0.003, -0.0029, 0.0002, 0.0047, -0.0025, respectively). Diet affected ham weight (bD = -0.0046, p = 0.01), belly weight (bD = 0.0188, p = 0.001) three-muscle ham weight ($b_D$ = -0.014, p = 0.001), boneless loin weight (bD = -0.010, p = 0.001), tenderloin weight ($b_D$ = -0.023, p = 0.001), sirloin weight ($b_D$ = -0.009, p = 0.034), and fat-free lean mass ($b_D$ = -0.0145, p = 0.001). Overall, feeding the LE diets had little impact on primal cut weight except to decrease belly weight. Feeding LE diets increased the weight of lean trimmed cuts by 1 to 2 percent at the same carcass weight.