Allometric Examination of Visceral Organ Size, Carcass Characteristics, and Blood Clinical Chemistry of Pigs Fed 20% DDGS Diets from 30 to 150 Kg

Visceral organs (VO) are essential for ingestion, digestion, and metabolism of dietary nutrients. Previous allometric studies report that VO are relatively early-developed compared to the development of whole body weight. However, an increase of VO weights has been observed in recent years concurrent with the decrease of backfat thickness in modern genetics. Therefore, the objective of this study was to assess serial allometric changes in VO size, carcass characteristics, and blood clinical chemistry of pigs from 30 to 150 kg. A group of 116 crossbred pigs (97.8 ± 0.3 d of age) were fed corn-soybean meal-DDGS diets formulated to meet or exceed NRC (2012) requirement estimates. A consistent level of 20% DDGS was included in diets throughout the experiment. At the beginning of the experiment (30 kg) and at 50, 75, 100, 125, and 150 kg, 8 pigs (4 female and 4 male pigs) were slaughtered for tissue collection (liver, heart, spleen, pancreas, kidney, and lung) and carcass measures. All data were subject to GLM procedure of SAS. Hot carcass weight, dressing percentage, backfat depth, loin muscle area, and loin muscle depth at tenth rib, as well as carcass lean tissue mass, increased with increasing BW (linear, P < 0.0001). However, the percentage of carcass lean mass relative to hot carcass weight decreased as BW increased (linear, P < 0.0001). Absolute weight of liver (624, 1,025, 1,455, 1,633, 1,776, and 2,018 g) and heart (151, 226, 292, 351, 421, and 483 g) increased as BW increased (linear, P < 0.0001), as did the absolute weight of other VO (linear, P < 0.0001). In contrast, the relative weight of VO to BW decreased as BW increased (linear, P < 0.0001). Total serum protein and albumin (linear, P < 0.0001), as well as globulin (quadratic, P = 0.001) increased with increasing BW. Serum minerals (calcium, phosphorous, and potassium) and glucose levels decreased (linear, P < 0.01), whereas serum triglyceride levels increased with increasing BW (linear, P = 0.0003). Serum cholesterol (linear and quadratic, P < 0.0001), urea nitrogen (quadratic, P = 0.001), and creatinine (linear, P < 0.0001) levels increased with increasing BW. The activity of serum alkaline phosphatase decreased (linear and quadratic, P < 0.05), but the activity of creatine kinase and lactate dehydrogenase (linear, P < 0.05) increased with increased BW. In conclusion, VO weight, carcass characteristics, and blood clinical chemistry of pigs are dependent on BW when measured.