39 Determination of net energy and nitrogen balance in group-housed pigs fed diets containing varying levels of starch and fiber.

Abstract An experiment was conducted to determine net energy (NE) and nitrogen (N) balance in growing pigs fed diets containing varying levels of starch and fiber. Five diets contained corn and soybean meal (SBM) and decreasing inclusion rate of corn distillers dried grains with solubles (DDGS; i.e., 35% to 7%). An additional diet contained corn, SBM, and 10% corn starch to achieve a high starch and a low fiber concentration. Ratios between digestible amino acids and metabolizable energy (ME) in all diets were adjusted to meet requirements. A total of 48 pigs (initial weight: 43.99 ± 8.38 kg) were used in two blocks of 24 pigs. The 24 pigs were assigned to 6 calorimeter chambers with 4 pigs per chamber. Chambers in each block were allotted to a 6 × 3 incomplete Latin square design with 6 diets and 3 periods. Therefore, each block provided 3 replicates per diet for a total of 6 replicates for each diet from the 2 blocks. Pigs had ad libitum access to feed and water. Diets were fed for 13 days in each period. After a 7-day adaptation period, O2 consumption and CO2 and CH4 productions were measured for 6 days to calculate total heat production. Fecal and urine samples were quantitatively collected for 6 days and analyzed for gross energy (GE) and N. The statistical model included diet as fixed effect and group, period, and chamber as random effects. Contrast coefficients were used to determine the linear and quadratic effects of increasing dietary starch in diets. Results indicated that the ATTD of GE and dry matter (DM) was increased (quadratic; P < 0.05) by increasing starch and decreasing fiber in diets (Table 1). Concentration of digestible energy in diets tended to be reduced (linear; P = 0.069), but ME and NE in diets tended to be increased (linear; P < 0.10) by increasing dietary starch and decreasing fiber. The ATTD of N and retention of N (% intake and % absorbed) were increased by increasing dietary starch (linear; P < 0.001). In conclusion, increasing starch and reducing fiber in diets increased digestibility and utilization of energy and N in group-housed pigs. Further research is warranted to determine energy digestibility and NE in diets containing varying levels of dietary fat and protein.