36 Greenhouse gas emission, nitrogen balance, and ileal digestibility of amino acids and acid hydrolyzed ether extract in diets containing different inclusion rates of hybrid rye fed to growing pigs.

Abstract Two experiments were conducted to test the hypothesis that greenhouse gas emission, nitrogen (N) balance, and ileal digestibility of amino acids (AA) and acid hydrolyzed ether extract (AEE) in diets are not affected by inclusion of hybrid rye in diets fed to growing pigs. Three diets were prepared and fed to pigs in both Exp. 1 and 2. A control diet containing corn and soybean meal as energy sources was formulated. Two additional diets were formulated by replacing 50% or 100% of the corn in the control diet with hybrid rye. All diets contained crystalline AA, minerals, and vitamins at or above the requirements for growing pigs. In Exp. 1, a total of 24 pigs (initial body weight: 52.38 ± 2.52 kg) were used. The 24 pigs were assigned to 6 calorimeter chambers with 4 pigs per chamber. Chambers were allotted to a replicated 3 × 3 Latin square design with 3 diets, 6 chambers, and 3 periods to have 6 replicates per diet. 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. Fecal and urine samples were quantitatively collected for 6 days and analyzed for N. In Exp. 2, twelve cannulated pigs (average body weight = 47.78 ± 4.40 kg) were allotted a quadruplicated 3 × 2 incomplete Latin square design with 3 diets and 2 periods in each square, to have 8 replicates per diet. An N-free diet was also formulated and fed to pigs during an additional period to determine the basal endogenous losses of AA. For both Exp. 1 and 2, the statistical model included diet as fixed effect and square, period, and pig within square as random effects. Contrast coefficients were used to determine linear effects of increasing hybrid rye in the diets. Results from Exp. 1 indicated that consumption of O2 and production of CO2 and CH4 and N balance were not affected by dietary treatment, however, the respiratory quotient of pigs in the fed state was reduced (linear; P = 0.047) by increasing hybrid rye in diets (Table 1). Results from Exp. 2 indicated that the ileal digestibility of AEE and most AA was reduced (P < 0.05) by increasing hybrid rye in the diets. In conclusion, replacing corn with hybrid rye in the diets for growing pigs did not impact greenhouse gas emissions or N balance, but it reduced the ratio of CO2 produced to O2 consumed and the digestibility of AEE and AA. Therefore, hybrid rye can be used as an alternative to corn without negatively impacting the environmental footprint of pig production systems.