Net energy content of hybrid rye fed to growing pigs and effects of particle size on energy values

Abstract

An experiment was conducted to determine the digestible energy (DE), metabolizable energy (ME), and net energy (NE) contents of hybrid rye fed to growing pigs using indirect calorimetry and to investigate the effects of particle size on energy values. Thirty growing barrows (18.06 ± 0.83 kg initial body weight) were individually housed in metabolism crates and randomly allotted to one of five dietary treatments to give six replicates per treatment. Two hybrid rye varieties (Bono and Gatano) were ground in a hammermill mounted with a 4.0-mm or 3.2-mm screen to obtain coarse and fine particle size, respectively. Dietary treatments included a corn-soybean meal basal diet and four additional diets containing 300 g/kg of the test ingredients in a 2 × 2 factorial based on hybrid rye variety (Bono or Gatano) and particle size (Coarse or Fine). Pigs were fed experimental diets for 15 days, including 10 days for adaptation and 5 days for total fecal and urine collection to determine the DE and ME of the experimental diets. Pigs were then moved into indirect calorimetry chambers to determine 24-h heat production and 12-h fasting heat production. All data were analyzed using the MIXED procedure of SAS with the individual pig as the experimental unit. The geometric mean diameter (Dgw) for coarsely versus finely ground Bono and Gatano were 1111 versus 594 µm and 1210 versus 717 µm, respectively. The coefficient of apparent total tract digestibility (CATTD) of dry matter (DM) and gross energy (GE) were greater (P < 0.05) in diets containing finely than coarsely ground hybrid rye. The DE and ME of finely ground hybrid rye were greater (P < 0.05) than those of coarsely ground hybrid rye, and the NE of finely ground hybrid rye tended to be greater (P = 0.084) than that of coarsely ground hybrid rye. No differences were observed for the DE, ME, and NE contents between Bono and Gatano. The determined NE for coarsely and finely ground Bono were 11.06 and 11.77 MJ/kg DM, and the respective NE values for coarsely and finely ground Gatano were 11.09 and 11.57 MJ/kg DM. In conclusion, the energy values of different hybrid rye varieties might be comparable. Particle size reduction could significantly improve the DE and ME values of hybrid rye fed to growing pigs, while the NE value was only numerically improved.