Nutritional value of cereal grains for animals02 April 2008
The energy value of cereal grains for livestock varies widely between grains and animal species. For example, the digestible energy content for pigs of wheat and barley grain ranges from 13.3 to 17.0 MJ/kg and 11.7 to 16.0 MJ/kg, respectively. However, the digestible energy content of sorghum grain for pigs shows little variation from 17.0 to 18.0 MJ/kg. Hughes & Choct reported a similar wide range across some grains in apparent metabolisable energy (AME) values for broiler chickens, being from 10.4 to 15.9 MJ/kg for wheat, 10.4 to 13.5 MJ/kg for barley and 8.6 to 16.6 MJ/kg for triticale. The chicken AME values for sorghum and maize, again, show a small range from only 15.6 to 16.1 MJ/kg, with a similar small range for oat grain (11.8 to 12.4 MJ/kg). Significant variation exists between grains in the digestibility of starch within the rumen of cattle, being 0.92 for oat grain, 0.65 for maize and 0.62 for sorghum starch. There are also striking differences between animal species in their capacity to digest cereal starch. The digestibility of sorghum starch across the whole digestive tract of poultry is extremely high (0.99) compared with 0.87 for cattle and 0.30 for horses. Reasons for these observed differences in the energy value of cereal grains are discussed.