Gross energy

Effect of sample preparation method and drying method on the concentration of energy in urine and the concentration of metabolizable energy in diets fed to pigs

To obtain accurate values for metabolizable energy (ME) in diets and ingredients, an accurate estimation of gross energy (GE) in urine is required. Urine samples are often prepared following the freeze-dried cotton-plastic bag method and GE is determined by the ignition of the sample in a bomb calorimeter. However, the concentration of GE in urine can also be determined by dripping urine on a cellulose pellet, which can then be ignited in a bomb calorimeter. Alternatively, energy in urine can be calculated from the concentration of N in urine assuming that all energy in urine originates from N. The latter 2 methods may be less expensive and less time consuming than using the freeze-dried cotton-plastic bag method. Likewise, oven drying instead of freeze drying of samples may reduce time and cost of the drying procedure. However, to our knowledge, no data comparing values for GE in urine and ME in diets among different sample preparation and drying methods are available. Therefore, the objective of this study was to test the hypothesis that there are no differences in GE of urine or ME values of diets among sample preparation methods (freeze-dried cotton-plastic bag, undried cellulose pellet, or N value method). The second hypothesis was that drying method (freeze drying or oven drying) of cotton-plastic bag urine samples from pigs do not influence analyzed the GE in urine or calculated ME in diets.

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Nutritional composition, gross energy concentration, and in vitro digestibility of dry matter in 46 sources of bakery meals

Yanhong Liu, Rajesh Jha, and Hans H. Stein. 2018. Nutritional composition, gross energy concentration, and in vitro digestibility of dry matter in 46 sources of bakery meals. J. Anim. Sci. 2018.96:4685–4692. Link to full text.

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