Some Factors Affecting True Metabolizable Energy of Fababeans (Vicia faba L.)

Abstract

Two experiments were conducted using adult Single Comb White Leghorn cockerels to estimate the effect of amount of feed administered and the duration of the excreta collection period on the TMEn values of raw and autoclaved fababeans, and fababean fractions (dehulled beans and hulls). In the first experiment, birds were given 30 g of each feedstuff in the second experiment, 30 or 80 g. Excreta were collected for 48 h in the first experiment and over a 96-h period in the second experiment. The results suggested that a 48-h collection period was adequate to allow for clearance of autoclaved and dehulled fababeans from the gastrointestinal tract; however, it may not have been of sufficient duration to allow for clearance of raw fababeans and particularly of fababean hulls. A 96-h collection period seemed to be of sufficient duration to allow for excretion of all fababean fractions except raw hulls. As a result, the calculated TMEn values of raw fababeans and fababean hulls when excreta were collected for 48 h were higher than those calculated from excreta collected for 96 h. Autoclaving apparently increased the rate of passage of fababeans, particularly that of fababean hulls. The amount of feedstuff administered did not affect the TMEn value of autoclaved fababeans, but it did affect the TMEn value of raw fababeans, probably because of tannins. The TMEn (MJ/kgDM, 1 MJ= .239 Mcal) of raw fababeans was 10.7 when fed at 30 g and 9.4 when fed at 80 g. The TMEn of dehulled fababeans, autoclaved fababeans, and autoclaved fababean hulls was 14.0, 12.2, and .004 MJ/kg DM, respectively.