EFFECTS OF BARLEY HULLS, DIETARY PROTEIN LEVEL AND WEIGHT OF PIG ON DIGESTIBILITY OF CANOLA MEAL FED TO FINISHING PIGS

Abstract

A factorial digestibility experiment with three dietary levels of canola meal (CM) (0, 15, 30%), two levels of barley hulls (0, 25%) and two basal diets (approximately 10 and 19% crude protein, CP) was conducted using crossbred pigs over the weight range 45 – 90 kg. Diets contained 0.5% chromium oxide as a fecal marker. Inclusion of barley hulls improved the apparent digestibility of dietary CP (83.3% with hulls vs. 81.9% without hulls) and of corn CP (74% for corn, 76% for corn + hulls). True digestibility of CP in corn was also improved (75% for corn, 90% for corn + hulls). The energy and CP components of barley hulls were 40 and 57% digestible, respectively. The digestibility values for CM were: CP 80% (apparent) and 85% (true); energy 68%; nonprotein energy 55% and these were not affected by the presence of barley hulls. Digestibility improved as the pigs matured; each 10-kg weight increase was associated with 0.65 and 0.37 percentage units increase in digestibility of CP and energy, respectively, but these values may be lower than those normally encountered because of the use of casein for adjusting dietary CP levels in this experiment. It is suggested the barley hulls may possess two opposing properties, one that depresses digestibility of protein by increasing metabolic fecal nitrogen output and which is related to the neutral detergent fiber component, and another that in some way enhances the digestibility of protein. Key words: Canola meal, barley hulls, protein level, digestibility, pigs