High concentrations of guar meal in broiler chicken diets reduce body weight and feed efficiency. The increased intestinal viscosity that is responsible for reduced measures of performance results from residual guar gum present in guar meal. Two experiments were designed to study the effects of 2 guar meal fractions at 3 different concentrations, germ (0, 5.0, and 7.5%) and hull (0, 2.5, and 5.0%), and the effectiveness of a beta-mannanase at three levels (0, 1x, and 4x; 1x = 1.09 x 10(5) units/ kg) on broiler growth and feed conversion. Growth and performance were measured as a function of intestinal viscosity. Addition of the germ fraction to rations did not reduce body weight, although feed conversion ratio was increased at 7.5% of the diet. Intestinal viscosity also increased significantly at this level. Enzyme addition significantly reduced intestinal viscosity. Due to an interaction that was present between hull and enzyme concentration, each treatment was compared separately. Inclusion of the hull fraction significantly reduced body weight at both levels of inclusion and increased feed conversion ratio at 5% inclusion. Addition of the enzyme significantly increased body weight and reduced feed conversion ratio in diets containing guar hull fractions. Supplementation of beta-mannanase to feeds containing either fraction of guar meal reduced intestinal viscosity and alleviated the deleterious effects associated with guar meal feeding.
Guar gum production yields a high protein guar meal that can be subdivided into germ and hull fractions. Feeding high concentrations of guar meal reduces body weight and feed efficiency in chickens due to the presence of a residual guar gum. Two experiments determined the upper feeding levels of guar meal and the hull and germ fractions in broiler chickens. An industrial source beta-mannanase (Hemicell) also was fed in combination with guar meals. Experiment 1 utilized a 3 x 4 factorial design to feed broiler chickens diets containing guar germ, guar hull, or guar meal at 4 levels (2.5, 5.0, 7.5, and 10.0%) compared with a negative control diet. Results indicated that any of the 3 guar meals could be fed at a 2.5% dietary inclusion rate without adversely affecting broiler chicken growth to 6 wk of age. In experiment 2, a 4 x 2 factorial design consisting of the 3 by-products meals at 5% inclusion and soybean meal control with and without enzyme tested whether Hemicell could increase inclusion rates without decreasing broiler growth or feed consumption to 6 wk of age. Addition of Hemicell to feed had no effect on measures of growth in chickens fed the control diet. Hemicell significantly improved feed:gain ratio of diets containing 5% of each fraction of guar meal versus the untreated diets. Feed:gain ratio for the Hemicell-treated 5% germ fraction diet was improved to control diet levels. Results indicated that the upper feeding level of guar meal and germ and hull fraction of guar meal is 2.5%, and addition of beta-mannanase (Hemicell) increases the upper feeding level for the germ fraction to 5%.
High concentrations of guar meal in poultry diets deleteriously affect growth, feed intake, and digesta viscosity. These effects are attributed to residual gum in the meal. A 2 x 5 factorial experiment investigated the impacts of two guar meal fractions (germ and hull) at five inclusion levels (0, 2.5, 5.0, 7.5, and 10.0%) on intestinal viscosity, measures of growth, and feed conversion in broiler chickens fed to 20 d of age. Growth and feed conversion ratio were not affected by inclusion of as much as 7.5% of the germ fraction into poultry diets, while inclusion of the hull fraction reduced growth at all concentrations. The hull fraction increased intestinal viscosity at all inclusion levels fed, although feed conversion was not affected until the inclusion rate exceeded 5.0%. The germ fraction significantly increased intestinal viscosity at 7.5 and 10% inclusion rates. When germ fraction was fed, relative organ weights remained constant through all concentrations except for the ventriculus and duodenum at 7.5 and 10% inclusion levels. Relative pancreas weight was significantly increased at the 10% level of the hull fraction. Increases in intestinal viscosity corresponded with growth depression. These results suggest that residual gum was responsible for some deleterious effects seen when guar meal was fed. The germ fraction was a superior ingredient when compared with the hull fraction. The guar meal germ fraction constituting as much as 7.5% of the diet supported growth and feed conversion measures similar to those observed with a typical corn-soybean poultry ration.
A complete nutrient characterization of three possible products of guar bean processing does not apparently exist in the literature. Guar meal is a high-protein byproduct produced during extraction of galactomannan gum from the guar bean. During the extraction process, two fractions are produced (germ and hull). Germ and hull fractions are usually combined to form the marketed product, guar meal. Analyses characterized the nutrient, trypsin inhibitor, and galactomannan gum content of the three guar meal byproducts to determine which fraction is more valuable as an ingredient in poultry diets. Analyses indicated that the germ fraction is most appropriate for inclusion in poultry diets. Trypsin inhibitor activity previously reported as an antigrowth factor associated with guar meal was negligible and not considered to be a significant factor limiting its use in poultry feeds.
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