Metabolizable Energy Value of Guar Meal for Broiler Chicks can be Influenced by Method of Determination

Guar meal (GM) is mostly used as a protein source in poultry diets. However it contains a broad range of galactomannan gum and some other anti-nutritional factors which decrease its metabolisable energy (ME) value. It is also showed that technique to measure metabolisable energy influences validity of results. In this regard, Sibbald (1987) showed that in comparison with the total collection method, the use of markers to determine ME and digestibility values avoids errors associated with inaccurate measurement of feed intake, excreta output, and contamination of excreta. Present study was carried out to determine ME of GM and soybean meal (SBM) using total collection and marker methods in 35 day-old broiler chickens. In the first experiment a total of thirty six 35 day-old broiler chickens (3 groups of 12 birds each) were housed individually in collection cages. The birds were fed three experimental diets including a corn-soybean meal reference diet and two test diets containing 30% GM and 30% SBM substituted in expense of corn and soybean of the reference diet. The excreta were collected daily (from 35 to 39 d) for each bird and stored at -20°C until further processing. Total feed intake of each bird was also measured during collection period. Chromic oxide (3g/kg) was added to the diets as an external marker. In the second experiment total of ten 35-day broiler chickens (2 groups of 5 birds each) were placed in individual metabolic cages to determine TME of guar meal according to McNab and Blair (1988).

Significant differences were found in AME and AMEn values between GM and SBM due to the applied method (P<0.05). Both AME and AME_n values for GM and SBM determined by total collection method were higher than marker method (P<0.05). In addition, the AMEn value for SBM was significantly (P<0.05) higher than GM in total collection assay (2496 vs. 2168 kcal/kg). On the other hand, in precision feeding experiment, TME value for GM was higher than SBM (2702 vs. 2551.5 kcal/kg). The findings of the current study indicate that high guar gum affect AME and AME_n values in broiler chickens. In addition, according to SEM of the means it seems than total collection method is a more reliable assay for metabolisable energy determination of GM and SBM.

Sibbald IR (1987) Canadian Journal of Animal Science 67: 221-300.
McNab JM & Blair JC (1998) British Poultry Science 29: 697-707.