Effect of dietary supplementation of crude glycerol or tallow on intestinal transit time and utilization of energy and nutrients in diets fed to broiler chickens

The objective of this experiment was to investigate the effect of dietary supplementation of crude glycerol or tallow on intestinal transit time and apparent total tract digestibility (ATTD) of energy and nutrients in diets fed to broiler chickens. A total of 36 three-week-old male broiler chickens (initial BW=780.5±27.0 g) were randomly allotted to 1 of 3 dietary treatments with 6 replicated cages consisting of 2 birds each. A basal diet was formulated to be adequate in energy and nutrients. Two additional diets were prepared by mixing 95.0% of the basal diet with 5.0% crude glycerol or 5.0% tallow. Birds were fed the experimental diets for 10 d, including 5 d of adaptation period and 5 d of collection period. Chromic oxide (0.3%) and ferric oxide (0.3%) were added to the diets at the start and conclusion of the collection period, respectively. Intestinal transit time was determined for each marker as the difference between the time of feeding the diet containing each marker and the time of the first appearance of each marker in excreta. Results indicated that intestinal transit time was greater (P<0.01) for birds fed the diet containing 5.0% tallow than for birds fed the basal diet, but birds fed the diet containing 5.0% crude glycerol had similar intestinal transit time to birds fed the basal diet. The diet containing 5.0% tallow had greater (P<0.05) ATTD of gross energy (GE), crude protein (CP), and crude fat than the basal diet. The diet containing 5.0% crude glycerol had greater (P<0.05) ATTD of dry matter (DM) and GE than the basal diet, but no differences were observed for the ATTD of CP, crude fat, crude ash, and phosphorus (P) between these 2 diets. In conclusion, dietary supplementation of crude glycerol has no effects on intestinal transit time of birds and nutrient utilization in diets. Inclusion of tallow in diets increases intestinal transit time of birds and improves nutrient utilization of the diet.