[Glycerol supplementation in broiler rations with low crude protein content]

In connection with the utilization of glycerol, which could become available as a by-product of the fuel production from rapeseed the influence of glycerol feeding with rations of low crude protein content was proved. 61 male day old broiler chickens received ad libitum 8 experimental rations based on maize and soybean meal. The experimental design included 3 factors: 15 or 18% CP; supplementation of essential amino acids or not and a content of pure glycerol of 0 or 10%. During the experimental feeding of 23 days body weight gain, feed conversion ratio, N-balance and the intake and excretion of glycerol was obtained. At the end of the trial the utilization of 15N-methionine and the glycerol content of blood plasma, liver and breast muscle was estimated. Due to the low crude protein content of the rations the body weight gain and N-balance was very low (BWG day 1 to 23: 8.6 to 17 g/animal.d; N-balance day 19 to 23: 0.4 to 1.0 g N/animal.d). The supplementation of essential amino acids was the factor with the highest improving effect on the body weight gain, feed conversion ratio and N-balance. Especially at the begin of the trial animals which received 10% glycerol had have an increased feed intake. The excretion of the supplemented glycerol by excreta amounted to 26% of the intake. However, the glycerol content of the rations did not effect body weight gain, feed conversion ratio, N-balance or utilization of 15N-methionine significantly. The assumption of a saving effect on glucoplastic amino acids due to glycerol feeding could not be manifested. In the mean feeding of glycerol elevated the glycerol level in blood plasma in comparison to the basal level up to 23 times (from 0.6 to 13.6 mumol/ml) and in the breast muscle up to 19 times (from 0.4 to 7.5 mumol/g). Nevertheless, these values were lower than the basal level of glycerol in the liver (17.1 to 19.0 mumol/g), which was significantly increased by glycerol feeding to 128%. Regarding the utilization of glycerol as a by-product of the production of renewable fuels it can be concluded that on the basis of the estimated parameters 10% pure glycerol in broiler rations instead of corn starch is without adverse effects.