The effect of previous exposure to dietary microbial phytase on the endogenous excretions of energy, nitrogen and minerals from turkeys
Résumé
1. A precision feeding experiment was conducted with turkeys, which were previously fed diets with or without phytase, to study the effects on the excretions of endogenous energy (EEL), nitrogen (ENL), amino acids (EAAL) and minerals. 2. Female turkeys (BUT 6), which had been fed one of four experimental diets (low P maize-soy diets (control, C), C + 250 international units of phytase per kilogram diet (FTU), C + 500FTU and C + 2500FTU) were used in this study. All birds were fasted and then fed 50ml of glucose solution at 46 days of age. Birds were allocated to individual metabolism cages in a randomised block design with eight replicates for each of the four previously fed diets. 3. The response of EEL and ENL to phytase pre-exposure was a linear function (P<0.05). An increase of 100 FTU reduced the EEL and ENL by approximately 1.6 kJ and 20 mg, respectively. The results suggest that a minimum activity of phytase of 500 FTU was needed to initiate the reduction of these losses. 4. Pre-exposure to phytase reduced the EAAL that was described best as a linear response (P<0.05) with increasing phytase dose in the pre-study period. An increase of 100 FTU reduced the losses of total endogenous amino acids by approximately 225 mg. 5. In contrast to the results for endogenous energy losses, turkeys pre-exposed to phytase linearly increased (P<0.05) the excretions of Ca and Mg with increasing phytase activity in the pre-study period. 6. The effects of feeding turkeys with supplementary phytase were continuing for at least four days after the diets were withdrawn. This suggests that exposure to phytase alters the functionality and secretions of the gastrointestinal tract which may influence the nutritive value of subsequently fed diets.
Domaines
Biologie animale
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