Water Intake in Broilers as Affected by Insoluble Fibres and Exogenous Protease In A Reduced Crude Protein Diet

Water is important for the overall health and performance of birds, yet less focus has been on water compared to the other nutrients. Increase or decrease in water to feed intake ratio (WI:FI) indicates issues related to nutrition, health or management of the shed particularly in broilers due to their fast growth. An automated water measurement system was developed at the University of New England to measure water intake in broilers. This system was used to measure water intake in two experiments to determine the effects of dietary inclusion of insoluble fibre and exogenous protease in a reduced crude protein (RP) diet. The hypothesis was that the reduction in dietary crude protein would decrease water intake and adding insoluble fibre or protease in RP diets would not affect water intake of birds beyond the effect produced by the RP diets. In both the experiments, day-old Ross 308 male parental birds were used and fed a common starter diet until d 10. The birds were reared in floor pens with wood shavings as bedding material.

The first experiment consisted of 8 treatments with 6 replicate pens each with 14 birds and arranged in a 2 × 2 × 2 factorial with dietary crude protein (CP) - normal (NP, 213 g/kg CP in grower and 195 g/kg CP in finisher diets) or reduced by 25 g/kg CP (RP), sugarcane bagasse- 0 or 20 g/kg and protease- 0 or 0.2 g/kg. Water intake was measured at two time points, 16 to 20 d and 20 to 24 d. In the second experiment, birds were assigned to 6 treatments with 8 replicate pens of 14 birds each. The treatments were NP diet (grower 211 g/kg CP, finisher- 195 g/kg CP), RP (reduced by 20 g/kg CP), and RP diets formulated in with sugarcane bagasse at 20 g/kg, lignocellulose based product at 10 g/kg, oat hulls at 30 g/kg, or soy hulls at 30 g/kg. The basal diet of the fibre treatments was same and the formulations were adjusted by adding Celite, an indigestible component as filler. Water intake was measured from d 10 to 35. In both the experiments, the reduction in dietary CP decreased (P < 0.001) water intake and WI:FI. The inclusions of 20 g/kg sugarcane bagasse had no effect (P > 0.05) on water intake and WI:FI. The addition of 0.2 g/kg protease had no effect (P > 0.05) on water intake but increased (P < 0.05) WI:FI. The inclusions of insoluble fibres in the RP diet had no effect (P > 0.05) on water intake and WI:FI. These experiments demonstrated that the automated system can be used to measure water intake in nutrition research. The findings showed that water intake can be decreased by lowering dietary crude protein level and the inclusion of insoluble fibres at moderate amounts in reduced crude protein diet will not affect water intake of birds.

Figure 1 - Effect of reduced crude protein diet and insoluble fibres on water to feed intake ratio (d 10 to 35)

ACKNOWLEDGEMENTS: This research was funded by the AgriFutures Australia.