Oat hulls and sugar beet pulp in diets for broilers 1. Effects on growth performance and nutrient digestibility

In total, 504 female broilers were used to study the effects of inclusion of oat hulls (OH) and sugar beet pulp (SBP) in the diet on growth performance, coefficient of total tract apparent retention (CTTAR) and coefficient of apparent ileal digestibility (CAID) of nutrients from 1 to 18days (d) of age. A control diet based on rice that contained 69g dietary fibre (16gcrudefibre)/kg was diluted with 25, 50 and 75g/kg of either OH or SBP. Each of the seven treatments was replicated six times (a cage with 12 chicks). Growth performance and CTTAR of nutrients were recorded at d 6, 12 and 18 and the CAID of organic matter and crude protein were determined at d 18. From d 1 to 18, fibre inclusion did not affect feed intake or body weight gain of the birds. However, feed conversion ratio was improved quadratically (Q) with OH (P<0.05) and SBP inclusion (P≤0.01). Moreover, the inclusion of OH or SBP in the diet improved linearly (L) energy efficiency from 1 to 18d of age (P=0.057 and P≤0.01 for OH and SBP; respectively). Fibre inclusion affected in different ways the CTTAR of nutrients depending on the level and type of fibre, as well as the age of the birds. In general, the inclusion of up to 50g of OH or SBP/kg diet increased the CTTAR of all nutrients. The increase in CTTAR of nitrogen (P<0.05 at d 18) and AMEn of the diet (P<0.05 at d 6 and P=0.062 at d 12) because of fibre inclusion was higher with OH than with SBP. Oat hulls inclusion increased the CAID of crude protein (L; P<0.05) and starch (L; P≤0.001 and Q; P<0.05) but no effects were observed with SBP. Therefore, the requirement for dietary fibre of young chicks varies between 82 and 101g/kg diet (20–29gcrudefibre/kg), depending on the trait considered and the source of fibre used. The data indicate that moderate levels of fibre inclusion improved feed conversion ratio and nutrient digestibility in young broilers but that an excess might affect digestive traits and hinder growth performance.