The efficacy of dietary xylanase and phytase in broiler chickens fed expeller-extracted camelina meal

A study was conducted to investigate the effects of dietary phytase (PHY) and xylanase (XYL) on growth performance, nutrient utilization, and intestinal characteristics in broilers fed corn-soybean meal-based diets with added expeller-extracted camelina meal (CM). The corn-soybean meal-based diets without or with CM was formulated to contain 2.9 or 2.7 g/kg non phytate phosphorus, respectively. A total of 384 male Ross 708 broilers were allocated to 8 dietary treatments in a randomized complete block design with 6 replicates per treatment, from 7 to 21 d post hatching. The experiment consisted of a 2 × 2 × 2 factorial arrangement of treatments with 2 dietary CM levels (zero or 100 g/kg), 2 dietary levels of XYL (zero or 800 unit/kg), and 2 dietary levels of PHY (zero or 4,000 unit/kg). Chromic oxide was included in the diets as an indigestible marker. Growth was measured throughout the experiment and excreta were collected on d 18 to 21 post hatching for measurement of nutrient and energy retention. On d 21 post hatching, broilers were euthanized by CO₂ asphyxiation, ileal digesta was collected for nutrient and energy digestibility measurements, and the left tibia was removed for bone ash measurement. Furthermore, duodenal digesta was collected and a segment of the mid jejunum was excised for viscosity and morphology measurement, respectively. Broilers fed 100 g/kg CM diets showed lower (P < 0.001) BW gain and G:F than those fed zero g/kg CM diets for 7 to 14 d and 7 to 21 d post hatching periods, respectively. Phytase supplementation improved (P < 0.05) all the growth parameters measured regardless of CM addition. Phytase supplementation resulted in an increase (P < 0.05) in jejunum villus height but there was no impact of CM or XYL. Additionally, duodenal digesta viscosity increased (P < 0.001) with added CM. Tibia ash and weight increased (P < 0.001) with PHY supplementation. There was a CM × PHY interaction (P < 0.05) on percentage tibia ash, with greater PHY effect in zero g/kg CM diets compared with 100 g/kg CM diets. Phytase supplementation increased (P < 0.05) ileal DM, N, energy, P, and neutral detergent fiber (NDF) digestibility. In diets with 100 g/kg CM, addition of PHY had a greater effect (CM × PHY; P < 0.05) on ileal P digestibility compared with diet without CM. There was a CM × PHY interaction (P < 0.05) for ileal digestible energy (IDE) in which PHY increased the IDE in birds fed CM supplemented diets. Both ileal digestibility and retentions of DM, N, energy, and IDE, AME, and AMEₙ were decreased (P < 0.05) by CM supplementation. Retention of ether extract and NDF decreased (P < 0.05) with CM supplementation. Nitrogen retention, AME, and AMEₙ decreased (CM × XYL; P < 0.05) with XYL supplementation in zero g/kg CM diets. There were CM × XYL interactions (P < 0.01) for P and Ca retentions in which XYL increased retentions in 100 g/kg CM diets. In conclusion, PHY was efficacious at improving P digestibility and retention of birds fed low P corn-soy based diets without or with CM. However, regardless of CM addition, XYL did not improve nutrient utilization and growth performance of broiler chickens. The present data also show that the mechanism underlying the detrimental effects of CM inclusion on nutrient utilization is not mediated through gut morphology and goblet cell density. The data also show that the villus height increase occurring with PHY addition might be a contributor to the improvements in ileal DM, N, and energy digestibility obtained with PHY supplementation.