2.3. Digestibility and AME assays

Concurrent with first run of the performance trials, digestibility (except d 7) and AME assays were conducted on the same batch of birds separately reared on floor. Therefore, 252 one-d-old off-sex male Ross 308 broilers were placed in an environmentally-controlled room and reared under similar management, temperature and lighting program as for the performance trials. All the birds were given a common commercial diet until d 15 when birds were transferred to metabolism group cages after being weighed. Each cage accommodated 4 birds in a total of 36 metabolism cages. Birds were assigned to 6 experimental diets each replicated 6 times for a 3-d adaption period followed by 3 d of total excreta collection on d 18, 19, and 20. Upon completion of AME procedure, 3 birds per cage were euthanized for jejunal and ileal digesta collection on d 21 of age. Using the remaining 108 male broilers, the exact same procedure was followed for finisher diets with an exception of placing 3 birds per cage due to higher body weight and growth rate. The adaption period and excreta collection were conducted from d 36 to 41 for AME followed by jejunal and ileal digesta collection from 2 birds per replicate on d 42. As previously indicated the digestibility assays for d 7 were performed on birds in rearing pens used in growth performance trials as the AME cages were not suitable for young birds. As such on d 7 of age, in each of the performance trial, 6 birds from each pen were euthanized for digesta collection obtaining 8 replicates per treatment.

At each age of d 7, 21 and 42, digesta was collected from the entire jejunum and ileum by gently squeezing the content into a container, placed on ice and subsequently frozen in −20 °C before being fully freeze-dried and ground to 0.1 mm. At the time of collection, digesta from birds within a cage/replicate were pooled.