Sample Preparation and Chemical Analysis
All analyses were performed in duplicate. Digesta
and fecal samples were freeze dried, and along with
diet samples, finely ground to pass through a 1-mm
mesh prior to chemical analyses. Bone samples were
thawed and cleaned to remove all adhering tissue and
then carefully broken into smaller pieces. Broken bones
were wrapped in Whatman’s No. 42 filter paper, stapled
at the tip, and then defatted in hexane for 48 h. The
bones were then air-dried and ashed in the furnace at
600°C for 12 h. Bone ash was expressed as a percentage
of dry fat-free bone weight (modified from Spencer et
al., 2000). Diet, digesta, and fecal samples were analyzed
for DM according to AOAC procedures (1990).
Phytate content in the diet, digesta, and fecal samples
was determined using the method of Haug and
Lantzsch (1983). Briefly 10 mL of 0.2 N HCl was added
to 100 mg of diet or 30 mg of feces and the mixture was
shaken for 3 h at room temperature and then filtered.
Distilled water (0.5 mL) and 2 mL of ferric solution
were then added to 0.5 mL of filtrate. The mixture was
boiled for 30 min, centrifuged at 2,400 × g, after which
1.5 mL of bipyridine solution was added to 1 mL of the
supernatant. The absorbance of the mixture was read
against distilled water at 519 nm with a Pharmacia
Ultrospec 2000 spectrophotometer. Total phosphorus
(percentage) was determined according to the AOAC
(1990) procedure. Chromic oxide was analyzed according
to the procedure described by Williams et al.
(1962). Diet and ileal digesta CP (N × 6.25) content