Abstract :
D1 (high digestion efficiency) and D2 (low digestion efficiency) genetic chicken lines selected for divergent digestion efficiency
were compared in this experiment. Gizzard functions were tested in terms of digesta mean retention time and reactions to high
dilution of a corn diet with 15% coarse sunflower hulls. The corn standard (S) and high fibre (F) experimental diets were given
from 9 days of age to chickens from both lines. Besides the measurements of growth efficiencies (9 to 20 days), digestibilities
(20 to 23 days) and gut anatomy (0, 9, 29, 42 and 63 days), two digestive transit studies were performed at 9 and 29 days of age.
For the transit studies, the S and F diets were labelled with 0.5% TiO2 and 1% Cr-mordanted sunflower hulls. These diets were
fed ad libitum during 3 days, and then the birds were euthanized. The digestive contents were analysed for the determination of
marker concentrations and mean retention times (MRTs) in digestive compartments (crop1oesophagus, proventriculus1gizzard,
duodenum1jejunum, ileum, rectum1cloaca and caeca) were determined. D1 birds were confirmed as better digesters than
D2 birds during the growth period, in association with larger gizzard and pancreas, and lighter small intestine in D1 than in
D2birds. The MRT in the proventriculus-gizzard system, higher in D1 than in D2 birds, was a major factor associated with
differences between D1 and D2 birds regarding digestion efficiencies and gut anatomy. Diet dilution with fibres reduced
differences in digestion efficiencies and proventriculus-gizzard MRT between lines. Differences in gut anatomy between lines
tended to disappear after 8 weeks of age. In conclusion, this study showed that MRT in the proventriculus-gizzard system was a
major factor associated with genotype differences between the D1 and D2 genetic chicken lines selected for divergent digestion
efficiency, with longer MRT found in D1 than in D2 birds.
Keywords :
genetics , digestion , transit time , chicken , Gastric
