Comparison of gizzard activity between chickens from genetic D+ and D- lines selected for divergent digestion efficiency.

Gizzard motility was compared between chickens from D(+) (high digestion efficiency) and D(-) (low digestion efficiency) genetic lines selected for divergent digestion efficiency, using strain gauge transducers. Motility was recorded continuously during 24 h in 6 birds per line. Two stimuli, a meal distribution after a feed-deprivation period and lighting after a dark period, were tested during the recording period. A functional test with intravenous injection of serotonin performed at the end of the recording day often resulted in a sharp reduction in gizzard motility, without a significant difference between lines. Compared with D(+) birds, gizzard activity in D(-) birds remained high during fasting or dark periods (P < 0.0006), which reduced the effects of stimuli in D(-) birds. So, coordination between bird activity and gizzard motility tended to be reduced in D(-) compared with D(+) birds (P = 0.0018). This coordination was observed to be positively correlated (P = 0.011) with the relative weight (g/kg of BW) of the stomach (gizzard + proventriculus). This experiment pointed out differences in gizzard motility between D(+) and D(-) chicken lines in terms of response to environmental stimuli, characterized by a failure in the gizzard relaxation process in D(-) birds during rest periods.