HABRI Central

Previous studies have indicated that intraruminal infusions of acetate and propionate condition flavour preference in sheep. Three experiments were conducted to evaluate and compare the preference-reinforcing effects of postabsorptive acetate and propionate. Eight wethers were used in Experiment 1, and a different eight wethers were used in Experiment 2 and 3. In Experiment 1, wethers were divided into two groups, and a half of each group (n=2) was given clove-flavoured straw and the other half was given cardamom-flavoured straw on odd-numbered days during a 12-d conditioning period. During straw ingestion, wethers in one group received intramesenteric infusion of sodium propionate (0.56 mmol/kg) and the other group received saline infusion. On even-numbered days, flavours and infusate were switched, so that each group received a new flavour and a new infusate. When wethers were offered a choice between the two flavoured straw, they preferred (P<0.01) the flavoured straw that had been paired with propionate infusion. In Experiment 2 and 3, two trials were conducted using four animals in each trial. In Experiment 2, wethers were given clove-flavoured (n=2) or nutmeg-flavoured (n=2) straw paired with intramesenteric infusion of sodium acetate (1.69 and 0.85 mmol/kg in Trial 1 and 2, respectively) on odd-numbered days and the other flavoured straw paired with saline infusion on even-numbered days during a 10-d conditioning period. In subsequent two-choice tests, wethers in Trial 1, but not in Trial 2, showed a preference (P<0.05) for the flavoured straw paired with the acetate infusion. Wethers used in Trial 2 were then given 10 additional days of conditioning with intrajugular infusion of 1.69 mmol/kg of sodium acetate and saline, but preferences for the flavour paired with acetate infusion were not developed. In Experiment 3, wethers were given fennel-flavoured (n=2) or nutmeg-flavoured (n=2) straw paired with sodium propionate infusion (1.69 and 0.96 mmol/kg in Trial 1 and 2, respectively) into the ruminal vein on odd-numbered days and the other flavoured straw paired with saline infusion on even-numbered days during a 10-d conditioning period. In subsequent two-choice tests, wethers in Trial 1 tended to prefer (P<0.10) the flavoured straw paired with propionate infusion to that with acetate infusion. In Trial 2, wethers avoided nutmeg-flavoured straw more than fennel-flavoured straw, but the intake of each flavoured straw tended to be higher (P<0.10) when it was paired with propionate. These results suggest that acetate and propionate generate preference-reinforcing signals in the portal-hepatic area, but the signal generated by acetate is weaker than that by propionate.

Researchers should cite this work as follows:

1. Animal behavior
2. Animal physiology
3. Feeding behavior
4. Feed preferences
5. Flavor
6. Mammals
7. peer-reviewed
8. rams
9. Sheep