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Flavour preference conditioned by postabsorptive propionate and acetate in wethers

By M. Sutoh, T. Imura, H. Tsukada, A. Yamada

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Abstract

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.

Date 2008
Publication Title Applied Animal Behaviour Science
Volume 111
Issue 3/4
Pages 274-285
ISBN/ISSN 0168-1591
DOI 10.1016/j.applanim.2007.08.001
Language English
Author Address National Institute of Livestock and Grassland Science, 2-Ikenodai, Tsukuba, Ibaraki 305-0901, Japan.madoka@affrc.go.jp
Additional Language English
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Tags
  1. Animal behavior
  2. Animal physiology
  3. Feeding behavior
  4. Feed preferences
  5. Flavor
  6. Mammals
  7. peer-reviewed
  8. rams
  9. Sheep
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  1. peer-reviewed