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This Article Full Text (PDF) All Versions of this Article: jas.2008-1109v1 87/1/340    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Villalba, J. J. Articles by Stott, R. Search for Related Content PubMed PubMed Citation Articles by Villalba, J. J. Articles by Stott, R.

Rumen distension and contraction influence feed preference by sheep

J. J. Villalba^*, F. D. Provenza^* and R. Stott

^* Department of Wildland Resources Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan 84322-5230

juan.villalba{at}usu.edu

Abstract

Distension of the rumen limits feed intake by livestock. Ruminal dysfunctions due to bloat, which causes distension by accumulation of excessive gas within the rumen, also reduce feeding. We hypothesized that excessive levels of rumen distension cause feed aversions, and that preference increases for feeds eaten in association with recovery from bloat. To test these hypotheses, we determined whether 12 commercial crossbred lambs (average initial BW 43 ± 2 kg) could associate ingestion of specific feeds with the consequences of increased intraruminal pressure and its subsidence. Six of the lambs were fitted with rumen cannulas and offered ground alfalfa for 30 min after a rubber balloon was inserted into the rumen of each animal and distended with air to volumes of 1.8, 2.5, or 4.5 L. Subsequently, balloons were deflated and alfalfa was offered again for a second period of 30 min. Feed intake was not affected when the balloon was not distended (P = 0.45 to 0.93), but distension reduced feed intake (P < 0.001) in direct proportion to the magnitude of distension at all 3 volumes (R² = 0.70). Relief from distension promoted a compensatory increase in feed intake (P = 0.006). During conditioning to determine if lambs acquired a preference for a feed associated with recovery from distension, fistulated lambs were offered novel feeds – wheat bran (Group 1; n = 3) and beet pulp (Group 2; n = 3) – and the balloon was distended for 30 min. Feeds were then switched and the balloons were deflated (recovery). Control lambs (n = 6) received the same feeding protocol without the balloons. Lambs formed strong aversions to feeds associated with distension and preferred feeds associated with recovery (P = 0.001 to P = 0.10). No preferences or avoidances were observed in Control lambs conditioned without rumen distension (P = 0.17 to P = 0.87). Thus, rumen distension and recovery from distension induced feed aversions and preferences, respectively, which may be critical in learning avoidances of bloat-inducing plants and preferences for plants and supplements that relieve the incidence of bloat.

Key Words: bloat • diet selection • foraging • learning • sheep