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Individual and socially learned preferences for biserrula ( Biserrula pelecinus L.) in sheep
Author(s) -
Thomas D. T.,
Milton J. T. B.,
Revell C. K.,
Ewing M. A.,
Lindsay D. R.
Publication year - 2015
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/gfs.12108
Subject(s) - biology , grazing , monoculture , pasture , forage , preference , agronomy , ruminant , phenology , lolium rigidum , mathematics , weed , statistics , herbicide resistance
Abstract This study examined how sheep develop a learned aversion to the annual legume biserrula ( Biserrula pelecinus L.). Merino sheep were grazed on paddocks sown with either (i) biserrula, (ii) biserrula + ryegrass ( Lolium rigidum Gaud.), (iii) crimson clover ( Trifolium incarnatum L.), (iv) crimson clover + ryegrass or (v) ryegrass, for 4 weeks. Relative preference (Chesson–Manly selection index) was determined by offering randomly ordered monoculture plots of the three forage species. The groups of sheep were then combined into a single group and grazed a paddock containing a monoculture sward of each plant type for 5 d. Relative preference of sheep was tested again after the completion of the combined grazing. The experiment was repeated at three stages of plant phenology: vegetative, reproductive and senesced. Relative preference for biserrula was lower in sheep that had grazed the paddock sown with only biserrula compared with sheep that grazed a combination of biserrula + ryegrass, at both the vegetative ( α ; −0·11 vs. 0·32) and reproductive ( α ; 0·18 vs. 0·63) stages. At each stage of phenology, when groups were combined and grazed together, preference for biserrula became uniform. This supported the hypothesis that sheep develop an aversion to biserrula when they graze a pasture containing biserrula. However, we concluded that the familiarity of sheep with biserrula did not result in low relative preference; rather, the aversion was more likely a response to the high proportion of this plant in their diet. Social facilitation may have enabled sheep to overcome rapidly the food aversion.