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Condensed tannins reduce browsing and increase grazing time of free-ranging goats in semi-arid savannas

By N. R. Mkhize, I. M. A. Heitkonig, P. F. Scogings, L. E. Dziba, H. H. T. Prins, W. F. de Boer

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Abstract

Tannin concentrations fluctuate spatially and temporally within and among plant species, with consequences for forage quality of herbivores. The extent to which these fluctuations influence foraging activities of goats is not fully understood. While accounting for the effects of the time of the day and season, we tested the hypothesis that goats exposed to high levels of condensed tannins (i) spend less of their foraging time browsing, (ii) spend more time grazing, and (iii) reduce their total foraging time, especially during the dry season when grasses dry out and deciduous trees lose leaves. We orally dosed 15 goats with (i) 20 g of condensed tannins extract dissolved in 50 ml of water (high tannin exposure), another 15 goats (ii) with 20 g of polyethylene glycol dissolved in 50 ml of water, which neutralizes the effects of tannins (low tannin exposure), and the last group of 15 goats (iii) with 50 ml of water (control). We recorded the time spent on grazing, browsing and these two activities together (i.e., foraging) for 30 days in the dry and wet season. As expected, dosing goats with condensed tannins reduced their browsing time and increased the time spent grazing. Goats dosed with polyethylene glycol increased their browsing time and lowered their time spent grazing. Animals dosed with polyethylene glycol foraged for longer than other treatment groups in the dry season, whereas the goats dosed with condensed tannins increased their foraging time in the wet season. Overall, all treatment groups spent a similar amount of time foraging, indicating an instinctive drive by goats to maintain high total foraging time while avoiding over ingestion of tannin-rich forages. We concluded that tannins do not supress total foraging time for free-ranging goats. Instead, they increase the amount of time animals spend on grazing on herbaceous plants and decrease the amount of time animals spend browsing on woody plants. Comparing time spent on different foraging activities by goats is a first step towards understanding how goats utilize feed resources and how tannins influence resource utilization patterns.

Publication Title Applied Animal Behaviour Science
Volume 169
Pages 33-37
ISBN/ISSN 0168-1591
DOI 10.1016/j.applanim.2015.04.012
Language English
Author Address Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3a, 6708 PB Wageningen, Netherlands.mkhizen@arc.agric.za
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Tags
  1. Animal behavior
  2. Animal nutrition
  3. Browse
  4. Dry season
  5. Effect
  6. Feeding
  7. Feeding behavior
  8. Fodder
  9. Foraging
  10. Grasses
  11. Grasslands and rangelands
  12. Grazing
  13. Herbivores
  14. Leaves
  15. peer-reviewed
  16. Plants
  17. plasticity
  18. resource management
  19. savannas
  20. tannins
  21. trees
  22. utilization
  23. wet season
Badges
  1. peer-reviewed