The effect of an antibloat treatment on the dietary preference of nonpregnant Holstein x Friesian heifers for ryegrass and white clover was studied. Eight groups of two heifers grazed 0.51 ha plots containing adjacent monocultures of grass alongside clover with either 25 or 75% clover (by ground area) and either with or without a monensin intraruminal antibloat device. Preference was measured by recording the time spent grazing grass or clover between dawn and dusk by manual scan sampling at 2 min intervals over a 48 h period. The observers also recorded a visual assessment of bloat (on a scale of 0-5). The heifers selected 51.2% clover when offered 25% clover and 76.6% clover when offered 75% clover. Analysis showed an overall partial preference for clover of 63.9% (mean value across all treatments), although the relative abundance of clover did influence preference. There was a diurnal pattern to preference, with a stronger preference for clover in the morning, and the preference for grass increasing towards the evening. These results are very similar to those previously reported for sheep, suggesting that there may be a common biological basis for partial preference for grass and clover in sheep and cattle. None of the animals showed any significant signs of bloat, and the antibloat treatment had no effect on the proportion of clover selected. This indicates that avoidance of moderate or severe bloat is unlikely to be the mechanism for partial preference in cattle. However, it is possible that mild, subclinical bloat could still play a role in diet selection.
|Publication Title||Applied Animal Behaviour Science|
|Author Address||Institute of Grassland and Environmental Research, North Wyke Research Station, Okehampton, Devon EX20 2SB, UK. email@example.com|
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