Voluntary intake and digestion of gorse (Ulex europaeus) by goats and sheep

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Abstract
Gorse (Ulex europaeus) was harvested in late spring, summer, autumn and winter and fed to six goats kept individually in metabolism cages for 21-day periods. The same gorse was also fed to sheep during the first two periods, but not in autumn and winter, as the hardness and sharpness of the needles caused total rejection by the sheep at these times. Measurements of voluntary intake and apparent digestibility were made over the last 7 days of each period. To minimize effect of diet selection the animals were fed at hourly intervals. Dietary lignin concentration was very high, ranging from 170 to 200g/kg D.M. Voluntary metabolizable energy (ME) intake for goats was respectively 1·60, 0·82, 0·72 and 0·41 times maintenance for the four harvesting times, late spring, summer, autumn and winter. Corresponding values for sheep were 0·90 and 0·33 for gorse harvested in late spring and summer. Thus, in late spring and summer, voluntary ME intake by goats was respectively 1·8 and 2·5 times that of sheep. The reduction in ME intake with time was attributed to increases in the contents of D.M. and of lignin + hemicellulose in depressing voluntary D.M. intake and apparent digestibility respectively. Voluntary intake of both supplementary water and total water per unit D.M. intake were consistently less for goats than sheep. From a comparison with published values, it was concluded that the superiority of. goats over temperate breeds of sheep in digestible dry matter intake (DDMI)/kg W0·75 per day increased as the lignin content of the diet exceeded 120 g/kg D.M., indicating that goats must possess some superior mechanism for breaking down highly lignified diets such as gorse and willow. It is proposed that cashmere fibre production from goats grazing gorse for a 7-month period of each year should be evaluated as an alternative to regulating gorse with chemicals.