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Nutrient selection by cattle, goats and sheep on natural Karoo pasture.

1. Digestibility of organic matter

P.J.L. Zeeman, P.G. Marais and M.J. Coetsee

Research Institute of the Karoo Region, Middelburg, Cape

The digestibility of organic matter (DOM) of material selected by cattle, Boer goats, Dorper and Merino sheep on natural Karoo pasture was investigated. A highly significant difference (P ≤ 0,01) in DOM selected between years, with an interclass (animal types) between years correlation of 0,88 (P ≤ 0,01) was recorded. A close relationship in pattern of DOM selection between years is evident. The difference in DOM selected by castrated male and dry female ewes was significant (P ≤ 0,05). However, this difference was not substantiated by a t-test between averages. Correlations ranging between r = 0,971 and r = 0,979 between sexes, within animal types, implies a close relationship for selected DOM. The difference in % DOM selected between Merino (58,57 ± 7,92) and Dorper sheep (57,76 ± 6,70) was not significant, but was higher than that selected by Boer goats (55,44 ± 6,47) (P ≤ 0,05) and by cattle (52,07 ± 7,98) (P ≤ 0,01). The value for Boer goats was also higher than that for cattle (P ≤ 0,01). A large discrepancy was established between the % DOM selected by the animals and the % DOM of material sampled by hand. It seems that the discrepancy between these two methods is larger on grazing with a divergent botanical composition. A substantial seasonal variation in the DOM content of selected material is illustrated. It seems that sheep and Boer goats are more proficient than cattle at selecting material with a sufficient DOM content at maintenance or exceeding it. Furthermore, a relationship between DOM selected and the active growth stage of pasture plants in the Karoo is suggested.





South African Journal of Animal Science 1983, 13(4)