Nutrient selection by cattle, goats and sheep on natural Karoo pasture. 2. Nitrogen

Author: P.J.L. Zeeman, P.G. Marais & M.J. Coetsee
Year: 1984
Issue: 4
Volume: 14
Page: 169 - 172

The nitrogen (N) content of material selected by cattle, Boer goats, Dorper and Merino sheep on natural Karoo pasture was investigated. A pronounced seasonal variation in the N content of selected material was found. No correspondence was recorded between the N content of oesophageal extrusa and hand-sampled material. Cattle selected material with a lower (P < 0,01) N content (1,28 ± 0,28%) than Boer goats and sheep, with Boer goats (1,60 ± 0,35%) lower (P < 0,05) than sheep. The difference between Dorper (1,88 ± 0,35%) and Merino sheep (1,87 ± 0,37%) was not significant. Close correlations between the small stock species (r = 0,81-0,89) indicates a similarity in the seasonal N selection pattern of small stock on Karoo veld. Lower correlations between cattle and small stock (r = 0,43 – 0,61) shows that the N selection pattern of cattle deviates from that of small stock. A small but significant (P < 0,01) difference in extrusa N content between dry female (1,72 ± 0,44) and castrated male (1,65 ± 0,43) animals was recorded. Notwithstanding, high correlations (r = 0,87 – 0,95) suggest that N selection of dry females can be predicted from castrated males and vice versa. A highly significant difference (P < 0,01) in the N content of selected material was determined between years. An intraclass (animal species) correlation of r = 0,95 between years indicated a correspondence in the seasonal N selection pattern. A difference (P < 0,01) was recorded in N content of extrusa pooled for the first and last 2 days of the 4-day sampling period. This difference (4,2% units or 0,07% N) was, however, small. The N content of selected material is discussed together with its digestibility. It is concluded that small stock selected material with a


higher nutritive value than cattle on Karoo veld.



Keywords: Karoo veld, nitrogen, ruminants, selective grazing
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