Effect of two levels of supplementary feeding and two stocking rates of grazing ostriches on irrigated lucerne dry matter intake and production
This study determined the effect of two stocking rates of ostriches (10 and 15 birds/ha) and two levels of supplementary feeding (0 and 800 g/bird/day) on the intake and production of irrigated lucerne pastures over a period of five months (January to May). A lucerne pasture was divided into 16 paddocks of approximately 0.85 ha each. One hundred and seventy ostriches (± 6 months old) were randomly allocated to four groups and four different lucerne paddocks were randomly allocated to each group. Each ostrich group rotationally grazed the four lucerne paddocks and was moved to a new paddock every two weeks or as soon as pasture became depleted. The available pasture dry matter was determined by cutting and collecting a 0.166 sq m size sample to ground level inside and outside exclosure cages placed inside each paddock every time the ostriches left a paddock. Pasture material were washed to remove soil and dirt and dried to a constant dry mass at 59 °C. The data was analyzed with analysis of variance, using the four paddocks as replicates and with two treatments and two treatment levels. For lucerne intake a significant interaction was found between level of supplementary feeding and month. Intake was not significantly influenced by supplementary feeding during January, February, March and April, but during May lucerne dry matter intake was significantly higher at 0 g/bird/day than at 800 g/bird/day. This seems to indicate an increasing level of replacement of grazed lucerne dry matter by supplementary feeding as the trial progressed. This is supported by the fact that there tended to be an interaction between stocking rate and level of supplementary feeding in terms of lucerne dry matter intake. This resulted in lucerne dry matter intake being higher at 15 birds/ha than at 10 birds/ha at 0 g supplementary feeding/bird/day, while at 800 g supplementary feeding/bird/day there was no difference in lucerne dry matter intake. In the case of lucerne dry matter production a significant interaction was found between stocking rate and month. During January, February and March lucerne dry matter production was significantly higher at the 15 birds/ha stocking rate than at 10 birds/ha, while there was no difference in April and lucerne production was significantly higher at 10 than at 15 birds/ha in May. The high stocking rate of 15 birds/ha therefore seems to have had a gradual depressing effect on lucerne dry matter production. The less severe levels of defoliation at the low stocking rate possibly promoted lucerne dry matter production. It can be concluded that stocking rate, as well as level of supplementary feeding, influenced lucerne dry matter intake, but only stocking rate influenced lucerne production. Supplementary feeding depressed lucerne intake only at the high stocking rate.
Keywords: Grazing ostriches, lucerne production, lucerne intake, supplementation