Liveweight gain and apparent diet selection by bulls grazing a perennial ryegrass-white clover pasture with and without sorghum-sudangrass hybrid (Sudax ST-6)

摘要

Forage production from perennial ryegrass-white cloverpastures during summer in the Manawatu is often insufficient for optimal animal production. A system consisting of 25 sudax and 75 pasture was compared with 100 pasture. Sudax was sown on 24 November. Grazing of both systems started on 14 January with sudax grazing starting on 12 February; grazed areas were back-fenced to allow regrowth. Sudax yield increased from 4.11 dry matter (DM)/ha on 29 January to 18.3 t DM/ha on 30 March. Regrowth (12 February#x2013;6 April) was higher on sudax (6.0 t DM/ha) than on pasture (2.8 t DM/ha). In the pasture and sudax system, sudax contributed 55#x2013;59 of the diet. The apparent composition of consumed sudax was 40 leaf, 18 sheath, 38 stem, and 4 inflorescence. On the pasture system, apparent composition of the diet was 28 grass, 38 white clover, and 34 dead matter. The in vitro DM digestibility of the total sudax plant was 66.8 and of pasture was 65.6#x2013;66.1. Liveweight gain over the 82-day experiment was 0.89 and 0.85 kg/day for the pasture and sudax, and pasture only systems respectively. All components of sudax were acceptable to bulls and there was no evidence of ill-health. Sudax has the potential to contribute large quantities of medium-quality forage during late summer-early autumn.