The intensity of grazing management influences lamb production from native grassland

Abstract

The intensity of grazing management required for optimal pasture and animal production from heterogeneous native grasslands has received little research in the high-rainfall zone of south-eastern Australia. The aim of this experiment was to determine how the intensity of grazing management, from continuous grazing (P01) to flexible 4- and 20-paddock rotational systems (P04 and P20), influenced the productivity and sustainability of a Merino ewe, terminal sire lamb production system run on a native grassland dominated by Microlaena stipoides and Rytidosperma spp. The present paper focuses on the animal production and feed-quality results from this experiment. There was a higher per head animal production for the P01 than the P20, with the P04 being intermediate. The differences were found for ewe liveweight and fat score, lamb growth rates and lamb liveweight at weaning. The P20 was able to run higher ewe numbers, in response to greater feed on offer than for P04 and P01, which enabled lamb production per hectare at weaning to be similar and greasy wool production per hectare to be greater than for P01. The organic matter digestibility of the ewe diet estimated from faecal analysis was lower for P20 and P04 systems than for P01 over a 7-month period and explained differences measured in sheep performance at that time. When lambs were retained after weaning, they could be kept for longer on the P20 and grown to a greater weight than for the P01 and P04, but the criteria for setting stocking rates and selling lambs from systems influenced the production from the systems. Further work is needed to investigate the interaction between stocking rate (ewe numbers and lamb sale time) and grazing management and examine different options for managing rotational grazing systems.