Influences of stocking rate and management system on the behaviour of merino wether hoggets grazing improved tussock grassland, and associated effects on dung distribution and nutrient transfer: A dissertation submitted in partial fulfilment of the requirements of Bachelor of Agricultural Science (Honours) in the University of Canterbury

Abstract

Observations were made of the behaviour and distribution of merino wether hoggets grazing on improved tussock grassland at Tara Hills Country Research Station, Omarama. The area the sheep were grazing was incorporated in an experiment comparing three stocking rates and three management systems over the November to April grazing period on the south-east facing slope. Sheep activity and distribution were recorded every half hour during daylight over two months in early summer. Dung frequency was measured over the whole trial at the end of the observation period. Soil test data was collected at the end of the grazing period. Sheep followed similar diurnal patterns of behaviour in the different treatments although there was a large range in recorded grazing time between treatments. Grazing time ranged from 50 to 72% of the time observed and appeared to be largely related to herbage allowance. An increase in stocking rate oi subdivision both led to a more even grazing distribution. There appeared to be an important interaction between stocking rate and management system with subdivision being effective in improved grazing distribution only at higher stocking rates. The evenness of resting distribution was improved only where higher stocking rates and intensive subdivision increased the effective density of sheep in the area being grazed. Selection of day camp site appeared to be largely related to features of microtopography. The importance of the mid-slope fence in modifying altitudinally related gradients of behaviour and sward factors is stressed. Dung distribution showed an accumulation in the night camp areas but little relationship to daytime activity.The possibility of a diurnal pattern of defecation is discussed. Changes in soil phosphorus and potassium levels showed little relationship to dung return indicating the complex nature of nutrient cycling in grazed ecosystems.Factors likely to influence the behaviour of P and K in the system studied are discussed. The importance of animal behaviour in the grazed tussock grassland is stressed, and avenues for further research are suggested.