Sheep and deer grazing of pasture within close proximity of cattle dung pats : A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science with Honours

Abstract

An experiment was performed to compare the grazing of deer and sheep on pasture with and without contaminating cattle dung pats. Sheep (35 ewes) and deer (24 hinds) were grazed separately on 0.4 ha ryegrass and white clover pasture plots. One half of each 0.4 ha plot was contaminated with artificially applied cattle dung pats (DP) which were 30 cm in diameter spread at an application rate of 1 every 4 m² , while the other half of plots were left uncontaminated (NDP). The mean pasture availability (kg DM/ha) was estimated daily with a rising plate meter on all DP and NDP plots. Sward heights (SH) (cm) were also measured daily at 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 cm from the edges of pre-marked dung pats and pegged areas of the plots (2 dung pats within each DP plot and 2 pegs within each NDP plot to give 16 data points to be measured daily. The experiment lasted for 10-11 days and the mean pasture availability declined from 2850 to 1500 kg DM/ha. The grazing pressure was controlled on each plot through altering the numbers of livestock to ensure a <250 kg DM/ha difference between each species plot. At no stage during the experiment did the difference in pasture availability between plots grazed by sheep or deer exceed the 250kg DM/ha threshold between species. The mean SH of dung pat areas was higher for deer than for sheep within 30 cm distant from dung pats (P<0.001). SH at 0, 10, 20, and 30 cm were 11.4, 10.6, 9.8, and 9.2 cm for deer versus 11.1, 8.8, 8.0, and 7.7 cm for sheep). Deer also grazed overall mean SH of non-dung pat areas to a lower height (P<0.001) than dung pat areas (7.4 and 9.0 cm in non-dung pat areas and dung pat areas respectively) in comparison to sheep (8.0 and 8.3 cm in non-dung pat areas and dung pat areas respectively). At pasture availabilities exceeding 2000 kg DM/ha, deer grazed non-dung pat areas to lower SH than in dung pat areas, (SH ranging from 9.8-12 cm in non-dung pat areas versus 12-14 cm in dung pat areas respectively. However at availabilities of approximately 1500 kg DM/ha, there was little difference between SH of dung pat and non-dung pat areas under deer grazing. Sheep on the other hand showed very little discrimination between dung pat and non-dung pat areas over the entire range of pasture availabilities. Results from this experiment indicate deer do graze pasture around cattle dung pats but not as effectively as sheep at high pasture availabilities. The implications are that integrated grazing of cattle and deer may require use of classes of deer that can be grazed to lower pasture availabilities. This finding should help to establish and enable further experimentation to study the potential for deer to substitute for sheep under mixed grazing situations involving cattle. Future studies would involve examining what effects the grazing strategy of deer and sheep has on their pasture intake rate as well as studying economic and management implications of running deer in place of sheep under cattle co-grazing situations.