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Cattle don’t care: Animal behaviour is similar regardless of grazing management in grasslands

Venter, Zander S., Hawkins, Heidi-Jayne, Cramer, Michael D.
Agriculture, ecosystems & environment 2019 v.272 pp. 175-187
animal behavior, biodiversity, cattle, ecological function, feces, forage, grasslands, grazing management, herds, lawns and turf, livestock productivity, normalized difference vegetation index, overgrazing, rangelands, spatial distribution, spatial variation, stocking rate, trampling damage, walking, South Africa
It is well known that rangelands lose productivity and ecosystem function under excessive rates of livestock stocking, however the role of the spatio-temporal distribution of grazing density remains debated. Multiple studies show that managing grazing for high livestock density has little effect on plant and livestock productivity, yet fewer explore animal behaviour as a mechanism that would explain these observations. We hypothesised that increasing cattle grazing densities under equivalent stocking rates will cause animals to concentrate more, spend more time grazing and thereby increase utilisation of forage, and reduce selection for palatable vegetation patches and species. We compared season-long grazing (SLG), four-camp grazing (FCG) and holistic planned grazing (HPG) over three years in an experimental trial in a mesic grassland of South Africa reflecting a range of grazing densities (SLG < FCG < HPG). We measured the spatio-temporal patterns of cattle behaviour, dietary composition, dung trampling, animal productivity, and normalised difference vegetation index (NDVI). The management approach did not change the time allocated to different animal behaviours, trampling of dung, nor the selection for particular plants. HPG cattle grazed at closer distances to one another than SLG but not FCG, and herds were equally concentrated when resting and walking. HPG cattle spent less time in patches of high vegetation NDVI compared to SLG, thereby reducing the spatial heterogeneity of NDVI over time. Cattle gained 0.2 ± 0.02 kg day−1 ha−1, and this did not differ between management approaches. The HPG approach is costly to set up and is predicted to take twice as long as FCG and SLG to become profitable. Depending on the management goal, HPG could reduce selection for palatable patches, possibly preventing overgrazing and formation of bare patches over the long term. Alternatively, SLG could increase selection for palatable patches and initiate the formation of grazing lawns and, in combination with fire, commonly used in FCG, might enhance biodiversity.