Grazing behavior of Mongolian sheep under different climatic conditions

Abstract

Ongoing climatic changes are one of the most serious environmental problems in Mongolia. Although research on the effect of heat stress on livestock was carried out in a barn or laboratory, the grazing behavior of livestock in rangeland is not well investigated. Therefore, the purpose of this study was to determine the effects of climatic conditions on sheep grazing behavior in the Mongolian rangeland. We used climatic data on air temperature and precipitation and Normalized Difference Vegetation Index (NDVI) as a vegetation factor. A bite counter and global positioning system were attached to the sheep to measure bite rate and moving distance as factors of sheep grazing behavior. To examine the effect of climatic conditions on the grazing behavior of sheep on a daily scale, we used generalized linear mixed models of daily bite rate, walking velocity, and bite rate/walking velocity with daily NDVI, temperature, precipitation, and the interaction of temperature and precipitation as fixed factors, and individual sheep as a random explanatory factor. We also conducted a regression analysis of each behavior with a mean temperature every 3 h for the within-day scale analysis. We observed a statistically insignificant effect of temperature on the bite rate of grazing sheep on a between-day scale and a positive effect on bite rate within a day scale, whereas temperature significantly decreased the walking velocity on both between-day and within-day scales. Precipitation did not affect mean bite rate or walking velocity values on either scale. The air temperature was the major climatic factor influencing the grazing behavior of sheep in semi-arid environments.