Seasonal rainfall patterns modify summer energy balance and nutritional condition of grazing sheep via vegetation communities

Abstract

Abstract Recent spring and summer rainfall patterns in Mongolian grasslands have shown high annual fluctuations and are thought to affect sheep energy balance and nutritious condition via plant community changes. To test this, we obtained climatic and vegetation data in Mongolian semi-arid grasslands from spring to summer for 3 years. Sheep energy intake and expenditure were calculated, and the energy balance and nutrition indicators were compared among years with different seasonal rainfall patterns. In 2019 and 2022, rainfall patterns were characterized by the presence or absence of an early summer drought, respectively. Compared to 2019, plants were tall and abundant in 2022, and thus mean bite size, energy intake, and body weights were greater. Estimated energy intake and expenditure were 4.56 and 2.10 Mcal in 2019, and 6.75 and 1.63 in 2022, respectively, demonstrating that rainfall timing and amount affected vegetation assemblage, plant height, herbage nutrition, grazing behavior, animal energy balance, and nutrition conditions. Insufficient rainfall events before early summer in semi-arid grazing lands resulted in low energy intake and balance, and the delayed body weight gain could not be recovered. The findings can inform management of grazing land to ensure optimal livestock condition.