Estimating winter energy balance and actual changes in nutrition of Mongolian grazing sheep

We aimed to estimate the energy intake and expenditure of grazing Mongolian sheep during the winter months using indirect methods of bite mass, number of bites, ME content per bite, traveling distance, body condition, and blood parameters. Energy intake was calculated as the bite mass × number of bites × ME per bite. Daily energy expenditure was calculated as the sum of the expenditures incurred for maintenance, grazing, and thermoregulating, as well as during pregnancy. We also investigated the sheep nutrition indicators (body condition and blood biochemical parameters) before and after winter. Average daily bite number, bite weight, and daily feed ME of sheep were 12,094, 53 mg in March, and 1.16 Mcal, respectively, and thus, total daily ME of intake was 0.86 Mcal. The daily energy expenditure for maintenance, grazing, thermoregulation, and fetus were 1.58, 1.56, 2.27, and 0.41 Mcal, respectively, accounting for a total daily energy expenditure per sheep of 5.82 Mcal. The total protein (70.2 to 49.1 g/L), albumin (37.4 to 16.9 g/L), and leptin contents (37.1 to 10.9 ng/mL) in the blood decreased remarkably after winter. The energy intake and expenditure results showed that the estimated total negative daily energy balance was 4.96 Mcal/d during the winter season. These results indicated that Mongolian sheep did not maintain a sufficient energy balance during winter and, thereby, required compensation for the negative energy balance using their body fat and protein stores.