Effect of grazing season and age on blood indices of sheep grazing in songnen grassland

The seasonal change of forage is the main factor that affects the nutrition of grazing livestock, and it is necessary to systematically study the influence and extent of forage quality changes on the grazing livestock. In this experiment, we clarified the influence of seasons and ages on these indexes through a dynamic monitoring routine and estimating mineral indices of blood sampled from sheep grazing in the Songnen Grassland. The purpose of this study was to screen and assess the sensitive indicators of the nutritional status of livestock, which can provide theoretical support for the nutrition management of grazing livestock. Eight 3-month-old lambs, 3-year-old ewes, and 6-year-old ewes grazing in all four seasons were chosen for this experiment. The results show that grazing season and sheep age had significant effects on the total protein, albumin, urea nitrogen, triglyceride, and glucose content in sheep blood (P<0.05), and there was a significant interaction between age and season. The results of analysis of the major minerals in the blood showed no significant effect of age on the blood sodium content(P<0.05), but season did have a significant effect on sodium, and there was no significant effect of the interaction between age and season on blood sodium content(P>0.05). Both age and season had significant effects on potassium and chlorine in the blood, and there was a significant effect of their interaction on chlorine. Age and season significantly impacted calcium levels in the blood, but there was no effect of their interaction. Age and season, as well as their interaction, had significant effects on phosphorus levels. No significant effect of age was observed on the blood magnesium levels, but season significantly affected magnesium. In conclusion, blood urea nitrogen and phosphorus are sensitive indicators of seasonal change.