Potential impact of botanically diverse pasture on the nutritional, physiological, and immunological status of grazing cows

The aim of this study was to reveal the potential impact of botanically diverse pasture on the nutritional, physiological, and immunological status of grazing cattle using multifaceted indices. Ten Japanese black beef cows (325.5 ± 40.6 kg of body weight [BW], 7.9 ± 3.8 years of age) were used in this experiment. Five of them grazed on a 1.8-ha grassland (botanically diverse pasture: DP) that was composed of sown grassland and grazable forestland (approximately 34 plant species). The other five cows grazed on 1.0 ha of sown grassland with only a few plant species (botanically monotonous pasture: MP, approximately 5 plant species) for 2 months. Blood samples were collected approximately every 2 weeks. In DP cows, the hemoglobin (HGB) concentration, hematocrit (HCT) ratio, and superoxide dismutase (SOD) activity increased linearly after the start of grazing, as did plasma sodium (Na), calcium (Ca), and potassium (K) concentrations. Urea nitrogen (UN) levels were higher in DP than in MP cows throughout the grazing period, whereas in MP cows, the red blood cell (RBC) count, HGB concentration, and HCT ratio decreased quadratically after the start of grazing. The DP cows gained more BW than the MP cows throughout the grazing period. Thus, the increased intake and/or the change in the ingested plant species in DP cows might have promoted the increase in the plasma UN concentration. In summary, the present study showed that grazing in botanically diverse pasture improved the nutritional and physiological status of cows; however, it aggravated the imbalance of protein and energy intake induced by grazing within 2 months.