Relationship of Circulating Eosinophils, Other Blood Cellular Components and Plasma Corticoids in Dairy Cattle Subjected to Nutritional Stress

Twenty-six first lactation dairy cattle were sampled biweekly for four months to determine the effect of five levels of nutrition on blood plasma corticoids, total and differential leucocytes, hemoglobin and packed cell volume. Cows completing their 305 day lactation during the four month sampling interval were removed from the experimental herd, but were sampled twice more. It was hypothesized that cows on ration s below NRC requirements for milk production would demonstrate stress symptoms of elevated plasma corticoids, elevated white blood count, neutrophilia and eosinopenia. It was also hypothesized that measuring the decrease in eosinophils would be a better method of quantifying nutritional stress than by measuring corticoids, since circulating eosinophils are not subject to rapid increases from stresses of sampling, as are the corticoids. Least squares analysis indicated a trend for increased corticoids with decreased level of nutrition, but the trend was not significant (p\u3e . 05). Eosinophil level was significantly (p \u3c . 05) correlated with ration indicating increased stress caused a rise in eosinophils in stead of a decline as was expected. Eosinophils were negatively correlated with corticoids (-.12) as expected but the relation ship was not significant (p\u3e.05). Ration was positively correlated with milk yield, body weight, and number of circulating neutrophils. Ration was negatively correlated with total leucocyte count. No significant change in hemoglobin or packed cell volume was detected. Significant (p \u3c • 01) increases in leucocytes, neutrophils and hemoglobin were observed in the cows after completion of the 305 day lactation. Significant (p\u3c.01) decreases in corticoids and milk production were also observed in these cows