Variations in Certain Blood Components of Holstein and Jersey Cows and their Relationship to Daily Range in Rectal Temperature and to Milk and Butterfat Production

Abstract

Winter and summer blood samples were taken from 96 Jersey and 78 Holstein cows. Laboratory determinations of the levels of reduced glutathione and hemoglobin and of red-cell volume were made. The data were analyzed statistically to determine all correlations of possible interest and meaning, to determine the relative importance of various assumed causes of variation in the blood components and in daily range in rectal temperature, another variable of interest observed on cows in milk during the summer. All of the blood components were significantly repeatable. Age variation seemed to have no influence on variation in the blood components or daily temperature range. Breed and season differences were significant, but significant sire differences were not observed, except in the case of glutathione in the Holstein breed. Stage of lactation and/or stage of gestation appears to have an influence on or be related to hemoglobin and daily temperature range, stage of lactation being the more important in Jerseys and stage of gestation the more important in Holsteins. Correlations of the blood components with most probable performing ability for milk production, fat production, and fat test were so small that the blood components were concluded not to be useful criteria of selection for these economic traits. © 1960, American Dairy Science Association. All rights reserved.