Repeatabilities of serum constituents in Holstein-Friesians affected by feeding, age, lactation, and pregnancy.

Effects of feeding regimen (pasture and drylot), physiological stage (lactating pregnant, lactating nonpregnant, and dry), and age on metabolites in blood serum were measured in 100 Holstein Friesian cows over 18 mo. Calcium, cholesterol, uric acid, total protein, albumin, and alkaline phosphatase were affected by physiological stage, whereas feeding regimen affected creatinine. Inorganic phosphate, blood urea nitrogen, glucose, lactic dehydrogenase, and glutamic oxaloacetic transaminase were affected by the interaction of stage and regimen. Age of animal affected cholesterol, glucose, and lactic dehydrogenase. Variances among and within cows were not consistent across physiological stages providing different repeatabilities for each stage. For example, total protein was highly repeatable in the two lactating stages but only moderately repeatable in dry animals (.61, .73, .26). Alkaline phosphatase and creatinine had consistently high repeatabilities.