Biochemical variables from Holstein-Friesian calves older than one week are comparable to those obtained from adult animals of stable metabolic status on the same farm.

BACKGROUND: Age-related changes in blood variables have previously been reported for cattle. A few studies have investigated differences in biochemistry analytes over time using repeat measures.
OBJECTIVES: The purpose of the study was to investigate the variation in select variables during the first 3 months of life of Holstein-Friesian calves using repeat sampling.
METHODS: Twenty healthy calves were sampled on the day of birth (0) and at 6, 13, 21, 30, 60, and 90 days of life. Analyzed variables included concentration of glucose, total protein, albumin, urea and creatinine, and activity of AST, GGT, and CK. Reference intervals (RI) were obtained from 40 adult cows using specific computer software. The variation in each analyte throughout the study period and differences relative to the RI in adult cattle were assessed.
RESULTS: With the exception of glucose, the studied variables were affected by the calf's age. However, for most of the analytes studied, the values obtained from calves from one week of age onwards remained within the RI determined in adult cattle. During the calves' first week of life, some variables outside the RI of adult cattle were due to the changes associated with birth and colostrum intake.
CONCLUSIONS: With the exception of AST and GGT activity, RI for standard biochemistry variables determined for adult cattle are likely to be valid for calves older than one week. However, special consideration is necessary for calves within their first week of life.