Concentrations of blood constituents from 12 to 72 weeks of age in genetically high and low milk production lines of Friesian and Jersey cattle

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Abstract
Summary: Blood samples were collected at 12-week intervals from 12 to 72 weeks from a total of 221 growing Friesian and Jersey calves and assayed for plasma concentrations of free fatty acids (FFA), ketones, glucose, calcium, phosphorus, magnesium, copper, albumin and globulin. Sixty-six of the animals could be allocated to genetically high and 73 to genetically low milk producing lines on the basis of being sired by the ‘best’ or ‘worst’ nationally available progeny tested sires. All animals were housed indoors and fed a complete pelleted diet ad libitum. There were no differences between genetically high and low milk production lines for any blood constituent and no useful indicators of genetic merit for milk production in later life. There were no differences between breeds for metabolites related to energy status (FFA, ketones, glucose). Friesians bad higher magnesium and lower mean copper concentrations than Jerseys and had higher phosphorus concentrations up to 36 weeks. Differences between breeds and ages in mineral concentrations were not related to breed differences in the discrepancy between observed intakes and predicted requirements of minerals. Concentrations of globulins were higher and of albumin lower in Jerseys than in Friesians at 12 and 24 weeks possibly owing to slightly higher disease incidence of Jerseys in early life. There were changes with age in concentrations of all constituents except FFA. There was evidence of genetic variation within breeds and lines for mean plasma concentrations of ketones, copper and globulin. There was no evidence for differences between females and castrates for any blood constituent.

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