Switch Hair as an Indicator of Magnesium and Copper Status of Beef Cows

The study examined the use of switch hair as an indicator of magnesium (Mg) and copper (Cu) status in 24 beef cows (11 Angus and 13 Angus-Charolais) over 5.5 months. It found significant differences in hair growth rates and mineral concentrations based on breed, season, and sward type. Black-pigmented Angus hair contained more Mg than light-pigmented Angus-Charolais hair. There were correlations between Mg concentrations in hair, serum, and urine, and between Cu concentrations in hair, serum, and liver. Cows with low Mg in hair were potentially hypomagnesemic. Environmental contamination increased Mg concentrations in hair over time, while Cu concentrations remained stable until later in the study. The study suggested that switch hair could be a useful non-invasive indicator of mineral status in cattle.