Magnesium status of dairy herds in Matamata County, New Zealand 1. Associations of serum magnesium and animal, management, pasture, and soil factors

Abstract

Blood samples were collected from 12–21 cows in each of 119 herds before calving (July 1978) and in early lactation (September 1978), and analysed for serum magnesium (Mg). Soils and pastures were also sampled on each occasion and management details were obtained in farmer interviews. At both samplings, the serum Mg concentration of cows decreased with increasing age of cow and increased with improving cow condition. Herd Mg status was higher where Mg supplementation was practised, and was positively associated with the feed level of the herd at both samplings. Herd Mg status was also associated with farm topography, proportion of hay in the diet, rate of potassium (K) application, and herd breed at one of the two samplings. The mean Mg status of herds was associated with soil Mg and soil phosphorus (P) but no significant relationship was found between herd Mg status and the chemical composition of pastures.

Keywords:

• magnesium
• serum Mg
• dairy herds
• cow age
• Mg supplementation
• feed level
• hay
• K application
• soil Mg
• pasture chemical composition