@conference {40555,
	title = {Within herd variability in the mineral status of grazing dairy cows in early lactation.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {27-30},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Two groups of 10 mature, crossbred cows received either a single 
daily dose of 10 g Mg or no supplemental Mg for two 5 day periods.  Blood 
was sampled twice daily and urine once daily.  On 3 days blood and urine 
were sampled four times.  Serum Mg levels of 3 unsupplemented animals fell 
from 0.74 {\textpm} 0.034 to 0.25 {\textpm} 0.020 mmol/1 within 5 days while other animals 
within this group maintained serum Mg levels despite the absence of Mg  
supplementation.  At any given sampling time serum Mg levels of individuals  
within the unsupplemented group varied from 0.22 to 0.88 mmol/1 and those of  
supplemented animals from 0.41 to 0.83 mmol/1.  Mean serum Mg, Ca, Na and  
K concentrations did not differ between the groups.  Unsupplemented animals  
had significantly (P<0.001) lower urinary fractional clearance ratios of Mg 
and Ca. 
 
The within and between animal variation in serum Mg levels was high for both  
Mg supplemented and unsupplemented animals.  The fractional clearance of  
Mg in urine indicated a likely benefit from Mg supplementation for 100\% of  
the unsupplemented animals while serum Mg concentrations only identified  
40\% of these animals.  Fractional clearance of Mg in urine has potential as 
an indicator of animal Mg status. 
 },
	issn = {1176-5283},
	author = {Dalley DE}
}
