Summary of Magnesium Pasture Spraying Fram Study
Independent Veterinary Supplies Ltd has produced an oral magnesium product for dairy cows. It is a magnesium oxide in a suspension which was tested for pasture spraying, initially at a Te Mawhai Road farm (near Te Awamutu). The aims of the study were to:
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Find a practical means of spraying the product.
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Supply elemental magnesium at 15gm per cow per day but change the base mixture to find the optimum for the equipment used.
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Ensure the cows were adequately supplemented with magnesium throughout the study.
Blood tests for trace elements had already been taken from the dry cows on June 13th and this provided a baseline magnesium level. A spray nozzle was attached to a quad bike already fitted with a CDAX spraying unit. Spraying started on July 23rd at 60ml per cow per day. The product was applied as a 50% mix providing 15gm per cow per day of elemental magnesium. This is a standard amount of magnesium to be giving dry cows at this time of the year.
Sprayting was done in the morning and took approximately 15 minutes. Up to the start of the study the cows had received 50gm per cow per day of magnesium oxide by pasture dusting.
Repeat blood tests were taken from the same cows three weeks after supplementation with the sprayed prodyuct began.
The results were:
Cow No.
Age
Calving Date
June 13 Blood mg nmol/l
July 15 Blood Mg nmol/l
123
5
Aug 4
0.50
0.53
161
8
July 26
0.41
0.42
169
6
July 26
0.78
0.88
235
3
July 22
0.80
1.12
285
9
Sept 20
0.52
0.86
313
6
Oct 1
0.65
0.70
318
4
Aug 8
0.45
0.70
461
3
Aug 9
0.50
0.55
Mean
0.58
0.72
Initial results were very encouraging. The blood magnesium levels of all the cows increased over the three weeks. This is at a time of year when it can be difficult to maintain magnesium levels, pasture magnesium being at its lowest level.
I believe the cows were well supplemented with magnesium throughout the study. A more definative trial should now be done to compare pasture dusting with pasture spraying and more accurately define the ideal application rates. There was insufficient time to carry the study beyond three weeks as half the cows had calved and their magnesium management changed.
Steve Cranefield BVSc
6 October 1998
Copyright - freely available for reprint as long as attribution is made to Independent Veterinary Supplies Ltd (NZ) and NZ veterinarian Steve Cranefield as source of material.
