New Zealand Journal of Agricultural Research abstracts

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The effect of high pasture molybdenum concentrations on the copper status of grazing horses in New Zealand

S. G. PEARCE
E. C. FIRTH

Institute of Veterinary, Animal and Biomedical
Sciences
Massey University
Private Bag 11222
Palmerston North, New Zealand.

N. D. GRACE*

AgResearch
Grasslands Research Centre
Private Bag 11008
Palmerston North, New Zealand

P. F. FENNESSY

AgResearch
Invermay Agricultural Centre
Private Bag 50034
Mosgiel, New Zealand

Abstract  The objective of this study was to determine whether Mo causes secondary Cu deficiency in pasture-fed horses. Twelve Thoroughbred weanling fillies were divided into two groups and fed either high Mo pasture (8 to 15 mg Mo kg^-1 DM) or a low Mo pasture (0.6 to 1.2 Mo kg^-1 DM) for 84 days. Both pastures contained 6 to 9 mg Cu kg^-1 DM. The animals were challenged with Cu over the last 14 days to determine change in their Cu status to 1.0 mg Cu kg^-1 liveweight d^-1 given orally three times a week. Copper status was assessed from liver, plasma, blood cell, and plasma trichloroacetic acid-insoluble Cu concentrations as well as the enzyme activities of plasma caeruloplasmin and red blood cell superoxide dismutase. None of these indices was affected by the increase in Mo intake. Horses grazing pasture high in Mo responded no differently to Cu challenge than did those on low Mo pasture. The results of this study suggest that Mo is unlikely to increase dietary Cu requirements and induce secondary Cu deficiency at the Cu and Mo concentrations normally found in New Zealand pastures grazed by Thoroughbreds.

Keywords  copper status; molybdenum; pasture; horse

New Zealand Journal of Agricultural Research, 1999, Vol. 42: 93-99

0028-8233/99/4201-0093 $7.00/0 (c) The Royal Society of New Zealand 1999

PDF file of entire paper: medium quality (571K); (scanned from paper original: notes about this process)

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