New Zealand Journal of Agricultural Research abstracts
Effect of dose and frequency of vitamin A supplements, and carry-over effects
on plasma carotenoid concentration in steers
T. W. KNIGHT
A. F. DEATH
AgResearch Grasslands
Private Bag 11008
Palmerston North, New Zealand
Abstract Experiments were carried out to determine the effect
on plasma carotenoid (PC) concentration of dose, frequency of dietary
supplements, and the carryover effect once vitamin A supplements ceased. Plasma
cholesterol (PChol) concentration and fat colour were also measured in one
experiment. Pasture-fed Angus and Simmental crossbred steers received 1 kg per
head per day of pellets fed from troughs in the paddock and vitamin A was
included in the pellets when required. Vitamin A supplements decreased PC
concentration but there were no differences between doses. Liver vitamin A
concentration increased as the dose increased. There were no effects on fat
colour despite vitamin A supplements decreasing PC concentration by 30-50%.
There were positive correlations between PChol concentration and fat colour,
but pre-treatment PC concentrations provided a better indication of fat colour.
All frequencies of vitamin A supplements decreased PC concentration but daily
supplements were more effective. After 35 days with daily supplements, PC
concentration had decreased 71% compared with a decrease of 46-49% when
supplements were given every 2-4 days. The PC concentration in vitamin
A-supplemented steers rapidly increased after supplements ceased but
significant differences still remained after 11 weeks.
Keywords cattle plasma carotenoids; vitamin A supplement;
liver vitamin A; fat colour
New Zealand Journal of Agricultural Research, 1999, Vol. 42: 385-391
0028-8233/99/4204-0385 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (549K); (scanned from paper original: notes about this process)
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