Turnover of Liver Vitamin A in Steers Fed a Low-Protein Ration

Bw, Hayes; Ge, Mitchell; Co, Little

doi:10.2527/jas1968.272516x

Cited by 5 publications

(2 citation statements)

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“…While these results confirm the longterm carry-over effect of vitamin A suggested by Deuel et al (1942), the magnitude of the effect after the first 21-37 days would be of little practical use. If the carry-over effect was caused by the slow reduction in liver vitamin A concentration ( Hjarde et al 1961;Hayes et al 1968), then increasing the dose of vitamin A, which increases the liver concentration of vitamin A, could increase the duration of the carryover effect on PC concentration. It is likely, however, that continuing the supplement for longer would be more effective than increasing the dose of vitamin A.…”

Section: Discussionmentioning

confidence: 98%

Effect of dose and frequency of vitamin A supplements, and carryover effects on plasma carotenoid concentration in steers

Knight

Death

1999

New Zealand Journal of Agricultural Research

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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.

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Section: Discussionmentioning

confidence: 98%

Effect of dose and frequency of vitamin A supplements, and carryover effects on plasma carotenoid concentration in steers

Knight

Death

1999

New Zealand Journal of Agricultural Research

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“…Thus the transfer from the circulating retinol-RBP complex, in both the placenta and the mammary gland, must involve surface receptors for RBP which have not yet been studied. Swanson et al (1968) found that the rate of loss of liver vitamin A by milk cows on a depletion diet was about the same as that found by Hayes et al (1968) for steers, and that there was no difference in depletion rates between high-and lowyielding cows. Thus the drain on liver stores through milk secretion may be lower than predicted from the amount secreted in the milk, perhaps through more efficient utilization or conservation.…”

Section: Maternal Status During Human Pregnancymentioning

confidence: 89%