Turnover of Liver Vitamin A in Steers

Bw, Hayes; Ge, Mitchell; Co, Little; Hb, Sewell

doi:10.2527/jas1967.264855x

Cited by 16 publications

(3 citation statements)

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“…50 OOO IU vitamin A; 0.9 per cent are equal to 450 IU per day). Hayes et al (1967) and W i l k (1988) derived an exponential decrease of vitamin A from the liver of growing cattle fed on unsupplemented diets. The logarithmic function shows a linear relation between liver vitamin A depot and its loss from the liver per day (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

Influence of Various Vitamin-A-supplies on its Concentration in Liver and Plasma of Calves

Flachowsky

Wilk

Löhnert

et al. 1992

Journal of Applied Animal Research

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Five individual feeding experiments with male calves were conducted to investigate variou influencing factors on t h retirzol plasma level and the vitamin-A-depot of liver Liver vitamin-A-depot of calves depends on carotene or vitamin-A-intake of cows an,d vitamin,-A-concentration of milk, respectively. ?Eoo to three weeks old calves born during the summer contained more liver-vitamin-A (>lo0 IU g-') than animals born during the winter season. Feeding of first colostrurn improves vitamin A supply of calves because of the decrease of vitamin A in milk with following milkings (1st milking: loo%, 2nd : 74%, 3rd : 41%). Besides the vitamin-A-depot of liver of calves carotene content of feeds and vitamin-A-supply influ.enced the vitamin-A-status of growing cattle. About 25000 IU vitamin A per 100 kg body weight per day wefe necessary to keep the liver vitamin A depot on a constant level (= 100 IU g-). The results show a homeostasis of retinol in plasma of calves. The concentration of retinol in plasma was regulated very exactly, i f the liver stores of calves were higher than 25 IU g-'. Therefore, the plasma level in,dicates the status of vitamin A storage only i f there is an extreme depletion of vitamin A. At marginal depletion, howevel; there is damage to peripheral tissu.e before changes in the vitamin-A-level in serum occur The determination of vitamin A in serum or plasma gives no information on the adequacy of liver reserves for ju&ng the necessity of a vitamin A su,bstitution.

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Section: Resultsmentioning

confidence: 99%

Influence of Various Vitamin-A-supplies on its Concentration in Liver and Plasma of Calves

Flachowsky

Wilk

Löhnert

et al. 1992

Journal of Applied Animal Research

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“…The next consideration in the development of the slow vitamin A release theory is the large variation in published results on the length of time for half the liver vitamin A to be released. Findings range from 28 to 184 days (Frey and Jensen, 1947;Church et aL, 1956;Hayes et al, 1966Hayes et al, , 1967Sewell et al, 1966;Swanson et al, 1968;Kohlmeier and Burroughs, 1970;Meacham et al, 1970). In an experiment in which rats were given exceptionally high levels of vitamin A, Davies and Moore (1935) found that it took only a little less than 14 days for the liver to be depleted of half of its vitamin A.…”

Section: Resultsmentioning

confidence: 99%

Liver Vitamin A Slow Release Syndrome in Cattle with a Multiple Nutrient Imbalance

Hb¹

1981

Journal of Animal Science

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Data on liver vitamin A concentrations in malnourished, debilitated, down cattle in tropical, northern Australia support the hypothesis that 12% annual cattle mortality was due, in part, to a slow release of liver vitamin A. High Ca and low Zn levels in the legume forage apparently contributed to the slow release. The cattle showed marked sensitivity to sunlight and exhibited problems of sight. The malnourished yearling steers averaged 183.3 micrograms vitamin A/g wet liver vs 152.3 micrograms for steers slaughtered off good green wet season forage. Indications of a slow release of liver vitamin A were that: (1) only 4 to 7 micrograms vitamin A/g liver were in the alcohol fraction or release form; (2) after adjustments for decreases in liver and blood volume in starving animals, blood vitamin A was lowered to 18 micrograms/100 ml, which was low in relation to the adjusted liver vitamin A level of 91.7 micrograms/g, and (3) after adjustments, the liver had released only 1,667 units of vitamin A/day in the dry season, or about 1/4 of maintenance needs. The cattle were grazing a legume forage pasture containing 7.1% protein and no measurable carotene. The forage was deficient in Zn (25 ppm), which would slow the release of liver vitamin A. High Ca levels in the legume forage (.4 to .54%) in combination with low P levels (.11 to .18%) would further aggravate the low Zn level.

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“…Since only a few mg of carotene are secreted daily in milk, this finding is a reflexion of the poor absorption of carotene by ruminants. This concentration of liver retinol was reached despite the fact that the average half-life of liver retinol in cattle is only 48 days (Hayes, Mitchell, Little and Sewell, 1967). The plasma retinol concentrations, increasing in general with the progression of lactation, reflect the high intake of either carotene or retinyl ester (Table 2).…”

Section: Discussionmentioning

confidence: 97%

Effect of dietary carotene on fertility of high-yielding dairy cows

et al. 1985

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Multiparous dairy cows were allotted at the beginning of the dry period to two groups, each of about 75 cows. In addition to a basal diet containing a very low concentration of carotene and a normal concentration of retinyl ester, the carotene group was given a daily supplement of 500 mg carotene during the dry period and 750 mg carotene during lactation, and the retinol group was given an equivalent amount of retinyl ester. Plasma carotene concentrations were much higher in the carotene group (ca. 4-2 mg/1 v. ca. .0-35 mg/1), but plasma retinol did not differ. Neither peripheral plasma progesterone concentration nor the interval between calving and first insemination were affected by carotene supplementation. Conception rate was greatly improved by carotene supplementation in the younger cows (second and third lactation) during the first part of the experiment (cows calving in September to December): conception rates at first insemination were 0-70 v. 0-33 (P < 0-05); for all inseminations, conception rates were 0-71 v. 0-38 (P < 0-01). However during the second part of the experiment (cows calving in January to April) no significant differences were found between the two groups.Plasma tocopherol concentration in cows given carotene was significantly higher during the dry period and the 1st weeks of lactation, but these differences disappeared in the later stages of lactation. Plasma cholesterol concentration in the carotene group was highly correlated with plasma carotene concentration {r = 0-52 to 0-59, P < 0-001); however even higher correlation coefficients were found between plasma cholesterol and plasma tocopherol in both the carotene and the retinol groups (r = 0-61 to 0-80, P < 0-001). Plasma concentrations of triglycerides, glucose, urea and aspartate aminotransferase were not affected by the treatment.A high plasma carotene concentration is not a prerequisite for conception; however, under certain conditions which need defining, the carotene concentration appears to be a limiting factor.

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Turnover of Liver Vitamin A in Steers

Cited by 16 publications

References 0 publications

Influence of Various Vitamin-A-supplies on its Concentration in Liver and Plasma of Calves

Influence of Various Vitamin-A-supplies on its Concentration in Liver and Plasma of Calves

Liver Vitamin A Slow Release Syndrome in Cattle with a Multiple Nutrient Imbalance

Effect of dietary carotene on fertility of high-yielding dairy cows

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