Flachowsky, G., Schneider, A., Qchrimenko, W.I. and Kronemann, H. 1994. Calcium release from various roughages and influence of Ca on dry matter degradability of roughages in the rumen and apparent digestibility of ration. J. Appl. Anim. Res., 6 : 43-57.
Five experiments with 18 to 36 male calves each of the black and white dairy cattle breed (age: 14-21 days, initial live weight: approximately 45 kg per animal) were carried out in order to investigate the influence of various vitamin A supply (0-80,000 IU per 100 kg LW and day) on dry matter intake and weight gain as well as the vitamin A status of liver and blood plasma over 84 days. The calves consumed a diet free of carotene and vitamin A consisting of milk replacer, concentrate and chopped wheat straw. The calves were fed in three experiments for a longer time in order to observe the further vitamin A depletion. Nine animals consumed an unsupplemented ration, nine other one got 10,000 IU vitamin A per 100 kg LW and day. Biopsies of liver and plasma samples were taken from 4 animals per group every four weeks. The various vitamin A supplementation did not significantly influence the dry matter intake (Mean: 1.67; 1.48 to 1.80 kg DM per animal and day) and the weight gain of calves (Mean: 702, 599 to 770 g per animal and day). First vitamin A deficiency symptoms (reduced feed intake, decreased weight gain, diarrhoea etc.) were observed in animals of unsupplemented group after 100 days of experiments. After 84 days the vitamin A concentration of liver of animals of unsupplemented groups decreased to 1.3-32.2% compared with the begin of experiments (60.6-155.7 mumol/kg fresh matter). Up to 51% of initial concentration were found when 10,000 IU vitamin A per 100 kg LW and day were fed. About 25,000 IU vitamin A per 100 kg LW and day were required in order to keep the initial level of vitamin A concentration of liver. The plasma vitamin A concentration is unsuitable for estimation of vitamin A status of calves. The concentration of vitamin A of liver and plasma amounted to 114 mumol per kg and 0.25 mumol per litre at the begin of experiments. The vitamin A concentration of liver of unsupplemented group decreased to 20 mumol per kg, that of plasma increased to 0.28 mumol per 1 at the end. A strong vitamin A deficiency (liver concentration: less than 10 mumol/kg) may cause a decrease of vitamin A concentration of blood.
Carotene is stored as a tissue reserve in the corpus luteum. With different carotene supplementations in heifers (0, 100, 200 and 300 mg/animal and day) it could be clearly seen that the carotene concentration in the corpus luteum (2.3, 27, 50 and 81 micrograms/g) was directly dependent on it. On the other hand, the weight of corpus luteum (3.8 to 4.6 g) was not influenced (P greater than 0.05) by carotene supplementation. Apart from corpus luteum carotene was also stored in orange coloured pigment corpuscles of ovary. The carotene concentration of the pigments was 6 to 70 times higher (158, 150, 334 and 487 micrograms/g) than in the corpus luteum. Weights of the pigments rose with increased carotene doses. However, the weights amounted to merely 4 to 11% of the corpus luteum's mass. The amount of carotene in corpus lutea of animals added with carotene contained was higher than that of pigments. Further investigations are necessary to characterize the physiological importance of the pigment corpuscles.
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