The present study was performed to investigate the effect of manganese (Mn) supply on metabolism of thyroid hormones in the rat. A study with rats was carried out over two generations. Female rats were raised with a Mn-deficient diet (0.1 mg Mn/kg), and mated to produce a second generation. The male rats of the second generation were used as subjects for the investigation. They were divided into five groups and fed diets with Mn concentrations of 0.1, 0.5, 2.2, 10, and 46 mg/kg for 40 d. For assessment of thyroid hormone metabolism, concentrations of thyroid hormones in serum and activity of hepatic type I 5'deiodinase (5'D-1) were measured. Feeding diets with 0.1 mg Mn/kg impaired growth and food conversion, influenced parameters of thyroid hormone metabolism, and changed some clinical-chemical parameters, such as concentrations of total protein, albumin, calcium (Ca) and magnesium (Mg) as well as activity of alkaline phosphatase in serum. Regarding the thyroid hormone metabolism, rats fed the diet with a Mn level of 0.1 mg/kg had a higher 5'D-I activity in liver, and consequently a higher concentration of triiodothyronine in serum than the rats fed the other diets. In contrast, the concentrations of total and free thyroxine were not influenced by the Mn intake. Growth, clinical-chemical parameters, concentrations of thyroid hormones in serum, and activity of hepatic 5'D-I were similar in the rats fed diets with Mn concentrations between 0.5 and 64 mg/kg. The present study shows that feeding a diet with a very low Mn concentration affects growth and thyroid hormone metabolism and that a dietary level of 0.5 mg Mn/kg is adequate for growth and thyroid hormone metabolism in the offspring of Mn-depleted dams.

Animals↗

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Endogenous excretion and true absorption of cobalt as affected by the oral supply of cobalt.

At the end of a 49-d experiment with 32 growing male rats, a period of 8 d was used to determine endogenous excretion and true absorption as well as apparent absorption and retention of cobalt with the aid of the isotope dilution technique. For this purpose, a single im dose of 58Co was applied at d 35 of the experiment. After that, urine and feces were collected separately from d 8 to 15 after injection of the isotope. The specific cobalt activity of the liver was used as an endogenous reference source. The basal diet provided 5.9 ppb cobalt, the different treatment groups were obtained by supplementing the diet with 0, 10, 50, 250, or 1250 ppb cobalt. The different diets were offered from the beginning of the experiment. In the balance period, apparent and true absorption as well as fecal excretion behaved similar to cobalt intake, whereas urinary excretion increased more rapidly with increasing cobalt supply. Endogenous fecal excretion accounted for 3.5 ng Co/d in the groups fed the diets without and with 10 ppb cobalt. An increase was not observed until supplementing the diet with 50 ppb cobalt. This increase between 250 and 1250 ppb cobalt was higher than the corresponding increase in the dietary cobalt supply. This indicates that endogenous fecal excretion might be more important for homeostatic regulation at a higher dietary cobalt concentration. Endogenous renal excretion as calculated from the results of the isotope dilution technique showed a similar kind of response to increasing cobalt supply as endogenous fecal loss. Nevertheless, the elimination of excessive cobalt mainly took place by adjusting urinary excretion, whereas the variations in true absorption and endogenous fecal excretion had no quantitative importance. Apparent and true absorption were on average 28.0 and 29.8%, respectively, of the cobalt intake. In the case of retention, a marked decline was observed from 19% in the depletion group to 3% with 1250 ppb cobalt, again demonstrating the importance of urinary excretion for controlling the cobalt content of the organism.

Administration, Oral↗

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[Nonessential amino acid content in early weaned piglets following qualitatively and quantitively different protein supplies].

A total of 60 piglets of German Landrace weaned at the age of 2 weeks were fed ad libitum with isoenergetic diets of different proteins (casein + dried skim milk, soybean protein + dried skim milk, only soybean protein) and different protein levels in the diet (20, 27, 34, 40% in D.M.). After 4 weeks the piglets were homogenized and examined for their content of non essential amino acids in the whole body mass by ion exchange chromatography. On the fresh and dried material the content of the non essential amino acids Asx, Ser, Glx, Pro, Gly and Ala increased with the higher protein contents of the diet. Decreasing protein quality reduced the content of serine, whereas coincidently the concentration of glycine, especially on the protein levels of 20 and 27% in the diet increased. On the contrary the protein quality had no effect on the concentration of Asx, Glx, Pro and Ala. Related to the whole body protein the highest contents of the non essential amino acids, excepting serine, were found in piglets which got few protein of low quality. Influenced by the different protein supply the proportion of glycine to lysine varied from 1.28 to 2.17. The mentioned changes in the amino acid composition of the piglets are mainly discussed as shiftings in the proportion of organs and tissues and their protein composition.

Amino Acids↗

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Milk urea and protein content to diagnose energy and protein malnutrition of dairy cows.

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Animals↗

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Nutritional aspects of nucleic acids in animals.

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Animal Feed↗