Effect of dietary carbohydrates and biotin level on cecal size and biotin concentration of growing chickens

Intestinal distribution and absorption of biotin in the chicken

The initial distribution and absorption of biotin in chickens was studied in vivo from either changes in the composition of intestinal contents or analysis of blood draining the gut. The progressive decline in biotin concentration and flow along the small intestine demonstrated absorption throughout this organ. Quantitatively the duodenum was the most significant site of biotin absorption when crystalline biotin was included in the diet and when dietary ingredients contained highly available biotin. In contrast, when diets of low biotin availability were given the distal segments of the small intestine contributed a relatively greater amount to biotin absorption. During passage of digesta from the ileum to the caecum there was a tenfold increase in biotin concentration. About half the amount was of ileal origin with the remainder presumably resulting from microbial synthesis. About 20% of caecal biotin was in a 'free' form but the degree of absorption from the caeca was not determined. The amount of biotin disappearing from the gut of birds given maize-based diets was similar to the quantity appearing in portal blood. Biotin absorption was not detected from wheat-based diets using arteriovenous differences.

The effect of dried and fresh eggs on plasma cholesterol and atherosclerosis in chickens

Oxidation products of cholesterol, which have been observed to be formed in powdered eggs and other dehydrated cholesterol-containing foods, have been suspected as the probable primary cause of atherosclerotic lesions. The feeding of powdered vs. fresh egg yolks to young male chickens up to 30 and 43 weeks of age, respectively, produced approximately the same increase in plasma cholesterol, liver fat, and liver cholesterol when compared to the feeding of a soybean-based cholesterol-free diet. Aortic atherosclerosis, however, was found to be more severe in a group of birds fed fresh egg yolks than in those fed powdered egg or the cholesterol-free diet. A previously demonstrated, enhanced feedback inhibition of cholesterol synthesis by oxidized cholesterol derivatives may at least partly explain these results.

Nitrogen balance studies in aging rats

Nitrogen balance studies were conducted to compare the protein requirements of aged (24-month-old) and mature (12-month-old) rats for possible age-related differences. Four diets with protein supplied as amino acid mixtures simulating casein protein at 4.5%, 4.5% plus 1.5% indispensable amino acids of casein, 4.5% plus 1.5% dispensable amino acids of casein or 6.0% casein protein were offered for one week each during a four-week counter-balanced dietary sequence. Lower food and nitrogen intake of aged rats resulted in a lower mean nitrogen balance compared to that of the mature animals. Calculations of the level of N intake necessary to provide for N equilibrium in the aged rats indicated an apparent increase in the actual net need for nitrogen and indispensable amino acids when compared with the needs of the mature animals.