{'fraction_non_alphanumeric': 0.016183986371379896, 'fraction_numerical': 0.019591141396933562, 'mean_word_length': 4.9045226130653266, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The effect of varying levels of dietary vitamin A on immune response in the chick.

The effect of dietary vitamin A on antibody production and T cell proliferative response was determined in broilers from 21 to 39 d old. Chicks were fed soybean meal-sorghum diets with levels of supplemented vitamin A from 0 to 13,200 micrograms/kg retinol equivalents from hatching and were immunized with beta-casein at 21 d of age. T cell proliferation response to beta-casein or an acetone precipitate of antigen to Mycobacterium tuberculosis was determined in vitro at 34 to 37 d old. Antibodies to beta-casein in serum were determined every 5 d from 21 d of age. In chicks with no added dietary vitamin A, antibody production and proliferative response were depressed in comparison with chicks receiving vitamin A. Addition of small amounts of vitamin A enhanced the responses; both antibody production and proliferative responses increased with dietary vitamin A until the diet contained 6,660 micrograms/kg, above which the responses decreased. This suggests that maximal immune responses in the chick may be achieved at dietary intakes considerably higher than NRC recommendations.