Thiamin requirements in some species are difficult to establish because of vitamin synthesis by microflora in ruminants and most likely for all species in the lower intestine. For poultry, it is doubtful whether the amount of thiamin produced by intestinal synthesis and absorbed is large enough to make a significant contribution to body needs. Poultry species thiamin requirements generally range between 0.8 and 2.0 mg per kg (0.36 to 0.90 mg per lb) diet (NRC, 1994) while classes of Japanese quail range between 1.6 to 3.2 mg per kg (0.72 to 1.5 mg per lb) diet (Shim and Boey, 1988).
Diet composition can dramatically influence thiamin requirements. Since thiamin is specifically involved in carbohydrate metabolism, level of dietary carbohydrate relative to other energy-supplying components influences thiamin requirement. The need for thiamin increases as consumption of carbohydrate increases. When dietary thiamin is deficient, body reserves become depleted more rapidly when animals are being maintained on a feed rich in carbohydrates than when they are receiving a diet rich in fat and protein. The "thiamin sparing" effect for fats and protein has long been known.
Size, genetic factors and metabolic status affect thiamin requirements. Thiamin requirement is also proportional to size. Light poultry breeds (Leghorn) seem to have higher thiamin requirements than heavy breeds (Thornton and Schutze, 1960) and Leghorn hens deposit more thiamin in eggs than do heavy hens. As an animal ages, its need for thiamin increases because efficiency of vitamin utilization likely diminishes. Olkowski and Classen (1996), working with broilers, indicated that there are organ-specific differences in the requirement for thiamin. The heart had an increased requirement compared with the liver and brain. Maternal thiamin nutrition affects thiamin status and metabolism of the offspring (Olkowski and Classen, 1999). Maternal thiamin supplementation of the hen increased heart thiamin in broiler offspring.
Thiamin requirements are obviously higher if feeds contain raw materials (e.g., fish) or additives with anti-thiamin action. Spoiled and moldy feeds may contain such antagonists or thiaminases. Chicks kept on a feed infected with Fusarium moniliforme developed polyneuritis that could be cured with thiamin injections (Fritz et al., 1973). Moldy feed analyses showed a thiamin content of less than 0.1 mg per kg (0.05 mg per lb), whereas the same feed not contaminated with Fusarium had a thiamin content of 5.33 mg per kg (2.4 mg per lb). This antagonistic factor could be destroyed by treatment with steam.
Disease conditions also result in increased thiamin requirements. When dietary thiamin is marginal, typical deficiency signs of thiamin are more likely to develop in infected animals than in normal animals. Endoparasites such as strongylids and coccidia compete with the host for thiamin contained in feed. It has been shown experimentally that infection with coccidia results in considerable reduction in thiamin blood levels. Thiamin levels found were directly correlated to infection severity (McManus and Judith, 1972). Likewise, conditions such as diarrhea and malabsorption increase the requirement.