It has been presumed that biotin deficiency does not result when corn and soybean meal are the main diet ingredients. However, conditions suggesting biotin deficiency have been observed in broilers in the field. In various university studies, a marginal biotin deficiency associated with a high incidence of foot pad lesions and breast blisters, which can cause downgrades at meat processing, was seen in broilers fed practical corn-soy rations (Harms and Simpson, 1975; Harms et al., 1977). Likewise, Oloyo and Ogunmodede (1989) indicated that a dietary biotin level of 120 µg per kg (54.5 µg per lb) was needed to prevent signs of FLKS. These studies, conducted in Nigeria, attempted to relate the level of biotin necessary to prevent FLKS in broilers fed palm kernel oil. Biotin supplementation has an additional benefit in that it favorably affects vitamin C metabolism (Lechowski and Nagorna-Stasiak, 1993). Results indicate that biotin supplementation accelerates ascorbic acid synthesis in some tissues of chickens and that by increasing ascorbic acid levels it indirectly affects all processes involving ascorbic acid.
In battery experiments, biotin deficiency signs were observed in turkey poults fed a commercial type ration containing 227 mg of biotin per ton (0.25 mg per kg, or 0.11 mg per lb) (Marusich et al., 1970). Concurrent feeding of increasing levels of biotin reduced or prevented the deficiency, as measured by foot pad, beak, shank and toe dermatitis and perosis (leg abnormalities) in three-week-old poults. About 409 mg of biotin per ton (0.45 mg per kg, or 0.2 mg per lb) of feed was required to prevent deficiency signs. Feeding this quantity of biotin for three additional weeks to poults previously fed the commercial ration without supplemental biotin for three weeks reduced the incidence of deficiency signs.
Evaluating the natural phenomenon in turkey breeder hens indicates that as the hen ages, the hatchability of eggs decreases. Robel (1983) suggested that biotin in eggs from certain hens may limit embryonic survival. In field studies, eggs from Large White turkey hens were injected with 87 µg of d-biotin, and subsequent hatchability values of fertile eggs were 4% to 5% higher for exogenous d-biotin-injected eggs than for noninjected controls (Robel and Christensen, 1987). Later, Robel (1991) reported that in turkey breeders a minimum of 38 µg of biotin per egg was needed to maintain adequate hatchability of fertile eggs. This translated into dietary levels of 500 to 800 µg per kg (227 to 364 µg per lb) of feed depending on the feed intake and age of the birds. Chen et al. (1994) reported that biotin supplementation of turkey breeder feeds is particularly important for older birds. Similar to Robel, these workers found that 750 µg per kg (341 µg per lb) of feed of supplemental biotin was needed to support adequate hatchability of fertile eggs.
The level of biotin in the yolk of turkey eggs was fairly constant regardless of supplemental biotin, while albumen biotin increased proportionally to dietary biotin levels. White et al. (1987) found that avidin tightly binds to biotin as it is deposited in the albumen through the oviduct. In a follow-up study, White et al. (1992) determined that the biotin content of yolk appeared to nurture the embryo, while the biotin content of the albumen appeared available only to the hatchling. Therefore, the biotin content of both yolk and albumen serve critical needs during the growth and maturation of both prehatch and posthatch chicks and poults.
Krueger and Brown (1987) reported a 3% to 4% improvement in hatch of total eggs in broiler breeder eggs when biotin was supplemented in the breeder hen diet at 1.8 to 2.3 times the NRC (1994) requirement. This improvement in hatch was mainly attributed to reduction in the percentage of eggs that did not hatch.
Losses of biotin during storage can occur. Biotin is readily destroyed by rancid fat (Pavcek and Shull, 1942). Preparing fresh feeds, storing them for only short periods and keeping them dry and in a well-ventilated storage area will minimize rancidity problems. Hamilton and Veum (1984) have suggested that overdrying, poor storage conditions and presence of mold may reduce the availability of biotin in corn. Also, the diet should be low in pro-oxidants and (or) properly protected by an effective antioxidant to avoid destruction of biotin, vitamin E, selenium and other nutrients.
Biotin is relatively stable in multivitamin premixes unless combined with choline or trace minerals. Biotin is relatively stable in multivitamin premixes as well as natural sources in feeds and is fairly stable during processing. Supplemental d-biotin should be added to poultry rations at levels that provide an appropriate margin of safety to offset the factors influencing the biotin needs of poultry.