Growth depression may become evident in biotin-deficient swine before clinical signs are seen. The first clinical signs are generally excessive hair loss and dermatitis, with complete hair loss in severe cases. Dermatitis first appears as scaly skin, often starting on the ears, neck, shoulder and tail and eventually spreading over the entire body. In later stages, crust and cracks appear on the face and extremities.
After five to seven weeks on a biotin-deficient diet, swine may show hoof defects. Foot lesions may be the most characteristic sign of biotin deficiency. In a biotin deficiency, the hoof horn becomes soft and rubbery and poorly resistant to abrasions. The slow growth and repair process in the hoof tissue and the considerable weight on the feet add to the problem. Depending on the type of flooring on which the animal is kept, this may have little effect or may lead to the development of cracks and necrotic lesions, resulting in extreme lameness (Glattli et al., 1975). Secondary infections may gain entry through hoof cracks and infect the joints, which may lead to premature removal from the herd. Feeding and breeding are also adversely affected; with hoof defects in particular, the sow becomes unable to support the weight of the boar. Also, because the hog's ability to eat may be impaired, these problems obviously lead to economic losses.
Supplementation of the diet of breeding sows with biotin from an early stage of development made a significant contribution to the maintenance of the hoof horn integrity (Simmins and Brooks, 1988). Tagwerker (1983) noted that foot lesions were responsible for 4% to 8% of all sows culled in Europe. Also, he noted a Denmark study that reported 8.5% of biotin-supplemented sows having hoof lesions, compared with 25% for controls. After biotin supplementation in Holland, culling rate due to lameness was decreased from 25% to 14% (de Jong and Sytsema, 1983).
Cunha (1984) noted that in most of the 40 countries he had visited during the past 30 years, biotin deficiency signs were observed in swine operations. These deficiency signs observed under field conditions occurred in only 10% to 20% of sows or fewer. Baby pigs nursing these sows usually showed no biotin deficiency signs but responded to biotin supplementation. Unfortunately, many swine producers are of the opinion that it is natural for a swine herd to have a few animals with hair loss, dermatitis and cracked feet and therefore are not overly concerned when a small percentage of sows exhibit these clinical signs (Cunha, 1984).
Biotin supplementation of sow diets has significantly improved reproductive performance, including the number of pigs farrowed and weaned, litter weaning weight and number of days from weaning to estrus (Brooks et al., 1977; Simmins and Brooks, 1983; Misir and Blair, 1984; Kornegay, 1986).
In a field study, sows had severe lameness and impaired reproduction (Fonge, 1977). After these sows received supplemental biotin, normal foot health and normal reproductive performance were restored. Recently researchers found that sows housed in total confinement showed a positive response in conception rate and interval from weaning to first estrus and a trend to larger litters when supplemented with biotin (Bryant et al., 1985b). In an earlier study (Brooks et al., 1977), sows fed supplemental biotin had more pigs born alive (9.8 versus 8.1), more pigs weaned (7.8 versus 6.8), increased litter weight at weaning (71.0 versus 64.5 kg) and reduced time interval from weaning to first estrus after weaning (6.2 versus 15.3 days) compared with unsupplemented controls.
