Folic acid needs for livestock are often met by good practical diets, and for most species, substantial quantities of folic acid are provided through microbial synthesis. Nevertheless, field observations have been made on folic acid insufficient diets. Green forage is an excellent source of folic acid. Supplementation of folic acid is most needed when animals are in confinement without access to green grazing or preserved green forages. The successful treatment of field cases of folic acid deficiency with supplemental folic acid has demonstrated that commercial feeds do not always supply adequate quantities of the vitamin to poultry (Pesti et al., 1991).
Folic acid may be of little benefit when poultry and swine receive only low levels of sulfa drugs, high levels of methionine and choline, and consume grains relatively free of toxin-producing molds. However, since a large percentage of the U.S. corn crop contains some mold contamination, folic acid supplementation should have a positive effect in many commercial poultry and hog operations as well as in other livestock enterprises (Purser, 1981). This is likely to be an even more important consideration in developing tropical countries, where climate conditions favor mold growth. Individual responses to folic acid supplementation to counteract mold effect vary with the class of livestock being fed, species of mold and levels of toxin encountered (Bhavanishankar et al., 1986).
Gadient (1986) considers folic acid to be very sensitive to heat and light, slightly sensitive to moisture, and insensitive to oxygen. Folic acid can be lost during storage of premixes, particularly at elevated temperatures (Frye, 1978). After three months of room-temperature storage, 43% of the original folic acid activity was lost. Verbeeck (1975) found folic acid to be stable in premixes without minerals, but there may be as much as 50% loss in a premix with minerals, kept at room temperature for three months. Adams (1982) reported only 38% retention of folic acid activity in a premix without minerals after three weeks at 45†C (113†F). However, he reported 57% retention of activity after three months at room temperature. One suggestion is to almost double the amount of folic acid in a premix at the time of manufacture to ensure that poultry receive the desired amount from that premix, since three to four months is not an unreasonable amount of time from premix manufacture to diet mixing and feeding.
Slinger et al. (1979) reported processing and storage losses of folic acid in fish feeds of 5% to 10% for steam-pelleted crumbles and 3% to 7% for extruded crumbles, depending on dietary level. Scott (1966) indicated that an adjustment of 10% to 20% in the folic acid level in poultry feed may be necessary because of pelleting losses.
Crystalline folic acid produced by chemical synthesis is available for feeds, foods and pharmaceuticals. Although folic acid is only sparingly soluble in water, the sodium salt is quite soluble and is used in injections as well as feed supplements (McGinnis, 1986; Tremblay et al., 1986). Oral supplementation appears to be desirable to maintain maternal stores and to keep pace with the increased folic acid turnover that is seen in rapidly growing tissue. Synthetic folic acid supplements are easy to administer and highly available; natural forms are approximately 50% less available than synthetic forms.
