Each school participating under section 1773 of this title shall, insofar as practicable, utilize in its program foods designated from time to time by the Secretary as being in abundance, either nationally or in the school area, or foods donated by the Secretary. Foods available under section 1431 of title 7 or purchased under section 612c or 1446a–1 of title 7, may be donated by the Secretary to schools, in accordance with the needs as determined by local school authorities, for utilization in their feeding programs under this chapter.