IX Uses for feed

Sweetpotatoes have long been used as a major source of feed, due in part to their self-sustaining nature (even the vines are suitable for feed). However, as stock-raising farmers have come to depend on purchased feed, shipments of sweetpotato-based feed have declined considerably. And despite its quality, sweetpotato feed requires considerable labor for harvest, preparation and storage; consequently, it is more expensive than imported alternatives.

However, if cut 2 or 3 times during their growing season, sweetpotatoes can yield 15-20 tons per 10 ares at harvest. The Japanese stock-raising industry depends on foreign grain for most concentrated feed, which lowers the industry's calorie-self-sufficiency rate. Such facts suggest that sweetpotatoes be seriously considered as a feed source, particularly given their suitability to the Japanese climate and landscape, easy cultivation, and unsurpassed calories per unit area.

Sweetpotatoes used for feed should provide certain characteristics (as outlined below), and should be cultivated using mechanized and labor-saving techniques to lower production costs.

○ Conditions for producing quality sweetpotato feed

Sweetpotato varieties for feed should satisfy the following conditions: High-quality, high-yielding vines and roots High carotene content and excellent nutrients for domestic animals For silage, vines should have an extremely high yield and be highly regenerative. (e.g., "Tsurusengan," 1981) Very high yields even if starch content is low Production of vines and roots should be 3 tons per 10 ares per 3 months. Capable of direct planting by mechanized means.

○ Black pigs and sweetpotatoes in Kagoshima

One of the trademark delicacies of Kagoshima is the black pig, known as the highest-quality meat in Japan for its tasty sweetness and excellent texture. Smaller than so-called "white" pigs such as Landrace, black pigs provide excellent-quality meat due to their fine muscle fibers. 　While black pigs fed on sweetpotatoes are generally considered especially tasty, it is difficult to provide a scientific basis for this notion. According to data from the Kagoshima Prefecture Livestock Experiment Station, pork from pigs fed on sweetpotatoes is generally light in color, and yields delicious lean meat and fat. One possible factor is that pigs raised on sweetpotatoes yield pork fat with a higher melting point. And since this fat does not melt out at low temperatures, their pork has better "mouthfeel" than that of other pigs. It is believed to be necessary to study the use of silage, and of releasing pigs in sweetpotato fields to enable them to eat sweetpotatoes directly.