The potato ( Solanum tuberosum) as a source of nutrients for pigs, calves and fowl — A review

Abstract

Potatoes outyield cereals in terms of nutrients produced per hectare, but the nutritive worth of the potato as an animal feed has long been disputed. Conventional descriptions of nutritive content, such as are satisfactory for cereals, are inadequate for the potato. The potential of the potato as an alternative to cereals as a source of nutrients can only be realised if predictable animal responses are obtained to potato feeding. The review attempts to quantify those factors which influence the nutritive value of potatoes and thereby to enable appropriate dietary inclusion levels of potato and potato products to be made. Potato products are diverse because of the many different processing methods. Potatoes may contain alkaloid toxins and trypsin inhibitor activity, while the concentration of starch and the quality of potato protein appear to be second to none amongst vegetable sources. Potato dry matter (DM) contains 17 MJ gross energy (GE)/kg and 13–17 g N/kg, the protein fraction being of biological value about 70. Cooked potato has a digestible energy (DE) content in the region of 16.0 MJ DE/kg DM for pigs, and a metabolizable energy (ME) content of 13.6–15.0 MJ ME/kg DM for fowl. Digestibility coefficients for energy and N in cooked potato are about 0.95 and 0.85 respectively for pigs, and 0.95 and 0.80 for fowl, while the digestibility of cooked potato starch for calves increases from 0.50 at 10 days of age to 0.74 at 24 days. The digestibility of raw potato is lower and more variable, particularly for N; digestibility coefficients for pigs range from 0.76 to 0.92 for energy and from 0.23 to 0.76 for N. In the case of fowl, digestibility coefficients as low as 0.22 and 0.36 have been determined for raw potato organic matter and N respectively. Cooked potato is of approximately equivalent nutritive value to maize, whereas raw potato is usually associated with a reduction in animal performance. Cooked potato products are particularly appropriate for inclusion in pig diets. With calves, potato has been associated in some instances with digestive disturbances, while the inclusion of potato in diets for poultry tends to increase the moisture content of the excreta.