[Determination of the true digestibility of amino acids in variously prepared potatoes in growing pigs. 1. Freshly steamed potatoes and silage made from steamed potatoes].
Freshly Steamed Potatoes of 6 varieties were investigated. With 3 varieties the true N and amino acid digestibilities were found to be in good agreement, while great variations were found in potatoes of the other 3 varities so that it appears to be a matter of some doubt whether the true amino acid digestibility could, in the case of potatoes, be reliably derived from data on the true N digestibility. Differences in the true amino acid digestibility data were found between the varities of potatoes grown in different years. A positive trend was found to exist in the relationship between the absolute amino acid content and true digestibility. The true lysine digestibility of freshly steamed potatoes varies between 76-90%, the average percentage being about 80%. The true methionine digestibility was found to vary within still wider limits, although the average percentages was also about 80%. Values established for the true cystine digestibility ranged from 80% to 90%. The true amino acid digestibility data did not provide a sufficiently reliable basis for making conclusions as to the existence of a limiting amino acid. Both the lowest value for true digestibility and the greatest variations were found in the case of the amino acids alanine, tyrosine, and methionine. It was observed that silage made from steamed potatoes had a lower true digestibility of N than steamed fresh potatoes although the value for true amino acid digestibility were the same, with the exception of methionine and cystine.