DIGESTION BY THE PIG OF THE ENERGY AND NITROGEN IN DRIED, ENSILED AND ORGANIC-ACID-PRESERVED CORN: WITH OBSERVATIONS ON THE STARCH CONTENT OF DIGESTA SAMPLES

Abstract

In the first experiment, three corn–soybean diets were made from either dried, propionic-acid-preserved or naturally ensiled high-moisture corn. In the second experiment, corn was harvested with 23% moisture and prepared for storage either by drying, by treatment with a mixture of propionic and acetic acids, with propionic acid alone or with acetic acid alone; a fifth batch was ensiled. The utilization of energy and nitrogen was measured in balance trials using barrow pigs of 30 kg liveweight. Histochemical examination of the acid-preserved corn indicated partial hydrolysis of the starch molecules, an observation which was supported by the higher levels of free glucose in these samples. The digestible and metabolizable energy values of the diet made with the dried corn were similar in both experiments. In the first experiment, the energy was less available in the propionic-acid-preserved corn than in the dried, but in the second, the energy was more available in that preserved with the organic acids than in the dried. There were no differences in nitrogen utilization between diets in the first experiment, but in the second, the nitrogen was less well utilized in the dried corn diet than in those containing the organic-acid-preserved corn. Examination of the α-linked polysaccharides in the digesta showed that they had been incompletely digested in the diet containing the dried corn in experiment 2.