THE NITRATE CONTENT OF SWINE SUPPLEMENTS,
FEEDS AND INGREDIENTS
Research Progress Report 84
October, 1963
by Don W. Hatcher and E. D. Schall, Department of Biochemistry
The degree of toxicity of nitrates to farm animals has been receiving increased attention during the past few years. There has been some evidence, for example, that in high amounts nitrates may be a factor in the conversion of carotene to Vitamin A. Excessive amounts were also demonstrated several years ago when drought conditions in Missouri resulted in the accumulation of nitrates in plant materials. With these experiences in mind the question has been raised as to the level of nitrates in the various feeds and ingredients found and used in the usual feeding practices on the farm.
Hays, grasses and silages have been studied extensively and analyzed by many workers. It is not unusual for these materials to contain 12, 000 to 15, 000 ppm of nitrate, and the average values are in the order of 1, 000 to 4, 000 ppm. Very little is known, however, regarding the content of swine feeds or supplements or of the ingredients used in preparing these items. The present study was undertaken to determine the nitrate levels in these products.
Experimental
Attempts to apply existing methods to the analysis of feeds and supplements were unsuccessful due to the large amount of other materials which went into solution with the nitrates and interfered seriously with their
determination. As a result the values obtained were very erratic. This problem was overcome by treating the sample extracts with lead acetate to remove a large part of these substances. The nitrate content was then determined by a modification of the method of Garner and co-workers 1/ in which nitrates are reduced microbiologically to nitrites and then determined colorimetrically.
Results
The samples analyzed in this study included swine feeds and supplements, soybean meal, tankage, meat and bone scraps, alfalfa meal and corn. These were secured from various locations in Indiana, including retail outlets, and represent a cross-section of sources. The results (Table 1) indicate that the nitrate level of all of these products is very low. The value for alfalfa meal agrees well with the values reported in the literature for hays and grasses. From these results it is apparent that the nitrate content of hays, silages and grasses is approximately 50 to 100 times that of supplements, grains and finished feeds. The question has been raised as to whether the soybean meal could contribute significant amounts of nitrates to a ration.
The results of this study indicate that it does not, since the maximum value obtained on all samples analyzed was 59 ppm with an average value of 37. It would be expected that if nitrates accumulated in a plant this accumula-
1/ Garner, G. B., Baumstark, J. S., Muhrer, M. E., and Pfander, W. H., Anal. Chem. 28, 1589 (1956).
PURDUE UNIVERSITY • Agricultural Experiment Station • Lafayette, Indiana