Pyrolysis Gas Chromatography of Five Ruminant Feedstuffs at Various Stages of Growth

¹ Ruminant Nutrition Laboratory, Livestock and Poultry Science Institute, US Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705

An investigation was conducted into how the products generated by pyrolysis of ground (20 mesh) feeds relate to measures of CP, fiber, lignin, and in vitro digestibility. Samples of alfalfa (n = 15), vegetative corn (n = 10), tall fescue (n = 16), orchardgrass (n = 15), and vegetative wheat (n = 11), collected from the field weekly or biweekly during the growing season, were pyrolyzed. Gas chromatography was performed on the products using a packed column containing 30% DC-550 on Chromosorb W-AW. Thirty discernable products (identified by retention times) were found. However, all products were not produced by all feeds. Statistical analysis showed that 9 of the 30 products were sufficient to correctly discriminate the five feeds, despite the various maturities. Regression analysis of pyrolysis products was generally best for CP and poorest for lignin content. Considerable variation, however, was found among the different feeds. Relationships generally were poorest for orchardgrass and best for the corn, fescue, and wheat samples. Near infrared analysis of intact feeds was, in general, unsatisfactory in determining percentages of pyrolysis products produced from the feeds. In conclusion, pyrolysis appears to have potential in the study and determination of the composition of feedstuffs.

Key Words: pyrolysis gas chromatography • pyrolysis • forages

Submitted on November 24, 1989
Accepted on March 19, 1990