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Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/3/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Barley, corn and oats are three feed ingredients commonly fed to dairy and beef cattle. These three feedstuffs are digested (broken down) at different speeds by the bacteria and other microbes that live in the rumen (one of the four chambers of a cow s stomach). An experiment was conducted using the same bacteria found in the rumen. A one gram sample of barley, corn or oats was placed into a series of glass vessels with the proper nutrients and buffers to grow the bacteria. Samples were taken from the different vessels after 0, 1, 2, 4, 6, 8, 12, 24, 48, and 96 hours of digestion. When the bacteria digest the feedstuffs, they produce volatile fatty acids from the starch and other carbohydrates like sugars found in the feedstuffs. The most important volatile fatty acids are acetic acid (found in vinegar), propionic acid (found in Swiss cheese) and butyric acid (found in butter). These volatile fatty acids are then used by the cow for energy, growth, and milk production. Our experiment showed that the starch in oats was digested or degraded at the fastest rate followed by barley and then corn. In addition, the rumen bacteria were able to make acetic acid, propionic acid and butyric acid faster from oats. The rumen bacteria made acetic acid faster from barley but made propionic acid and butyric acid faster from corn. Barley was able to supply the most propionic acid and butyric acid, whereas oats and barley supplied the most acetic acid. The experiment demonstrates that rumen bacteria make the volatile fatty acids at different rates and amounts depending on which feedstuffs they are fed. Technical Abstract: Barley, corn and oats are three carbohydrate sources commonly fed to ruminants that have divergent rates of starch degradation. However, limited information is available regarding ruminal volatile fatty acid production rates. A study was conducted to evaluate the influence of barley, corn, or oats on batch in vitro ruminal VFA production rats. Barley, corn or oats were incubated in rumen fluid with buffer and samples were removed over 96 h of fermentation. Acetic, propionic, and n-butyric acid concentrations were determined and amounts of each acid were corrected for initial VFA concentrations. Rate and final production of each VFA formed were predicted using a modified Weibull model ([VFA]t = [VFA]inf(1 - e^-kt), where [VFA] is the concentration of VFA at the time of measurement or at the end of incubation ([VFA]inf), k is the fractional rate constant, and t is the time of measurement. Final acetate production was greater for oats (49 mM)and barley (46 mM) compared to corn (39 mM). Production rate of acetate was greatest for oats (.43 h-1) followed by barley (.29 h-1) then corn (.22 h-1). Barley (61 mM) had the highest final concentration of propionate followed by oats (43 mM) then corn (39mM). Conversely, oats (.30 -1) had the fastest rate of propionate production followed by corn (.16 h-1) then barley (.13 h-1). Butyrate production was greatest for barley (36 mM) followed by corn (22 mM) then oats (17mM). Butyrate production rate was fastest for oats (.26%/h) followed by corn (.11 h-1) then barley (.07 h-1). Production rates, final concentrations and profiles of VFA differed for barley, corn and oats when incubated in vitro. |
