Initial reaction rates were determined for various concentrations of both substrates, where n-amyl alcohol was varied in the range between 0.15 and 2.35mol/[dm.sup.3] and isobutyric acid in the range between 0.15 and 2.40mol/[dm.sup.3].
where [v.sub.0] is the initial reaction rate, [V.sub.max] is the maximum reaction rate, [Km.sub.al] and [Km.sub.ac] are Michaelis constants for n-amyl alcohol and isobutyric acid, and [K.sub.ial] is the n-amyl alcohol inhibition constant.
However, no significant changes in the propionic acid, acetic acid, butyric acid, and
isobutyric acid concentrations were detected.
The presence of more isobutyric acid in lower-density bales from the 587 g [kg.sup.-1] moisture silage indicates the degradation of lactic acid by Clostridium bacteria.
Silage (moisture) High density Low High Low Measurement ([dagger]) density density density 587 g [kg.sup.-1] 524 g [kg.sup.-1] PH 4.7 b 4.9 ab 4.8 b 5.1 a ([double dagger]) Lactic acid 70.0 a 64.6 a 71.4 a 62.8 a Acetic acid 23.9 ab 38.0 a 32.6 a 19.9 b Propionic acid 1.73 a 0.77 b 0.41 b 0.67 b Isobutyric acid 1.14 b 7.01 a 1.82 b 2.99 b Butyric acid -([section]) 0.40 a 0.20 a 0.54 a Isovaleric acid 0.02 a 0.20 a -- -- Valeric acid 0.34 a 0.27 a 0.56 a 0.40 a ([dagger]) High density baled at 358 kg [cm.sup.-2] hydraulic pressure, low density baled at 179 kg [cm.sup.-2] hydraulic pressure.
Experiments later revealed that the wayward individuals had a specific anosmia to
isobutyric acid. The fruity smell they detected was the result of the byproducts and impurities usually found in commercial samples of the acid.
The interfacial tension of the
isobutyric acid and water system was determined by using a spinning drop tensiometer (SDT).
On the other hand, we also found, as the proportion of dietary corn increased, the propionate, butyrate,
isobutyric acid, valerate, isovalerate and TVFA concentrations increased, while the ruminal lactic acid concentration was low, not exceeding 0.5 mM.
The concentrations of propionic acid, isobutyric acid, butyric acid, isovaleric acid and valeric acid were low and varied little throughout the incubation.
The decrease in pH from 6.16 to 5.73 which occurred during fermentation was most likely the result of increased acetic acid as the concentrations of propionic acid, isobutyric acid, butyric acid, isovaleric acid and valeric acid remained below 2.5 mmol/kg after 30-day fermentation.
Ruminal fluid from cows fed GCS, WCS and ESB had lower proportions of butyric acid and
isobutyric acid compared with cows fed CON (p<0.05).
Leucine, isoleucine and valine are extensively metabolized within the rumen by anaerobic bacteria, yielding large quantities of isovaleric, 2-methylbutyric and
isobutyric acids, respectively (Feng, 2004).