2.5. pH, VFAs, and ammonia nitrogen
After the fattening process, another five sheep from each treament were slaughtered after 12 h fasting; rumen liquor was obtainedimmediately and pH was measured. Eight milliliters of the rumen liquor
was mixed with 2 mL metaphosphoric acid at 25% to determine VFA
and ammonia N. The samples were then frozen at −20 ◦C until analysis.
Volatile fatty acids were analyzed by gas chromatography using the Erwin
et al. (1961) technique.
Ammonia nitrogen was determined using the McCullough (1967)
technique, and concentration was measured through absorbance in an
ultraviolet light spectrophotometer at 630 nm.