Immediately after withdrawal, rumen contents were strained through four
layers of cheesecloth to obtain rumen fluid in which the following determinations were
made: pH – using a CP-1-4 type pH meter, ammonia nitrogen by the Nessler method
[Szumacher-Strabel et al. 2002], and volatile fatty acids according to Tangerman
and Nagengast [1996] using a gas chromatograph (VARIAN STAR CP 3800) with
a Nukol™ – Bonded Free Fatty Acid Phase column (30 m × 0.25 mm, df 0.25 µm,
SUPELCO)