The effects of adding whole cottonseed (WCS) and live yeast culture (YC) to a diet of
60% alfalfa and 40% concentrate on ruminal fermentation and liquid dilution rate in steers
were examined in two trials. Twelve dally cannulated Hereford steers (approximately
420 kg) were used. Concentrates were 1) a basal grain mix composed of ground corn,
ground barley and rice bran, 2) basal mix with 10% WCS, 3) basal mix with 1.6% YC and
4) basal mix with 10% WCS and 1.6% YC. No differences were detected (P > .lo) in
ruminal pH of steers fed WCS or YC in either trial. Ruminal ammonia levels tended to be
higher (P > .lo) in steers fed WCS. Acetate was higher and butyrate was lower in steers
receiving 10% WCS (P < .lo) compared with controls. Molar proportions of acetate and
butyrate increased while propionate decreased (P < .05) over time after feeding. Intake and
apparent digestibility of dry matter was not influenced by treatments. Whole cottonseed
and(or) YC appear to have minimal effects on ruminal fermentation, but they might alter
ruminal liquid passage rate with diets containing 60% ground alfalfa and 40% concentrate.
(Key Words: Cottonseed, Yeast, Rumen Fermentation.)