Journal of Dairy Science 86, Suppl. 1, p. 151. In: A Joint Meeting of the American Dairy Science Association (ADSA), the American Society of Animal Science (ASAS) & the Mexican Association of Animal Production (MAAP) (Abstract No. 595), p. 151. 22-26 de Junio de 2003. Phoenix, Arizona (Estados Unidos).The effects of pH and enzyme addition were examined in continuous
culture using a 4 x 4 Latin square design, with four 9-d periods consisting
of 6 d for adaptation and 3 d for measurements. The buffer pH
was adjusted to 100% (high) or 60% (low) of the normal concentration
of artificial saliva. Fermenters were fed twice daily a diet consisting of
30% alfalfa hay, 30% corn silage, and 40% rolled corn (DM basis). The
silage was milled fresh and the TMR was fed fresh to the fermenters
(64% DM). The EM was a protease containing no other major activities,
and was applied daily to the TMR, at least 12 h before feeding.
Treated feed was stored at 4◦C until fed. Ranges of pH were 6.0-6.6,
and 5.4-6.0 for high and low, respectively. Degradability of OM, NDF,
ADF, and cellulose were reduced (P < 0.05) by low pH, but hemicellulose
and protein degradation were not affected. EM addition increased
(P < 0.01) NDF degradability (by 43% and 25% at high and low pH, respectively),
largely due to an increase in hemicellulose degradation (by
79% and 51%, respectively). Total volatile fatty acids (VFA) and its
molar proportions were decreased (P < 0.05) by low pH, but were not
affected by EM. Protein degradation was only numerically (P = 0.17)
increased by EM. Total N flow tended (P = 0.07) to be reduced with
EM, but neither bacterial nor dietary N flow was affected by the treatments.
Microbial protein synthesis was not affected by either pH (P =
0.29) or EM (P = 0.86). Methane production, expressed as a proportion
of total gases, was decreased (P < 0.001) at low pH, but was not
affected by EM. It is concluded that it is possible to adapt the CC system
to use fresh feeds instead of dried feeds. Overall, the results indicate
that the EM used in this study has significant potential to increase fiber
degradability without increasing methane production.Peer reviewe