Abstract:
The focus of this study was to determine the effect of exogenous enzyme supplementation on
rumen fermentation parameters, since a healthy or improved rumen environment favors more efficient
growth performance and contributes to higher total tract digestibility, the focus being on the South African
feedlot industry. The effects on total tract digestibility, in sacco digestion and dry matter disappearance of
Neutral detergent fibre (NDF) as well as rumen fermentation patterns were studied using three differing
levels of formulated fibre. The primary energy component were different combinations of maize and
hominy chop, leading to differing dietary fibre levels. Hominy chop is a by-product of the South African
maize milling industry and often a raw material used extensively in feedlots around the country due to the
ease of supply and possible cheaper acquisition price than maize.
The experimental trial was designed as a 6x6 latin square, repeated in time, within a factorial
arrangement of treatments (3x2). The treatments included non-enzyme and enzyme treatment of three
diets differing in starch and fibre content, the primary constituents being maize and hominy chop. During
each feeding cycle, enough time for adaption to the new diet was allowed as well as enough time for
enzyme washout to avoid carry-over effects from the previous treatment. Digestibility was measured
using an internal marker, in sacco incubation was performed on the different experimental diets as well as
hominy chop on its own, and lastly, rumen fluid samples were analysed for pH, volatile fatty acid (VFA)
and ammonia-nitrogen levels.
Total tract crude protein and starch digestibility did not differ significantly between treatments
(P<0.05), but fibre digestibility was affected by enzyme treatment. For both the 75HC:25M and 25HC:75M
diets, the enzyme supplementation increased ADF digestibility (P<0.05) from 43.79% to 54.12% and
46.11% to 54.49% respectively. No significant effects were seen between the same the diets on the
different treatments for NDF digestibility, while there were significant effects across all the diets for both
ADF and NDF digestibility (P<0.05). The mean NDF digestibility (P<0.05) improved from 54.73% to
60.10%, while the mean ADF digestibility (P<0.05) improved from 46.11% to 54.49% for the non-enzyme
vs enzyme treatment respectively.
The enzyme supplementation did not affect the in sacco DM and NDF disappearance for either the
hominy chop or the TMR when comparing results within experimental treatments. There were also no
overall effects of enzyme vs non-enzyme supplementation on in sacco hominy chop and TMR DM and
NDFom ruminal digestibility (P < 0.05).
Within experimental diets as well as overall, enzyme supplementation did not affect any of the
rumen fermentation parameters measured. Results suggest that enzyme supplementation can play an
important role in improving apparent total tract fibre digestion when feeding diets where part of the maize
component is replaced with hominy chop, as is many times the case in Southern African feedlots.
