Although molasses is being used by
dairy farmers, particularly certified organic
dairies, as a lower cost energy alternative
to corn, little research currently
exists evaluating the effects of molasses
as the sole supplement on the ruminal
fermentation of grazing dairy cows. This
study evaluated the effects of pasture
supplementation with molasses, corn
meal, or a combination of molasses and
corn meal, on ruminal nutrient digestibility
and bacterial N synthesis in continuous
culture fermenters. Experimental
treatments were 1) orchardgrass (Dactylis
glomerata L.) pasture only (control;
70 g DM/d); 2) molasses plus orchardgrass
pasture (MOL; 3.5 g DM/d of
molasses plus 66.5 g DM/d of pasture);
3) corn meal plus orchardgrass pasture
(CM; 4.9 g DM/d of corn meal plus 65.1
g DM/d of pasture); and 4) molasses
plus corn meal plus orchardgrass pasture
(MOL+CM; 3.5 g DM/d of molasses
plus 4.9 g DM/d of corn meal plus 61.6
g DM/d of pasture). Treatment did not
affect (P > 0.05) apparent DM, OM, and
NDF digestibility values; true DM and
OM digestibility values; molar proportions
of VFA; or acetate-to-propionate
ratio. Mean ruminal pH tended (P =
0.071) to be greater for MOL. Maximum
ruminal pH was greatest (P < 0.05) for
MOL. Ruminal NH3-N was lowest (P
< 0.05) for MOL+CM. Crude protein
digestibility was greatest (P < 0.05)
for MOL and lowest for MOL+CM.
Bacterial N flow (g/d) and efficiency of
bacterial N synthesis were not affected
(P > 0.05). At low levels of inclusion,
molasses showed results similar to corn
meal in improving ruminal fermentation
and N utilization, with both supplements
showing only minimal improvement compared