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In this trial conducted by the University of Minnesota, high-producing dairy
cows were assigned to 6 ration treatments balanced on NDF from forage and rumen
undegradable protein. Dietary forage NDF (NDF from corn silage and hay) were 17,
20 and 22% of the ration dry matter. Each of the three forage NDF levels was
combined with two protein supplements, one containing 39% rumen undegradable
protein and the other one containing 50% rumen undegradable protein. The
combination of three levels of forage and two types of protein resulted in 6
different ration treatments. Rations consisted of 31 to 44% TMF100 corn silage,
28 to 12% corn grain, 10% alfalfa hay, 30% protein supplement, and 0 to 1.8%
rumen inert fat (Megalac� ) as a percent of dry
matter. The percentage of every ingredient in the ration – with the exception
of corn silage, corn grain and Megalac� - was kept
constant. Also the percentage of protein supplement was kept constant, however,
the ingredient composition of the two supplements were different in order to
have the two levels of undegradable protein in the ration. As the percentage of
corn silage in the diet increased, the percentage of corn grain decreased and
the percentage of Megalac� increased. The 17% Forage
NDF diet contained 28% corn grain and 0% Megalac�
compared to 12% grain and 1.8% Megalac� in the 22%
Forage NDF diet.
Authors reported no differences in milk production (93 lbs. average) among
the six ration treatments. Dry matter intake decreased as NDF from forage
increased in the diets. Cows fed the highest silage ration were the most
efficient at converting feed to milk at 1.7 lb. of milk per pound of dry matter
fed. It was interesting to observe no differences in milk production among
diets. Diets had similar energy levels due to the increased percentage of
Megalac� . However, the rumen microbes do not
utilize fat as primary source of energy. It appears that TMF100 provided enough
substrate for the rumen microbes to grow, so that milk production was not
compromised. One could envision that in the long term, a ration with greater
forage percentage would result in a healthier rumen. There should be an
advantage in feeding more TMF corn silage and less corn grain in the ration like
it was done in this study. |
