Abstract
To investigate the effects of coarsely or finely ground corn on milk yield and ruminal fermentation in a hot and humid season, we conducted a feeding trial with mixed diets composed two different ground corns, coarsely ground corn (CGC) or finely ground corn (FGC) . Four mid- or late-lactating Holstein cows were assigned to two groups; CGC group or FGC group. This experimental design, a switch back trial with three 7-day periods followed by a 7-day adaptation period, started in June 2002. DMI, milk yield, or fat-corrected milk yield were not affected by the size of ground corn. Milk fat percentage in CGC was higher than that in FGC (P=0.172), whereas Milk protein percentage in CGC was lower than that in FGC (P=0.095) . Then, acetate-to-propionate ratio in the rumen fluid in FGC was significantly lower than that in CGC (P=0.023) .
These results indicate that the choice of coarse or fine ground corn in mixed diets is important on the control of milk protein and fat in a hot and humid season of Kumamoto.
