Effect of oil content and kernel processing of corn silage on digestibility and milk production by dairy cows

Corn silages were produced from a high oil corn hybrid and from its convent ional hybrid counterpart and were harvested with a standard silage chopper or a chopper equipped with a kernel processing unit. High oil silages had h igher concentrations of fatty acids (5.5 vs. 3.4% of dry matter) and crude protein (8.4 vs. 7.5% of dry matter) than the conventional hybrid. Processe d silage had larger particle size than unprocessed silage, but more starch was found in small particles for processed silage. Dry matter intake was no t influenced by treatment (18.4 kg/d), but yield of fat-corrected milk (23. 9 vs. 22.6 kg/d) was increased by feeding high oil silage. Overall, process ing corn silage did not affect milk production, but cows fed processed conv entional silage tended to produce more milk than did cows fed unprocessed c onventional silage. Milk protein percent, but not yield, was reduced with h igh oil silage. Milk fat percent, but not yield, was higher with processed silage. Overall, processed silage had higher starch digestibility, but the response was much greater for the conventional silage hybrid. The concentra tion of total digestible nutrients (TDN) tended to be higher for diets with high oil silage (71.6 vs. 69.9%) and tended to be higher for processed sil age than unprocessed silage (71.7 vs. 69.8%), but an interaction between va riety and processing was observed. Processing conventional corn silage incr eased TDN to values similar to high oil corn silage but processing high oil corn silage did not influence TDN.