The effects of corn silage particles size and fat supplement on feed intake, digestibility, ruminal function, chewing activity, and performance in mid-lactating Holstein dairy cows

An experiment was carried out to determine the effect of corn silage particle size and fat supplements on performance, solid passage rate through the digestive tract, and chewing behavior in dairy cows. The forages were coarse or fine corn silage with geometric means of 8.8±2.7 and 5.6±2.8 mm, and alfalfa with geometrics means of 7.0±3.3 mm, and fat supplements were neutral fat (palm) and soy-oil. Diets were: 1) coarse corn silage and four percent neutral fat supplement, 2) coarse corn silage and four percent soy-oil supplement, 3) fine corn silage and four percent neutral fat supplement, and 4) fine corn silage and four percent soy-oil supplement. The forage to concentrate ratio was 43:57 percent in all diets. A 2×2 factorial balanced change-over design experiment with two replicates was used. Physically effective factor (pef) was affected by corn silage particles size and was higher in coarse corn silage diets, but diets Xgm was not affected by silage particles size. Intake of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), and non-fibrous carbohydrates (NFC) was not affected by corn silage particles size, fat supplement, and their interactions. However, physically effective NDF (peNDF) intake was significantly higher (P<0.0107) in coarse corn silage diets. Digestibility of DM, OM, EE, NDF, and ADF was significantly higher in fine corn silage diets but not affected by fat supplements. Duration of chewing activity was longer in coarse corn silage diets (P<0.05). Rumination activities per kg of DM, OM and NDF were longer in coarse corn silage diets. Ruminal solid retention time was longer in coarse corn silage and soy-oil diets (P<0.05). Fat yield, total milk solids, and 3.5% fat- corrected milk yield (3.5%FCM) were the highest in the fine corn silage and neutral fat diets. Protein and 3.5% fat-corrected milk efficiencies were higher in diets containing neutral fat supplement. Inert fat supplement can increase energy density of the diets, thus resulting in improved cow performance.