Dose-response of amylolytic enzyme on dry matter total apparent digestibility, and milk yield and composition of dairy cows

Enzymes have been added to poultry and swine diets, but they still underused in ruminant feeding. The objective of this study was to evaluate the effects of increasing dietary doses of amyolytic enzyme on dry matter digestibility, milk yield and composition of dairy cows. The enzyme used comes from an Aspergillus oryzae extract enriched with ?-amylase activity (Amaize, Alltech Inc., Nicholasville, KY, USA), and was supplied as a dry powder mixed with the concentrate. Twenty-four multiparous Holstein cows (162 ? 107.9 days in milk and 31.6 ? 6.5 kg/d of milk yield at the start of experiment, mean ? SD) were used in a 4 x 4 Latin square design experiment consisted of 21-d periods (14 d to treatment adaptation and 7 d of sampling). Cows received four treatments: Control (CON), no enzyme addition; or CON containing 150, 300 and 450 FAU/kg DM of the enzyme product. One FAU (fungal ?-amylase unit) is the amount of enzyme which breaks down 1 g starch in 1 h at pH 4.7 and 30?C. Cows were fed at 110% expected intake, diet had 48:52 of forage to concentrate ratio, and corn silage was the forage source. The feed offered and refusals were weighed daily, and samples of feed ingredients and orts were collected during the sampling period to determine DM content and intake. Feces were collected every 9 h from d 16 until d 18 of each period to form a composite sample. Dry matter digestibility was determined based on indigestible acid detergent fiber intake and it concentration in feces. Cows were mechanically milked twice daily, and samples were collected on d 15, 16 and 17 of each experimental period. Milk samples were analyzed for fat, protein and lactose (Lactoscan(R), Entelbra, SP, Brazil). Data were submitted to simple polynomial regression using the PROC MIXED of SAS 9.4. Dry matter intake was not affected by treatments, but DM digestibility tended to linearly increase (P = 0.060) with the enzyme addition. Milk yield (32.6 kg/d of mean) and composition were not affected (P > 0.275) by treatments. In addition, the efficiency of milk production (milk yield to DM intake ratio) was not affected (P > 0.570). Diets containing up to 450 FAU/kg diet DM did not affect milk yield and efficiency of milk production of dairy cows.