Maximal replacement of forage and concentrate with a new wet corn milling product for lactating dairy cows

Three experiments were conducted to determine the maximal amount of concent rate and forage that could be replaced with a new wet corn milling product. The corn milling product contained 23.1% crude protein, 9.9% ruminally und egradable protein, 13.7% acid detergent fiber, 40.3% neutral detergent fibe r, and 2.6% ether extract (% of dry matter; DM). In experiment 1, 16 Holste in cows were assigned to one of four diets in a replicated 4 x 4 Latin squa re design with 28-d periods. The four diets contained 54.3% forage (alfalfa :corn silages, 1:1 DM basis) with the wet corn milling product replacing 0, 50, 75, or 100% of the concentrate portion (corn and soybean meal) of the diet (DM basis). The diets containing wet corn milling product resulted in 7.8% lower DM intake, equivalent milk production (28.5 kg/d), and 13.6% gre ater efficiency of 4% fat-corrected milk (FCM) production than the control diet. There was no effect of diet on ruminal pH. In experiment 2, 16 Holste in cows were assigned to one of four diets in a replicated 4 x 4 Latin squa re design with 28-d periods. The 100% concentrate replacement diet from exp eriment 1 was used as control diet. For the test diets, forage was replaced with 15, 30, or 45% of the corn milling product (DM basis). Efficiency of FCM production (1.16) was not affected by diet. Rumination time was reduced for the 30 and 45% forage replacement diets, but ruminal pH was unaffected . In experiment 3, 30 Holstein cows were assigned at parturition to either a control diet (no corn milling product) or a diet containing 40% corn mill ing feed in place of both forage and concentrate (optimal levels from exper iments 1 and 2) for 9 wk. The diet containing corn milling feed resulted in 21% greater efficiency of FCM production than the control diet. These resu lts indicate that a new feed product based on wet corn milling ingredients has the potential to effectively replace all of the concentrate and up to 4 5% of the forage in the diet for lactating dairy cows.