Invited review: Summary of steam-flaking corn or sorghum grain for lactating dairy cows

Nineteen lactation trials (43 grain processing comparisons) are summarized, in addition to digestibility and postabsorptive metabolism studies. The ne t energy for lactation (NEL) of steam-flaked corn or sorghum grain is about 20% greater than the NEL for dry-rolled corn or sorghum. Based on lactatio nal performance, steam-flaked sorghum grain is of equal value to steam-flak ed corn, and steam-flaked corn is superior to steam-rolled corn. Steam-flak ing of corn or sorghum compared to steam rolling of corn or dry-rolling of corn or sorghum consistently improves milk production and milk protein yiel d. This result is because of a much greater proportion of dietary starch fe rmented in the rumen, enhanced digestibility of the smaller fraction of die tary starch reaching the small intestine, and increased total starch digest ion. Steam-flaking increases cycling of urea to the gut, microbial protein flow to the small intestine, and estimated mammary uptake of amino acids. S team-rolling compared to dry-rolling of barley or wheat did not alter total starch digestibilities in two trials, one with each grain source. Lactatio n studies with these processing comparisons have not been reported. Most ci ted studies have been with total mixed rations (TMR) and alfalfa hay as the principal forage. Additional studies are needed with lactating cows fed st eam-flaked corn or sorghum in TMR containing alfalfa or corn silage. Optima l flake density of steam-processed corn or sorghum grain appears to be abou t 360 g/L (similar to 28 Ib/bu).