title: Comparison of barley and sorghum grain processed at different densities for lactating dairy cows.
abstract: To vary ruminally degradable starch, sorghum grain was dry-rolled or steam-flaked to different densities and compared with dry-rolled barley in total mixed diets fed to 40 lactating cows (111 d of lactation) assigned to five dietary treatments. Diets contained (percentage of dry matter) 35% alfalfa hay, 4.1% cottonseed hulls, 10% whole cottonseed, 2% fish meal, 4% soybean meal, and 4.9% of a molasses, mineral, and vitamin supplement. Treatments were 40% sorghum grain either dry-rolled or steam-processed at flake densities of 437, 360, and 283 g/L. A fifth diet containing 42% dry-rolled barley was fed. Cows were blocked according to pretreatment (14 d) milk yield and received experimental diets for 56 d. Increasing ruminal starch degradability by including steam-flaked sorghum grain or barley in the diet did not increase milk yield or milk protein percentage and yield, as was shown in eight previous studies. Steam-flaked sorghum or dry-rolled barley in the diet decreased dry matter intake, resulting in a 10 to 19% higher efficiency of conversion of feed dry matter to milk than that for dry-rolled sorghum. Milk urea N was decreased, and milk casein yield tended to be increased, by steam-flaking sorghum at the moderate density compared with dry-rolling or fine flaking. Dietary protein was more efficiently converted to milk protein and casein from flaked sorghum and dry-rolled barley than from dry-rolled sorghum. In this study, increasing ruminal starch degradability resulted in higher feed efficiency and lower feed intakes, bu optimal flake densities for steam-processed sorghum gain to maximize milk and milk protein yield were not clarified.
authors.affiliation: Department of Animal Sciences, University of Arizona, Tucson 85721-0038, USA.
authors.forename: F A
authors.initials: FA
authors.lastname: Santos
authors.forename: J T
authors.initials: JT
authors.lastname: Huber
authors.forename: C B
authors.initials: CB
authors.lastname: Theurer
authors.forename: R S
authors.initials: RS
authors.lastname: Swingle
authors.forename: Z
authors.initials: Z
authors.lastname: Wu
authors.forename: J M
authors.initials: JM
authors.lastname: Simas
authors.forename: K H
authors.initials: KH
authors.lastname: Chen
authors.forename: S C
authors.initials: SC
authors.lastname: Chan
authors.forename: J
authors.initials: J
authors.lastname: Santos
authors.forename: E J
authors.initials: EJ
authors.lastname: DePeters
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D002417:Cattle; D002523:Edible Grain; D005260:Female; D005511:Food Handling; D001467:Hordeum; D007774:Lactation; D050356:Lipid Metabolism; D008892:Milk / Q000378:metabolism; D008894:Milk Proteins / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D014508:Urea / Q000378:metabolism
chemical_list: D008894:Milk Proteins; D014508:Urea; D009584:Nitrogen