title: Effect of dietary energy source and level on nutrient digestibility, rumen microbial protein synthesis, and milk performance in lactating dairy cows.
abstract: This study was conducted to examine the effects of dietary energy source and level on intake, digestion, rumen microbial protein synthesis, and milk production in lactating dairy cows, using corn stover as a forage source. Eight multiparous Holstein cows, 4 of which were fitted with rumen cannulas, were evaluated in a replicated 4 × 4 Latin square design, with each period lasting 21 d. The cows were randomly assigned into 4 treatment groups: low-energy (LE) ground corn (GC), LE steam-flaked corn (SFC), high-energy (HE) GC, and HE SFC. Changes to ruminal energy degradation rates were induced by feeding the cows diets of either finely ground corn or SFC as components of diets with the same total energy level. Milk yield, milk protein content and yield, and milk lactose yield all increased in response to higher levels of dietary energy, whereas contents of milk fat and lactose were unaffected. Cows fed HE diets had a higher crude microbial protein yield and total-tract apparent digestibility than those receiving LE diets. Milk yield, milk protein yield, and microbial protein yield were also higher when SFC replaced GC as the main energy source for lactating cows fed LE diets. These results suggest that an increased dietary energy level and ruminal degradation rate are beneficial to milk protein production, which we suggest is due to increased yields of microbial proteins, when cows are fed corn stover as a dietary forage source.
authors.affiliation: College of Animal Science and Technology, Northeast Agricultural University; Harbin 150030, P. R. China; State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China.
authors.forename: X Q
authors.initials: XQ
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China.
authors.forename: Y D
authors.initials: YD
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China.
authors.forename: M
authors.initials: M
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China.
authors.forename: T
authors.initials: T
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China.
authors.forename: D
authors.initials: D
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China; Synergetic Innovation Center of Food Safety and Nutrition, Harbin, 150030, P. R. China; Chinese Academy of Agricultural Sciences-International Center for Research in Agroforestry, Joint Laboratory on Agroforestry and Sustainable Animal Husbandry, World Agroforestry Centre, East and Central Asia, Beijing 100193, P. R. China. Electronic address: budengpan@126.com.
authors.forename: D P
authors.initials: DP
authors.lastname: Bu
authors.affiliation: College of Animal Science and Technology, Northeast Agricultural University; Harbin 150030, P. R. China; State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China. Electronic address: wang-jia-qi@263.net.
authors.forename: J Q
authors.initials: JQ
authors.lastname: Wang
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying; D004032:Diet / Q000662:veterinary*; D004063:Digestion; D002149:Energy Intake; D005260:Female; D007774:Lactation; D007785:Lactose / Q000378:metabolism; D008892:Milk / Q000378:metabolism*; D008894:Milk Proteins / Q000378:metabolism; D018515:Plant Leaves; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology; D003313:Zea mays
chemical_list: D008894:Milk Proteins; D007785:Lactose
keywords: corn stover; energy; lactation performance; microbial protein; nutrient digestibility