title: Digestibility, ruminal fermentation, ingesta kinetics and nitrogen utilisation in dairy cows fed diets based on silage of a brown midrib or a standard maize hybrid.
abstract: The aim of the present experiment was to investigate an experimental brown midrib (Bm) maize hybrid in comparison with a control (Con) non-Bm maize hybrid on ruminal and total tract digestibility, ruminal fermentation, ruminal ingesta kinetics, nitrogen (N) utilisation and microbial efficiency. A total of six ruminally and duodenally cannulated German Holstein cows were used. Animals were fed diets of either 11.5 kg dry matter (DM) of a Con or a Bm maize silage plus 4.1 kg DM of concentrate. Ruminal and total tract digestibility of organic matter, neutral detergent fibre and acid detergent fibre did not differ between hybrids. Short-chain fatty acid concentrations and pH in the rumen were not affected, but ruminal mean retention time was lower for Diet Bm (Con: 45.4 ± 2.39 h; Bm: 40.6 ± 2.39 h; least squares means ± standard error). Cows fed Diet Bm had greater efficiency of N utilisation (Con: 30.1 ± 1.37%; Bm: 33.1 ± 1.37%) and increased flow of microbial crude protein at the duodenum (MCPF) (Con: 7.0 ± 0.37 g/MJ metabolisable energy (ME); Bm: 8.1 ± 0.37 g/MJ ME). Thus, MCPF and utilisable crude protein at the duodenum (uCP) were greater for Diet Bm (MCPF - Con: 1117 ± 52.1 g/d; Bm: 1306 ± 52.1 g/d; uCP - Con: 1594 ± 57.9 g/d; Bm: 1807 ± 57.9 g/d) and ruminal N balance was lower for Diet Bm (Con: 98.7 ± 8.92 g/d; Bm: 65.6 ± 8.92 g/d). The present results show that the Bm maize hybrid might be advantageous for dairy cow nutrition with regard to N utilisation and MCPF. However, further research is necessary to draw more precise conclusions on the potential of Bm maize hybrids in general.
authors.affiliation: a Institute of Animal Nutrition, Friedrich-Loeffler-Institute (FLI) , Federal Research Institute for Animal Health , Braunschweig , Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Gorniak
authors.forename: Liane
authors.initials: L
authors.lastname: Hüther
authors.forename: Ulrich
authors.initials: U
authors.lastname: Meyer
authors.forename: Peter
authors.initials: P
authors.lastname: Lebzien
authors.forename: Gerhard
authors.initials: G
authors.lastname: Breves
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Südekum
authors.forename: Sven
authors.initials: S
authors.lastname: Dänicke
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004063:Digestion; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005260:Female; D005285:Fermentation; D005766:Gastrointestinal Contents / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009584:Nitrogen / Q000378:metabolism*; D012417:Rumen / Q000737:chemistry / Q000502:physiology*; D012820:Silage / Q000032:analysis; D003313:Zea mays / Q000737:chemistry* / Q000235:genetics
chemical_list: D005232:Fatty Acids, Volatile; D009584:Nitrogen