Contents lists available at ScienceDirect Animal Feed Science and Technology journal homepage: www.elsevier.com/locate/anifeedsci Modulation of ruminal fermentation profile and microbial abundance in cows fed diets treated with lactic acid, without or with inorganic phosphorus supplementation E. Mickdam a,b,d , R. Khiaosa-ard a,d , B.U. Metzler-Zebeli c,d , E. Humer a,d , H. Harder a , A. Khol-Parisini a,d , Q. Zebeli a,d, ⁎ a Institute of Animal Nutrition and Functional Plant Compounds, Department of Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria b Nutrition and Clinical Nutrition Department, Faculty of Veterinary Medicine, South Valley University, 83523 Qena, Egypt c University Clinic for Swine, Department of Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria d Research Cluster “Animal Gut Health”, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Vienna, Austria ARTICLE INFO Keywords: Grain processing Phosphorus nutrition Ruminal microbial abundance Ruminal fermentation ABSTRACT This study evaluated the effects of lactic acid (LA) treatment of concentrates without or with inorganic P supplementation on ruminal fermentation profile and microbial abundances in non- lactating cows. Six rumen-fistulated Holstein cows were assigned to a double 3 × 3 Latin square design with 3 experimental periods. Each period lasted 14 d, whereby the measurements were performed during the last 2 days. Cows were fed 3 diets containing untreated control concentrate supplemented with inorganic P, and two LA-treated concentrates, either without (LA - P) or with (LA + P) the inorganic P supplementation. The concentrate mixtures of the LA diets were soaked in 5% LA for 24 h before feeding, whereas the concentrate of control diet was not. All diets were offered as a total mixed ration (forage to concentrate ratio of 53:47). Ruminal pH, ammonia and short-chain fatty acid (SCFA) concentrations were determined in free ruminal liquid (FRL) and particle associated ruminal liquid (PARL) that was collected at 0, 2, 4, 8, and 12 h post-morning feeding. Target ruminal microbes in FRL and rumen solid digesta collected at 2 h post-feeding were analyzed using quantitative PCR. Cows consumed on average 17 ± 1.0 kg DM/d (mean ± SEM), irrespective of the treatment. The concentration of total SCFA in FRL was increased by LA treatment (P< 0.001) without affecting the pH. Irrespective of P supplementa- tion, feeding of LA-treated diets shifted SCFA profile towards more propionate in the FRL and PARL. The LA - P diet lowered ammonia concentration compared to the other diets (P< 0.05). The LA - P diet also reduced the fungal gene copies in solid digesta by 7.6% compared to the LA + P diet (P< 0.05). The total bacterial abundance in both ruminal fractions was not affected by diet; however, compared to the control, LA treatment enhanced (P< 0.05) the relative abundance of genus Prevotella in FRL (18%) and in solid digesta (27%). In contrast, the same treatment decreased the abundances of Clostridium cluster IV (23%) in FRL and Selenomonas ruminantium group (30%) in solid digesta (P< 0.05). Abundances of fibrolytic microbes http://dx.doi.org/10.1016/j.anifeedsci.2017.05.017 Received 12 February 2017; Received in revised form 22 May 2017; Accepted 24 May 2017 ⁎ Corresponding author at: Institute of Animal Nutrition and Functional Plant Compounds, Department of Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria. E-mail address: Qendrim.Zebeli@vetmeduni.ac.at (Q. Zebeli). Abbreviations: A:P, acetate to propionate ratio; CON + P, control diet with the untreated concentrate mixture supplemented with inorganic phosphorus; CP, crude protein; DM, dry matter; FRL, free ruminal liquid; LA, lactic acid; LA + P, lactic acid-treated concentrates with supplemental inorganic phosphorus; LA - P, lactic acid-treated concentrates without inorganic phosphorus; SCFA, short-chain fatty acid; PARL, particle associated ruminal liquid; P, phosphorus; TMR, total mixed ration Animal Feed Science and Technology 230 (2017) 1–12 0377-8401/ © 2017 Elsevier B.V. All rights reserved. MARK