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Effects of Ascophyllum nodosum meal and monensin on ruminal fermentation and microbiota.

L. H. P. Silva



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Effects of Ascophyllum nodosum meal and monensin on ruminal fermentation and microbiota.
L. H. P. Silva*1, A. T. O. Melo1, S. F. Reis2, B. P. Jackson3, F. Evans4, A. F. Brito1. 1University of New Hampshire Durham, NH, 2Faculdade de Ci�ncias Biom�dicas de Cacoal Cacoal, RO, Brazil, 3Dartmouth College Hanover, NH, 4Acadian Seaplants Ltd Dartmouth, NS, Canada.

Ascophyllum nodosum meal (ASCO) is known to contain high concentrations of phlorotannins and iodine, which can impact the ruminal microbiota. However, there are few studies that have evaluated how ASCO affect ruminal microbiota. Five ruminally-cannulated Jersey cows were used in a 5 � 5 Latin square design to evaluate the effects of incremental levels of ASCO (0, 57, 113, and 170 g/d) or monensin (MON; 300 mg/d) on ruminal fermentation and microbiota. Each experimental period lasted 28 d with 21 d for diet adaptation and 7 d for sample collection. Cows were housed in a freestall equipped with Calan doors. A basal diet with a 65:35 forage:concentrate ratio (DM basis) was offered twice daily. Ruminal fluid was collected 3 h after the morning feeding for 3 consecutive days (d 23—25) of each sampling period and pooled for protozoa count, total bacteria, and microbiota analysis. Ruminal fluid was also collected at 0, 1, 2, 4, 6, and 8 h after feeding on the d 27 for ruminal pH, NH3-N, and VFA analysis. Total bacteria were quantified by RT-qPCR. Microbiota analysis was performed on a MiSeq platform and processed using QIIME2. All data were checked for normality by Shapiro-Wilk test, and when necessary log-transformed. Data were analyzed in SAS following a 5 � 5 Latin square design with repeated measurements for ruminal pH, NH3-N, and VFA. Contrasts were used to 1) compare linear and 2) quadratic effects of ASCO levels, 3) ASCO vs. MON, and 4) control vs. MON. Ruminal pH and NH3-N were not affected by treatments. Total VFA concentration in the rumen was not affected by MON but decreased linearly with ASCO supplementation (P = 0.02). Ruminal butyrate and the acetate:propionate ratio showed quadratic responses to ASCO (P < 0.05). Protozoa count and total bacteria were not changed by treatments, as well as bacterial and archaeal diversity. The protozoal Simpson diversity index and the protozoal genera Entodinium and Isotricha reduced linearly with incremental levels of ASCO (P < 0.05). Overall, ASCO did not affected protozoa count and total bacteria but reduced protozoal diversity with minimal effect on ruminal fermentation parameters.

Keywords: microbiota, rumen, seaweed.