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Driemel, Ashley Winter

Animal and Veterinary Sciences

2023

M.S.

Seaweed supplementation in ruminants is not a novel practice but has recently regained popularity due to promising nutritional benefits for the animal as well as the presence of bioactive compounds that reduce methanogenesis within the rumen. It is important to broaden our assessment of different seaweed species and identify key seaweed species that have the most efficient CH4-reducing potential, do not negatively impact rumen fermentation parameters, and are abundant enough to meet consumer demand. Chapter 1 of this thesis reviews the published literature relevant to seaweed supplementation in ruminants, with a focus on the comparison of seaweed processing methods utilized in these studies and how they impacted ruminal fermentation parameters such as methanogenesis. Seaweed species that can be harvested in the northeastern United States are also highlighted. The objectives of Experiment 1 (Chapter 2) were to evaluate northeastern USsourced seaweed supplements from Saccharina latissima (SL) and Ascophyllum nodosum (AN) and their processing methods on rumen fermentation and methanogenesis using continuous culture fermentation. Experiment 1 utilized a 4x4 Latin Square design consisting of four, 10-d periods. The four experimental treatments in addition to a TMR diet were: 1) unwashed, coarsely milled SL at 4.6% dry matter (DM; UNW), 2) 3-min rinsed SL at 4.5% DM (3MR), 3) 20-sec blanched SL at 3.8% DM (20SB), and 4) a crude phlorotannin extract from AN at 4.7% DM (PHLT). Treatment did not impact pH, DM, organic matter (OM), or the apparent degradabilities of neutral detergent fiber in amylase, organic matter (aNDFom) or acid detergent fiber (ADF). The processed SL treatment 3MR produced less CH4 in vitro than the unprocessed SL treatment (UNW). These findings serve as an indication of the importance of washing seaweed supplements and its possible effects on fermentation. The objective of Experiment 2 (Chapter 3) was to evaluate the dietary inclusion rate of Chondrus crispus (CC) on these rumen fermentation parameters relative to negative and positive controls in vitro. Experiment 2 utilized a 5x5 Latin Square design, consisting of five, 10-d periods. The five experimental treatments were: 1) negative control (CON) of TMR only, 2) TMR + 6% DM inclusion of CC (CL), 3) TMR + 10% DM inclusion of CC (CH), 4) positive anti-methanogenic control containing TMR + 2.5 mL of 0.6 mM bromoform (BL), and 5) positive anti-methanogenic control containing TMR + 5 mL of 0.6 mM bromoform (BH). No effects of treatment on pH, DM, OM, aNDFom or ADF apparent degradabilities were observed. Both inclusions of CC (treatments CL and CH) produced more CH4 than the controls (CON, BL and BH). Despite similarities in processing of CL, CH and UNW, as CC treatments were also unwashed, further investigation into washing methods as well as dietary cation: anion difference (DCAD) in CC are warranted. Further studies are necessary to determine the feasibility and practicality of implementing SL and CC in ruminant diets. Our findings only reaffirm the importance of effective seaweed processing methods and dietary inclusion rates, and that these factors affect methanogenesis, even in vitro.