Date of Award

Winter 2023

Project Type


Program or Major

Animal Sciences

Degree Name

Doctor of Philosophy

First Advisor

André F. Brito

Second Advisor

Peter S. Erickson

Third Advisor

Elizabeth Latham


Enteric methane (CH4) emissions from ruminants contribute significantly to global warming and represent a loss of dietary energy for the animal. Dietary manipulation is a promising approach for CH4 mitigation. Nitrate can effectively reduce CH4, but it can also be toxic in non-adapted ruminants. Supplementing with Paenibacillus fortis, a denitrifying probiotic strain, is a potential strategy to prevent toxicity. The interest in using macroalgae to mitigate CH4 emissions while improving animal health and production in ruminants has increased in recent years. The overall objective of this dissertation is to investigate nutritional-based strategies to mitigate enteric methane emissions and improve the health and performance of dairy cows. The content in Chapters 2, 3, and 4 is presented under the Journal of Dairy Science publication format. An experiment was conducted to investigate the effects of supplemental nitrate administered alone or with the denitrifying direct-fed microbial strain Paenibacillus fortis on enteric CH4 emissions, milk production, ruminal fermentation, and microbial composition in dairy cows. Nitrate supplementation decreased CH4 by 9% but increased H2 emissions, and increased nutrient digestibility, but did not enhance milk production. Moreover, the direct-fed microbial did not provide any further benefit under the conditions of the study (Chapter 2). A second experiment was conducted to evaluate the effect of increasing dietary levels (0, 3, and 6% of dry matter intake) of the red macroalga Chondrus crispus on enteric CH4 emission, milk production, iodine metabolism, hematological parameters, nutrient utilization, and ruminal fermentation in organic dairy cows. Feeding incremental amounts of C. crispus decreased enteric CH4 by 8% and H2 by 17%. However, a decrease in dry matter intake was also observed, but milk production remained unaffected, indicating energy partitioning towards milk production. Iodine concentration and output in milk, feces, and urine were increased, but thyroid hormone concentrations and hematological parameters remained unaffected (Chapter 3). A third experiment was conducted to investigate the effects of supplementing increasing amounts (0, 57, and 113 g/d) of the brown alga Ascophyllum nodosum (ASCO) or ethylenediamine dihydroiodide on markers of metabolic status, thyroid hormone concentrations, and performance in transition dairy cows. Treatments did not affect prepartum performance but increasing ASCO meal levels resulted in higher blood nonesterified fatty acids. Postpartum blood metabolites and milk yield were unaffected by treatment. Among I sources, ASCO meal tended to increase milk fat concentration. Overall, ASCO meal supplementation did not improve the transition status of cows in this study.

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