Date of Award

Summer 8-18-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Animal Sciences

Advisor

Juan Romero Gomez

Second Committee Member

Glenda Pereira

Third Committee Member

Brian Perkins

Abstract

The main objective of this thesis is to improve the understanding and awareness of methodologies to decrease phytoestrogens in conserved legumes without sacrificing forage nutritive value. In chapter 1, we discussed the main factors influencing each stage of hay production and our current understanding of the hay microbiome dynamics. The primary objective of haymaking is to dry forage enough (80-85% DM) to inhibit the growth of undesirable microbes and halt residual plant enzymatic activity that causes nutrient losses. During the field and storage phases of haymaking, the environment, management practices, and other factors influence the extent of DM losses. This chapter discusses these factors and the strategies that have been developed to mitigate these nutrient losses. A major emphasis was placed on hay microbiota dynamics, as it has been scarcely studied despite its importance on nutrient losses during storage and harvest, especially in high moisture conditions. Since soil particles are a significant source of undesirable microbes and ash contamination, the effects of cutting height, mower type, and swath manipulation on soil contamination were discussed. Also, the impact of environmental conditions and swath manipulation on wilting time was analyzed for both humid and arid conditions. Special attention was given to design improvements in harvesting equipment to reduce curing time and field losses. Furthermore, we assessed the nutrient losses during storage caused by undesirable microbial and residual plant enzymatic activity resulting from excessive moisture at baling or re-introduced moisture during storage. The extent of spoilage during storage depends not only on bale moisture but also on bale size, density, shape, wrapping, forage type, and storage facilities. A Venn diagram analysis condensed all relevant hay microbiology research and showed that each phase of the haymaking process has a unique microbiome. It also showed that certain fungal and bacterial genera could be shared across more than one hay production phase. For instance, Aspergillus, Cladosporium, and Alternaria are fungal genera that tend to be present throughout the haymaking process. In order to take corrective actions, hay producers need to be aware of the increased susceptibility to nutrient losses associated with particular field and storage practices, environmental conditions, and forage types.

In Chapter 2, we evaluated the effects of insufficient (WET) or ample (CUR) wilting on the phytoestrogen levels, nutritional value, microbial populations, in vitro ruminal methane emissions, and in situ degradability of red clover silage (29.4 and 45.3% DM) and hay (65.1 and 89.1, respectively) across the storage stages. Measurements were taken at the start of storage (STRT), after 14 d (MicA), and once storage processes had stabilized for hay and silage (50 and 78 d, respectively; LATE). Only LATE samples of hay and silage were tested for the in situ procedure. Data were analyzed as a RCBD (5 blocks) with a 2 (wilting extents) x 2 (conservation methods) x 3 (storage stages) factorial. Results showed that storage DM losses were higher for WET hay than CUR but no differences were observed between WET and CUR silage. Ample wilting of hay and silage preserved better water-soluble carbohydrates during storage relative to insufficient wilting. Due to microbial spoilage, the NH3-N of WET hay was higher than CUR hay after 14 d of storage, but the opposite was observed after 50 d. For the WET and CUR silage, NH3-N increased across the ensiling period. The neutral detergent fiber of WET hay increased across storage stages while it remained stable for CUR hay. In contrast, the neutral detergent fiber of WET and CUR silage decreased during the ensiling period. The WET hay favored the growth of molds during storage, while CUR hay reduced their counts after 50 d of storage. For silage, mold counts were lower in WET compared to CUR after 14 d of storage but no differences were observed after 78 d. When the ensiling period is limited to 14 d, CUR silage that was aerobically exposed for 7 d was more susceptible to storage DM losses and subsequent heating relative to WET. However, if the ensiling period is extended to 78 d, no differences were observed between WET and CUR silage in terms of HDD and storage DM losses after being aerobically challenged. Ample wilting preserved the optimal ruminal fermentation kinetics of hay compared to insufficient wilting, while the ruminal fermentation kinetics of silage was not affected by the wilting extent. In vitro ruminal fermentation of WET silage resulted in higher methane yield than CUR, whereas methane yield of WET and CUR hay were not different. For both conservation methods, insufficient wilting reduced methane yield only at the end of storage. The in situ rumen degradability kinetics showed that ensiling increased the soluble DM fraction relative to haymaking. Ensiling reduced the potentially degradable DM fraction compared to haymaking but increased the rate of degradation of DM. Within insufficient wilting, silage had a higher degradation rate of NDF than hay. Ample wilting was more beneficial for silage than hay in terms of decreasing the levels of phytoestrogens. Across storage stages, hay had lower formononetin and biochanin A than silage. Formononetin and biochanin A of red clover hay decreased after 14 d of storage due to microbial degradation. Overall, ample wilting helped conserve the nutritional quality of hay and silage and decreased the phytoestrogens, especially in silage.

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