- Title
- Development of a novel medium for storing bull spermatozoa at room temperature
- Creator
- Klein, Erin K.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2024
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Compared to the dairy industry, the beef industry has been slow to adopt artificial insemination (AI) programs. This is largely due to the logistical challenges surrounding AI in an industry that employs a less hands-on management approach. Successful AI relies on insemination at observable signs of oestrus or a fixed-time following oestrus synchronisation, both of which require handling or monitoring of individual animals. This is considerably easier when cows are regularly seen for milking, but less so when herds are managed extensively as is typically done in northern Australia. Additionally, bovine AI traditionally uses cryopreserved spermatozoa with expected conception rates of approximately 50%. Although there are logistical challenges to these programs, AI offers the fastest way for producers to disseminate diverse genetics throughout a herd, allowing producers to keep fewer breeding bulls and shortening calving periods. Selective breeding can be used to promote some of the more hereditable traits, including fertility-related traits (such as age at puberty) that will ultimately improve productivity. In consideration of the significant damage that cryopreservation induces upon spermatozoa, one way to improve AI may be the use of spermatozoa maintained at room temperature. The dairy industry has found higher success rates through the use of chilled sperm storage (5 °C), however, the limitation of chilled storage is reduced fertility when used more than 48 h after collection. To bridge the gap between 48 h and indefinite storage (with the caveat of damage), we sought to develop a novel sperm storage medium (‘SpermSafe-B’) capable of maintaining the fertility of bull spermatozoa at room temperature for at least seven days. Storage for seven days without the requirement of temperature-controlled devices to keep samples chilled or tanks of liquid nitrogen to keep samples cryopreserved, would greatly improve the logistics related to transporting samples to more remote locations and significantly decrease expenditure. The overarching aim of this thesis was to develop a novel method of storage for bull spermatozoa that would encourage uptake of AI by beef producers in northern Australia. To achieve this, a series of studies were conducted, comprising a literature review, in silico analysis, laboratory studies and field trials. In Chapter 1, we reviewed recent discoveries in proteomics, transcriptomics, and metabolomics that have been correlated to bull fertility status to gather a better understanding of the current knowledge surrounding biomarkers of bull fertility. In Chapter 2, we performed an in silico analysis of bull sperm membrane proteins to assess their functions related to fertility and identify ways in which to better support spermatozoa during in vitro storage. In Chapter 3, we investigated the in vitro storage requirements of bull spermatozoa with regard to pro-survival factors, energy substrates, and antioxidants, culminating in the initial formulation of SpermSafe-B. This medium successfully maintained motility of bull spermatozoa at levels suitable for using in AI programs through 10 days of room temperature storage (commercial threshold applied: total motility >60% and progressive motility >16%). In Chapter 4, we optimised protocols for best use of this medium, and compared ambient temperature storage in SpermSafe-B against more traditional methods of sperm storage for AI, finding that spermatozoa stored at room temperature in SpermSafe-B for seven days maintained higher motility and acrosome integrity than spermatozoa stored chilled and attained in vitro fertilisation (IVF) success comparable to that expected of cryopreserved semen. In Chapter 5, we assessed the field fertility of seven day SpermSafe-B stored spermatozoa. In two trials, using both Bos taurus and Bos indicus breeds, pregnancies were achieved, confirmed by ultrasonographic pregnancy diagnosis and the production of live calves. In summary, this thesis describes a series of investigations that culminated in a novel strategy for sperm storage and demonstrates the potential of ambient temperature storage to enhance artificial insemination practices in the cattle breeding industry. The work presented in this thesis was funded by a grant from Meat and Livestock Australia (B.GBP.0030) to help facilitate this advancement.
- Subject
- reproduction; spermatozoa; sperm storage; bovine reproduction; bull fertility; artificial insemination; livestock production; biomarkers of fertility
- Identifier
- http://hdl.handle.net/1959.13/1513620
- Identifier
- uon:56747
- Rights
- Copyright 2024 Erin K. Klein
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 11 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 214 KB | Adobe Acrobat PDF | View Details Download |