Date of Award
Master of Science
Max F. Rothschild
To maximize efficiency and meet the demand for animal-derived products of an increasingly population, livestock production systems need to evolve and be fine-tuned to increase their efficiency both in the use of resources and output of products. The first manuscript investigated the effects of climatic variables on the quality grade and quantity of in vivo derived cattle embryos in the Midwestern United States. The response variables included the number of ovarian structures, viable embryos, quality grade 1 embryos, quality grade 2 embryos, quality grade 3 embryos, freezable embryos (sum of quality grade 1 and quality grade 2 embryos), transferable embryos (sum of quality grade 1–3 embryos), degenerate embryos and unfertilized ova. A negative effect of greater temperatures during the early embryonic development stage tended (P < 0.10) to be associated with a decrease in the quality of embryos recovered. Wind speed during the estrous synchronization period was also associated with a lesser number of embryos recovered (P < 0.05). Increased wind speed at the early antral follicular phase 40–45 days prior to ovulation was associated with an increase in the percentage of quality grade 1 embryos recovered (P < 0.05). This retrospective study confirms that climatic variables have significant effects on the in vivo production of cattle embryos and that wind speed should be considered in future analyses of factors affecting embryo quality.
The second manuscript aimed to determine the possible existence of any effects of lunar cycles and other variables on boar ejaculate variables and to examine those effects relative to other possible factors. Moon phase, greatest daily temperature (T), least daily T, average daily relative humidity (RH), temperature-humidity index (THI), season and the interaction of moon phase with season were analyzed at the day of collection and 45 days prior to date of collection as a proxy of initiation of spermatogenesis. For both dates analyzed, season and the interaction of season with moon had significant effects (P < 0.05) on the volume of the ejaculate, the concentration of sperm in the ejaculate and the number of doses obtained per ejaculate. The significant interaction of season and moon phase on boar semen traits found in this study suggests that to maximize productivity of modern swine production systems determining a collection schedule in some seasons relative to moon phase may be advantageous.
The third manuscript has the objective of developing a manual weight prediction method that can accurately be used on African goats to empower small-holders and improve their food security. One linear model and two quadratic models were developed, and their accuracy was compared to a commonly used equation. In all cases, the models produced smaller mean prediction errors than the commonly used equation.
Overall, this thesis provides insight on different alternatives to adapt and improve the efficiency and output of livestock production systems and small producers in rural Africa with the aim of improving resilience in an era of rapid climatic changes.
Josue Chinchilla- Vargas
Chinchilla- Vargas, Josue, "Food security and the effects of climatic factors on livestock reproduction" (2018). Graduate Theses and Dissertations. 16561.