Graduation Year

Spring 2014

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts



Reader 1

Newton Copp

Reader 2

Marion Preest

Rights Information

© 2013 Genevieve G. Heger


The juxtaposition of a forage-fed diet versus a high-energy grain-based diet for beef cattle has become a prevalent issue concerning consumers today. Because the influence of media, and modern culture’s general push for a return to natural and healthy living, people have developed an opposition to the way in which corporations produce the meat we as customers purchase and consume. There is reason to react, but it must be noted that much of the evidence and information made public is not conclusively proven through scientific research, and even still, experimental studies have yet to determine substantial evidence.

The primary goal of this proposed experiment is to investigate the correlation between Escherichia coli O157:H7 growth and the diet of beef cattle, focusing on grass-based versus grain-based diets. I would like to investigate this phenomenon further and discover—with the majority of factors thought to foster E. coli O157:H7 growth eliminated (change in environment, feed and feeding method)—whether diet is actually the significant issue promoting the population growth of E. coli O157:H7.

The secondary goal of this proposed experiment is to investigate the correlation between diet and the nutritional content of the beef produced. Grass-fed beef has been popularized and marketed as a healthier option to conventionally raised grain-finished beef. It has developed a reputation based on little scientific evidence, so I would like to examine this topic further by issuing nutritional profiles of the beef produced by steers from this study and contribute to the ongoing research.

Sixty newborn Angus calves from Hearst Ranch will undergo a 1-2 year study. Groups of steers, differentiated by diet, will be organized using color-coded identification tags that attach to the ears of the steer. Group 1 will consist of 15 steers fed a 100% forage diet based off of the regimen. Group 2 will consist of 15 steers fed a forage diet that is 25% high grain concentrate. Group 3 will consist of 15 steers fed a forage diet that is 50% high grain concentrate. Group 4 will consist of 15 steers fed a forage diet that is 75% high grain concentrate. Monthly rectal swab fecal samples should be collected and assessed according to the procedures of Davis et al. 2005. I hypothesize that E. coli O157:H7 growth will not show statistically significant differences between diets. I do believe population growth will show an increase during summer months as opposed to winter months, however.

After steers have reached their optimal weight of 1100-1200 pounds, they will be slaughtered. A USDA professional will grade the carcasses, and further nutritional profiling tests will be done at to University of Georgia Meat Science Technology Center. Proximate, cholesterol, and fatty acid compositions for each of the steers will be profiled according to the procedures of Duckett et al. 2009. I predict that the nutritional profile of the beef produced will show significant differences, where the grass-fed steers will have a much higher concentration of omega 3 fatty acids, vitamins, and minerals.

This thesis is restricted to the Claremont Colleges current faculty, students, and staff.