Investigations on biological indicators for feed efficiency in cattle

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Montanholi, Yuri Regis

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University of Guelph


This thesis aimed to identify potential indicators for feed efficiency and also better understand the biological factors influencing the efficiency of feed utilization by cattle. The growing focus of the beef industry on feed efficiency has resulted in the demand for more reliable low-cost alternatives for predicting feed efficiency. Many researchers have indicated the association between heat production and feed efficiency. Given the technical complexity of performing indirect heat production measurements on a large number of animals, in Chapter 3 the relationship between indirect heat production and infrared thermography was evaluated. The evaluation of thermographs of different body locations indicated the strongest correlation between feet temperature and heat production (r = 0.88). Moreover, a strong correlation between methane production by the cow and the difference in temperature between right and left flanks was discovered. In Chapters 4 and 5, the evaluation of the association between feed efficiency traits and infrared thermographs of different body locations revealed moderate associations between body extremities (cheek, snout and feet) and feed efficiency traits. In addition, alternative models for defining residual feed intake were investigated in Chapter 4. The different models evaluated indicated a positive influence of including ultrasound traits in the base model for defining residual feed intake, specifically ribeye area and backfat thickness. Furthermore, in Chapter 5, associations between residual feed intake and feeding behavior and glucocorticoid levels indicated that more efficient steers consume smaller meals, eat slower, visit the feeder less often and have greater levels of fecal cortisol metabolites than less efficient steers. Infrared thermography was the main factor explaining residual feed intake variation in both Chapters 4 and 5, which indicates a promising potential of this technology as a predictor of feed efficiency.



cattle, feed efficiency, biological indicators, heat production, infrared thermography