UC Davis

Finishing cattle are fed high-concentrate diets with minimal forage included. With the health complications that can arise from rapid consumption of concentrate, it is surprising that these animals will choose to consume a diet that is similar or even lower in forage than a typical finishing ration. Studies of diet selections indicate finishing cattle choose between 8 to 20% roughage, but tests of motivation, how much they want forage in their diet, are rare and have not included rumen health. The objective of this dissertation was to measure the motivation of finishing cattle to access forage when fed a high-concentrate diet and in the context of reticulorumen pH. I designed two novel measures of motivation for feedstuffs in finishing cattle and carried out the first experiment that measured the importance of forage while also monitoring reticulorumen pH. Using a thwarting test (Chapter 1) and then an electric current as an aversive stimulus (Chapters 2 and 3), I found that finishing cattle interacted with three different types of forage when offered it in addition to their primary diet: beardless wheat hay (78% of animals tested interacted when offered; Chapter 1), alfalfa hay (75%; Chapter 2), and Sudan grass hay (64%; Chapter 3). Animals were not motivated to access an empty bunk behind an electrified barrier (Chapter 2) and showed reduced motivation for additional feed as current increased, demonstrating the effectiveness of electric current for measuring motivation (Chapters 2 and 3). I also observed contrafreeloading for an additional offering of the primary diet (Chapters 2 and 3). Despite previous research in self-selection of high-concentrate diets by feedlot cattle, the contrafreeloading observed in Chapter 3 was unexpected since chronic, low reticulorumen pH was widespread in the study population. These findings support earlier work that show finishing cattle prefer a diet high in concentrate, with minimal roughage. However, these results also raise questions about the function contrafreeloading serves for these animals, as the behaviour has now been observed for both high- and low-energy rations. Further research is needed to elucidate the implications for animal welfare of contrafreeloading in feedlot cattle.