UC Davis

Dairy cattle are often raised in feed-restricted environments and perform abnormal repetitive behaviors (ARBs) indicative of welfare concerns under these settings. Research has commonly focused on ability to suckle milk as the driver of these behaviors, but forage restriction, and ability to chew and ruminate, has been understudied. The objectives of this dissertation were to evaluate the immediate and later-life effects of hay restriction on oral behaviors in dairy cattle. This was supported by additional goals of documenting the ways cattle use their mouths, circadian and diurnal patterns of behavior, and whether normal behaviors could be expressed abnormally. To achieve these aims, I used robust sampling and narrow behavioral definitions across all chapters. I found that access to hay in the milk-fed period increased time spent chewing, which occurred most around milk feeding, and ruminating, which was performed most overnight (Chapter 1). Hay also reduced nonnutritive oral manipulation (NNOM), a commonly scored ARB in cattle, in the immediate environment (Chapters 1 and 2), regardless of how forage was presented (Chapter 2). Behavioral differences from the milk-fed period did not persist through weaning (Chapter 1) or to the heifer stage (Chapter 3). However, tongue rolling and NNOM were more prevalent at the heifer stage than they were at calves (Chapters 2 and 3). Most behaviors were not correlated across ages (Chapter 3), and diurnal patterns of behavior also differed. While NNOM was performed most around feedings as calves (Chapter 2), it was more prevalent in the evening as heifers (Chapter 3). Across ages, many oral behaviors were expressed in extreme ways, including excessive grooming bouts, polydipsia, and possible pseudorumination (Chapters 1 and 2), and outliers were present in many of these (Chapter 3). Overall, early life access to hay appears to be important to calves, and can mediate the expression of some abnormal behaviors in the immediate environment, but this effect is short-lived. The intensity of sampling used, in terms of hours (24-h or 12-h), resolution (1-min or 5-s intervals, or continuous recording), and discrete definitions for all oral behaviors expressed, revealed more abnormality than has previously been described in dairy cattle. These results and methodology also serve as a baseline for future work elucidating the underlying cause of abnormal behavior in cattle, and appropriate interventions to improve welfare.