Hay provision affects 24-h performance of normal and abnormal oral behaviors in individually housed dairy calves.

Dairy calves often perform abnormal repetitive behaviors (ARBs) including tongue rolling and nonnutritive oral manipulation (NNOM) when opportunities to perform feeding behaviors are restricted. Many US dairy farms limit access to milk, a well-studied risk factor for ARBs. However, farms also commonly do not feed forage to young calves, and the motor patterns of oral ARBs resemble those necessary for acquiring and chewing solid feed. Our objective was to assess how access to hay from birth influenced time engaged in normal and abnormal oral behaviors across 24 h. Holstein heifer calves were housed individually on sand bedding and fed ad libitum water and grain (control, n = 11) or given additional access to hay (hay, n = 11) from birth. Calves were fed 5.7 to 8.4 L/d (step-up) of milk replacer via a teat. At the start of step-down weaning (50 ± 1 d), all calves were given access to a total mixed ration. Feed and water intake were measured daily. Oral behaviors (eating, ruminating, sucking milk, drinking water, panting, grooming, tongue flicking, tongue rolling, and NNOM) were recorded by direct observation at wk 2, 4, 6, and 8 using 1-0 sampling at 1-min intervals for 24 h. Grain, hay, and water intake increased over time in the preweaning period. One polydipsic calf regularly consumed >10 L of water/d. During weaning, hay calves tended to consume increasingly more total mixed ration, significantly more water, and less grain than control calves. Access to hay led to more observations spent eating solid feed (7% vs. 5%, mean percentage of intervals) and ruminating (24% vs. 16%) during the preweaning period compared with calves fed only grain, though control calves appeared to ruminate in absence of forage to re-chew. Rumination occurred, to a large extent, overnight. Hay calves also spent less time self-grooming (12% vs. 14%), tongue flicking (14% vs. 18%), and performing NNOM (17% vs. 21%) than control calves. Although NNOM peaked around milk feedings, all 3 behaviors were performed throughout the day. Tongue rolling was rare across treatments, as was panting, which occurred most frequently around 1400 h. There were no behavioral differences during weaning (wk 8). Overall, we found that hay provision affected most oral behaviors that calves perform; it promoted natural feeding behaviors and reduced abnormal ones, suggesting hay should be provided. We also found that calves performed other behaviors, including polydipsia, repetitive grooming, and apparent sham rumination, that may suggest a degree of abnormality in these behaviors that has not been previously identified. These results highlight the importance of considering all oral behaviors to better understand calf welfare.