209. Influence of Early-life Experiences on Post-weaning Oral Behaviors in Dairy Calves.

Abstract Dairy calves are typically raised with low milk allowances, no forage, and are weaned at young ages, restricting motivated behaviors like chewing, ruminating, and suckling. These experiences can increase abnormal repetitive behaviors (ARBs) like tongue rolling (TR), non-nutritive oral manipulation (NNOM), and cross-sucking (CS), which reflect welfare challenges and cause producer concerns. Restricting natural feeding opportunities can also affect short-term adaptation to new environments or feed. However, it is unknown whether early-life restriction of natural feeding behaviors has lasting effects on normal and abnormal behaviors. Our objective was to investigate how rearing practices influence the behavior of weaned dairy calves on pasture. Thirty-eight Holstein heifer calves were enrolled from birth and housed individually. Calves were either provided ad libitum access to water and grain with a 6L/d bottle-fed milk allowance (Standard; similar to conventional US practices), or ad libitum water, grain, and hay with a 9L/d milk allowance (Enhanced). Weaning occurred at either 8- or 12wks through a 10d step-down process, resulting in a 2x2 design (Standard-8wks [S8; n = 10], Standard-12wks [S12; n = 9], Enhanced-8wks [E8; n = 10], and Enhanced-12wks [E12; n = 9]). Calves were moved at 5-18d post-weaning to a ∼1900m² pasture with access to water, grass, supplemented grain, and up to 8 total calves. We observed calves for 24h (05:00-05:00) in person biweekly until 8wks post-introduction (OBS1-4) using instantaneous sampling at 5min intervals. We analyzed the proportion of visible intervals grazing, eating grain, ruminating, TR, CS, and performing NNOM using a generalized linear mixed model with feeding, weaning, day, and their interactions as fixed effects and calf as a random effect. Grazing was similar (6.7±0.5 mean±SE percentage of intervals) across feeding treatments, weaning ages, and days (p ≥ 0.430). Calves weaned at 12wks spent less time eating grain (7.9±0.6%) during OBS1 than those weaned at 8wks (11.0±0.8%; P ≤ 0.002), but not from OBS2 onwards (P ≥ 0.068). There was a feeding, weaning, and day interaction for rumination, as E12 calves spent less time ruminating (5.4±1.3%) on OBS1 than any other treatment (14.8±1.7%; P ≤ 0.019). This was similar on OBS2 (8% vs. 15-18%; P ≤ 0.037), but there were no differences by OBS3-4 (P ≥ 0.608). There was no overall difference in NNOM by treatment (P ≥ 0.581), but all calves performed NNOM each day. TR and CS were sporadic and not evaluated with a model; however, 100% of calves performed TR and 92% performed CS. These results suggest that weaning and pre-weaning rearing can influence post-weaning performance of some natural feeding behaviors, but these effects diminish over time. All calves performed ARBs, even after extended exposure to pasture, suggesting these behaviors may emerge earlier in life and become hard to disrupt.