Response to novel feed in dairy calves is affected by prior hay provision and presentation method

**Background:** Dairy calves raised in intensive environments often lack foraging complexity, which may impair their ability to adapt to novel feeds at weaning. Food neophobia—including startle responses, long latencies to eat, and low intake—can hinder the transition from liquid to solid diets. Early life exposure to forage may improve behavioral flexibility and processing skills, but the influence of forage presentation method on neophobia is not well understood.

**Methods:** Twenty-seven Holstein heifer calves were housed individually in outdoor hutches with attached pens and assigned at birth to one of three treatments (n=9 each): Control (no hay), Bucket (chopped mountaingrass hay in a bucket), or Pipe (same hay in a PVC pipe feeder mounted at head height). All calves received starter grain and milk replacer (5.7–8.4 L/d step-up). At 50 d of age, step-down weaning began and calves were briefly confined while a bucket of novel TMR (89.7% DM; alfalfa, almond hulls, cottonseed, corn, barley, beet pulp) replaced the hay bucket (Bucket) or empty bucket (Control, Pipe). Behavior was video-recorded for 30 min and scored by a blinded observer for latency to eat TMR, startles/flinches/retreats, time spent eating, and lying down. Intake was measured by weighing refusals. Statistical analyses used beta regression, generalized linear models (Gamma distribution), and chi-square tests.

**Key Results:** Bucket calves began eating TMR significantly faster (5 ± 1 s) than both Control (60 ± 12 s, P=0.008) and Pipe calves (38 ± 14 s, P=0.012). Control and Pipe calves did not differ in latency (P=0.511). The number of calves performing startles, flinches, or retreats differed by treatment (Control: 9, Pipe: 6, Bucket: 2; P=0.004), with 86% of these events occurring within the first 200 s. Bucket calves spent less time eating TMR than Control calves (P<0.001), while Pipe calves tended to spend less time than Controls (P=0.070). Total TMR intake did not differ among groups (43.8 ± 30.1 g; P=0.178). Lying down after eating occurred in 2 Control, 6 Pipe, and 4 Bucket calves, but this difference was not significant (P=0.135).

**Clinical Implications:** Early access to hay reduces neophobia toward novel forage at weaning, with familiarity of presentation method playing a key role. Calves with hay experience (especially bucket-fed) adapted more quickly and efficiently, consuming the same amount of TMR in less time. Forage-naïve calves showed transient neophobia but were highly motivated to consume TMR, suggesting that forage deprivation may increase motivation. Providing forage early in life may improve weaning transitions, reduce stress, and support development of efficient feeding behaviors in dairy calves.