Data from: Providing long hay in a novel pipe feeder or a bucket reduces some, but not all abnormal oral behaviors in milk-fed dairy calves

Many milk-fed dairy calves are not provided forage. In these settings, calves often perform abnormal repetitive behaviors (ARBs), including tongue rolling and nonnutritive oral manipulation (NNOM), that, based on their form, seem similar to movements used when processing feed. Feeding hay, typically presented as a short chop (≤5 cm) in a bucket, reduces ARBs. Our objective was to evaluate whether altering the presentation method of long hay (approx. 19 cm), by providing it in a bucket or a novel polyvinyl chloride (PVC) pipe feeder, could reduce ARBs. Holstein heifer calves were housed individually on sand and fed ad-libitum starter grain and limited milk replacer (5.7-8.4 L/d step-up) via a bottle (Control, n=9) or given access to mountaingrass hay in a bucket (Bucket, n=9) or in a PVC pipe feeder (Pipe, n=9). The 56 x 10.2 cm (length x diameter) PVC pipe feeder had four 6.4 cm-wide openings that required the calf to insert her tongue into the pipe and curl her tongue to extract hay. Treatments were applied from birth through 50 d of age, when step-down weaning began and TMR was provided to all calves. Calves were fully weaned at d 60. At wk 4 and 6, oral behaviors (eating, ruminating, drinking water, sucking milk, self-grooming, NNOM, tongue rolling, tongue flicking, and panting) were recorded by direct observation for 24 h using 1-0 sampling during 5-s intervals. Feeding long hay, regardless of presentation method, increased overall DMI, grain intake, and ADG compared to Control calves. Hay provision also increased rumination (25% vs. 15% of 24-h observations in Control) and eating time (5.5% vs. 2% in Control). Abnormal behaviors were seen in all calves. Hay provision reduced some of these, including NNOM (5% vs. 9% in Control). There was no difference in NNOM between calves fed hay in a pipe or bucket, even though Bucket calves ate more hay (178 vs. 129 g/d in wk 6) and tended to spend more observations eating hay than Pipe calves (4.5% vs. 3%). Hay provision did not affect other behaviors: drinking water (0.5%), grooming (3%), or tongue flicking (3%). We also found evidence of other abnormal oral behaviors that have received less attention. Calves showed signs of polydipsia, and displayed excessive grooming, the latter indicated by overall duration, number of bouts per day, and duration of individual bouts (up to 25 min). Tongue rolling was expressed at low levels (up to 0.4% of intervals) but by 85% of calves. Feeding hay, both in a bucket and using novel methods, was not enough to counteract the welfare challenges associated with individual housing and limited ability to suck milk (<1% of time). Provision of long hay, regardless of presentation method, promotes rumination, improves performance (higher grain intake and ADG) and reduces at least some, but not all, of the considerable abnormal oral behaviors these calves performed.

多数哺乳期奶犊牛无法获得粗饲料供给。在这类饲养场景中，犊牛常表现出异常重复行为（abnormal repetitive behaviors, ARBs），包括卷舌动作与非营养性口腔操作（nonnutritive oral manipulation, NNOM）；从行为形式判断，这些动作与犊牛处理饲料时的运动模式高度相似。采用桶饲短切段干草（≤5厘米）的方式，可有效降低此类异常重复行为的发生频率。本研究旨在评估，改变长干草（约19厘米）的饲喂方式——将其置于普通饲料桶或新型聚氯乙烯（PVC）管饲槽内——是否能够减少犊牛的异常重复行为。

试验选取荷斯坦青年犊牛，单栏饲养于垫沙地面，分为三组进行饲喂：对照组（n=9）通过奶瓶饲喂自由采食的开食料，以及按5.7~8.4升/日阶梯式递增的限量代乳粉；桶饲组（n=9）可自由采食置于饲料桶内的山地禾草干草；管饲组（n=9）可自由采食置于PVC管饲槽内的山地禾草干草。该PVC管饲槽尺寸为56×10.2厘米（长×直径），带有四个6.4厘米宽的采食口，犊牛需将舌头探入管内并卷曲舌头，方可取食干草。试验周期覆盖犊牛出生至50日龄，期间启动阶梯式断奶流程，并为所有犊牛提供全混合日粮（Total Mixed Ration, TMR）；所有犊牛于60日龄完成完全断奶。

分别在第4周和第6周，采用5秒间隔的1-0取样法，开展24小时直接观察，记录犊牛的口腔行为，包括采食、反刍、饮水、吮乳、自我理毛、非营养性口腔操作、卷舌、弹舌与喘气。

与对照组犊牛相比，无论采用何种饲喂方式，供给长干草均可提升犊牛的总干物质采食量、精料采食量与平均日增重（average daily gain, ADG）。供给干草还可显著增加犊牛的反刍时长（占24小时总观察时长的25%，对照组仅为15%）与总采食时长（占比5.5% vs. 对照组的2%）。所有受试犊牛均出现异常行为，供给干草可减少部分此类行为，例如非营养性口腔操作（占比5% vs. 对照组的9%）。管饲组与桶饲组犊牛的非营养性口腔操作占比无显著差异，尽管桶饲组犊牛的干草日采食量更高（第6周时为178克/日 vs. 管饲组的129克/日），且其采食干草的观察时长占比也略高于管饲组（4.5% vs. 3%，呈边际显著趋势）。供给干草对其他行为无显著影响，包括饮水（占比0.5%）、理毛（占比3%）与弹舌（占比3%）。本研究还发现了此前受关注较少的其他异常口腔行为：犊牛表现出多饮症（polydipsia）迹象，并存在过度理毛行为——该行为可通过总持续时长、每日发生频次与单次理毛时长（最长可达25分钟）进行量化判定。卷舌行为的发生水平较低（最高占观察间隔的0.4%），但有85%的受试犊牛会出现该行为。无论采用何种饲喂方式，供给长干草均无法完全缓解单栏饲养与限量吮乳（吮乳时长占比不足1%）所带来的福利挑战。

综上，供给长干草，无论采用何种饲喂方式，均可促进犊牛反刍、改善生产性能（提升精料采食量与平均日增重），并至少可减少部分但并非全部犊牛表现出的大量异常口腔行为。