Long-term effects of pre-weaning social housing on response to a social and housing transition in pregnant heifers.

Dairy cattle are routinely managed in social groups and subject to various management and social transitions, yet conventional approaches to rearing dairy calves limit social experience during early weeks of life. The objective of this study was to evaluate long-term effects of dairy calf social housing, with calves housed individually or in pairs, on long-term behavioral responses observed in pregnant heifers following social regrouping and introduction to a novel housing environment. Holstein heifers were raised during the milk-feeding period (provided 8 L/d milk replacer) in either individual pens (n = 20 heifers) or paired pens (n = 20 pens; 1 focal heifer/pen) and subsequently identically managed in groups on pasture from 9 weeks of age. At 30 d before expected calving, pregnant heifers were moved from pasture to a free stall barn, which represented introduction to a novel social group and an unfamiliar housing environment. Behavior was continuously recorded from video for 24 h, beginning at 0000 h on the day after introduction, to characterize feeding behavior, locomotor activity, and stall usage, as well as social proximity and competitive behavior surrounding the feed bunk and stall. Stocking density of the free stall barn fluctuated and was categorized as low (≤75%, 100 × animals in pen/available stalls), medium (>75%, 100%), or high (≥100%). Body weights obtained following calving indicated that previously PH heifers were heavier (632.3 vs. 593.4 kg; PH vs. IH), and body weight was included as a covariate in analysis of feeding behavior. Upon introduction to the free stall pen, previously PH heifers spent more time walking (1.9 vs. 1.3 min/h) with no effect of calf social housing on duration of lying time. However, stall use was subject to an interaction between previous housing treatment and stocking density and differed overall between previous housing treatments; previously PH heifers spent less time in the stall, particularly at high stocking density (29.4 vs. 48 min/h), due to shorter (29.6 vs. 95.7 min/visit) but marginally more frequent stall visits. Previously pair-housed heifers were also less likely to be displaced from a stall (44 vs. 85% of heifers replaced; PH vs. IH). Feeding behavior was similarly influenced by previous housing treatment particularly at high stocking density, with previously PH heifers spending more time feeding (8.2 vs. 4.2 min/h) and visiting the feed bunk more frequently (1.5 vs. 0.8 visits/h). These results suggest that preweaning social housing had long-term effects on behavior and ability to adapt to a novel environment which became most apparent under heightened competitive pressure.

Social contact from birth influences personality traits of group-housed dairy calves.

The objective of this study was to assess effects of prior social contact on the expression of personality traits in group-housed calves. Holstein heifer and bull calves were housed in either individual pens (n = 16), or in pairs (n = 8 pairs) at birth before they were mingled between treatments and moved to group pens at approximately 2 wk of life (8 calves/pen). During wk 4 of life, calves were tested in a series of standardized behavioral tests: an open field test, a novel object test, an unfamiliar calf test, and an unfamiliar human test. Responses in the open field test and novel object test were analyzed using principal component analysis, yielding 2 factors interpreted as bold and inactive/grooming. Calves housed in pairs before grouping had greater scores for bold and tended to have lower scores for inactive/grooming. Responses in the unfamiliar calf and human tests were similarly analyzed, yielding 3 factors interpreted as calf-directed, active, and human-directed. Calves housed in pairs before grouping had lower scores for calf-directed, tended to have lower scores for active, and scores for human-directed did not differ. Following grouping, average daily gain, milk replacer intake, and meal frequency did not differ between previous housing treatments. Our results suggest that behavioral traits reflective of personality in group-housed calves may be influenced by social contact from birth even following adaptation to group-housing.

Development of human-directed behavior in dairy calves reared individually or in pairs.

Although social contact between dairy calves has broad effects on their behavioral development, influences of calf social housing on human-animal relationships are less well understood, despite implications for longer-term calf management and welfare. We characterized human-animal interactions in 3 distinct testing contexts to examine effects of social housing on development of human-directed behavior. At birth, Holstein heifer calves were randomly assigned to individual housing (n = 17 calves) or pair housing (n = 17 calves; 1 focal calf/pair). A human approach test was performed twice in the home pen (wk 3 and 5 of life), within an open testing arena (13 × 7 m; wk 4 of life), and within group-housing pens 6 d after all calves were weaned, mingled between treatments, and moved to groups (4 calves/pen; wk 8 of life). For these tests, a human approached, and then extended their hand, over a 2 min period for home and group pen tests and a 5 min period for the arena test, and behavior was recorded from video. During preweaning human approach tests in the home pen, individually housed calves had shorter latencies to contact the human (22.4 vs. 45.1 s; individual vs. pair housing) and spent more time in contact with the human [80.5 vs. 41.1 s; standard error (SE) = 9.9; individual vs. pair housing], with similar responses between repeated tests. In the arena approach test, individually housed calves spent more time oriented toward the human (134.6 vs. 81.3 s; SE = 16.5; individual vs. pair housing), whereas pair-housed calves were more likely to perform pen-directed non-nutritive oral behavior (60 vs. 40% of calves; pair vs. individual housing), suggesting differences in interest directed toward the human compared with the novel environment. We also found that total duration of human contact was correlated between the first home pen approach test and the novel arena test, but that specific response to human approach varied between testing contexts. Effects of treatment persisted during the postweaning group pen approach test, with previously individually housed calves tending to spend more time looking toward the human (53.0 vs. 30.0 s; SE = 9.4; individual vs. pair housing) and more likely to contact the human (47 vs. 12% of calves; individual vs. pair housing). Overall, these results show persistent effects of early life social housing on human-directed behavior which may have implications for longer-term management.

Effects of early social contact on dairy calf response to initial social grouping and regrouping.

Social contact affects social development and response to novelty in dairy calves, but the age of introduction to social housing varies on-farm and may have implications for behavioral development and response to social grouping. The objective of this experiment was to evaluate the effects of early social contact during approximately the first 2 wk of life on calf early life behavior and performance and responses following initial social regrouping, followed by subsequent regrouping. At birth, calves were randomly assigned to individual (IH; n = 16 calves) or pair-housing (PH; n = 8 pairs). Calves were mingled between treatments and initially grouped (4 calves/pen) at 13 ± 2 d of age (mean ± standard deviation) and then regrouped (8 calves/pen) at 20 ± 5 d of age. Calf ability to learn to feed independently from the teat bucket in early life, and from the autofeeder following grouping, was monitored. Calf health, feed intake, and weight gain were recorded throughout the first 3 wk of life. Activity and social interactions were continuously recorded from video for the first 24 h following grouping and regrouping (except for allogrooming, hay consumption, and social play, which were observed for 12 h due to nighttime visibility). During the period of exposure to different housing treatments, calf feed intake and weight gain did not differ, but calves housed in pairs tended to scour for fewer days [4.1 vs. 5.6 d; PH vs. IH; standard error (SE) = 0.58]. Previously pair-housed calves spent more time lying socially (within 1 body length of another calf) than previously individually housed calves following both initial grouping (9.8 vs. 5.7 h/d; PH vs. IH; SE = 0.83) and regrouping (11.3 vs. 9.1 h/d; PH vs. IH; SE = 1.1). We saw no effects of previous social contact on duration of brush use (31.5 min/d; SE = 4.2), hay feeding (5.1 min/12 h; SE = 1.6), allogrooming (4.1 min/12 h; SE = 0.16), or social play (0.52 min/12 h; SE = 0.19) following initial grouping or regrouping. However, previously pair-housed calves tended to have greater lying time after regrouping. These results suggest that early life social contact before social grouping in the first weeks of life may not greatly affect activity within the pen or active social interactions following the transition to group housing. However, persistent differences in duration of social lying suggests that early life social contact may influence overall comfort toward other calves following social grouping.