Novel object test
Behavioural response of calves towards fear to novelty was evaluated in a novel object test by presenting the calves with a red coloured pyramid. The results of behavioural response of the calves obtained in the novel object test are summarized in Table 2.
Latency to touch novel object
The WI calves took longer (P<0.001) latency to touch the novel object compared to other groups. Across the groups, the SG calves touched the novel object much faster followed by the WG calves and SI calves. However, the latency to touch the novel object was statistically insignificant among SG, WG and SI groups. One of the primary concerns of livestock welfare is: the fear to novelty. As reviewed by
Van Reenen et al., (2004) the latency to approach a novel object has been used as a reference measurement of fear in poultry, pigs and cattle, with long latencies putatively indicating high levels of fear and vice versa. The longer latency to approach the novel object by the WI calves indicates the impact of early maternal separation and social isolation from conspecifics may have provoked fearfulness behaviour in these calves. Moreover as these calves were housed individually, they were less acquainted with novel situations compared to calves of other groups. Studies have found that dairy calves weaned from their mothers have shown low growth performance, lowered immunity and altered oral behaviours as compared to suckled calves
(Singh et al., 2019; Bharti and Kamboj, 2024). Our findings are in agreement with previous studies
(Meagher et al., 2015; Gaillard et al., 2014) who reported longer contact latency to novel object in individually reared calves than in calves housed in groups or pairs. The reduced fear towards the novel object in our experimental calves (SG, WG and SI groups) are consistent with other studies suggesting early social contact reduces behavioral and physiological reactivity to environmental novelty (
De Paula Vieira et al., 2012). Dairy calves reared in complex social environments were reported to taste novel food faster than the calves reared in socially isolated conditions
(Costa et al., 2014).
Interaction with novel object
Across the group, the SG calves interacted significantly (P<0.001) more duration of time with the novel object however, no significant difference was found among SI, WG and WI groups. The longer duration of interaction with the novel object by the SG calves can be attributed to the social privileges of both mother and peers received by these calves over other groups, who received either one of them (SI and WG groups) or neither of them (WI group). Maternal contact of calves provides opportunities for social transmission of information from a mother to her young such as information about food sources and predators
(Thorhallsdottir et al., 1990; Mateo and Holmes, 1997). The present findings are in line with
Chen et al., (2015) who reported that naturally suckled calves (2 months) spent significantly more time (682.5±258.5 vs. 192.8±112.9 min, P<0.05) in exploring the novel object (novel decoy of a Holstein calf) compared to calves fed artificially from buckets. Though the SI and WG groups in the present study received the social contact of either mother or peers, but were reluctant or showed less interest to interact with the novel object, highlighting the importance of mother as well as peer contact essential for the overall development of calves. Similarly, we assume that the detrimental effect of maternal and social deprivation in our WI calves induced more fear in approaching and interacting with the novel object.
Exploring test arena
The time spent on exploring the maze was lowest (P<0.001) in WI calves compared to other groups. The SI calves were more active and spent more time exploring followed by SG calves and WG calves. However, there was no significant difference among SG, SI and WG groups. The presence of the novel object (red pyramid) was thought to provoke fear response in the WI calves taking longer latency to touch and less time interacting with the novel object, ultimately leading to less interest in exploration of the test arena.
Standing idle
The time spent on standing idle differed (P<0.001) across the groups. The WI calves spent significantly more time standing idle followed by SI, WG and SG calves. The individually housed calves (WI and SI groups) preferred standing idle for more duration of time compared to group reared calves (SG and WG groups). The WI calves were inactive and preferred simply standing idle compared to other groups. The higher time spent on standing idle is indicative of fear and less interest towards the novel object (red pyramid). Similar studies have also suggested that individually housed calves are more fearful than group-housed calves, when introduced to new social situations or when isolated in a novel arena
(Jensen et al., 1997).
Attention directed towards exit door
The results revealed that SG calves looked towards the door for more (P<0.001) duration of time followed by WG, WI and SI calves. The SG and WG groups differed significantly to each other however; the duration of time looking toward the exit door was statistically insignificant between SI and WI groups. This suggests that the group housed calves (SG and WG groups) looked towards the exit door more often compared to the individually housed calves (SI and WI groups). The results obtained in our study share similarities with findings of
Wagner et al., (2013) who observed more escape attempts in calves reared with their mothers in an isolation test as compared to artificially reared calves at 43 days of age. Similar to the escape attempts, looking towards gate as evidenced in our calves indicates a strong social bonding between the peer calf group and the eagerness to unite with their social mates. This idea is also supported by earlier findings by
Napolitano et al., (2008) and
Sevi et al., (1999) in lambs.
Locomotion
The time spent on locomotion was highest in SI group followed by WG group, SG group and WI group. However, there was no significant difference among the groups for the time spent on locomotion. These findings are in line with
De Paula Vieira et al., (2012) who observed no difference in locomotion time in the calves irrespective of different housing systems during novel object test.
Vocalization
Perusal of the results revealed significant (P<0.001) differences across the groups for vocalizations. The SG calves vocalized more frequently followed by WG, WI and SI. The group housed calves (SG and WG groups) vocalized more frequently as compared to individually housed calves (SI and WI groups). Between the group housed calves, the vocalization was more (P<0.001) frequent in SG calves when compared to WG calves. However, no statistical difference was observed between SI and WI calves. The frequent vocalizations observed the in group housed calves (SG and WG groups) may be due to the separation responses and stronger social bonds shared by the group mate with their social companions, corroborating with similar findings (
De Paula Viera et al., 2012; Jensen and Larsen, 2014) reporting higher vocalizations in pair housed calves as compared to individually reared calves. Moreover, frequent vocalizations also indicating a higher motivation of the group house calves to meet and unite with their social partners. In contrast, the SI and WI groups were socially deprived and were reared in individual pens with no access to peers, so were expected to have limited social connection resulting in less frequent vocalization.
Social novelty test
The social novelty test was performed to evaluate the calf’s behavioural response, especially the “fear response” when confronted with an unfamiliar calf of about similar age group. The behavioural response of the experimental calves toward an unfamiliar calf is summarized in Table 3.
Latency to initiate social interaction
Similar to the novel object test, the WI calves took significantly (P<0.001) longer latency to initiate social interaction with the unfamiliar calf as compared to other groups. These results clearly suggest that the WI calves were less interested to initiate social interaction with an unfamiliar calf compared to other groups. These findings corroborates with previous studies reporting deficits in social behavior for calves reared individually (
De Paula Viera et al., 2012;
Veisser et al., 1994; Jensen et al., 1997). The calves of SG, SI and WG groups in the present study had access to some kind of social contact either with mother or peers which may have helped to develop social skills in these calves. Calves reared with their mother have intense social behaviour towards unfamiliar calves (
Flower and Weary, 2001). Our findings support the idea that social interaction is a cardinal prerequisite in early stages of calf’s life.
Social interaction with unfamiliar calf
There was a significant effect of treatment on social interaction with an unfamiliar calf. The SG calves were more socially active spending more duration of time in social interaction, when confronted with an unfamiliar calf followed by the WG and SI calves. Across the groups, the WI calves were least interested (P<0.001) to interact with the unfamiliar calf. However, the duration of social interaction was statistically insignificant among SG, SI and WG calves. Our results are in agreement with previous studies
(Jensen et al., 1997) which suggests that calves that have been reared individually appear to be more fearful of unfamiliar calves. It is also reported that individual housing of dairy heifers could lead to serious implications like reduced ability to cope within groups later on in the future (
Broom and Leaver, 1978). However, according to
Duve and Jensen, (2012) cows housed with full social contact with a peer are more socially active than calves housed individually, with limited contact through bars. Rearing of calves with mother for unrestricted or restricted contact increases the opportunities for social experiences (
Arnold and Taborsky, 2010), which might have led to increased social interaction with the unfamiliar calf. This explains the social activeness of our experimental calves of SG, SI and WG groups compared to WI group of calves.
Exploring test arena
The duration of time spent on exploring the test arena did not differ significantly across the groups. However, it was observed that the calves housed individually (SI and WI) spent longer duration of time exploring the test arena than the calves housed in groups (SG and WG). The results obtained in the present study can be explained by the fact that, the space constriction in the individually housed groups (SI and WI groups) may have restricted them to investigate and explore their surroundings. However, when provided access to a bigger area these calves were more eager to explore the arena in the form of sniffing and licking the floors and wall of the test arena rather than establishing social connection with the unfamiliar calf. This clearly demonstrates the negative impact of individual housing system on the development of early social behaviours in the calves which can even have detrimental consequences in the future for example; socially isolated calves are more submissive when mixed in groups later in life compared to calves reared with their conspecifics
(Veissier et al., 1994).
Standing idle
Across the groups the WI calves spent significantly (P<0.001) more duration of time standing idle. The duration of time standing idle did not differ significantly among other groups. The WI calves spending approximately/about double (1.8× ~ 2×) the time on simply standing idle without any activity when compared to other groups provides evidence that the calves housed in individual pens are fearful to new environments and may take more time in adjusting to novel surroundings. The results are in agreement with
De Paula Vieira et al., (2012) who reported that individually housed calves spent more time standing inactive than did the calves housed in pairs (mean 302.20 sec vs. 232,20 sec SEM 30.20, respectively). The calves having access to mother or social companions are thought to learn about potential threats and develop agonistic behaviours, which is of paramount importance when calves are mixed in herds in future. Earlier studies have demonstrated that mother reared calves showed more submissive behaviour in order to reduce the risk of being attacked during integration into the cow herd compared with heifers reared without mothers contact
(Wagner et al., 2012). Our results are suggestive of the fact that individually housed calves may not develop the social skills necessary to cope with group living later on, being either more or insufficiently aggressive, or more fearful of other calves.
Locomotion
The time spent on locomotion was found to be non-significant across the groups. However, the time spent locomotion was highest in SI group followed by WI, WG and SG. This clearly suggests that the calves reared in individual housing (SI and WI calves) showed more locomotory behaviour compared to calves reared in group housing (SG and WG). The results corroborate with findings of
De Paula Vieira et al., (2012) who reported individually housed calves showed more locomotory behaviour in the form of running compared to the paired housed calves (83.2±19.1 vs. 57.3±19.1 sec). Similar explanations as suggested by the
De Paula Vieira et al., (2012) explains our results that, housing of calves in individual pens limits the expression of calf’s innate play behaviour and access to large test arena might have been rewarding for these calves.
Vocalization
The effect of housing showed significant effect on vocalizations. The group housed calves (SG and WG) vocalized more frequently (P<0.001) compared to the individually housed calves (SI and WI). Similar trend was also observed in novel object test when calves were presented with a red pyramid. Similar explanations as explained in novel object test supports the findings in the present study. Moreover in cattle, the presence of conspecifics is known to reduce behavioral reactions to social separation (
Boissy and Le Neindre, 1997;
Piller et al., 1999). For example, calves vocalize less in a novel arena when in companionship with familiar calves compared with when they are placed with unfamiliar calves
(Faerevik et al., 2006). Similarly, in the current study the strong social attachment between the group mates led to more frequent vocalizations in the group housed calves.
