Effects of the early social environment on behavioral responses of dairy calves to novel events

Providing young animals the opportunity to engage in more complex social interactions is hypothesized to improve their capacity to cope with changing environments. To test the effects of the early social environment on the behavioral responses of dairy calves to novelty we compared (1) individual with pair housing and (2) group housing with companions of similar age with group housing with a more experienced conspecific. Fifty-four dairy calves were separated from the cow soon after birth and housed individually (n=6 calves) or in pairs (n=6 pairs), or in pens composed of groups of 3 young calves (n=6 groups) or groups of 2 young calves and an older calf (n=6 groups). At 65 to 69 d of age, calf responses were tested in an environmental novelty test and a social novelty test. Individually housed calves were more active [i.e., spent less time standing (means ± SEM): 201.4 vs. 280.3±30.5 s/test; and more time running: 83.2 vs. 57.3±19.1 s/test] and more reactive (i.e., defecated more frequently; 1.3 vs. 0.6±0.2 events/test) when tested in the novel arena, compared with pair-housed calves. During the social novelty test, individually housed calves spent less time running (51.8 vs. 96.4±11.6 s/test), showed a longer latency to socially interact (111.1 vs. 20.4±21.7 s/test), and spent more time involved in social interactions (130.7 vs. 79.7±19.0 s/test) with the unfamiliar calf than did pair-housed calves. Individually housed calves were also more reactive to the presence of an unfamiliar calf as indicated by increased rates of defecation (2.3 vs. 0.7±0.5 events/test) and kicking (2.2 vs. 0.7±0.4 events/test) compared with pair-housed calves. Calves housed in groups with an older companion were more reactive to the novel environment than were calves housed in groups of similar age: they defecated (1.0 vs. 0.6±0.2 events/test) and vocalized (23.6 vs. 15.3±3.8 events/test) more during the test. These calves also spent less time exploring (266.3 vs. 355.0±27.4 events/test) and had a lower frequency of kicking (0.1 vs. 2.0±0.5 events/test) when tested with an unfamiliar calf. We conclude that calves housed individually are more reactive to environmental and social novelty when compared with calves housed in pairs and that calves housed with an older companion are less reactive to a novel calf when compared with calves housed in groups of similar age.     

Effects of pair versus individual housing on the behavior and performance of dairy calves

This study compared the health, performance, and behavior of individually and pair-housed calves fed milk ad libitum by artificial teats. Calves were separated from their dams within 24 h of birth and assigned to housing in either a single pen (10 calves) or a group pen (10 pairs of pair-housed calves). Calves were gradually weaned at approximately 5 wk of age and remained on the experiment until wk 8. Behavior was video recorded during wk 2 to 8. Before and after weaning, calves gained weight steadily with no differences between treatments. During the week of weaning, pair-housed calves continued to gain weight normally, but the individually housed calves experienced a growth check. There were no differences between groups in the amounts of milk, starter, or hay consumed, or in the incidence of scouring. There were also no differences in the amount of time spent self-grooming, sucking on the teat, or lying down. However, pair-housed calves spent more time standing inactive, more time moving, and less time with their head out of the pen than individually housed animals. Paired calves spent approximately 2% of the day in social contact, and the incidences of agonistic behavior and cross-sucking were very low. These results indicate that housing dairy calves in pairs allows benefits such as increased space for movement and social opportunities with no disadvantages in health and weight gains.     

The effect of pair housing on dairy calf health,performance, and behavior

Individual housing of dairy calves prevails in Europe and North America despite its negative effects on calf development. One of the main reasons is that farmers find individual housing of calves more practical than group housing. A compromise between practice and welfare could be housing calves in pairs. Therefore, we aimed to compare health, feed intake, growth, and behavior in a novel arena of 22 individually (INDI) and 44 pair-housed calves that were randomly assigned a treatment. Diarrhea and respiratory problems were recorded every day for the period of 49 d. Intake of calf starter and milk were measured every day for the period 48 and 49 d, respectively. Calf body weight gains were calculated as average daily gain. Calves were individually tested in a novel arena at 11 to 18 d, and their behavior was recorded according to an ethogram including 8 behavioral categories. Behavioral categories were first diminished by principal component (PC) analysis. We found that 2 PC explained 66% of the total variation in calf behavior. Movement-related behaviors (activity, play, and crossing the stair) loaded positively on PC1, and PC2 had positive loading on self-grooming and negative loading on exploration. There were no effects of housing on calf health, feed intake, or average daily gain. The INDI calves had higher PC1 scores than pair-housed calves, indicating a rebound effect of movement. Our results are consistent with other studies that found no negative effect of pair housing of calves on their health, feed intake, or growth compared with individually-housed calves. The rebound effect of movement-related behaviors of INDI calves in a novel arena implies that individual housing of calves causes activity deprivation by the second week of age.     

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.     

Effects of pair versus single housing on performance and behavior of dairy calves before and after weaning from milk

This experiment tested the effects of pair versus single housing on the performance and behavior of dairy calves before and after weaning. Twenty-seven Holstein calves were separated from the dam within 6 h of birth, housed in individual pens for 4 d, and then assigned to either continued individual housing (n = 9 calves) or pair housing (n = 9 pairs). Calves had ad libitum access to starter, hay, and water via buckets. Pasteurized whole milk was fed via teat twice a day for 2 h at ad libitum volumes until d 36. During the milk-feeding period, paired calves showed higher intakes of starter than did the individually housed calves (averaging 93 vs. 59 ± 11 g/d per calf). Calves were weaned from milk from d 37 to 41 by progressive dilution of milk with water, and the teat was removed on d 49. Calves in both treatments vocalized in response to teat removal but this response was less in paired calves than in individually housed calves (84 vs. 194 ± 12 calls/2-h period per calf on d 49). On d 56, calves were moved to group pens, mixed with other calves, and observed for 15 d. Starter, water, and hay were available ad libitum via automatic feeders. Compared with calves previously housed in single pens, paired calves had a shorter latency to start feeding (9.1 ± 2.6 vs. 49.5 ± 4.1 h/calf), visited the starter feeder more frequently (41.6 ± 3.0 vs. 26.4 ± 3.3 visits/d per calf), spent more time at the feeder (87.8 ± 2.5 vs. 65.3 ± 2.9 min/d per calf), and consumed more starter (3.4 vs. 2.3 ± 0.2 kg/d per calf). Weight gains at mixing were higher for paired than for individually housed calves on d 2 and 3 after mixing (0.5 vs. −2.4 ± 0.3 kg/d per calf; and 0.8 vs. −0.9 ± 0.3 kg/d per calf, respectively). The results indicate that pair housing during the milk-feeding stage reduces calf responses to weaning and improves performance after weaning when calves are housed in groups.     

Complex social housing reduces food neophobia in dairy calves

Animals are often reluctant to consume novel feeds. Research suggests that social housing can reduce fearfulness in animals. The aim of this study was to test the prediction that social housing reduces food neophobia in dairy calves. Beginning immediately at birth, Holstein bull calves were either reared individually (n = 18) or in a complex social group with other calves and cows (n = 18). In food neophobia tests, calves were exposed to 2 identical buckets, one empty and the other filled with a novel food (chopped hay in trial 1 and chopped carrots in trial 2). Calves were tested for 30 min/d on 3 consecutive days starting at 70 d of age. Regardless of the type of food, socially housed calves consumed more of the novel feed compared with individually housed calves. In trial 1, intake of hay as fed averaged 35 ± 6 versus 18 ± 6 g/d for socially versus individually housed calves. In trial 2, intake of chopped carrots as fed averaged 27 ± 6 versus 6 ± 6 g/d for socially versus individually housed calves, respectively. Social rearing decreased the latency to eat the novel feed. Calves housed in a complex social group began eating the hay after 1:23 ± 1:13 versus 3:58 ± 1:10 min:s for individually housed calves. Latency to begin eating the chopped carrots averaged 3:09 ± 1:17 versus 6:38 ± 1:13 min:s for socially versus individually housed calves. Treatment had no effect on time spent eating, latency to approach the food bucket or the empty bucket in either trial, or on time spent manipulating the empty bucket. These results indicate that housing dairy calves in a complex social group reduces food neophobia. More generally, this study contributes to a series of studies showing that calves raised in more complex social environments may be better able to transition to other changes in their environment.     

Social housing influences the behavior and feed intake of dairy calves during weaning

We investigated the effect of social housing on the behavioral, intake, and physiological changes that occur at weaning for dairy calves fed milk ad libitum. These changes were evaluated during the weaning (d 40 to 48 of age) and postweaning (d 49 to 56 of age) stages. Twenty male Holstein calves were fed milk replacer ad libitum and weaned gradually by dilution over 9 d starting at d 40 of age. Calves were housed in pairs (10 calves) or individually (10 calves) from birth until the beginning of the postweaning phase, when all calves were paired. Feed and water intake were monitored daily. Feeding time was video-recorded, and blood β-hydroxybutyrate concentration was measured on alternate days beginning on d 40 and ending on d 56 of age. Electronic accelerometers continuously recorded standing and lying behavior for the 17-d study. Solid feed consumption increased by more than 5-fold over the weaning phase in all calves; during this phase pair-housed calves consumed more than twice (0.96 vs. 0.50 kg/d on d 48) that of the individually housed calves. Postweaning all calves rapidly increased their solid feed intake, and to a greater extent for previously individually housed calves, such that intake was similar between treatments by d 56. Free water intake was stable during weaning; however, a decrease (of 6.6 L) occurred in the constituent milk replacer water intake across this phase. As result, total water intake (free water + milk replacer water content) decreased (by 6.0 L) over the weaning phase between d 40 (14.9 L/d) and d 48 (8.9 L/d). On the first day postweaning (d 49), total water intake for all calves increased sharply (to 19.0 L/d) and then returned to a lower baseline (13.2 L/d) the next day (d 50), and slowly increased over the following week. During the weaning phase, feeding time and feeding rate increased with time for all calves, whereas pair-housed calves had greater feeding rates than individually housed calves (13.4 vs. 6.6 g of DM/min). After weaning, calves previously housed individually spent more time feeding in the early hours of the day than calves housed in pairs. Lying time and lying bout frequency decreased with calf age during the weaning period across treatments, and pair-housed calves tended to spend less time lying than individually housed calves (1,015 vs. 1,039 min/d) during this time period. Blood β-hydroxybutyrate increased across treatments over the weaning period, with the largest increase occurring between d 48 (0.05 mmol/L) and d 50 (0.2 mmol/L). These results show that calves alter their behavioral patterns during weaning and that housing calves in pairs may ease the transition from milk to solid feed.     

The effect of individual versus pair housing of dairy heifer calves during the preweaning period on measures of health,performance, and behavior up to 16 weeks of age

Pair housing of dairy heifer calves during the preweaning period helps meet the natural social needs of the calf and has been shown to improve growth and starter intake during the preweaning period as compared with individual housing. However, there is little evidence to suggest that pair-housed calves maintain their social and growth advantages past the weaning phase. The objective of this study was to investigate the effect of pair housing on measures of calf performance, health, and behavior up to 16 wk of age. Healthy Holstein and crossbred heifer calves were enrolled in the study after colostrum feeding, with the first calf randomly assigned to 1 of 2 housing treatments: pair (PR; 2 hutches with common outdoor space) or individual (INDV; 1 hutch plus outdoor space). All calves were bucket fed 4 L of milk replacer twice daily and weaned at 50 d of age. Weaned calves (6/group) remained with their treatment group until exit from the study at 16 wk. A venous blood sample was collected from each calf between 24 h and 7 d of age to test for serum total protein (g/dL). Body weights (kg) were obtained at birth, weaning, and 16 wk. Each enrolled calf was scored for health each week and calf health treatments were also collected. A hair sample was collected from the left shoulder at birth and 16 wk to assess hair cortisol (pg/mL). At enrollment, each calf was fitted with a triaxial accelerometer on the left hind leg for continuous recording of standing and lying time (min/24 h) for 16 wk. Latency to find feed, water, and lie down (min) at entrance to the weaned pen were recorded by continuous video observation. Open field testing with a novel object was performed at 5, 10, and 16 wk. Behaviors analyzed by video observation included latency to approach the object (s), vocalizations (n), and time spent immobile, walking, or running (s/10 min). Linear mixed models were used to determine the effect of treatment (INDV or PR) on calf growth, activity, and behavioral outcomes, which accounted for time, breed, the interaction of time and treatment, the random pen, and variability in testing day and repeated measurements within calf when appropriate. Twenty-four Holstein and crossbred calves (PR: n = 12, 6 pairs; INDV: n = 12) were enrolled from November 2 to December 23, 2018. The PR calves were 7.1 kg heavier at weaning and gained 0.15 kg/d more during the preweaning period as compared with INDV calves. In the 24 h after movement to the postweaning pen, PR calves lay down for longer periods of time (14.3 vs. 11.0 ± 0.4 h/d), and PR calves urinated more during novel object testing at 5 wk of age. Our study demonstrated benefits, such as better growth and increased lying time, of pair housing calves during the preweaning period.     

Holstein calves' preference for potential physical enrichment items on different presentation schedules

Impoverished housing environments are thought to prevent motivated behaviors and may result in frustration. We first aimed to investigate an effective physical enrichment protocol to improve dairy calves' welfare and initially determine their use of various items. Thereafter, we aimed to determine dairy calves' preference for and ways of interacting with various items, and whether this was influenced by social housing. In experiment 1, at 21 ± 3 d of age, 27 individually housed calves were assigned alternately into 1 of 3 treatments: control (CON, no additional items), rotating enrichment (RE, one item each week on a rotating presentation schedule), and fixed enrichment (FE, 4 types of item at the same time). The items were stationary brushes, ropes, springs, nets filled with strawberry-scented hay, and dry teats. Calves' behaviors were observed from 4 to 7 wk of age using focal observations after feeding, followed by instantaneous scan sampling. Their behavioral responses to a novel object were assessed at 43 ± 1 d of age. In the instantaneous scans, calves in FE tended to interact with items more often than calves in RE. Calves in RE and FE expressed less non-nutritive oral behavior than those in CON. Latency to touch novel objects did not differ significantly between treatments. Calves in RE and FE interacted with nets filled with strawberry-scented hay more often than with other items in instantaneous scans. In experiment 2, 24 calves were assigned alternately into 8 individual pens and 8 pair pens at 2 d of age. All pens were provided with a stationary brush, plastic chain, net filled with strawberry-scented hay, and dry teat. Calves' behaviors were collected from 2 to 5 wk of age using instantaneous scan sampling. Calves interacted with nets filled with strawberry-scented hay more often than with other items. Pair housing reduced calves' interactions with items compared with individual housing. Individually and pair-housed calves' frequencies of overall interaction with items varied with time of day, with frequencies increasing to peaks at 0700, 1500, and 1900 h. Calves showed scratching, sniffing, sucking, butting, and hay intake toward nets filled with strawberry-scented hay and showed the first 3 behaviors toward stationary brushes, plastic chains, and dry teats. In conclusion, dairy calves are likely to prefer a fixed multi-item enrichment presentation schedule over a rotating schedule with a single enrichment item presented at one time. For the fixed multi-item enrichment presentation schedule, items were used more in individual pens than in pair pens, and a diurnal pattern was observed for use of the items. Nets filled with scented hay might be the most multifunctional and attractive item of the items tested.     

A method of outdoor housing dairy calves in pairs using individual calf hutches

Interest in housing dairy calves in groups is currently growing. Group housing using individual calf hutches, a resource already available in most dairy farms in North America, could provide a novel housing method that can be a simple way to implement group housing on farm. The main objective of this study was to determine whether pair housing dairy calves in hutches outdoors would result in similar weight gain and milk intake compared with individual housing in hutches. The study was designed to avoid competition for resources (including milk and solid feed, teat, bucket, outdoor space, and hutch) to test a setup that has the potential to maximize performance and calf growth. Secondary objectives were to document how calves in both treatments use their environment in terms of time spent and behaviors performed in each area, how paired calves interact, and the time they spend together. Single calves (n = 6/season) were housed in 1 hutch with an attached outdoor environment; paired calves (n = 6 pairs/season) were given twice the resources. Calves were fed up to 16 L/d of milk replacer. Daily milk intake and weekly weight gains were recorded. Behavioral observations were recorded live once per week for 5 (summer) or 4 (winter) nonconsecutive periods. Paired and single calves had similar weight gain (averaging from 1.1 to 1.3 kg/d across trials) and milk intake (averaging from 11.1 to 13.7 kg/d across trials), showing no difference in performance between treatments. Low occurrences of cross sucking (averaging from 0.1 to 0.4 bouts/h of observation per pen across trials) and displacements at the teat (0.8 to 1.4 bouts/h of observation per pen across trials) were found. All calves altered their behavior in some way to accommodate companions; paired calves were seen interacting and spending time together (i.e., lying in the same hutch), and in the summer trial single calves spent less time lying inside the hutch than paired calves, presumably to have visual access to other calves. The solution of mixed indoor and outdoor housing environments tested as part of this study showed that calves make use of all spaces provided to them in winter and in summer conditions while maintaining good performance. Housing calves in pairs using individual hutches can be a suitable alternative to housing calves individually in hutches outdoors.     

Short communication: Pair housing dairy calves in modified calf hutches

The objective of this study was to test if body weight (BW) and starter intake increased and reaction to novelty decreased for preweaning Holstein heifer calves pair housed in modified hutches (n = 8 pairs) versus individually housed in a single hutch (n = 14 calves). Calves were alternately assigned to housing treatment at d 5 of age. Cross sucking was recorded in 5-min scans for 30 min after milk feeding once per week over 14 wk. Calf health and BW were measured weekly from birth until approximately 88 d. When calves were 60 d old they underwent a food neophobia test where they were exposed to a novel feed for the first time. Cross sucking was observed only 5 times (in 4 different pairs) over the entire milk-feeding period. Pair-housed calves ate more starter than individually housed calves [0.89 (0.72–1.08) vs. 0.48 (0.42–0.56) kg/d; median and confidence interval], these calves also consumed 2.6 times more novel feed in the neophobia test (150 ± 27 vs. 58 ± 20 g/30 min). We observed no effect of treatment on BW. We concluded that social housing in modified hutches promotes solid feed intake and decreases fearfulness in dairy calves.     

Optimizing weaning strategies of dairy replacement calves

Two experiments were conducted to evaluate whether performance could be improved and incidence of respiratory problems decreased either by allocating 6 additional days of individual housing after weaning or by moving calves in groups before weaning at 2 different ages. The first experiment involved 320 female calves that received 2 L of milk replacer (MR) twice daily until 49 d of age, and then 2 L of MR once daily until weaning at 56 d of age. Half of the calves were allowed to remain individually housed for an additional 6 d after weaning, and the other half were moved immediately after weaning to a different pen holding 8 calves. The second experiment involved 240 female calves that received 2 L of MR twice daily until 49 d of age, and then 2 L of MR once daily. Half of the calves were moved at 49 d of age to superhutches holding 8 calves with an elevated trough that was used to continue delivering MR; the other half remained individually housed until the age of 56 d and were then moved to the superhutches, where they also continued to receive MR. Growth and incidence of respiratory problems were recorded in both experiments, and feed intake was recorded in experiment 2. Calves moved to groups immediately after weaning reached the target BW 6 d earlier and experienced a lesser incidence of respiratory afflictions than those grouped 6 d after weaning. From experiment 2, calves grouped at 49 d of age had a greater average daily gain and BW at 56 d of age as a result of a greater total solid feed consumption compared with those grouped at 56 d of age. Calves grouped at 56 d, however, had a greater average daily gain between 56 and 64 d of age (the week following grouping for the calves in the 56-d treatment) than those grouped at 49 d of age. Overall, the proportion of animals affected by a respiratory problem between 49 and 112 d of age did not differ between treatments. However, calves grouped at 49 d of age had a lower number of respiratory cases than those grouped at 56 d of age. It is concluded that moving calves from individual hutches to groups of calves in superhutches immediately after weaning is preferable to waiting an additional 6 d. In addition, moving calves from individual hutches to groups of 8 in superhutches at 49 d of age and starting to reduce MR offering once grouped is preferable to starting to reduce MR while calves are individually housed.     

Feeding Acidified Milk Replacer Ad Libitum to Calves Housed in Group Versus Individual Pens

The purpose of this study was to evaluate group versus individual housing with a cold ad libitum feeding system for calves. Twelve Holstein calves were assigned to group or individual housing at birth. The experiment had two replications, each consisting of one group of 3 calves and 3 individually housed calves. All calves were fed cold acidified milk replacer ad libitum plus calf starter and water. Behavior was studied for one 48-h period during wk 1, 3, and 6. Four male calves were slaughtered at wk 6 for determination of carcass composition. Milk replacer and water intakes in the preweaning period (wk 1 to 5) tended to be higher for group-fed calves. Calf starter intake was not different. Group-housed calves had a higher BW and a slightly higher (although not statistically significant) average daily gain than calves fed in individual pens. Packed cell volume was lower for group calves due to their higher liquid intake, but plasma glucose and urea N concentrations were similar. Individually housed calves spent more time using the nipple and group-fed calves spent more time drinking water. Amount of time eating starter did not differ between treatments but differed with age. Carcass composition was not different between calves housed individually or in groups.Because individually housed calves spent more time using the nipple, but consumed less milk replacer, they may have been exhibiting a form of purposeless behavior. Higher milk replacer intake by group-fed calves did not result in greater carcass fat content at 6 wk of age.     

Effects of group composition on the incidence of respiratory afflictions in group-housed calves after weaning

A study consisting of 2 experiments was conducted with the aim of determining the effects of previous history of bovine respiratory disease (BRD) on animal performance and health status of transition calves housed in groups. In both experiments, calves were housed in individual hutches until weaning age at 58 d. Before weaning, BRD incidences were individually recorded on a daily basis. Following weaning, calves were moved into super hutches in groups of 8, based on their history of respiratory afflictions, and growth performance and BRD incidences were recorded for 57 d. In experiment 1, 144 female Holstein dairy calves (initial BW = 72.6 ± 1.2 kg; age = 58.5 ± 0.8 d) were distributed in 6 super hutches composed of 8 calves with no previous history of BRD (HHH), 6 super hutches composed of 6 calves without and 2 calves with a previous episode of BRD (HHR), and 6 super hutches housed 5 calves without a history of BRD and 3 calves with previous respiratory afflictions (HRR). In experiment 2, 144 Holstein female calves [58.0 ± 0.9 d; 72.5 ± 0.9 kg of body weight (BW)] were distributed in 2 treatments consisting of 9 super hutches housing integrally 8 calves with no previous BRD, and 9 super hutches housing integrally calves with a previous BRD case. The number of BRD cases after weaning progressively increased from HHH to HRR as the proportion of calves previously affected by BRD within super hutch increased, mainly due to the fact that both animals affected by BRD before weaning and those with no previous history of BRD had more relapses in HHR and HRR groups than in the HHH group. Odds of incurring BRD after grouping were 3.89 greater in calves that had a previous case of BRD than in those that did not. The average time elapsed between commingling the animals and the appearance of the first BRD case was shorter when calves that had at least one BRD episode prior to weaning were present in a group (10.8 ± 3.3 d) than when the group was formed with calves that had never experienced BRD before weaning (22.5 ± 3.3 d). Final BW (at 115 d of life) and average daily gain tended to decrease as the number of BRD cases incurred increased. In experiment 2, calves in the HHH group reached a greater BW at the end of the study than those in the RRR group and tended to have a greater average daily gain in the HHH group than in the RRR group. It is concluded that forming groups of animals with a previous BRD history should minimize the incidence of respiratory cases in those groups of calves formed by animals without a previous history of respiratory disease.     

The effect of a furnished individual hutch pre-weaning on calf behavior,response to novelty,and growth

Housing preweaned dairy calves in individual outdoor hutches is common in North America. However, this type of housing lacks stimulation and minimizes calves' ability to express natural behavior. Providing a social companion has been shown to stimulate natural behavior and promote growth, but no research has assessed the effect of providing physical enrichment items to calves pre-weaning. The objective of this study was to determine calf use of physical items added to an individual hutch, and if providing these items affected growth, behavior (e.g., locomotor play and sucking on pen fixtures), and response to novelty after weaning. At birth, Jersey heifer calves were allocated to 1 of 2 types of hutches: furnished (n = 9 calves) or standard (n = 10 calves). Calves were housed in individual hutches on loose gravel and bedded with straw. The outdoor enclosure of furnished hutches contained 2 artificial teats, a stationary brush, a calf “lollie,” and a rubber chain link for calves to manipulate. Calves were video-recorded continuously between 0800 and 2000 h twice weekly at 1, 3, 5, and 7 wk of age; behavioral data were collected using the Noldus Observer software program (Noldus Inc., Wageningen, the Netherlands). At 63 d of age (after weaning), calf response to social and environmental novelty was tested. Starter consumption was measured daily, and calves were weighed at birth and weekly thereafter. Pre-weaning behavioral data were not normally distributed, so raw data were square-root-transformed before analysis. Calves used all of the items depending on the time of day, but they spent the most time using the brush. Calves housed in furnished hutches spent almost 50% more time engaged in locomotor play, but they spent the same amount of time sucking pen fixtures as calves housed in standard hutches. We observed no effect of treatment on growth, starter intake, or behavioral response to social and environmental novelty after weaning. Results suggest that providing some physical complexity to a standard hutch has some benefits for young calves, but further research is encouraged to determine the long-term effects of physical and social complexity for young dairy heifer calves.     

Effects of mixing on drinking and competitive behavior of dairy calves

Group housing provides increased access to space and social interactions for calves while reducing labor costs for producers. However, group housing necessarily requires that calves be mixed and no research to date has addressed the effects of mixing on behavior of milk-fed dairy calves. The objective of this study was to monitor the feeding and competitive behavior of individual dairy calves (n = 8) after introduction into an established group of older calves fed ad libitum by a computer-controlled milk feeder. Milk feeding was monitored for 2 d before introduction into the new group and both milk feeding and competitive behaviors were monitored for 4 d after mixing. Mean (± SE) milk consumption before mixing was 9.7 ± 0.7 kg/d, dropped slightly on the day of mixing to 8.6 ± 0.6 kg/d, but increased on d 1 to 3 after mixing to 11.1 ± 0.3 kg/d. Calves visited the feeder less frequently on the day of mixing (6.0 ± 1.8 visits/d) than on either the days before mixing (20.3 ± 2.5 visits/d) or the days after mixing (25.3 ± 6.9 visits/ d). The mean duration of feeder visits and mean milk consumption per visit increased from 4 min 15 s ± 21 s and 0.53 ± 0.06 kg per visit before mixing to 8 min 17 s ± 1 min 28 s and 1.87 ± 0.51 kg per visit on the day of mixing. Competitive displacements from the milk-feeding stall were rare. In summary, feeding behavior of young calves is altered on the day of mixing, but calves are able to maintain milk intake when using a milk feeder fitted with a stall that prevents calves from displacing one another.     

Improved performance and heightened neutrophil responses during the neonatal and weaning periods among outdoor group-housed Holstein calves

The objective was to determine if outdoor group housing of Holstein calves influences metabolic status, leukocyte responses, and behavior compared with individually housed calves. Forty-nine Holstein heifer calves (2 ± 1 d of age) were randomly assigned to 1 of 2 treatments: individually housed (G1; n = 22) or group housed [3 calves per pen (G3); n = 27]. The space allowances per calf were 4.8 and 7.0 m² for G1 and G3, respectively. All calves were offered an identical plane of milk replacer nutrition (747 and 1,010 g of DM/d of a 28% CP:20% fat milk replacer from wk 1 to 2 and wk 3 to 6, respectively). Weaning was initiated during wk 7 by removing the p.m. feeding and calves were completely weaned when they consumed 900 g of calf starter/d (as fed) for 2 consecutive days after d 54. At d 90, calves were commingled into random outdoor groups of 5 calves per pen. Peripheral blood was collected during the neonatal (d 3, 10, and 21), weaning (d 46, 48, and 54), and commingling periods (d 90, 93, and 98) and was analyzed for neutrophil oxidative burst (OB) capacity when cocultured with Escherichia coli, neutrophil surface L-selectin protein expression, and whole-blood secretion of tumor necrosis factor-α when cocultured with lipopolysaccharide. Starter intake was greater for G3 during the postweaning period (wk 8 to 12). Average daily gain was greater for G3 than G1 from d 54 to 68 and tended to be greater after commingling from d 113 to 133. During the neonatal period, G3 calves had more activated neutrophils, as evidenced by increased neutrophil L-selectin protein expression and a tendency for increased percentage of neutrophils producing an OB than G1 calves. During weaning, G3 calves continued to have more activated neutrophils with increased L-selectin expression on d 46 and 48 and a greater OB intensity throughout the period. No differences were observed among leukocyte responses between treatments at d 93 and 98. Outdoor group-housed Holstein calves had improved performance and heightened neutrophil responses compared with individually housed calves.     

Effect of co-eating on unfamiliar food intake among Japanese young adults

The present study explored whether partner presence (pair vs. individual) affects unfamiliar food intake. In the experiment, participants were asked to taste pieces of 13 kinds of snacks, including three unfamiliar and ten neutral snacks, and were informed that they did not have to eat a snack if they did not want to. The total amounts and ratios of all kinds of snacks consumed for unfamiliar and neutral snacks were compared between participants in the pair condition and those in the individual condition. Results demonstrated that the ratio of participants who consumed all three kinds of unfamiliar snacks was higher in the pair condition than in the individual condition. Furthermore, the results of communication analyses showed that participants in the pair condition tried unfamiliar snacks even after the peer expressed a negative evaluation of a snack. These results suggest that social motivation such as risk-taking and conformity affect unfamiliar food intake in co-eating situations.     

Group housing of Holstein calves in a poor indoor environment increases respiratory disease but does not influence performance or leukocyte responses

The objective of the current study was to determine if group-housing Holstein heifer calves in indoor pens with poor ventilation and drainage influences performance, health, leukocytes, and behavioral responses compared with individually housed calves. Ninety colostrum-fed calves (2 ± 1 d of age) were randomly assigned to 3 treatments: individually housed (G1; n = 30 calves), 2 calves per pen (G2; n = 30 calves), or 3 calves per pen (G3; n = 30 calves). The space allowance per calf was 2.5 m² for all treatment groups. All calves were fed 747 and 1,010 g/d of dry matter of a 28% CP and 20% fat milk replacer during the first 2 wk and wk 3 to 6, respectively. Weaning was initiated on d 46 by removing the evening feeding, and calves were completely weaned when they consumed 800 g/d of dry matter calf starter for 2 consecutive days after d 54. Calves were randomly commingled at d 90 in groups of 5 calves per pen in outdoors pens with an attached hutch. Peripheral blood was collected during the neonatal (3, 10, 21 d), weaning (46, 48, 54 d), and commingling periods (90, 93, 98 d) and was analyzed for neutrophil oxidative burst capacity when cocultured with an Escherichia coli, neutrophil surface L-selectin protein concentration, and whole blood secretion of tumor necrosis factor-α when cocultured with lipopolysaccharide. Behavior of each calf was assessed using 2 independent tests: an approach response to a human subject and the response of the calf when placed in an isolated cage. Calf starter intake was greater for G2 and G3 during wk 8 and 9, and also at wk 11 for G3 compared with G1. No treatment × time interaction or treatment effect for average daily gain was observed. Additionally, no treatment × time or treatment effect was noted for any leukocyte or biochemical variable of biological significance throughout the entire study. Individually housed calves tended to have a reduced incidence of respiratory disease during the first 90 d of life. No other treatment differences for the other health outcomes were observed. Group-housed calves also relied more on calf-to-calf interactions than calf-to-human interactions, as evident by their reduced approach of the human observer and more frequent movement when placed in an isolated pen. Group housing in an environment with poor ventilation and drainage may increase the risk of respiratory disease.     

Repeated mixing and isolation: Measuring chronic,intermittent stress in Holstein calves

Objectives of this study were to determine the physiological effects of psychological stress applied to dairy calves and to test if molasses consumption could be used to validate that a stressed condition was achieved. Twenty male calves (3 wk old) received jugular catheters and were randomly assigned to control (CTR; n = 4 pens of 1 calf per pen) or social stress treatments (STR; n = 4 pens of 4 calves per pen). The STR treatment included 5 cycles of 24-h isolation followed by regrouping with unfamiliar animals for 48 h (over 15 d). An ACTH challenge (0.1 IU/kg of body weight) was used to determine adrenal fatigue. Peak and total cortisol concentrations were greater for STR calves until the ACTH challenge. After the ACTH challenge, CTR calf cortisol increased and STR calf cortisol continued to decrease, suggesting adrenal fatigue. The number of calves that became positive for fecal shedding of Salmonella after the acute stress of being moved and the number of calves that were positive after the move decreased with each move. Fifty-six percent of STR calves changed from negative to positive for shedding after the first move compared with 18.75% of STR calves remaining negative after the third move. Difference in fecal shedding of Enterobacteriaceae from samples taken before and after moving calves on d 6 was less than that on d 2, 3, and 5. Leukocyte counts were not different, but trends for day effects were detected for neutrophil and monocyte percentages. Molasses consumption was greater for STR calves on d 2 and 11, as was total consumption. Latency to lie after eating also increased as the study progressed; STR calves required more time to lie after eating on d 12 than on d 3, and latency to lie was greater for STR than CTR on d 4, 8, 12, and 14. The STR calves also stood more than the CTR calves in the 4-h afternoon period on d 4, 5, 7, and 14. However, during the 4-h morning observations on d 14 (ACTH challenge), CTR calves stood more than STR calves. This model induced chronic stress, as characterized by adrenal fatigue, which was confirmed by molasses consumption and behavior changes. Therefore, molasses consumption could be used to confirm social stress in experimental models.