J. Dairy Sci. 89:229–233
 American Dairy Science Association, 2006.
Effects of Mixing on Drinking and Competitive Behavior of Dairy Calves
K. O’Driscoll,1 M. A. G. von Keyserlingk,2 and D. M. Weary
Animal Welfare Program, Faculty of Land and Food Systems, University of British Columbia,
Vancouver, Canada V6T 1Z4
ABSTRACT
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 computercontrolled 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 milkfeeding 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.
Key words: dairy calf, competition, milk-feeding behavior, regrouping
INTRODUCTION
Group rearing of milk-fed dairy calves is thought to
provide advantages in terms of labor but it creates challenges in terms of calf management (Kung et al., 1997).
For example, calves in groups may need to compete
with group mates for access to key resources including
milk. In a recent study, we found that group-housed
calves frequently compete for access to milk teats, especially when the teat-to-calf ratio declines (von Keyserlingk et al., 2004).
Changes in social environments can have pronounced
effects on the physiology and behavior of animals (Zelena et al., 1999). Competitive interactions generally
peak when new animals are introduced into a group,
resulting in increased social stress and reduced feed
intake (Boe and Faerevik, 2003). Milk-fed calves in
groups are often kept in dynamic groups, with new
calves introduced soon after birth and older calves removed at weaning (Jensen, 2003), resulting in considerable variation in calf age within the group. Studies on
other farm animals have shown that problems related
to social integration are normally greater for the introduced animal than for the resident ones (Mench et al.,
1990), and that younger animals are more frequently
displaced from the feed source than are older individuals (Onsrud, 1999). Recent studies with growing-finishing pigs showed that the feeding behavior of the small
pigs is altered in more competitive environments;
namely, they consumed a larger proportion of their
daily feed intake during the nighttime hours than during the day compared with pigs in a less competitive
situation (Georgsson and Svendsen, 2002).
One convenient way of feeding milk to group-housed
calves is using computer-controlled nipple feeding systems (Hepola, 2003), but no work to date has examined
the effects of mixing on calves introduced into a new
group. The objective of this study was to investigate
the effect of mixing on feeding and competitive behavior
of young calves following introduction into a group pen
when using a computer-controlled milk feeding system.
We predicted that calves introduced into a preformed
group of older animals would experience an increased
frequency of displacements and disturbances from the
feeder by older calves, leading to disrupted feeding behavior and reduced milk intake.
MATERIALS AND METHODS
Received March 31, 2005.
Accepted September 8, 2005.
1
Current address: Teagasc, Moorepark, Fermoy, Cork, Ireland.
2
Corresponding author: nina@interchange.ubc.ca
Animals, Housing, and Management
This study was carried out at the University of British
Columbia Dairy Education and Research Center in
229
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O’DRISCOLL ET AL.
Agassiz (BC, Canada). All animals were cared for according to the guidelines outlined by the Canadian
Council on Animal Care (1993). Holstein (n = 8; 7 female
and 1 male) calves were separated from their mothers
within 24 h of birth and moved to individual pens (1.2
× 1.7 m) with milk supplied from an artificial teat (MilkFlow Peach teats, Skellerup Industries, Ltd.,
Christchurch, NZ) positioned at right angles to the wall
at a height of 0.6 m.
At approximately 11 d of age (11.25 ± 2.12 d) calves
were moved to an individual training pen, measuring
1.2 × 1.8 m, with solid wooden walls 1.2 m high. The
computer-controlled milk feeder (DeLaval CF150, DeLaval, Tumba, Sweden) was positioned between the
individual training pen and the group pen (5.3 × 1.8 ×
1.2 m). All calves were fed whole milk, including milk
from cows in the withdrawal period following antibiotic
treatment. The amount of the milk from withdrawal
cows varied across the experiment depending upon the
number of cows being treated. Milk composition was
tested monthly by British Columbia Dairy Herd Improvement Services (Chilliwack, BC, Canada). Composition averaged 12.1 ± 0.1% DM and (DM basis) 28.0 ±
0.1% fat, 26.9 ± 0.1% protein, and 45.1 ± 0.0% lactose.
All calves had ad libitum access to a 21.6% CP barleybased calf starter (Unifeed Ltd., Chilliwack, BC, Canada), and to water from a bowl, but intake of starter
and water were not monitored. Fecal scores were recorded daily for each calf according to Larson et al.
(1977).
Experimental Procedure
Each calf was housed in the training pen for 7 d (−7
to −1 d of the experiment). From d −7 to −4 inclusive,
calves were provided with ad libitum access to milk
through a single teat identical to that described earlier.
On d −3 to −1, calves were trained to use a computercontrolled milk feeder. All experimental calves were
fitted with a passive transponder encased in a plastic
ear tag (All Flex, Inc., Dallas, TX) and attached to the
left ear. When a calf placed its head within 25 cm of
the milk-feeding station, the calf’s identification number was transmitted to the reader panel. Access to milk
was provided through a teat attached to a peristaltic
pump that provided milk at a rate of 8 g/s when the calf’s
nose was pressed against a metal switch positioned
directly behind the teat. Milk was stored in a covered
plastic bucket and mechanically agitated for 2 s every
5 min. Milk was warmed by passing through copper
coiling in a 37°C water bath before delivery to the calf.
All milk-feeding equipment was cleaned at 0700 and
1800 h before adding fresh milk to the reservoir. The
Journal of Dairy Science Vol. 89 No. 1, 2006
milk feeder was calibrated weekly, as per the manufacturer’s instructions (DeLaval, 2003).
Milk Consumption and Behavioral Recording
Milk consumption and feeding patterns for each focal
calf (calf under observation) were monitored in the
training pen for 48 h immediately before mixing (premixing period), and milk consumption, feeding, and
competitive behaviors were monitored for the 24 h after
mixing (mixing day) and the subsequent 72 h (postmixing period). Each focal calf was introduced into a different group of 3 nonexperimental calves (approximately
4, 5, and 6 wk of age).
Measuring Milk Intake. Milk intake was recorded
by the feeder every 24 h. Feeding behavior was monitored using video cameras connected to a multiplexer
and a time-lapse videocassette recorder. One camera
was positioned 1.2 m directly above the entrance to the
feeder, and the other was positioned 1.2 m above and
0.9 m in front of the entrance to the feeder. Tapes were
recorded in 72-h mode and scored continuously for visits
to the feeder and competitive interactions. A feeder visit
was defined as occurring when a calf was positioned so
that it was standing with its head facing the machine,
and shoulders beyond the entrance to the stall leading
to the milk feeder.
Measuring Aggressive Behavior. Competitive behaviors were scored only during feeder visits and included contacts and displacements. A contact was
scored when either the head or shoulders of a calf outside the stall touched any part of the body of the calf
inside the stall. A displacement was scored if a calf
vacated the stall immediately following a contact and
the contacting calf immediately entered the milk
feeder.
Data Analysis
All analyses considered the focal calf as the observational unit. Preliminary graphical analysis revealed
that behavior and intake measures were generally similar on the 2 d before mixing, and the 3 d following
mixing, but disrupted on the day of mixing. Therefore,
responses were averaged for these 3 periods (premixing
period, mixing day, and the postmixing period). Behavior and intake on the day of mixing were compared with
responses during the adjacent periods using paired ttests. The log10-frequency distribution of the interval
lengths between these feeder visits for each individual
calf for d −2 to 3 was used to determine the meal bout
criterion, following von Keyserlingk et al. (2004). However, no clear distributions could be identified so no
meal criterion was established. Thus, for the purpose
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MIXING OF GROUP-HOUSED CALVES
Table 1. Mean (SEM) feeding behavior measures for calves in days before mixing (Pre), the day of mixing
(d 0), and the days postmixing (Post)1
Time relative to day of mix (d 0)
Milk intake (kg/d)
Meals/d
Intake/meal
Meal duration (min)
Meal rate (kg/h)
Time on teat (h/d)
Pre vs. d 0
d 0 vs. Post
Pre
d0
Post
SEM
P
P
10.1
11.6
0.94
6.43
8.9
1.19
8.7
4.0
2.84
11.67
14.1
0.66
10.5
9.3
1.19
5.95
12.5
0.91
0.5
1.1
0.34
0.91
1.1
0.08
<0.05
<0.001
<0.002
<0.002
<0.005
<0.001
<0.01
<0.005
<0.005
<0.001
>0.1
<0.05
Premixing and postmixing periods are the means of d −2 and −1 and d 1, 2, and 3, respectively.
1
of this paper, each individual visit to the feeder was
defined as a meal.
RESULTS AND DISCUSSION
Calves consumed on average more than 10 kg of milk
per day both before and after mixing, but consumption
declined by approximately 20% on the day that calves
were mixed (Table 1). More dramatically, the number
of meals that calves consumed declined by more than
50% on the day of mixing. However, calves appeared
to compensate for the reduced meal number at mixing
by more than doubling their average intake per meal
on this day. These larger intakes were achieved in part
by increased meal duration (from just over 6 min to
just under 12 min per meal). Calves also increased their
intake rate from approximately 9 kg/h before mixing
to 14 kg/h on the day of mixing. However, unlike the
other measures of feeding behavior, intake rate also
remained high during the days after calves were mixed.
Overall, calves spent less time on the teat at mixing
compared with either before or after mixing. This decline occurred especially in the 3 h following introduction into the new group (i.e., 1400 to 1700 h on Figure
1). The 24-h distribution of visits to the feeder on other
days was relatively uniform.
Other calves rarely contacted calves in the milk-feeding stall with calves receiving 4.6 ± 1.6 contacts on d 0
and the day following, and 9.2 ± 2.4 contacts on d 2 and
3. However, these contacts rarely led to displacements,
with only 6 displacements from the milk-feeding stall
observed during the entire experiment.
Milk consumption in the present study was within
the range previously reported for calves of this age fed
milk ad libitum by teat (Chua et al., 2002; Jasper and
Weary, 2002) and for those fed ad libitum using a computerized milk feeder (Jensen, 2003). There was a decline in intake on the day of mixing when calves were
moved to the group-housed pen, but intakes increased
on the days after mixing.
In a recent study, von Keyserlingk et al. (2004) found
that calves drank less milk when competition for teats
increased. This reduction in intake was likely mediated
by increased competitive behavior, and specifically by
increased displacements from the teats. Although we
observed decreased intakes on the day of mixing, we
did not see a prolonged decline in intake. Hyun et al.
(1998) reported that mixing had no effect on daily feed
intake when pigs were fed using an individual feed
intake recording system that enabled only one pig to
feed at a time. Likely the presence of the milk-feeding
stall in the current study provided some protection to
the calves during milk-feeding events as evidenced by
the low number of aggressive interactions observed
throughout the study. Jensen and Holm (2003) and
Weber and Wechsler (2001) reported considerably more
displacements per day in their study. However, they
had 8 and 15 calves in each group, respectively, compared with our groups of 4. Thus, future research should
examine the effects of mixing into larger groups of
calves.
The time spent on the teat in the present study was
similar to the amount of times calves spend suckling
their dams (about 1 h/d; Day et al., 1987), indicating
that calves fed milk from artificial teats exhibit a similar motivation to suck. Teat-based systems allow calves
Figure 1. The total number visits to the feeder by all calves (n =
8) on d 0 and the mean of d 1 to 3 in relation to time of day. Columns
represent the number of visits in the hour up to that time. The xaxis begins at 1400 h, as the calves were mixed at 1400 h on d 0.
Treatment means ± SEM are provided in Table 1.
Journal of Dairy Science Vol. 89 No. 1, 2006
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O’DRISCOLL ET AL.
to perform natural sucking behavior (Hammell et al.,
1988), likely increasing the secretion of the digestive
hormones insulin and cholecystokinin (de Passillé et
al., 1992; Lupoli et al., 2001).
There was no clear pattern in the frequency distribution of the intervals between feeder visits, thus preventing an objective definition of a meal criterion (De
Vries et al., 2003; von Keyserlingk et al., 2004). The
lack of any clear pattern may be attributed to the type of
milk delivery system used in this study. The automatic
milk-feeding unit delivered warm milk to calves at every visit to the feeder. In previous studies (Appleby et
al., 2001; von Keyserlingk et al., 2004), milk was warm
only immediately after delivery of fresh milk to the
feeder in the morning and evening. These previous
studies also provided no milk-feeding stall to protect
calves from displacements while sucking, likely increasing the number of short intervals between visits as
described by von Keyserlingk et al. (2004).
Although the number of meals consumed by calves
before and after mixing was similar to that previously
reported by von Keyserlingk et al. (2004), meal number
was reduced by 67% on the day of mixing. Interestingly,
calves appeared to compensate for the reduced number
of meals on the day of mixing by increasing both meal
duration (44%) and average meal size (64%), resulting
in only a modest overall decline in milk intake. Similar
compensatory behaviors were reported by Hyun et al.
(1998) who found that although mixing tended to cause
pigs to decrease the number of visits to the feeder, they
tended to increase the duration of each visit such that
daily intake was maintained. Although the pigs adjusted their feeding behavior for 4 to 5 d after mixing
before returning to baseline levels (Hyun et al., 1998),
the calves in the present study were able to reestablish
their premixing feeding patterns after just 1 d. This
difference may be because pigs generally show more
overt signs of aggression following mixing (Stookey and
Gonyou, 1994), and might require longer to establish a
stable social hierarchy. Calves and older cattle in nature rarely compete for resources (von Keyserlingk et
al., 2004) and thus, may prefer to adjust their behavior
in ways that prevent physical contact with other calves.
Unlike the findings of Appleby et al. (2001), who
showed that teat-fed calves fed individually consumed
their largest meal just after the delivery of fresh milk,
our results show that the calves appeared to distribute
their visits to the feeder throughout the day. Again,
this may be explained by the fact that calves in this
study were provided milk at a constant temperature
throughout the day. When housed in larger groups of
20 calves, and fed from a single milk feeder, some calves
do preferentially feed at night (Babu et al., 2004), likely
due to competition during peak feeding times. In the
Journal of Dairy Science Vol. 89 No. 1, 2006
current study, calves were rarely seen to wait to gain
access to the milk feeder. Morita et al. (1999) housed
calves in a group of 26 and noted that some calves
waited for up to 60 min to access the feeder.
CONCLUSION
For small groups of calves fed from a computerized
feeder, mixing young calves has only transitory effects
on feeding behavior. On the day of mixing, calves visit
the feeder less frequently, but compensate by increasing the duration and amount of milk consumed per
meal. More research is required to understand the effects of mixing when keeping calves in larger groups.
ACKNOWLEDGMENTS
We thank the staff and students at the University
of British Columbia’s Dairy Education and Research
Center. We especially thank Danica Olenick, Lizanne
Steunenberg, Timothy Leung, and Nelson Dinn for
their help in running this experiment. We are also
grateful to Doug Veira for his help and support throughout the project. General support for the Animal Welfare
Program is provided by the Natural Sciences and Engineering Research Council through the Industrial Research Chair in Animal Welfare, and by contributions
from the Dairy Farmers of Canada, the BC Dairy Foundation, the BC SPCA, members of the BC Veterinary
Medical Association and many others listed at
www.landfood.ubc.ca/animalwelfare.
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