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Original research
Flank or belly nosing in weaned pigs
B.E. Straw, DVM, PhD; P. Bartlett, DVM, MPH, PhD
Straw BE, Bartlett P. Flank or belly nosing in weaned pigs.
J Swine Health Prod. 2001;9(1):19-23. Also
available as a PDF (128k).
Department of Large Animal Clinical Science, College of Veterinary
Medicine, Michigan State University, East Lansing, MI 48824, phone:
(517) 432-5199,
email: straw@cvm.msu.edu
Summary
Objective: To examine growth rate of pigs that engaged
in, or were the recipients of, flank or belly nosing.
Methods: Data was collected from 332 weaned pigs during
a 6-week period after they were weaned at 16 to 18 days of age.
Sixteen pens of pigs were observed for nosing activity during
the first 16 days postweaning, and associated skin lesions and
growth rate throughout the entire 6 weeks in the nursery were
recorded.
Results: Nosing activity was not observed until 3 days
postweaning and peaked in number of pigs involved and duration
of activity about 1 week after weaning. Nearly half of all pigs
were observed performing some flank- or belly-nosing activity.
Pigs that nosed were more likely to become the smallest pigs,
although initial weight did not differ between pigs that nosed
and those that didn't. In this study, sexes were housed separately,
and no difference between gilts and barrows was detected in amount
of nosing activity, measured either by number of days observed
nosing or total seconds observed nosing. However, barrows had
more skin lesions caused by nosing than did gilts.
Implications: Although flank or belly nosing is esthetically
annoying to animal caretakers, it did not slow the growth rate
of recipients. However, there was confounding of effect, since
the most rapidly growing pigs were the most attractive targets
for the perpetrators. While being a recipient of belly nosing
did not affect growth, being a perpetrator was strongly associated
with a reduction in growth rate.
Keywords: Swine, weaning, performance,
belly nosing, skin lesions
Received: June 8, 2000
Accepted: August 8, 2000
Flank or belly nosing, also referred
to as navel sucking, flank rubbing, and persistent inguinal nose
thrusting, is considered a maladaptive behavior pattern.1
On occasion, flank rubbing has resulted in severe necrosis of
skin with ulcer formation at the site of attack, and in one pig,
total deterioration of the flank wall and evisceration.2
However, in most cases, flank or belly nosing produces less severe
lesions, which appear as hyperemia and edema of the skin with
loss of hair and superficial erosion.
Behavioral aspects of belly nosing have been well documented.
The onset of belly nosing is first seen several days or occasionally
even longer after weaning,3,4,5,6 and peak nosing activity
occurs about 2 to 4 weeks later.3,6,7 The time that
pigs spend in belly-nosing activity rarely exceeds 2% of their
total time budget.3,5,6,7,8 Belly nosing is more prevalent
in pigs weaned at earlier ages,3,5,6,8,9,10 and occurs
more often in barren rather than complex environments.7,8
Pigs that perform nosing are different individuals than pigs that
are recipients of the activity,4,6 and nosers are more
restless than recipients.5,6 The pattern of development
of the behavior over time and within pens suggests that belly
nosing might be contagious.3,4
Several theories have been proposed to explain why nosing develops.
Belly rubbing may extend from udder-seeking or exploratory rooting
behavior, or may represent a coping mechanism. Some feel that
inguinal rubbing is related to maternal loss, and theorize that
with removal of the sow, piglets not only are deprived of her
familiar presence, but also appear to miss the oral and nasal
gratification of nursing, be it suckling or non-nutritive.11
At 3 weeks of age, piglets are still strongly motivated to suck.12
The frustration that results from removal of the sow may cause
suckling behavior to be redirected towards pen mates.5,8,13
Another theory is that nosing may be redirected rooting or exploratory
behavior.7 Because the onset of nosing is delayed for
a few days after weaning, and nosing activity doesn't peak until
2 to 4 weeks postweaning, this behavior may represent a gradually
learned coping mechanism.6 All theories include a component
of frustration or stress, which has been confirmed by Worsaae
and Schmidt, who found significant correlations on the individual
pig level between specific behavioral reactions to early weaning
and plasma cortisol concentration.14
Information on the growth performance of pigs performing nosing
is minimal and conflicting. Two studies used individual pig analyses
to examine growth rate of nosers. Gonyou et al6 found
no effect on growth, while Fraser3 reported lower growth
rate in nosers. Dybkjar analyzed data by treatment group and reported
that weaned pigs in a barren environment with a high pig density
did more belly nosing and grew more slowly than pigs at a lower
animal density in a complex environment.7 Information
about the growth rate of recipients of nosing activity has not
been documented.
In commercial situations, it is common to observe that nosing
behavior is more frequently performed by the smaller, less thrifty
pigs in the pen. Producers often move these small, persistently
nosing pigs to another pen in order to eliminate the (perceived)
negative effects of the behavior on the other pigs in the pen,
and to place the perpetrator with other smaller pigs in an effort
to reduce competition and social stress that are felt to trigger
the behavior. The validity of this reasoning and management strategy
has not been demonstrated.
Concerns about flank or belly nosing center around animal well-being.
Dybkjar has called belly nosing a "behavioral indicator of
stress." However, while it has been established that the
behavior is more prevalent in earlier weaned piglets housed in
barren environments, and it is presumed that earlier weaning is
more stressful, the cause of belly nosing is largely unknown.
Knowing how belly nosing affects the growth rate of perpetrators
and recipients is important because it provides an economic incentive
to alleviate the condition (or the stress that precipitates its
development).
In this study, relationships among nosing behavior, initial
weight at weaning, rate of gain, and development of skin lesions
in piglets weaned at 16 to 18 days of age were examined. The primary
objective was to determine the association of belly nosing with
the perpetrators' and recipients' rates of gain.
Materials and methods
Animals and behavior sampling
Pigs used in this study originated from a 1200-sow herd that
weaned litters at 16 to 18 days of age into a 3000-head, six-room,
off-site nursery. Approximately 500 pigs were weaned each week,
half on Tuesday and half on Friday, and placed by weight and gender
into pens in a nursery room. Each pen measured 1.8 x 3 m (6 x
10 ft) and was equipped with two nipple-type drinkers. The feeder
provided 122 cm (48 in) of trough space. The pen floor consisted
of metal slat (Tri-bar(R)) over a pull-plug waste removal
system.
For this trial, some of the pigs in two nursery rooms were
used. In each nursery room, four gilt pens and four barrow pens
were observed. Pens were randomly selected within room, gender,
and fill date. Overall, a total of 16 pens, initially containing
332 pigs (168 gilts and 164 barrows) were included in this study.
During the 6-week period of the study, 25 pigs were lost to follow-up.
Five pigs died and 20 pigs were removed by the nursery manager
to a "sick pen" which was not one of the 16 pens included
in the trial. Most of these 20 pigs were moved within 3 to 4 days
after weaning. Six of these pigs had a medical problem (lame,
hernia, eye injury) that had not been observed at weaning, but
was identified the next day. The other 14 pigs "fell back"
after weaning. They were gaunt with tucked up abdomens, indicating
that they had not been eating, and were moved to the "sick"
pen where gruel feeding was employed.
Pens used in this study contained 20 to 23 pigs each and represented
mid-weight range pigs in the rooms. Because nursery rooms were
filled twice a week using the available number of pigs from that
weaning group, numbers of pigs per pen differed at the start of
the trial. Removal of pigs due to death or illness did not substantially
change the group sizes or pig densities in the pens. At the time
of placement into nurseries, pigs were individually ear-tagged
and weighed. At the start of the trial, the mean weight of the
332 pigs was 6.54 kg, SD 1.09 kg (14.5 lb, SD 2.4 lb), with a
range of 4.0 to 9.9 kg (8.9 to 22 lb).
Because nosing has been reported to occur most frequently in
the early weeks after weaning,6,11,12 pigs were specifically
observed during the first 16 days of the trial to identify those
performing nosing activity. Pens were observed daily for the first
10 days after placement, then at 2-day intervals for another three
observations. The pens in each room were not observed in the same
order on consecutive days. Observers entered the room approximately
15 minutes before beginning each observation period, which lasted
30 minutes and was performed between 9 am and 11 am. Feed was
added to feeders at 8 am, and sufficient feed was added each day
so that feeders were never empty during the first 16 days in the
nursery. Persistent nosing activity, i.e. nosing that lasted at
least 10 seconds, was recorded with respect to the identity of
the perpetrator ("noser"), time spent in the nosing
activity, and the site rubbed (ventrum, flank, head, tail, or
leg). During a 30-minute observational period, all pigs in the
pen were observed simultaneously. Two observers watched two adjacent
pens (1 pen per observer) simultaneously and communicated with
each other during observation periods. Preliminary datacollected
prior to the start of this trial indicated a high degree of agreement
between observers (duration of nosing episodes agreed within 10%).
Production and lesion measures
Twice a week over the 6-week period, pigs were individually
weighed and examined for lesions that developed as a result of
nosing activity. Pigs with lesions were classified as "recipients."
Lesions, rather than observational data, were used to define recipients,
because lesions reflect all nosing activity rather than just what
occurs during limited observation periods, and the severity of
lesions reflects the intensity or persistence of nosing activity.
Lesion location and severity (normal = 0, mild = 1, moderate =
2, severe = 3) were recorded. Mild lesions were barely detectable
as a reddening or slight swelling of the skin. Moderate lesions
were readily observed as reddening and (or) swelling of the skin,
and severe lesions involved the loss of the superficial layer
of skin. Photographs of lesions representative of each class were
referred to at the times of inspection and weighing. At the end
of the study, in addition to the lesion score recorded each time
they were weighed, pigs were given a cumulative lesion score that
was the sum of all the individual lesion scores throughout the
trial.
Statistical analyses
Descriptive summaries of the data were produced using a statistical
analysis package (SAS).15 Summary statistics were used
to describe nosing behavior by gender, time postweaning, number
of seconds and days observed in nosing activity, number of pigs
per pen nosing, body area nosed, and the presence of lesions on
any area of the body.
General linear models and chi-square analysis were used for
comparisons of gender and extent of nosing activity. The association
between gender and nosing activity was also evaluated with a repeated
measures logistic regression model using the Genmod procedure
of SAS.
The individual pig was used as the unit for analysis. A primary
objective of this study was to examine the effect of nosing on
individual recipients of the activity, and in a preliminary analysis,
room and pen were included in our model as random-effects variables
and found not to be significant. Rate of gain for each piglet
was evaluated for an association with the number of days on which
the pig was observed in nosing activity, and the total number
of seconds observed in nosing activity. Rate of gain for each
piglet was also evaluated for an association with the cumulative
score of lesions on the navel or sheath, on the flank, and at
any location. Linear and quadratic polynomials were evaluated,
but not included in the final model because they were not statistically
significant (P<.05). Gender and initial starting weight
were included in these analyses as fixed-effect independent variables,
and room and pen (within room) were included as random-effect
variables.
General linear models were used for comparison of initial weight
with severity of the cumulative score of lesions at any location,
the number of days on which a pig was observed in nosing activity,
and the total number of seconds observed in nosing activity.
Results
Behavior
Nosing activity was not observed until 3 days postweaning,
and on that day was seen in only four of the 16 pens. Increasing
numbers of animals engaging in nosing activity were observed in
subsequent observation periods. The number of pigs per pen engaged
in nosing activity, the total seconds of nosing activity per pen,
and the time that each pig spent in nosing activity began to increase
a few days after weaning and reached a relative plateau 5 to 7
days postweaning.
Table 1 gives the percent of nosing incidents directed toward
each targeted body area. Within the first 3 days after weaning,
there were a limited number of nosing incidents, and nosing was
mostly directed towardsthe head, tail, and flank. Subsequently,
as nosing became more frequent, activity was directed primarily
towards the ventrum or flank. Some pigs nosed only one pen mate
during the observation period, while other pigs nosed three or
more pen mates. Nosing activity was broken off when the recipient
walked away, and nosers then re-directed their activity to another
(usually more stationary) pig.
Number of days and total duration of nosing behavior observed
was examined. Half of the pigs were observed on at least one occasion
to engage in nosing behavior. The distribution of the cumulative
time that individual pigs were observed in nosing activity is
shown in Table 2. Pigs that were seen engaging in nosing behavior
did not differ from their non-nosing pen mates in starting weight
(P=.44). Starting and final weights for pigs are shown
in Table 2, and are expressed according to the number of days
and number of seconds that they were observed in nosing behavior.
The proportion of nosers was not different between genders:
51.2% of barrows engaged in nosing activity compared to 48.4%
of gilts (chi-square P>.10). Barrows spent no more time
engaged in nosing behavior than did gilts, as measured by either
the total number of seconds observed in nosing activity (P=.50)
or the number of days on which a pig was observed in nosing activity
(P=.56). Total seconds of nosing observed per pig over
the trial period was not higher for barrows than for gilts (barrows
110.6 sec, gilts 72.1 sec, P=.26). Number of days per pig
that each animal was observed in nosing behavior was also numerically,
but not significantly, higher for barrows than for gilts (barrows
1.195 days, gilts 0.944 day, P=.17).
Room and pen within room had been included in the models testing
effects of nosing on rates of gain, but did not have significant
effects. Nosing and severity of lesions were fairly evenly distributed
across pen and room. Using the repeated-measures logistic regression
model, the overall association between gender and nosing activity
was not significant (P=.20). However, gilts were significantly
less likely to engage in nosing activity than were barrows on
day 5 (P=.020) and day 6 (P=.052). On day 9, gilts
were more likely to be engaged in nosing activity than were barrows
(P=.057). At all other times, comparisons between gilts
and barrows were not significant (P>.1).
Lesions
Lesions were seen infrequently early in the trial, gradually
increased to a maximum 17 to 20 days after weaning, and then decreased.
Lesions were observed on 88% of the pigs, although most lesions
were mild. On the scoring system of 0 to 3, there were no grade
3 lesions, and only 5% of recorded lesions were grade 2. Therefore,
the cumulative score of lesions at any location for each pig generally
reflected the number of days with lesions (Table 3). Barrows (cumulative
score 3.28) were much more likely (P=.0001) to have lesions
than gilts (cumulative score 1.91).
Performance
The mean growth rate for all pigs during the 6 weeks in the
nursery was 0.33 kg per day (SD 0.09). Growth rate was examined
for nosers with respect to number of days observed in nosing activity
and total seconds of nosing activity. Growth rates of pigs with
lesions were examined with respect to cumulative severity of lesions
at individual sites and overall. Weight at the time of entry into
the nursery was compared between nosers and recipients.
Table 4 shows the association between rate of gain and nosing
behavior (measured as the total number of seconds and days on
which a pig was observed in nosing activity), and the cumulative
severity of lesions caused by nosing at the navel, flank, or all
sites combined. Each line represents a separate statistical model,
each of which also includes gender and initial starting weight
as fixed-effects variables and room (and pen within room) as random-effect
variables. Both measures of nosing behavior have negative coefficients
for the linear model, indicating that smaller, slower growing
pigs were associated with increased nosing behavior. In contrast,
lesions caused by being the recipient of nosing were more severe
in larger pigs with a greater rate of weight gain.
When the total number of seconds that pigs were observed nosing
was displayed in a histogram, there was a Poisson distribution
between 0 and 300 seconds that included most of the pigs, with
the values for 13 pigs lying far to the right of the Poisson curve.
These 13 pigs were observed to nose for a total of 400 or more
seconds during the study. Their mean starting weight (6.46 kg,
14.4 lb) did not differ (P=.44) from that of other pigs
(mean starting weight 6.55 kg, 14.5 lb), but they grew more slowly
during the 6 weeks in the nursery (P=.0015), with an ADG
of 0.276 kg (0.61 lb), compared to 0.333 kg (0.74 lb) for the
rest of the pigs. On the other hand, recipients that accumulated
total lesions of 5 or more were heavier at the time of entry to
the nursery (P=.0002): mean starting weight of recipients
was 6.78 kg (15.1 lb) compared to 6.50 kg (14.4 lb) for the rest
of the pigs. Throughout the 6 weeks, recipients continued to be
heavier and have higher rates of gain (P=.0002).
Discussion
Flank or belly nosing is esthetically annoying to animal caretakers,
but did not slow the growth rate of recipients, although there
was confounding of effect since the most rapidly growing pigs
were the most attractive targets for the perpetrators. While being
a recipient of belly nosing did not affect growth, being a perpetrator
was strongly associated with a slower growth rate. Nosers were
not smaller at weaning than non-nosers, but became smaller over
time. Pigs that were observed nosing for 400 or more seconds during
the observation periods gained, on average, 1.8 kg (4 lb) less
during the 6 weeks in the nursery than pigs that were never observed
to nose.
Nosing appeared as a behavioral expression concurrent with
a pig's failure to adapt to its new environment. Half of the pigs
were observed on at least one occasion to engage in nosing behavior,
but because there were only 13 observations on each animal, by
random chance, a proportion of pigs would not be observed nosing
even though they were nosers. The proportion could be calculated
as the probability of a pig not being observed in one observation,
raised to the 13th power, or about 16%.
The results of this study are in agreement with findings of
other studies that reported that belly nosing did not occur in
the days immediately after weaning.3--6
Gender differences in nosing behavior were minor. Barrows were
observed to perform slightly (but not significantly) more nosing
behavior than were gilts, and had significantly more lesions.
The more severe lesions in barrows may have resulted from a greater
amount of undetected nosing behavior in barrows, because data
was collected during 30-minute observation periods rather than
continuously. Another explanation may be that the amount of nosing
is not different between barrows and gilts, but because the barrow's
sheath protrudes from the abdomen, it receives more abrasion from
the same amount of nosing behavior. Even in the absence of nosing
behavior, the sheath may receive lesions from contact with the
floor. However, on subsequent examinations of these pigs when
they weighed between 25 and 50 kg (55.6 to 111 lb), no lesions
on the sheaths were observed.
An interesting finding of this study is that pigs that became
nosers did not differ from their pen mates in weight at the time
of placement into nursery pens. Apparently, absolute weight at
weaning, and body size relative to other pigs in the pen, play
little or no role in determining whether a pig will develop nosing
behavior. Other factors that might trigger or alleviate nosing
behavior were not identified in this study.
Pigs that accumulated the most lesions were heavier at the
start and remained heavier throughout the study. In the study
of Gonyou et al, nosing other pigs and being nosed were negatively
correlated.6 The biggest pigs may have been the target
of nosing because they did not engage in nosing themselves, and
therefore moved around less, making them more available to be
nosed.
Implications
- Absolute weight and body weight relative to other pigs placed
in the same pen at weaning do not determine whether a pig will
develop nosing behavior.
- The bigger pigs in a pen are less likely to be engaging in
nosing behavior.
- The bigger pigs in a pen are usually recipients of nosing
behavior, and have the most lesions caused by this behavior.
Acknowledgments
This work was supported by the David J. Ellis Professorship
fund. The authors are grateful to Kelley Meyers, Jeremy Boge,
Jeff Fortna, and Jill Borgman for their assistance in data collection.
References--referred
1. Bryant MJ. The social environment: behaviour and stress
in housed livestock. Vet Rec. 1972;90:351-358.
2. Allison CJ. Snout-rubbing as a vice in weaned pigs. Vet
Rec. 1976;98:254-255.
3. Fraser D. Observations on the behavioural development of
suckling and early-weaned piglets during the first six weeks after
birth. Anim Behav. 1978;26:22-30.
4. Blackshaw, JK. Some behavioural deviations in weaned domestic
pigs: persistent inguinal nose thrusting, and tail and ear biting.
Anim Prod. 1981;33:325-332.
5. Metz JHM, Gonyou HW. Effect of age and housing conditions
on the behavioural and haemolytic reaction of piglets to weaning.
Applied Anim Behav Sci. 1990;27:299-309.
6. Gonyou HW, Beltranena E, Whittington DL, Patience JF. The
behaviour of pigs weaned at 12 and 21 days of age from weaning
to market. Can J Anim Sci. 1998;78:517-523.
7. Dybkjar L. The identification of behavioural indicators
of 'stress' in early weaned piglets. Applied Anim Behav Sci.
1992;35:135-147.
8. Van Putten G, Dammers J. A comparative study of the well-being
of piglets reared conventionally and in cages. Appl Anim Ethol.1976;
2:339-356.
9. Hohenshell LM, Lay Jr DC, Zimmerman DR, Cunnick JE. The
effect of weaning age on behavior of commercial crossbred pigs.
J Anim Sci. 1997;75(Suppl. 1):156 (Abstr.).
10. Worobec EK, Duncan IJH, Widowski TM. The Effects of weaning
at 7, 14 and 28 days on piglet behaviour. Appl Anim Behav Sci.1999;62:173-182.
11. Varley MA. Behavioral patterns of the weaned pig. Proc
Pig Veterinary Society 1996;71-97.
12. Newberry RC, Wood-Gush DGM. Development of some behavioural
patterns in piglets under semi-natural conditions. Anim Production.
1988;46:103-109.
13. Fraser, D. The behaviour of growing pigs during experimental
social encounters. J of Agric Sci. Cambridge. 1974;
82:147-163.
14. Worsaae H, Schmidt M. Plasma cortisol and behavior in early
weaned piglets. Acta Vet Scand. 1980;21:640-657.
15. The SAS System for Information Delivery (Release 6.03).
1988. SAS Institute, Inc, Cary, North Carolina.
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