- Email: [email protected]
Investigations on feed intake and social behaviour of fattening pigs fed at an electronic feeding station
Applied Animal Behaviour Science 139 (2012) 58–64
Contents lists available at SciVerse ScienceDirect
Applied Animal Behaviour Science journal homepage: www.elsevier.com/locate/applanim
Investigations on feed intake and social behaviour of fattening pigs fed at an electronic feeding station Steffen Hoy ∗ , Sonja Schamun, Carmen Weirich Department of Animal Breeding and Genetics, Justus Liebig University, Bismarckstr. 16, D-35390 Giessen, Germany
a r t i c l e
i n f o
Article history: Accepted 14 March 2012 Available online 20 April 2012 Keywords: Fattening pig Feed intake behaviour Electronic feeding station Social hierarchy Phenotyping
a b s t r a c t For the study from a total of 679 female pigs kept in a progeny test station in 64 groups mostly with 12 pigs each, the data from all visits at an electronic feeding station (EFS) were analysed. In 93 pigs (8 groups) all agonistic interactions at the EFS were recorded in continuous observations using infrared video technique during 3× 48 h at the beginning, in the middle and at the end of the fattening period and registered in a 12 × 12-matrix in order to calculate the rank index (from −1 to +1) and rank place (from 1 to 12) for each animal. All EFS visits, the duration of each stay at EFS (MDS) and the recorded amount of feed at each EFS visit (MFI) were downloaded from the Compident EFS for the 3× 48 h periods during the whole observation period. Means were calculated for pigs with high (1–6) or low rank position (7–12) and for pigs according to their individual rank places (1–12). The pigs with the fewest EFS visits had a significantly longer MDS (5.1 min) and a significantly higher MFI (176.7 g) than pigs which came to the EFS most frequently (MDS = 3.4 min, MFI = 109.8 g). At all stages of the fattening period, high ranking pigs had less EFS visits during 48 h, a longer MDS and a higher MFI compared with low ranking group-members. The two pigs with the highest rank places of each group had significantly less visits at the EFS (745) during the whole observation period than subdominant pigs (1637). Dominant pigs occupying the first three places in the social hierarchy of the group had a longer MDS (6.6 min on average) and in tendency a higher MFI (228 g) compared with subdominant pen-mates (3.2 min, 101 g). The routinely collected and stored data (EFS visits, MDS and MFI) of the Compident EFS could be used as a tool for phenotyping the behaviour of fattening pigs, especially the feed intake and social behaviour which might be leading to long-term breeding decisions. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The feed intake behaviour of fattening pigs fed at an electronic feeding station (EFS) or at a wide animal:feeding place-ratio (PFR, e.g. 12:1) at dry/wet feeders is influenced by different factors like genotype, stocking density, group size, feed consistency, pig:feeding place-ratio (De Haer and Merks, 1992; De Haer and De Vries, 1993; Young and Lawrence, 1994; Hyun et al., 1997; Hall et al., 1999; Baumung et al., 2006). Following Council directive
∗ Corresponding author. Tel.: +49 641 99 37622; fax: +49 641 99 37639. E-mail address: [email protected] (S. Hoy). 0168-1591/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2012.03.010
2008/120/EC of December 18, 2008 laying down minimum standards for the protection of pigs ‘each pig must have access to the food at the same time as the others in the group, where pigs are fed in groups and not ad libitum or by an automatic system feeding the animals individually’. To raise and test progeny of boars under conditions similar to commercial pig production group housing of fattening pigs in groups of 12 each is allowed (in Germany). The fattening pigs are fed at an electronic feeding station with a pig:feeding place-ratio of 12:1. It is important to note that with increasing PFR the trough is more frequently occupied by pigs eventually leading to an obstructed equality concerning the access to feed between pigs with high or low rank position in the group (Knoop, 2007; Hoy, 2009).
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
Leiber-Schotte (2009) found that dominant boars in a test station fed at an ACEMO feed station visited the feeding place more frequently, but the visits were shorter and the amount of feed intake was lower compared with subdominant group-mates. The aims of our study were a) to investigate whether different parameters which were automatically registered by an electronic feeding station (number of EFS visits, duration of stay at EFS per visit, feed intake per visit) can be used to describe the individual rank position of the group-members instead the results of time-consuming video or direct ethological observation and b) to analyse whether the rank position of the individuals may influence the performance (daily gain) under the defined housing and feeding conditions of a progeny test station taking into account the animal:feeding placeratio of 12:1. 2. Materials and methods 2.1. Animals and housing conditions The analysis took place in a progeny test station in Germany with 64 groups mostly with 12 fattening pigs per group. A total of 679 female pigs were included in the study. The pigs came from 15 different breeders and were mostly (84.7%) crossbred pigs (sires: Pietrain boars, mother lines: JSR, Hypor, Dalland, Danline). Only 15.3% of the test pigs were purebred pigs (German Landrace, Duroc, Pietrain). All pigs were delivered to the progeny test station as weaners with an age of 4–6 weeks and with a live weight between 6 and 10 kg. All pigs were equipped with a health certificate signed by a veterinarian stating that the pigs originated from a healthy herd and were examined upon arrival. The pigs got an ear tag for individual identification containing the individual transponder. All pigs were correctly dewormed and free of external parasites before delivery to the test station as slaughterhouse findings demonstrated. During the first five weeks after delivery the weaners were kept in the raising unit of the test station. After this period, the pigs were housed in the fattening units with 4 pens with the measurement of 3.2 m × 3.3 m (width × length) and (normally) 12 pigs each. The group size per pen ranged between 11 and 12 in our study, sometimes between 10 and 12 (if not enough test animals were available in this round) and was – like the composition of the groups concerning the genotype – not to be influenced by us. Pigs from different breeders were combined in the groups and not regrouped between raising and fattening unit. Following the German directive for the protection of farm animals the space allowance was 0.8 m2 per pig in minimum. The pigs were kept on fully slatted floor. The microclimate in the units was controlled by a negative pressure ventilation system realizing a temperature between 16 and 22 ◦ C and a humidity between 60 and 70%. The pigs had permanent access to a hanging piece of wood to allow investigation and manipulation activities. All pigs also had permanent access to fresh water (nipple waterer) and food ad libitum. The pigs were fed at the EFS Compident Pig progeny test (Schauer Company, Austria).
59
All test animals were equipped with a chip in the ear for the identification of each pig at each EFS visit. The progeny test was implemented under the directive (of September 4, 2007) for test-on-station on growth performance, carcass value and meat quality in pigs (Central Association of the German Pig Producers). 2.2. Methods 2.2.1. EFS-data At the Compident EFS, each visit of each pig with call for food is automatically registered in the EFS computer with the time (day, hour, minute) of entering and leaving the EFS and the amount of feed (in gram), which was retrieved at each EFS visit. It is possible to download these data and to calculate on this basis of the number of EFS visits, the duration of a stay at the EFS and the feed intake amount per EFS visit for each day, for defined periods of time or for the whole test period. In our study, for each pig the number of EFS visits, the mean duration of a stay at EFS (MDS) and the mean feed intake amount per EFS visit (MFI) were calculated for the whole period between beginning and end of the fattening period in which all members of the group were completely present and for 3× 48 h each at the beginning, in the middle and at the end of the fattening period while simultaneously video observations took place. The beginning of fattening was defined as one week after moving the test pigs from the raising to the fattening unit. The middle of the fattening period was determined as 4 weeks later and the end of fattening further 4 weeks later. All EFS visits with a feed intake of less than 3 g were defined as artifacts following the results of testing the normal distribution of this parameter and excluded from the analysis. For the analysis all pigs were divided in two or three subgroups depending on the number of EFS visits during the whole observation period either with 1 for those 50% of pigs having less EFS visits and 2 for the other approximately 50% having more EFS visits than the average of the group or with 1 for the 2 most dominant pigs (smallest number of visits), with 2 for pigs with a medium number of visits and 3 for the 2 most subdominant pigs (highest number of visits) in the group. 2.2.2. Behavioural observations We hypothesize that pigs with a relatively low number of EFS visits but the longer stay at trough and the higher amount of feed intake per visit are more dominant pigs, which are less frequently displaced from the feeder by other group-mates and claim their place for a longer time. To analyse the agonistic interactions between the group-members around the EFS in a total of 8 groups with 93 pigs a camera was installed on the ceiling directed to the trough of the EFS and continuous infrared videorecordings during 3× 48 h (at the beginning, in the middle and at the end of the fattening period) took place to define the individual rank position for each individual pig. All pigs were marked with black numbers on the back. All agonistic interactions around the EFS during the 144 h of observation per group were registered and added to a winner–loser-matrix (12 × 12-matrix). As the winner was defined that pig in a dyad which displaced another feeding
60
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
pig from the trough to take this place by itself or which repulsed the attempt of displacement by another pig and continued to hold the feeding place. Thus, the loser was categorized as the displaced animal or the pig which was unable to displace another group-mate. The individual rank index (RI) was calculated on the basis of wins (S), defeats (N), number of defeated group-mates (PS ), number of group-mates against was lost (PN ) and group size (n) according to Puppe et al. (2008): RI =
(S × PS ) − (N × PN ) (S + N) × (n − 1)
The rank index RI can take values from −1 to +1. In descending order of the RI rank places were assigned from 1 for the pig with the highest social rank in the group (= highest RI) until 12 for the pig with the lowest social rank (= lowest value for RI). For further analysis pigs with individual rank places 1–6 were characterized as high ranking whereas pigs with individual rank places 7–12 were defined as low ranking. To perform this classification, the individual rank place of each pig in the group had been calculated as the average of the 6 values from the 6 days of observation (2× 24 h at the beginning, in the middle and at the end of the fattening period each) leading to a representative result concerning the rank position during the whole fattening period (Schamun, 2011). 2.3. Statistical analysis The statistical analysis of data was carried out using the Programme Package IBM SPSS Statistics version 19. The analysed traits number of EFS visits, MDS and MFI were normally distributed (tested with Kolmogorov–Smirnovtest) and showed equal variances within subgroups of fixed effects so that multiple comparisons of means (onefactorial ANOVA and Student–Newman–Keuls-test) and univariate analysis of variance were calculated using the following model (example): Yabc = + RPa + Gb + Fc + eabc
Fig. 1. Number of wins of fattening pigs in 48 h in dependence on social rank and fattening stage.
those pigs had wins as well – mostly against other low ranking pigs of the group (Fig. 1). In the next step, the parameters of the feed intake behaviour (number of EFS visits, MDS, MFI) were calculated for high and low ranking pigs during the 3 periods of 48 h each at the beginning, in the middle and at the end of the fattening period. The number of EFS visits significantly decreased during the fattening period. At each stage, high ranking pigs had less EFS visits during 48 h than low ranking animals. The difference between both categories remained approximately the same with 3.5 EFS visits (Fig. 2). In tendency, pigs with a high rank position had at each stage a longer MDS (Fig. 3) and a higher MFI (Fig. 4) compared with low ranking group-mates. The MDS of high ranking pigs was 4.7 ± 3.4 min at the beginning and 5.44 ± 3.1 min at the end of the fattening period whereas pigs with a low ranking position had values of 3.7 ± 1.4 min, 4.79 ± 1.8 min, respectively. Related to the increasing MDS during
with Yabc is the number of EFS visits, MDS, MFI, daily gain; RPa is the fixed effect of rank position (1 = high, 2 = low or 1 = high, 2 = medium, 3 = low) or rank place; Gb is the fixed effect of genotype (German Landrace, Duroc, Pietrain, hybrid with Pietrain as sire line); Fc is the fixed effect of farm (farm = 1–15); eabc is the random residual error. 3. Results 3.1. Behavioural investigation The frequency of agonistic interactions (displacement or claiming the place after an attack of a group-mate) decreased during the fattening period – from 1594 (8.6 per pig and day) at the beginning to 797 (4.3 per pig and day) at the end of fattening based on 8 groups and 48 h continuous observation of each. Following our definition, an agonistic interaction always resulted in one winner and one loser. As expected, pigs with a high rank position had more wins compared with low ranking group-members although
Fig. 2. Number of EFS visits of fattening pigs in 48 h in dependence on social rank and fattening stage.
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
61
Fig. 4. Mean feed intake per EFS visit (in 48 h each) of pigs with high or low rank position in the fattening stages.
Fig. 3. Mean duration of EFS visit (in 48 h each) of pigs with high or low rank position in the fattening stages.
3.2. Feed intake analysis fattening the MFI was significantly increased as well both in high and low ranking individuals. Pigs with a high rank position fed 22.4 g feed more per EFS visit at the beginning of fattening than group-members with a low rank position. This difference was reduced to 13.9 g at the end of the fattening period in favour of high ranking pigs. So, the different parameters which were automatically registered by the electronic feeding station (number of EFS visits, MDS, MFI) can be used to describe the individual rank position of the group-members.
Analysing the data of the Compident EFS, it was noticed that large differences occurred between the pigs in each group concerning the number of EFS visits during the whole test period, the mean duration of stay at the trough (MDS) and the mean feed intake amount per EFS visit (MFI). As an example the values for two test groups with 12 pigs each are given in Table 1 representative for all groups. The data show that the number of EFS visits ranged from 495 to 1877 in one group and from 519 to 1265 in the other group during the same time with the longer mean duration of a stay at
Table 1 Parameters of feed intake behaviour at Compident station of 12 pigs each of two test groups (Group A and B as examples) – sorted by ascending number of EFS visits. Pig number Group A 8657 7504 3957 7503 8828 3958 7531 9437 7457 7532 8658 8357 Total Group B 3610 369 86,819 86,820 76,438 2764 76,439 2823 3114 2744 2743 2013 Total
Number of EFS visits
Mean duration of a stay at EFS − MSD (min) mean ± SD
Mean feed intake amount per EFS visit − MFI (g) mean ± SD
519 524 641 691 772 792 817 892 990 1118 1152 1265 10,173
6.4 7.2 6.5 5.4 4.6 5.6 4.2 4.2 3.9 4.2 2.9 4.0 4.7
± ± ± ± ± ± ± ± ± ± ± ± ±
5.4 5.2 5.8 4.0 4.4 4.2 3.1 3.9 3.7 4.2 2.8 4.0 4.3
260.5 345.2 212.2 245.6 167.5 151.9 174.5 146.9 124.4 143.7 125.5 91.6 166.1
± ± ± ± ± ± ± ± ± ± ± ± ±
258.1 288.6 222.5 218.7 174.6 149.5 153.7 156.6 126.1 146.5 132.3 97.7 181.8
495 575 757 904 1004 1017 1279 1294 1366 1478 1587 1877 13,633
5.9 5.0 4.6 4.1 3.7 4.0 3.3 2.4 3.2 3.2 3.0 2.1 3.3
± ± ± ± ± ± ± ± ± ± ± ± ±
4.9 5.7 4.3 3.6 2.9 3.6 3.5 2.3 2.6 3.2 2.9 1.5 3.4
241.7 227.7 186.6 144.4 125.1 152.4 99.1 106.4 101.4 95.1 78.7 69.9 117.6
± ± ± ± ± ± ± ± ± ± ± ± ±
226.1 282.1 203.0 141.4 120.1 173.2 120.2 123.2 114.1 124.3 93.4 63.0 146.8
62
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
Table 2 Parameters of feed intake behaviour at Compident station of pigs with less (group 1) or more EFS visits (group 2) during the whole period than the average of the group. Parameter
Groups
n
Mean ± SD
Number of EFS visits During observation period Mean duration of a stay At EFS − MDS (min) Mean feed intake amount Per EFS visit MFI (g) Daily gain (g)
1 2 1 2 1 2 1 2 1 2
340 339 340 339 340 339 340 339 340 339
897.0 1403.0 5.5 3.6 189.0 117.1 837 837 109.7 109.5
Final weight (kg) a,b Different (p < 0.01).
superscript
types
characterize
significant
± ± ± ± ± ± ± ± ± ±
249 a 379 b 1.9 a 1.1 b 62 a 32 b 85 81 5.2 5.1
differences
EFS and the higher mean feed intake amount in these pigs having the smallest number of visits compared with the group-mates. In the next step of analysis all 679 female pigs were divided in two subgroups (group 1 and 2) with approximately 50% of the pigs each depending on the number of EFS visits during the whole period (in the examples given in Table 1 from pig number 3610 to 2764, 8657 to 3958, respectively = group 1 and from 76,439 to 2013, 7531 to 8357, respectively = group 2). In group 1, the 340 pigs of the total sample had significantly less EFS visits (897.0 ± 249) than the pigs in group 2 (1403.0 ± 379; Table 2). The pigs with the fewest EFS visits (group 1) had a significantly longer MDS (5.5 min) and a significantly higher amount of feed (MFI, 189.0 g) compared with pigs of group 2 that most frequently came to the EFS for feeding and showed the shortest MDS (3.6 min) and the lowest MFI (117.1 g). But, the significant differences in feed intake behaviour did not influence the daily gain and the final weight. The pigs of both groups 1 and 2 reached the same daily gain (837 g on average in both subgroups) and the same final weight (109.7 and 109.5 kg; Table 2) whereby it should be noted that the final weight was determined by the conditions of the progeny test. Although the pigs of group 2 intook less feed per EFS visit they compensated the reduced feed intake by the higher number of EFS visits thus leading to nearly the same total amount of feed which was taken in by the pigs on average during the whole period (group 1: 897.0 is the × 0.189 = 169.5 kg, group 2: 1403 × 0.1171 = 164.3 kg). The number of EFS visits per hour showed a clear circadian rhythm in both groups. Summarizing all hour-values of the observation period, as expected, the number of EFS visits was lower in each hour in pigs of group 1 (representing more dominant pigs – see above) than in group 2. In both categories the daily rhythm with an increase in the number of EFS visits in the morning (between 4 and 6 am) and a decrease in the afternoons (after 4 pm 9 was seen. Between 7 am and 5 pm the difference in the hourly EFS visits in favour of the dominant pigs (less visits than the low ranking pigs) was especially high (twice as much) (Fig. 5). Classifying the pigs in 3 subgroups with the special focus on the most dominant (group 1) and subdominant pigs (group 3) concerning the number of EFS visits during the fattening period the differentiation in the feed intake
Table 3 Parameters of feed intake behaviour at Compident station depending on the number of EFS visits during the whole period. Parameter
Group
n
Mean ± SD
Number of EFS visits During observation period
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
119 437 123 119 437 123 119 437 123 119 437 123 119 437 123
743.3 1123.4 1635.9 6.6 4.4 3.2 228.0 147.5 100.5 836 837 841 109.5 109.7 109.3
Mean duration of a stay At EFS − MDS (min) Mean feed intake amount Per EFS visit − MFI (g) Daily gain (g)
Final weight (kg)
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
204 a 298 b 407 c 2.3 a 1.4 b 0,9 c 70 a 44 b 27 c 81 842 87 4.7 5.2 5.5
a,b,c Different superscript types characterize significant differences (p < 0.01). Group 1 = the 2 most dominant pigs with the smallest number of EFS visits, group 2 = neither particularly dominant or subdominant pigs in the middle of the social hierarchy, group 3 = the 2 most subdominant pigs with the most frequent number of EFS visits.
behaviour becomes more distinct (Table 3). The dominant pigs of group 1 with the significantly smallest number of EFS visits (743.3) showed the longest MDS (6.6 min, p < 0.01) and the largest MFI (228.0 g, p < 0.01), and the subdominant pigs of group 3 with the highest number of EFS visits (1635.9), the shortest MDS (3.2 min) and the lowest MFI (100.5 g). In all three behavioural patterns the pigs of group 2 reached medium values. Similar to the results shown in Table 2, the differences in feed intake behaviour did not influence the daily gain. In tendency, pigs with the highest number of EFS visits but the lowest mean feed intake per visit (group 3) had a higher daily gain by 5 g compared with pigs of group 1. The pigs of both groups reached nearly the same total amount of feed intake (169.5 and 164.4 kg, respectively). In the last step, all EFS visits during the whole fattening period were calculated for the pigs according to the individual rank places (from 1 for the highest place to 12 for the lowest place in each group). A significant influence of rank place was shown only for the number of EFS visits (Fig. 6). The two pigs with the highest rank places 1 and 2 each in the 64 groups (with 689, 800 EFS visits, respectively) had a
Fig. 5. Diurnal numbers of EFS visits per hour of high or low ranking pigs during the whole observation period.
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
Fig. 6. Number of EFS visits of fattening pigs during the whole observation period in dependence on rank place.
lower feed intake frequency than the pigs on places 10–12 in the social hierarchy (1488–1713 visits). 4. Discussion An animal:feeding place-ratio of 12:1 must be classified as a very wide ratio because 12 pigs have access to one feeding place (Hoy, 2009). After the first analysis (Table 1), it was assumed that the differences in the feed intake behaviour (number of EFS visits, MDS, MFI) between the group-mates were caused by different rank positions in the social hierarchy. The differences in feeding behaviour became even more apparent when subgroups with approximately 50% each of the pigs in the groups or with the most dominant or subdominant pigs according to the number of EFS visits were compared (Tables 2 and 3). On the basis of continuous infrared video recordings, the calculation of the individual rank index of all group-members and the classification in high ranking (rank places 1–6) and low ranking pigs (rank places 7–12) showed, as expected, that dominant pigs had more wins than subdominant pigs (Puppe et al., 2008). Because of an increased feed intake speed from the start to the end of the fattening period the number of displacements at the EFS decreased as already Bornett et al. (2000) had pointed out. The rank numbers for each pig at the different periods of investigation (at the beginning, in the middle, at the end of fattening) varied but nevertheless significantly positive correlations between the values were shown indicating a relative constancy of the rank order during the fattening period (Schamun, 2011). High ranking pigs came less frequently to the EFS for feeding, stayed longer there at the trough and intook a greater amount of feed compared with low ranking pigs. With decreasing frequency of the number of EFS visits during fattening in general the rank position related difference between high and low ranking group-members was maintained. Subdominant pigs are often displaced from the trough and have to come more frequently to the EFS to get enough feed. This is in contrast to the results of Leiber-Schotte (2009) in young boars. High ranking boars showed more frequent and shorter visits with lower amount of feed intake per day than the lower ranking group-mates. The reason for
63
the difference to our results remains unclear. The results of feed intake and social behaviour found in our studies represent the expected typical behaviour: high-ranking animals have a longer stay at trough and take a greater amount of food per visit compared with low-ranking pigs. Baumung et al. (2006) pointed out that differences in the feed intake strategies might exist between different breeds (e.g. Large White, Landrace). In the study of Baumung et al. (2006) Large White pigs had more frequent EFS visits with short duration and low feed intake, whereas Landrace pigs were characterized by less visits with longer duration. High ranking pigs have more fighting successes and therefore an advantage in obtaining limited resources so that rank position and feed intake should be correlated especially when using a pig:feeding place-ratio of 12:1 (Erhard and Schouten, 2001; Bouissou et al., 2001). Though, no correlation between rank position and daily gain was found in our analysis. There were differences in the mean daily gain between the breeds and sowith between the pigs from different breeding farms. But, also the use of univariate analysis of variance with the fixed factors rank position, genotype and breeding farm did not show any significant influence of rank position on daily weight gain. The composition of the groups regarding genotype and breeding farm was not to be influenced by us. Low ranking pigs indeed fed less feed per EFS visit but they compensated this disadvantage compared with high ranking group-members by the larger number of EFS visits. The assignments to the categories high rank or low rank or to the different rank places from 1 to 12 in groups of 12 each on the basis of 3× 48 h video recordings with infrared video technique, the counting of all agonistic interactions (displacements or attempts of displacement at the EFS) of each pig against each other in a 12 × 12-matrix and the calculation of the rank index for each animal were very time-consuming. Therefore from the methodological point of view, one approach was to use the routinely recorded data on the number of EFS visits, the duration of stay at trough and the feed intake amount for characterization of high and low ranking pigs. The most obvious differences in the animal parameters are expected between the most dominant pigs with the highest 2 rank positions and the subdominant group-mates on the last 2 places in social hierarchy. With the given investigation, the first working hypothesis could be confirmed that parameters which were automatically registered by the EFS can be used to describe the individual rank position of the group-members. The correlation was at least indicated concerning the stay at trough and the feed intake amount. Some outliers could be caused by the effect of genotype. For future evaluations a categorization of the 16–25% pigs (n = 2–3 in groups of 12 pigs each) with the fewest or most frequent visits, with the smallest or largest amount of feed or with the shortest or longest duration of stay at trough could be made as well as classifying the pigs as high ranking or low ranking animals to control the impact of social position on performance with a higher number of animals with a uniform genotype. Also, the routinely collected and stored data from the Compident EFS could be used as a tool to phenotype the behaviour of pigs for long-term breeding decisions. Despite significant differences in feed intake behaviour between dominant and
64
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
subdominant group-members obviously equal opportunities were given for all pigs in the group concerning the performance. So, the second issue of our investigations can be answered as follows: equal opportunity is provided for all animals in an animal:feeding place-ratio of 12:1 regarding feed intake and performance. Acknowledgements The investigations took place as a part of the PHAENOMICS network ‘Phenotyping of the behaviour’. The authors would like to thank the German Federal Ministry for Education and Research for support. References Baumung, R., Lercher, G., Willam, A., Sölkner, J., 2006. Feed intake behaviour of different pig breeds during performance testing on station. Arch. Tierz. Dummerstorf 49, 77–88. Bornett, H.L.I., Morgan, C.A., Lawrence, A., Mann, J., 2000. The effect of group-housing on feeding patterns and social behaviour of previously individually-housed growing pigs. Appl. Anim. Behav. Sci. 70, 127–141. Bouissou, M.-F., Boissy, Y.A., Le Neindre, P., Veissier, I., 2001. The social behaviour of cattle. In: Keeling, L.J., Gonyou, H.W. (Eds.), Social Behavior in Farm Animals. CABI Publishing, Wallingford, New York, pp. 113–145. De Haer, L.C.M., Merks, J.W.M., 1992. Patterns of daily feed intake in growing pigs. Anim. Prod. 54, 95–104.
De Haer, L.C.M., De Vries, A.G., 1993. Effects of genotype and sex on the feed intake pattern of group-housed growing pigs. Livest. Prod. Sci. 36, 223–232. Erhard, H., Schouten, W., 2001. Individual differences and personality. In: Keeling, L.J., Gonyou, H.W. (Eds.), Social Behavior in Farm Animals. CABI Publishing, Wallingford, New York, pp. 333–352. Hall, A.D., Hill, W.G., Bampton, P.R., Webb, A.J., 1999. Predicted responses to selection from indices incorporating feeding pattern traits of pigs using electronic feeders. Anim. Sci. 68, 407–412. Hoy, St., 2009. Methoden der Nutztierethologie. In: Hoy, St. (Ed.), Nutztierethologie. Verlag Eugen Ulmer, Stuttgart. Hyun, Y., Ellis, M., McKeith, F.K., Wilson, E.R., 1997. Feed intake pattern of group-housed growing-finishing pigs monitored using a computerized feed intake recording system. J. Anim. Sci. 75, 1443–1451. Knoop, St., 2007. Untersuchungen zur Entwicklung und Erprobung eines neuen Fütterungssystems für Absetzferkel – der Ferkelfeeder. Thesis. Justus Liebig University Giessen. Leiber-Schotte, Ch., 2009. Einfluss der Rangordnung bei Jungebern im Eigenleistungstest auf Futteraufnahme und Futteraufnahmeverhalten unter Berücksichtigung endokrinologischer und immunologischer Parameter. Thesis. University of Veterinary Medicine, Hannover. Puppe, B., Langbein, J., Bauer, J., Hoy, St., 2008. A comparative view on social hierarchy formation at different stages of pig production using sociometric measures. Livest. Sci. 113, 155–162. Schamun, S., 2011. Untersuchungen zum Futteraufnahmeverhalten von Mastschweinen an einer elektronischen Abrufstation unter Berücksichtigung der Rangordnung. M.Sc.-Thesis. Justus Liebig University Giessen, Department of Animal Breeding and Genetics. Young, R.J., Lawrence, A.B., 1994. Feeding behaviour of pigs in groups monitored by a computerized feeding system. Anim. Prod. 58, 145–152.
Contents lists available at SciVerse ScienceDirect
Applied Animal Behaviour Science journal homepage: www.elsevier.com/locate/applanim
Investigations on feed intake and social behaviour of fattening pigs fed at an electronic feeding station Steffen Hoy ∗ , Sonja Schamun, Carmen Weirich Department of Animal Breeding and Genetics, Justus Liebig University, Bismarckstr. 16, D-35390 Giessen, Germany
a r t i c l e
i n f o
Article history: Accepted 14 March 2012 Available online 20 April 2012 Keywords: Fattening pig Feed intake behaviour Electronic feeding station Social hierarchy Phenotyping
a b s t r a c t For the study from a total of 679 female pigs kept in a progeny test station in 64 groups mostly with 12 pigs each, the data from all visits at an electronic feeding station (EFS) were analysed. In 93 pigs (8 groups) all agonistic interactions at the EFS were recorded in continuous observations using infrared video technique during 3× 48 h at the beginning, in the middle and at the end of the fattening period and registered in a 12 × 12-matrix in order to calculate the rank index (from −1 to +1) and rank place (from 1 to 12) for each animal. All EFS visits, the duration of each stay at EFS (MDS) and the recorded amount of feed at each EFS visit (MFI) were downloaded from the Compident EFS for the 3× 48 h periods during the whole observation period. Means were calculated for pigs with high (1–6) or low rank position (7–12) and for pigs according to their individual rank places (1–12). The pigs with the fewest EFS visits had a significantly longer MDS (5.1 min) and a significantly higher MFI (176.7 g) than pigs which came to the EFS most frequently (MDS = 3.4 min, MFI = 109.8 g). At all stages of the fattening period, high ranking pigs had less EFS visits during 48 h, a longer MDS and a higher MFI compared with low ranking group-members. The two pigs with the highest rank places of each group had significantly less visits at the EFS (745) during the whole observation period than subdominant pigs (1637). Dominant pigs occupying the first three places in the social hierarchy of the group had a longer MDS (6.6 min on average) and in tendency a higher MFI (228 g) compared with subdominant pen-mates (3.2 min, 101 g). The routinely collected and stored data (EFS visits, MDS and MFI) of the Compident EFS could be used as a tool for phenotyping the behaviour of fattening pigs, especially the feed intake and social behaviour which might be leading to long-term breeding decisions. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The feed intake behaviour of fattening pigs fed at an electronic feeding station (EFS) or at a wide animal:feeding place-ratio (PFR, e.g. 12:1) at dry/wet feeders is influenced by different factors like genotype, stocking density, group size, feed consistency, pig:feeding place-ratio (De Haer and Merks, 1992; De Haer and De Vries, 1993; Young and Lawrence, 1994; Hyun et al., 1997; Hall et al., 1999; Baumung et al., 2006). Following Council directive
∗ Corresponding author. Tel.: +49 641 99 37622; fax: +49 641 99 37639. E-mail address: [email protected] (S. Hoy). 0168-1591/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2012.03.010
2008/120/EC of December 18, 2008 laying down minimum standards for the protection of pigs ‘each pig must have access to the food at the same time as the others in the group, where pigs are fed in groups and not ad libitum or by an automatic system feeding the animals individually’. To raise and test progeny of boars under conditions similar to commercial pig production group housing of fattening pigs in groups of 12 each is allowed (in Germany). The fattening pigs are fed at an electronic feeding station with a pig:feeding place-ratio of 12:1. It is important to note that with increasing PFR the trough is more frequently occupied by pigs eventually leading to an obstructed equality concerning the access to feed between pigs with high or low rank position in the group (Knoop, 2007; Hoy, 2009).
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
Leiber-Schotte (2009) found that dominant boars in a test station fed at an ACEMO feed station visited the feeding place more frequently, but the visits were shorter and the amount of feed intake was lower compared with subdominant group-mates. The aims of our study were a) to investigate whether different parameters which were automatically registered by an electronic feeding station (number of EFS visits, duration of stay at EFS per visit, feed intake per visit) can be used to describe the individual rank position of the group-members instead the results of time-consuming video or direct ethological observation and b) to analyse whether the rank position of the individuals may influence the performance (daily gain) under the defined housing and feeding conditions of a progeny test station taking into account the animal:feeding placeratio of 12:1. 2. Materials and methods 2.1. Animals and housing conditions The analysis took place in a progeny test station in Germany with 64 groups mostly with 12 fattening pigs per group. A total of 679 female pigs were included in the study. The pigs came from 15 different breeders and were mostly (84.7%) crossbred pigs (sires: Pietrain boars, mother lines: JSR, Hypor, Dalland, Danline). Only 15.3% of the test pigs were purebred pigs (German Landrace, Duroc, Pietrain). All pigs were delivered to the progeny test station as weaners with an age of 4–6 weeks and with a live weight between 6 and 10 kg. All pigs were equipped with a health certificate signed by a veterinarian stating that the pigs originated from a healthy herd and were examined upon arrival. The pigs got an ear tag for individual identification containing the individual transponder. All pigs were correctly dewormed and free of external parasites before delivery to the test station as slaughterhouse findings demonstrated. During the first five weeks after delivery the weaners were kept in the raising unit of the test station. After this period, the pigs were housed in the fattening units with 4 pens with the measurement of 3.2 m × 3.3 m (width × length) and (normally) 12 pigs each. The group size per pen ranged between 11 and 12 in our study, sometimes between 10 and 12 (if not enough test animals were available in this round) and was – like the composition of the groups concerning the genotype – not to be influenced by us. Pigs from different breeders were combined in the groups and not regrouped between raising and fattening unit. Following the German directive for the protection of farm animals the space allowance was 0.8 m2 per pig in minimum. The pigs were kept on fully slatted floor. The microclimate in the units was controlled by a negative pressure ventilation system realizing a temperature between 16 and 22 ◦ C and a humidity between 60 and 70%. The pigs had permanent access to a hanging piece of wood to allow investigation and manipulation activities. All pigs also had permanent access to fresh water (nipple waterer) and food ad libitum. The pigs were fed at the EFS Compident Pig progeny test (Schauer Company, Austria).
59
All test animals were equipped with a chip in the ear for the identification of each pig at each EFS visit. The progeny test was implemented under the directive (of September 4, 2007) for test-on-station on growth performance, carcass value and meat quality in pigs (Central Association of the German Pig Producers). 2.2. Methods 2.2.1. EFS-data At the Compident EFS, each visit of each pig with call for food is automatically registered in the EFS computer with the time (day, hour, minute) of entering and leaving the EFS and the amount of feed (in gram), which was retrieved at each EFS visit. It is possible to download these data and to calculate on this basis of the number of EFS visits, the duration of a stay at the EFS and the feed intake amount per EFS visit for each day, for defined periods of time or for the whole test period. In our study, for each pig the number of EFS visits, the mean duration of a stay at EFS (MDS) and the mean feed intake amount per EFS visit (MFI) were calculated for the whole period between beginning and end of the fattening period in which all members of the group were completely present and for 3× 48 h each at the beginning, in the middle and at the end of the fattening period while simultaneously video observations took place. The beginning of fattening was defined as one week after moving the test pigs from the raising to the fattening unit. The middle of the fattening period was determined as 4 weeks later and the end of fattening further 4 weeks later. All EFS visits with a feed intake of less than 3 g were defined as artifacts following the results of testing the normal distribution of this parameter and excluded from the analysis. For the analysis all pigs were divided in two or three subgroups depending on the number of EFS visits during the whole observation period either with 1 for those 50% of pigs having less EFS visits and 2 for the other approximately 50% having more EFS visits than the average of the group or with 1 for the 2 most dominant pigs (smallest number of visits), with 2 for pigs with a medium number of visits and 3 for the 2 most subdominant pigs (highest number of visits) in the group. 2.2.2. Behavioural observations We hypothesize that pigs with a relatively low number of EFS visits but the longer stay at trough and the higher amount of feed intake per visit are more dominant pigs, which are less frequently displaced from the feeder by other group-mates and claim their place for a longer time. To analyse the agonistic interactions between the group-members around the EFS in a total of 8 groups with 93 pigs a camera was installed on the ceiling directed to the trough of the EFS and continuous infrared videorecordings during 3× 48 h (at the beginning, in the middle and at the end of the fattening period) took place to define the individual rank position for each individual pig. All pigs were marked with black numbers on the back. All agonistic interactions around the EFS during the 144 h of observation per group were registered and added to a winner–loser-matrix (12 × 12-matrix). As the winner was defined that pig in a dyad which displaced another feeding
60
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
pig from the trough to take this place by itself or which repulsed the attempt of displacement by another pig and continued to hold the feeding place. Thus, the loser was categorized as the displaced animal or the pig which was unable to displace another group-mate. The individual rank index (RI) was calculated on the basis of wins (S), defeats (N), number of defeated group-mates (PS ), number of group-mates against was lost (PN ) and group size (n) according to Puppe et al. (2008): RI =
(S × PS ) − (N × PN ) (S + N) × (n − 1)
The rank index RI can take values from −1 to +1. In descending order of the RI rank places were assigned from 1 for the pig with the highest social rank in the group (= highest RI) until 12 for the pig with the lowest social rank (= lowest value for RI). For further analysis pigs with individual rank places 1–6 were characterized as high ranking whereas pigs with individual rank places 7–12 were defined as low ranking. To perform this classification, the individual rank place of each pig in the group had been calculated as the average of the 6 values from the 6 days of observation (2× 24 h at the beginning, in the middle and at the end of the fattening period each) leading to a representative result concerning the rank position during the whole fattening period (Schamun, 2011). 2.3. Statistical analysis The statistical analysis of data was carried out using the Programme Package IBM SPSS Statistics version 19. The analysed traits number of EFS visits, MDS and MFI were normally distributed (tested with Kolmogorov–Smirnovtest) and showed equal variances within subgroups of fixed effects so that multiple comparisons of means (onefactorial ANOVA and Student–Newman–Keuls-test) and univariate analysis of variance were calculated using the following model (example): Yabc = + RPa + Gb + Fc + eabc
Fig. 1. Number of wins of fattening pigs in 48 h in dependence on social rank and fattening stage.
those pigs had wins as well – mostly against other low ranking pigs of the group (Fig. 1). In the next step, the parameters of the feed intake behaviour (number of EFS visits, MDS, MFI) were calculated for high and low ranking pigs during the 3 periods of 48 h each at the beginning, in the middle and at the end of the fattening period. The number of EFS visits significantly decreased during the fattening period. At each stage, high ranking pigs had less EFS visits during 48 h than low ranking animals. The difference between both categories remained approximately the same with 3.5 EFS visits (Fig. 2). In tendency, pigs with a high rank position had at each stage a longer MDS (Fig. 3) and a higher MFI (Fig. 4) compared with low ranking group-mates. The MDS of high ranking pigs was 4.7 ± 3.4 min at the beginning and 5.44 ± 3.1 min at the end of the fattening period whereas pigs with a low ranking position had values of 3.7 ± 1.4 min, 4.79 ± 1.8 min, respectively. Related to the increasing MDS during
with Yabc is the number of EFS visits, MDS, MFI, daily gain; RPa is the fixed effect of rank position (1 = high, 2 = low or 1 = high, 2 = medium, 3 = low) or rank place; Gb is the fixed effect of genotype (German Landrace, Duroc, Pietrain, hybrid with Pietrain as sire line); Fc is the fixed effect of farm (farm = 1–15); eabc is the random residual error. 3. Results 3.1. Behavioural investigation The frequency of agonistic interactions (displacement or claiming the place after an attack of a group-mate) decreased during the fattening period – from 1594 (8.6 per pig and day) at the beginning to 797 (4.3 per pig and day) at the end of fattening based on 8 groups and 48 h continuous observation of each. Following our definition, an agonistic interaction always resulted in one winner and one loser. As expected, pigs with a high rank position had more wins compared with low ranking group-members although
Fig. 2. Number of EFS visits of fattening pigs in 48 h in dependence on social rank and fattening stage.
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
61
Fig. 4. Mean feed intake per EFS visit (in 48 h each) of pigs with high or low rank position in the fattening stages.
Fig. 3. Mean duration of EFS visit (in 48 h each) of pigs with high or low rank position in the fattening stages.
3.2. Feed intake analysis fattening the MFI was significantly increased as well both in high and low ranking individuals. Pigs with a high rank position fed 22.4 g feed more per EFS visit at the beginning of fattening than group-members with a low rank position. This difference was reduced to 13.9 g at the end of the fattening period in favour of high ranking pigs. So, the different parameters which were automatically registered by the electronic feeding station (number of EFS visits, MDS, MFI) can be used to describe the individual rank position of the group-members.
Analysing the data of the Compident EFS, it was noticed that large differences occurred between the pigs in each group concerning the number of EFS visits during the whole test period, the mean duration of stay at the trough (MDS) and the mean feed intake amount per EFS visit (MFI). As an example the values for two test groups with 12 pigs each are given in Table 1 representative for all groups. The data show that the number of EFS visits ranged from 495 to 1877 in one group and from 519 to 1265 in the other group during the same time with the longer mean duration of a stay at
Table 1 Parameters of feed intake behaviour at Compident station of 12 pigs each of two test groups (Group A and B as examples) – sorted by ascending number of EFS visits. Pig number Group A 8657 7504 3957 7503 8828 3958 7531 9437 7457 7532 8658 8357 Total Group B 3610 369 86,819 86,820 76,438 2764 76,439 2823 3114 2744 2743 2013 Total
Number of EFS visits
Mean duration of a stay at EFS − MSD (min) mean ± SD
Mean feed intake amount per EFS visit − MFI (g) mean ± SD
519 524 641 691 772 792 817 892 990 1118 1152 1265 10,173
6.4 7.2 6.5 5.4 4.6 5.6 4.2 4.2 3.9 4.2 2.9 4.0 4.7
± ± ± ± ± ± ± ± ± ± ± ± ±
5.4 5.2 5.8 4.0 4.4 4.2 3.1 3.9 3.7 4.2 2.8 4.0 4.3
260.5 345.2 212.2 245.6 167.5 151.9 174.5 146.9 124.4 143.7 125.5 91.6 166.1
± ± ± ± ± ± ± ± ± ± ± ± ±
258.1 288.6 222.5 218.7 174.6 149.5 153.7 156.6 126.1 146.5 132.3 97.7 181.8
495 575 757 904 1004 1017 1279 1294 1366 1478 1587 1877 13,633
5.9 5.0 4.6 4.1 3.7 4.0 3.3 2.4 3.2 3.2 3.0 2.1 3.3
± ± ± ± ± ± ± ± ± ± ± ± ±
4.9 5.7 4.3 3.6 2.9 3.6 3.5 2.3 2.6 3.2 2.9 1.5 3.4
241.7 227.7 186.6 144.4 125.1 152.4 99.1 106.4 101.4 95.1 78.7 69.9 117.6
± ± ± ± ± ± ± ± ± ± ± ± ±
226.1 282.1 203.0 141.4 120.1 173.2 120.2 123.2 114.1 124.3 93.4 63.0 146.8
62
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
Table 2 Parameters of feed intake behaviour at Compident station of pigs with less (group 1) or more EFS visits (group 2) during the whole period than the average of the group. Parameter
Groups
n
Mean ± SD
Number of EFS visits During observation period Mean duration of a stay At EFS − MDS (min) Mean feed intake amount Per EFS visit MFI (g) Daily gain (g)
1 2 1 2 1 2 1 2 1 2
340 339 340 339 340 339 340 339 340 339
897.0 1403.0 5.5 3.6 189.0 117.1 837 837 109.7 109.5
Final weight (kg) a,b Different (p < 0.01).
superscript
types
characterize
significant
± ± ± ± ± ± ± ± ± ±
249 a 379 b 1.9 a 1.1 b 62 a 32 b 85 81 5.2 5.1
differences
EFS and the higher mean feed intake amount in these pigs having the smallest number of visits compared with the group-mates. In the next step of analysis all 679 female pigs were divided in two subgroups (group 1 and 2) with approximately 50% of the pigs each depending on the number of EFS visits during the whole period (in the examples given in Table 1 from pig number 3610 to 2764, 8657 to 3958, respectively = group 1 and from 76,439 to 2013, 7531 to 8357, respectively = group 2). In group 1, the 340 pigs of the total sample had significantly less EFS visits (897.0 ± 249) than the pigs in group 2 (1403.0 ± 379; Table 2). The pigs with the fewest EFS visits (group 1) had a significantly longer MDS (5.5 min) and a significantly higher amount of feed (MFI, 189.0 g) compared with pigs of group 2 that most frequently came to the EFS for feeding and showed the shortest MDS (3.6 min) and the lowest MFI (117.1 g). But, the significant differences in feed intake behaviour did not influence the daily gain and the final weight. The pigs of both groups 1 and 2 reached the same daily gain (837 g on average in both subgroups) and the same final weight (109.7 and 109.5 kg; Table 2) whereby it should be noted that the final weight was determined by the conditions of the progeny test. Although the pigs of group 2 intook less feed per EFS visit they compensated the reduced feed intake by the higher number of EFS visits thus leading to nearly the same total amount of feed which was taken in by the pigs on average during the whole period (group 1: 897.0 is the × 0.189 = 169.5 kg, group 2: 1403 × 0.1171 = 164.3 kg). The number of EFS visits per hour showed a clear circadian rhythm in both groups. Summarizing all hour-values of the observation period, as expected, the number of EFS visits was lower in each hour in pigs of group 1 (representing more dominant pigs – see above) than in group 2. In both categories the daily rhythm with an increase in the number of EFS visits in the morning (between 4 and 6 am) and a decrease in the afternoons (after 4 pm 9 was seen. Between 7 am and 5 pm the difference in the hourly EFS visits in favour of the dominant pigs (less visits than the low ranking pigs) was especially high (twice as much) (Fig. 5). Classifying the pigs in 3 subgroups with the special focus on the most dominant (group 1) and subdominant pigs (group 3) concerning the number of EFS visits during the fattening period the differentiation in the feed intake
Table 3 Parameters of feed intake behaviour at Compident station depending on the number of EFS visits during the whole period. Parameter
Group
n
Mean ± SD
Number of EFS visits During observation period
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
119 437 123 119 437 123 119 437 123 119 437 123 119 437 123
743.3 1123.4 1635.9 6.6 4.4 3.2 228.0 147.5 100.5 836 837 841 109.5 109.7 109.3
Mean duration of a stay At EFS − MDS (min) Mean feed intake amount Per EFS visit − MFI (g) Daily gain (g)
Final weight (kg)
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
204 a 298 b 407 c 2.3 a 1.4 b 0,9 c 70 a 44 b 27 c 81 842 87 4.7 5.2 5.5
a,b,c Different superscript types characterize significant differences (p < 0.01). Group 1 = the 2 most dominant pigs with the smallest number of EFS visits, group 2 = neither particularly dominant or subdominant pigs in the middle of the social hierarchy, group 3 = the 2 most subdominant pigs with the most frequent number of EFS visits.
behaviour becomes more distinct (Table 3). The dominant pigs of group 1 with the significantly smallest number of EFS visits (743.3) showed the longest MDS (6.6 min, p < 0.01) and the largest MFI (228.0 g, p < 0.01), and the subdominant pigs of group 3 with the highest number of EFS visits (1635.9), the shortest MDS (3.2 min) and the lowest MFI (100.5 g). In all three behavioural patterns the pigs of group 2 reached medium values. Similar to the results shown in Table 2, the differences in feed intake behaviour did not influence the daily gain. In tendency, pigs with the highest number of EFS visits but the lowest mean feed intake per visit (group 3) had a higher daily gain by 5 g compared with pigs of group 1. The pigs of both groups reached nearly the same total amount of feed intake (169.5 and 164.4 kg, respectively). In the last step, all EFS visits during the whole fattening period were calculated for the pigs according to the individual rank places (from 1 for the highest place to 12 for the lowest place in each group). A significant influence of rank place was shown only for the number of EFS visits (Fig. 6). The two pigs with the highest rank places 1 and 2 each in the 64 groups (with 689, 800 EFS visits, respectively) had a
Fig. 5. Diurnal numbers of EFS visits per hour of high or low ranking pigs during the whole observation period.
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
Fig. 6. Number of EFS visits of fattening pigs during the whole observation period in dependence on rank place.
lower feed intake frequency than the pigs on places 10–12 in the social hierarchy (1488–1713 visits). 4. Discussion An animal:feeding place-ratio of 12:1 must be classified as a very wide ratio because 12 pigs have access to one feeding place (Hoy, 2009). After the first analysis (Table 1), it was assumed that the differences in the feed intake behaviour (number of EFS visits, MDS, MFI) between the group-mates were caused by different rank positions in the social hierarchy. The differences in feeding behaviour became even more apparent when subgroups with approximately 50% each of the pigs in the groups or with the most dominant or subdominant pigs according to the number of EFS visits were compared (Tables 2 and 3). On the basis of continuous infrared video recordings, the calculation of the individual rank index of all group-members and the classification in high ranking (rank places 1–6) and low ranking pigs (rank places 7–12) showed, as expected, that dominant pigs had more wins than subdominant pigs (Puppe et al., 2008). Because of an increased feed intake speed from the start to the end of the fattening period the number of displacements at the EFS decreased as already Bornett et al. (2000) had pointed out. The rank numbers for each pig at the different periods of investigation (at the beginning, in the middle, at the end of fattening) varied but nevertheless significantly positive correlations between the values were shown indicating a relative constancy of the rank order during the fattening period (Schamun, 2011). High ranking pigs came less frequently to the EFS for feeding, stayed longer there at the trough and intook a greater amount of feed compared with low ranking pigs. With decreasing frequency of the number of EFS visits during fattening in general the rank position related difference between high and low ranking group-members was maintained. Subdominant pigs are often displaced from the trough and have to come more frequently to the EFS to get enough feed. This is in contrast to the results of Leiber-Schotte (2009) in young boars. High ranking boars showed more frequent and shorter visits with lower amount of feed intake per day than the lower ranking group-mates. The reason for
63
the difference to our results remains unclear. The results of feed intake and social behaviour found in our studies represent the expected typical behaviour: high-ranking animals have a longer stay at trough and take a greater amount of food per visit compared with low-ranking pigs. Baumung et al. (2006) pointed out that differences in the feed intake strategies might exist between different breeds (e.g. Large White, Landrace). In the study of Baumung et al. (2006) Large White pigs had more frequent EFS visits with short duration and low feed intake, whereas Landrace pigs were characterized by less visits with longer duration. High ranking pigs have more fighting successes and therefore an advantage in obtaining limited resources so that rank position and feed intake should be correlated especially when using a pig:feeding place-ratio of 12:1 (Erhard and Schouten, 2001; Bouissou et al., 2001). Though, no correlation between rank position and daily gain was found in our analysis. There were differences in the mean daily gain between the breeds and sowith between the pigs from different breeding farms. But, also the use of univariate analysis of variance with the fixed factors rank position, genotype and breeding farm did not show any significant influence of rank position on daily weight gain. The composition of the groups regarding genotype and breeding farm was not to be influenced by us. Low ranking pigs indeed fed less feed per EFS visit but they compensated this disadvantage compared with high ranking group-members by the larger number of EFS visits. The assignments to the categories high rank or low rank or to the different rank places from 1 to 12 in groups of 12 each on the basis of 3× 48 h video recordings with infrared video technique, the counting of all agonistic interactions (displacements or attempts of displacement at the EFS) of each pig against each other in a 12 × 12-matrix and the calculation of the rank index for each animal were very time-consuming. Therefore from the methodological point of view, one approach was to use the routinely recorded data on the number of EFS visits, the duration of stay at trough and the feed intake amount for characterization of high and low ranking pigs. The most obvious differences in the animal parameters are expected between the most dominant pigs with the highest 2 rank positions and the subdominant group-mates on the last 2 places in social hierarchy. With the given investigation, the first working hypothesis could be confirmed that parameters which were automatically registered by the EFS can be used to describe the individual rank position of the group-members. The correlation was at least indicated concerning the stay at trough and the feed intake amount. Some outliers could be caused by the effect of genotype. For future evaluations a categorization of the 16–25% pigs (n = 2–3 in groups of 12 pigs each) with the fewest or most frequent visits, with the smallest or largest amount of feed or with the shortest or longest duration of stay at trough could be made as well as classifying the pigs as high ranking or low ranking animals to control the impact of social position on performance with a higher number of animals with a uniform genotype. Also, the routinely collected and stored data from the Compident EFS could be used as a tool to phenotype the behaviour of pigs for long-term breeding decisions. Despite significant differences in feed intake behaviour between dominant and
64
S. Hoy et al. / Applied Animal Behaviour Science 139 (2012) 58–64
subdominant group-members obviously equal opportunities were given for all pigs in the group concerning the performance. So, the second issue of our investigations can be answered as follows: equal opportunity is provided for all animals in an animal:feeding place-ratio of 12:1 regarding feed intake and performance. Acknowledgements The investigations took place as a part of the PHAENOMICS network ‘Phenotyping of the behaviour’. The authors would like to thank the German Federal Ministry for Education and Research for support. References Baumung, R., Lercher, G., Willam, A., Sölkner, J., 2006. Feed intake behaviour of different pig breeds during performance testing on station. Arch. Tierz. Dummerstorf 49, 77–88. Bornett, H.L.I., Morgan, C.A., Lawrence, A., Mann, J., 2000. The effect of group-housing on feeding patterns and social behaviour of previously individually-housed growing pigs. Appl. Anim. Behav. Sci. 70, 127–141. Bouissou, M.-F., Boissy, Y.A., Le Neindre, P., Veissier, I., 2001. The social behaviour of cattle. In: Keeling, L.J., Gonyou, H.W. (Eds.), Social Behavior in Farm Animals. CABI Publishing, Wallingford, New York, pp. 113–145. De Haer, L.C.M., Merks, J.W.M., 1992. Patterns of daily feed intake in growing pigs. Anim. Prod. 54, 95–104.
De Haer, L.C.M., De Vries, A.G., 1993. Effects of genotype and sex on the feed intake pattern of group-housed growing pigs. Livest. Prod. Sci. 36, 223–232. Erhard, H., Schouten, W., 2001. Individual differences and personality. In: Keeling, L.J., Gonyou, H.W. (Eds.), Social Behavior in Farm Animals. CABI Publishing, Wallingford, New York, pp. 333–352. Hall, A.D., Hill, W.G., Bampton, P.R., Webb, A.J., 1999. Predicted responses to selection from indices incorporating feeding pattern traits of pigs using electronic feeders. Anim. Sci. 68, 407–412. Hoy, St., 2009. Methoden der Nutztierethologie. In: Hoy, St. (Ed.), Nutztierethologie. Verlag Eugen Ulmer, Stuttgart. Hyun, Y., Ellis, M., McKeith, F.K., Wilson, E.R., 1997. Feed intake pattern of group-housed growing-finishing pigs monitored using a computerized feed intake recording system. J. Anim. Sci. 75, 1443–1451. Knoop, St., 2007. Untersuchungen zur Entwicklung und Erprobung eines neuen Fütterungssystems für Absetzferkel – der Ferkelfeeder. Thesis. Justus Liebig University Giessen. Leiber-Schotte, Ch., 2009. Einfluss der Rangordnung bei Jungebern im Eigenleistungstest auf Futteraufnahme und Futteraufnahmeverhalten unter Berücksichtigung endokrinologischer und immunologischer Parameter. Thesis. University of Veterinary Medicine, Hannover. Puppe, B., Langbein, J., Bauer, J., Hoy, St., 2008. A comparative view on social hierarchy formation at different stages of pig production using sociometric measures. Livest. Sci. 113, 155–162. Schamun, S., 2011. Untersuchungen zum Futteraufnahmeverhalten von Mastschweinen an einer elektronischen Abrufstation unter Berücksichtigung der Rangordnung. M.Sc.-Thesis. Justus Liebig University Giessen, Department of Animal Breeding and Genetics. Young, R.J., Lawrence, A.B., 1994. Feeding behaviour of pigs in groups monitored by a computerized feeding system. Anim. Prod. 58, 145–152.