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Effects of stall or small group gestation housing on the production, health and behaviour of gilts
Livestock Science 102 (2006) 171 – 179 www.elsevier.com/locate/livsci
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Effects of stall or small group gestation housing on the production, health and behaviour of giltsB M.J. Harris a,*, E.A. Pajor a, A.D. Sorrells a,b,1, S.D. Eicher b, B.T. Richert a, J.N. Marchant-Forde b a
Department of Animal Sciences, Poultry Science Building, Purdue University, 125 S. Russell Street, West Lafayette, Indiana, 47907-2042, USA b Livestock Behavior Research Unit, USDA-ARS, Poultry Science Building, Purdue University, 125 S. Russell Street, West Lafayette, Indiana, 47907-2042, USA Received 11 March 2005; received in revised form 18 November 2005; accepted 19 December 2005
Abstract The effects of housing gestating gilts in groups of four ( G, n = 8) or individual stalls (S, n = 14) on production, health and behavioural time budget were evaluated. Gilts were allocated to a gestation treatment by d 7 after breeding. They were housed in a single room, floors were fully slatted with no bedding, and all conditions except for housing type were identical. Gilts were weighed and their backfat measured at wk 1 (just after moving to gestation housing), 5, 9 and 13 of pregnancy. After farrowing, litter size, sex ratio, piglet weights and mortality percentages were recorded. Skin lesions were scored using a 6-point scale every 2 wk. Gait was scored using a 6-point scale at the end of gestation. Heart rate was assessed at wk 14 to 15 after breeding. Behaviour was videotaped to collect data on body postures and ingestive behaviour for 24 h at wk 4, 6, 9 and 13 of gestation. Apart from at wk 5, when S gilts had higher backfat than G ( P b 0.05), G and S gilts did not differ in body weight or backfat during the study. Reproductive performance did not differ. While skin lesion scores did not differ at wk 1, by wk 13 lesion scores for several regions of the head, face, body, feet and legs were higher in G than S animals ( P b 0.05). There were no differences in heart rate, but gait scores at the end of pregnancy tended to be poorer in G than S gilts ( P b 0.1). As gestation progressed gilts spent less time standing ( P b 0.0001) and more time lying ( P b 0.05), but behavioural time budgets (percentages of time spent standing, lying, sitting, eating and drinking) of animals housed in G and S did not differ. In conclusion, there were few differences detected between gilts housed for one pregnancy in groups of four or stalls. Stalls in this study were relatively spacious, while group pens were relatively small and barren. Effects of gestation housing on sows’ welfare
B Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. * Corresponding author. Department of Clinical Veterinary Science, University of Bristol, Langford House, Langford, North Somerset, BS40 5DU, UK. Tel.: +44 0117 928 9404; fax: +44 0117 928 9582. E-mail address: [email protected] (M.J. Harris). 1 Present address: 513 Parnassus, UCSF-LARC, MRI 325B Box 0564, San Francisco, California, 94117, USA.
1871-1413/$ - see front matter D 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2005.12.004
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may be cumulative, taking several parities to emerge, and care must be taken in the design and management of group housing systems to ensure that they achieve their objective of improved welfare for all group members. D 2006 Elsevier B.V. All rights reserved. Keywords: Pig; Gestation; Housing; Production; Behaviour; Welfare
1. Introduction Housing pregnant pigs in individual stalls is a controversial practice. Stalls allow for easy management, individual feeding, and reduce aggressive encounters between individuals. However, freedom of movement is severely restricted, and confined sows have been shown to have reduced cardiovascular fitness (Marchant et al., 1997), reduced muscle weight and bone strength (Marchant and Broom, 1996), increased morbidity (Tillon and Madec, 1984), and engage in more unresolved aggression (Broom et al., 1995). Confinement in stalls, in conjunction with feed restriction, has been implicated in the development of oral stereotypies, repetitive, apparently functionless behaviours that probably indicate reduced welfare (Terlouw et al., 1991; Vieuille-Thomas et al., 1995). Welfare concerns have led to gestation stalls being banned or phased out in several European countries, and from 2013 the use of stalls will be restricted to the first four weeks of gestation throughout the European Union. However, stall housing is common in North America: at the time of the study approximately twothirds of sows in the United States spent their pregnancy in stalls (Barnett et al., 2001; USDA, 2001). The simplest method of converting stall housing to groups is to remove the back from gestation stalls, continuing to use the stalls for feeding and adding a communal area. Where complete re-fitting is not an option, this is likely to be the method of first choice adopted by farmers changing from stall to group gestation. While this practice might meet with the letter of legislation it is unclear whether or to what extent it would improve sow welfare, since this type of small group system offers increased freedom of movement but is otherwise rather barren. Broom et al. (1995), in the UK, compared the effects of straw-based group gestation systems with unbedded gestation stalls over four parities, finding more welfare problems in stalls than groups. By sows’ fourth parity, those housed in stalls weighed less but there were no differences in reproductive performance over all four
parities. North American sows are of different genotypes from those in the United Kingdom, and housing designs differ. Bates et al. (2003), in Kansas, compared the performance of sows housed in groups with electronic sow feeders (ESFs) with those in stalls, reporting a similar or improved performance in sows that gestated in ESF groups. In another American study, Friend et al. (1995) compared productivity of sows housed during their first three parities in groups of 3–5, comprising an indoor straw-bedded area and an outdoor area, with those in unbedded stalls. Culling rates were greater in the stall-housed than grouphoused sows and sows from stalls produced fewer liveborn piglets. No published North American study has directly compared the effects of small group and stall gestation housing under controlled conditions. The present study was designed to evaluate the effects on production, health and behavioural time budget of housing gilts for one gestation in either individual stalls or groups of four with feeding stalls. It was part of a larger, multidisciplinary examination of the effects of gestation housing on the welfare of domestic sows and their piglets.
2. Materials and methods 2.1. Facilities and animals The study was conducted at the Purdue University Swine Research and Education Center between October 2000 and March 2001. The Purdue University Animal Care and Use Committee approved all procedures. Forty-eight crossbred Yorkshire Landrace gilts were bred to crossbred Hampshire Duroc boars and allocated to either one of eight groups ( G) of four (pens measured 3.94 2.44 m and included four, 2.21 0.61 m, individual feeding stalls without backs and a rear communal area measuring 2.44 1.73 m) or 16 individual stalls (S, 2.21 0.61 m) by d 7 after breeding. Animals were allocated to a G or S based on availability and groups were composed of
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unrelated, unfamiliar females. Gilts were introduced into the housing systems in two blocks, one month apart. Within each group, a paint mark across the animals’ back or shoulders was applied to facilitate individual identification during videotaping. Individuals that returned to estrus were not re-bred but remained in gestation accommodation; only data from pregnant females were included in analyses. The single gestation room contained 8 group pens and 16 stalls. Natural lighting was provided via several windows and supplemented by fluorescent lights, which were turned on for approximately 8 h each day. Four, 25 W red lights facilitated night-time videotaping. Floors were fully slatted concrete with no bedding. Gilts were fed 1.8–2.3 kg once per day of a standard corn and soybean meal-based gestation diet, the amount dependent on stage of gestation. Temperature in the gestation room averaged 18.0 8C (range 9.3 to 27.7 8C) and relative humidity averaged 37.3% (range 24.8% to 90.6%), but both temperature and humidity fluctuated with time of day and outside weather conditions. The same stockpersons cared for all animals. Herd veterinarians checked the health of all animals monthly. No animals were removed from the study because of illness. Approximately 5 d before they were due to farrow, gilts were loaded onto a trailer and transported 100 m to the farrowing unit. Farrowing accommodation comprised two interconnected rooms, each of which contained 12 standard farrowing crates. Temperature in the farrowing rooms was set at 21 8C, with supplemental heat pads and heat lamps provided for piglets. Pre-partum gilts in the farrowing room were fed approximately 2.3 kg, once per day, of a standard corn and soybean meal-based lactation diet; intake was increased gradually to ad libitum after farrowing. Both gestation and lactation diets were formulated to meet or exceed NRC (1998) requirements for all nutrients. Farrowing was not artificially induced. If a female exhibited signs of difficulty at farrowing, she was first examined manually by a stockperson, followed if necessary by the administration of oxytocin (1 cc IM) to aid the delivery of piglets. 2.2. Production Gilts were weighed approximately 1 wk after breeding, and again at wk 5, 9 and 13 after breeding.
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On each occasion that they were weighed, gilts’ backfat was measured at the 10th rib site, 2.5 cm from the midline on the right and left sides of the body, and the mean of these two measurements recorded. Piglets from each gilt were counted within 24 h after birth, and numbers of stillborn and mummified piglets recorded. Lung floatation was used to distinguish stillborn piglets from those that had died soon after birth. Piglet deaths up to the age of weaning were noted, and stockpersons recorded the probable cause of death. Within 72 h after birth piglets were individually weighed, their sex noted, their tails were docked, needle teeth clipped, ears notched for identification, an iron injection given, and males were castrated. After weaning at 21 d, numbers of sows culled, reasons for culling and days taken to return to estrus were recorded. 2.3. Health Skin injuries were evaluated every 2 wk throughout gestation, starting 1 wk after breeding, using a scoring system adapted from Arey (1999) and Boyle et al. (2000). Seven regions of the head and body (the head, ears and face; shoulders and neck; mid-body; udder; rump; tail; and vulva) and six regions of the feet and legs (the elbows; carpal joints; fetlocks; accessory digits; hocks; and tarsa–metatarsal joints) were visually inspected and given a lesion score between 0 and 5 (Table 1). The same person (MH) assigned scores at each session. Cardiovascular function was assessed by measuring heart rate at wk 14 to 15 after breeding. At this stage, any cardiovascular effects of gestation housing would have had time to develop. Gilts were fitted with Polar Vantage NV (Polar Electro Oy, Kempele, Finland) monitors (see methodology in Marchant et al., 1995), set to record and store data Table 1 Six-point scoring system used to evaluate skin lesions for seven regions of the head and body, and six regions of the feet and legs Score
Head and body
Feet and legs
0 1 2 3
Normal (no blemish) Some reddening or callus Less than 10 scratches Less than 5 cuts or small wound 10 or more scratches 5 or more cuts or large wound
Normal (no blemish) Alopecia or callus Redness Wound or swelling
4 5
Severe wound Severe wound and severe swelling
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Table 2 Six-point scoring system used to evaluate gait (adapted from Main et al., 2000) Score
Standing posture
Gait
0
Stands squarely on all four legs
1 2
Stands squarely on all four legs Uneven posture
3
Uneven posture. Will not bear weight on affected limb Affected limb elevated off floor Will not stand unaided
Even strides. Caudal body sways slightly while walking. Able to accelerate and change direction rapidly Abnormal stride length. Movements no longer fluent. Pig appears stiff. Shortened stride. Lameness detected. Swagger of caudal body when walking. No hindrance in agility Shortened stride. Minimum weight-bearing on affected limb. Swagger of caudal body while walking. Will still trot and gallop May not place affected limb on floor while moving Does not move
4 5
averaged every 5 s, and both heart rate and behavioural data collected over a 1 h period in mid-afternoon. Gait was scored by a single observer (MH), using an adaptation of a 6-point lameness scoring system described by Main et al. (2000; Table 2), as each animal walked down the corridor during transfer to farrowing. 2.4. Behaviour During wk 4, 6, 9 and 13 of gestation, time-lapse videotape recordings were made of gilts’ behaviour. A time-lapse videocassette recorder (Panasonic AG6540P; Panasonic Video Imaging Systems Company, Secaucus, NJ), multiplexer (Panasonic WJ-FS216) and black and white video cameras (Panasonic WVBP330) were used to make a 24 h recording for all gilts. One camera was used to film one group of gilts or four stall-housed individuals. Due to technical difficulties during wk 9, for three groups of gilts and eight stalls, data from wk 8 of gestation were substituted. Preliminary observations showed that very little activity occurred in either group-housed or stall-housed animals during hours of darkness (98% of time was spent lying). Therefore behavioural observations were confined to daylight hours. From 0600 to 1800, instantaneous samples were made of each gilt’s behaviour at 10 min intervals, recording ingestive activity (eat; drink) and, when not eating or drinking, postural behaviour (stand; lie; sit).
interaction of block and housing treatment (df = 1) and time (df = 3) on body weight, weight gain, backfat and behavioural measures of activity were analysed using a repeated measures analysis of variance (Proc GLM; SAS Institute Inc., 1990), using means per group for G gilts and individual measures for S gilts. Skin lesion scores and gait scores for S and G animals were compared using Wilcoxon one-way analyses of variance (Proc NPAR1WAY; SAS Institute Inc., 1990), using mean scores per group for G females and individual scores for S females. Heart rate data were analysed to determine mean heart rates for each sow in different postures and compared between treatments using two-sample Student’s t-tests. For farrowings where intervention had taken place, percentages of piglets stillborn were removed from reproductive performance data prior to analysis, although outcomes did not differ if these data were not removed. Effects of block and housing treatment on reproductive performance were measured using analysis of variance (Proc GLM; SAS Institute Inc., 1990). Chi-square analysis was used to compare the effects of housing treatment on numbers of sows culled after weaning, and time taken to return to estrus (3–5 d; 6–8 d; 20 d or longer).
3. Results 3.1. Production
2.5. Statistical analysis All percentage data were transformed using the arcsine prior to analysis to achieve an approximately normalized distribution. The main effects of block (df = 1), gestation housing treatment (df = 1), the
Seven individuals returned to estrus, five from G and two from S; this difference was not significant. Unsurprisingly, all pregnant gilts gained weight ( P b 0.0001; Fig. 1) and their backfat measurements increased ( P b 0.0001; Fig. 2) over the course of
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3.2. Health Tables 4 and 5 show skin lesion scores from wk 1 to wk 13 of gestation for the head and body (Table 4)
210
Group Stall
Body weight (kg)
200 190 180
2.70
Group Stall
2.50 Backfat (cm)
gestation. Gilts allocated to groups or stalls did not differ in body weight or backfat at entry to gestation. During pregnancy, body weight did not differ with housing type. From wk 1 to 5 of gestation, S animals gained more backfat than those housed in G ( P b 0.01), and at wk 5, S females had higher backfat measurements than G ( P b 0.05; Fig. 2). Animals housed in G tended to gain more weight than those housed in S from wk 5 to 9 ( P b 0.1); similarly, from wk 5 to 9, G animals tended to gain more backfat than S ( P b 0.1). One female that had been G housed during gestation died in the farrowing house before giving birth, leaving data from 40 (26 G, 14 S) farrowings. There were no differences in reproductive performance between G and S gilts (Table 3). Four out of fourteen gilts that had gestated in S (28.6%) and nine out of 26 former G occupants (34.6%) were culled after their first farrowing, because of poor health, litter problems, difficulty at farrowing or failure to return to heat. Differences in numbers culled were not significant (chi-square = 0.17; df = 1). The mean weaning to re-breeding interval for previously G females bred at their first postweaning heat was 4.8 d, compared to 5.6 d in previously S females. Differences in weaning to rebreeding intervals were not significant (chi-square = 0.92; df = 2).
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2.30
*
2.10 1.90 1.70 Week 1
Week 5
Week 9
Week 13
Time after breeding * Means differ (P<0.05)
Fig. 2. Backfat measurements (least squares means F standard error) for group-housed and stall-housed gilts, at wk 1, 5, 9 and 13 after breeding.
and feet and legs (Table 5) of G and S gilts. There were no significant differences between gilts allocated to G and S at the time of transfer to gestation. From wk 3 after breeding (2 wk after entry to gestation housing), skin lesion scores for six of the seven regions of the head and body were higher in G than S gilts (Table 4). Lesion scores for the seventh body region, the vulva, did not differ between G and S gilts, either at wk 1 ( G mean score = 0.09; S mean score = 0.31) or at any time during gestation. At wk 13 the feet and legs of gilts housed in G were in significantly poorer condition (as evidenced by higher lesion scores) than those of S animals for all regions except the hocks (Table 5). There were no differences between treatments in basal heart rates, i.e. heart rates while lying inactive with eyes closed ( G = 95.0 beats per minute [bpm]; S = 97.9 bpm), or in heart rates while standing ( G = 115.6 bpm; S = 118.7 bpm) or sitting ( G = 105.9 bpm; S = 107.0 bpm). The mean gait score for G gilts tended to be worse than that for S gilts (group mean score = 0.67; stall mean score = 0.29; P b 0.1).
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3.3. Behavioural time budget
160 150 140 Week 1
Week 5
Week 9
Week 13
Time after breeding
Fig. 1. Body weight measurements (least squares means F standard error) for group-housed and stall-housed gilts, at wk 1, 5, 9 and 13 after breeding.
Groups in which all individuals were pregnant (n = 4), or less than all members were pregnant (n = 4) did not differ in percentages of time spent standing, lying or sitting by pregnant gilts (all statistical comparisons were non-significant). As gestation progressed, gilts spent less time standing (23.3% during
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Table 3 Reproductive performance data (least squares means F standard error) for gilts housed during gestation in groups or stalls Variable
Group
Gestation length (d) Litter size (total no. piglets) Live litter size (no. piglets born live) Percentage of piglets stillborn Litter sex ratio (males / (males + females)) Piglet weight at birth (kg) Litter weight at birth (kg) Percentage preweaning mortality (of piglets born alive)
115.30 F 0.31 9.01 F 0.66
115.33 F 0.41 9.56 F 0.86
7.81 F 0.71
8.90 F 0.93
12.6 F 5.0 0.518 F 0.043
12.0 F 6.2 0.590 F 0.057
1.687 F 0.053 15.18 F 0.93 18.1 F 4.1
1.732 F 0.071 16.83 F 1.25 13.4 F 5.5
those of Friend et al. (1995) who reported fewer liveborn piglets in stall-housed sows, and Bates et al. (2003) who observed higher birth weights and weaning weights in ESF-fed group-housed sows. Broom et al. (1995) found that sows in small or large groups, though initially lighter in weight than stallhoused individuals, were heavier by their fourth pregnancy. Grouped gilts in our study were, on average, 20% heavier than stall-housed gilts by the end of pregnancy, though this difference was not significant. While there were no differences in backfat by the end of pregnancy, our group-housed gilts gained less backfat in the first four weeks, an effect which might have been due to the social stress of mixing leading to higher energy expenditure (Mendl et al., 1992). It is possible that the relatively low numbers of gilts used in this study contributed to our finding of few production differences. Almost every gilt in the study developed calluses on several areas of her feet and legs, perhaps due to the condition of the slatted floor, which was uneven in places. Leeb et al. (2001) suggested that the opportunity to move around reduces the incidence of callosities, but we found no greater incidence of calluses in stall-housed animals. However, callused areas did not appear to cause pain or impair mobility. By the end of gestation grouped gilts had higher skin lesion scores than stalled animals. Unfamiliar sows fight when first mixed, but in a stable group aggression declines as dominance ranks are established (Meese and Ewbank, 1973). Although aggression was not systematically recorded in this study, informal observations suggested that fighting oc-
Stall
All differences are non-significant.
wk 4 vs. 15.1% during wk 13; P b 0.0001) and more time lying (66.3% during wk 4 vs. 72.6% during wk 13; P b 0.05). Percentages of time spent sitting, eating and drinking did not change over time. On average, gilts spent 5.3% (range 3.7% to 6.9%) of their time sitting, 3.9% (range 3.8% to 4.1%) eating, and 2.2% (range 1.3% to 3.2%) drinking. Time spent standing, lying, sitting, eating and drinking did not differ between the housing treatments.
4. Discussion There were few differences in production or reproductive performance between the two gestation housing treatments. These findings are in accordance with those of Broom et al. (1995), but differ from
Table 4 Skin lesion scores (least squares means) and probability values ( P) for group-housed ( G) and stall-housed (S) gilts, for six regions of the head and body, at wk 1 to 13 after breeding Region
Head, ears and face
Week
G
S
P
G
S
P
G
S
P
G
S
P
G
S
P
G
S
P
1 3 5 7 9 11 13
1.91 1.25 1.47 1.28 1.94 1.84 2.22
1.88 1.00 0.88 0.69 1.06 1.00 1.25
ns ns *
2.50 1.53 1.50 1.44 1.94 2.09 2.03
2.88 0.25 0.38 0.25 0.13 0.50 0.00
ns *** ** *** *** ** ***
1.81 1.38 1.25 1.53 2.13 1.78 2.50
1.63 0.00 0.13 0.00 0.00 0.38 0.25
ns *** *** *** *** ** ***
0.81 0.38 0.03 0.34 0.78 1.28 2.06
0.63 0.00 0.06 0.00 0.00 0.00 0.13
y
1.66 1.69 1.59 2.03 2.41 2.41 2.69
1.63 0.06 1.00 1.06 1.00 1.06 1.13
ns *** *** *** *** *** ***
0.19 0.56 0.63 0.59 0.91 0.84 0.91
0.50 0.69 0.25 0.19 0.69 0.19 0.25
ns ns * *** ns * **
y
y
* y
*
Shoulders and neck
Mid-body
Udder
Rump
*** ns * *** *** ***
Tail
Within a row and region, means differ ( P b 0.1); *within a row and region, means differ ( P b 0.05); **Within a row and region, means differ ( P b 0.01); ***within a row and region, means differ ( P b 0.001).
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Table 5 Skin lesion scores (least squares means) and probability values ( P) for group-housed ( G) and stall-housed (S) gilts, for six regions of the feet and legs, at wk 1 to 13 after breeding Region
Elbow
Week
G
S
P
Carpal joint G
S
P
G
S
P
G
S
P
G
S
P
G
S
1 3 5 7 9 11 13
0.63 1.06 1.09 1.00 1.25 0.97 1.31
1.06 0.88 1.25 0.56 1.00 0.25 0.88
ns ns ns
1.28 1.13 1.02 1.00 1.00 1.19 1.09
1.00 0.88 1.13 0.81 1.00 0.94 1.00
ns ns ns ns ns * *
0.88 0.97 1.22 1.06 1.06 1.06 1.16
1.44 0.94 0.69 0.56 0.88 0.88 0.69
ns ns
0.99 0.81 1.00 0.78 1.19 1.06 1.09
1.25 0.44 0.75 0.63 1.13 0.88 0.88
ns ns ns ns
0.78 1.00 1.06 0.88 1.06 1.50 1.31
0.81 1.13 1.00 0.81 0.81 1.13 1.25
ns ns ns ns
0.84 1.28 1.16 0.97 1.22 1.19 1.38
1.25 0.81 0.75 0.69 0.94 0.88 1.06
y
ns ** *
Fetlock
Accessory digit
y
* ns ns **
Hock
y
ns *
Tarsa–metatarsal joint
y y
ns
P ns y y
ns ns ns **
y
Within a row and region, means differ ( P b 0.1); *within a row and region, means differ ( P b 0.05); **within a row and region, means differ ( P b 0.01).
curred after mixing, but aggression quickly declined to very low levels. Had skin lesions in the groups resulted primarily from aggression, injuries such as cuts, scratches and bites would have been expected to appear soon after mixing followed by an improvement in skin health as aggressive interactions declined. However, in this study, lesion scores increased progressively throughout the course of gestation suggesting that injuries might have been inflicted in other ways such as by contact with pen fittings or flooring, or non-agonistic interactions between individuals such as gilts stepping on one another. This seems particularly likely in the case of the feet and legs, since aggression-related injuries are usually concentrated around the head, shoulders and torso (McGlone, 1985; Geverink et al., 1996). Gilts housed in groups had more opportunity to move around, and thus increased opportunity to sustain minor injuries, than did stall inhabitants. An exception to this finding was the lack of evidence of injuries such as bites or scratches to gilts’ vulvas. Vulva biting, a problem behaviour exhibited by sows in some group systems (den Hartog et al., 1993), was not apparent during this study, perhaps because the simultaneous stall feeding system discouraged queuing. The poorer condition of grouped gilts’ feet and legs was reflected in a tendency for higher gait scores at transfer to farrowing. Gait was not scored before gilts were allocated to gestation housing treatments, and therefore we cannot rule out the possibility that it could have differed at the start of the study. However, since animals were similar in genetic background, age, weight and experience, they probably did not differ initially. Pen design features and the opportunity
for increased locomotion on uneven slatted flooring probably contributed to the development of lameness in grouped animals. Since non-pregnant sows remained in groups, mounting by estrus sows might also have contributed. Heart rate did not differ between treatments, in contrast to a previous study in which stalled sows had higher heart rates than group-housed sows (Marchant et al., 1997). In the study of Marchant et al. the group system was straw-based and provided more space, factors which both probably encouraged higher levels of activity than were seen in the current study. We also used gilts as opposed to multiparous sows, and thus the effects of increased space had less time to exert any influence on cardiovascular fitness. The reduction in time spent standing and corresponding increase in lying time over the course of gestation reflects pregnant gilts’ increasing body weight and probable consequent reduction in ease of mobility. We observed no differences in time spent standing, lying, sitting, eating or drinking. Our behavioural observations did not include locomotion; group inhabitants obviously have more opportunity to walk than gilts housed in stalls, and time spent in locomotion would almost certainly have differed between the two housing treatments. These findings suggest that stalls confer no advantage over small groups in terms of production or reproductive performance. Higher skin lesion scores and higher gait scores did not lead to reduced production or reproduction. Skin lesions were probably uncomfortable — but the assessment of such potentially aversive sensation was not within the scope of this study. Behavioural time budget did not
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differ between group-housed and stall-housed animals. The lack of differences between the two housing treatments is perhaps not surprising. Stalls used in this study were relatively spacious, particularly for gilts whose bodies are smaller than those of mature sows. Groups provided increased opportunity for social interaction and more freedom of movement, but were otherwise rather barren, with no bedding or other environmental enrichment and little environmental complexity. Nutritional intake, which can differ between group and stall housing systems due to differences in feeding method or the opportunity to ingest bedding material, was very similar for females in our two housing treatments. Housing effects are dependent on the design of the housing system, and aspects including space allowance, feeding system and enrichment measures (for both stalls and groups), group size and group design will affect the outcome. The results of this study might not generalise to other group systems (such as those for large and/or dynamic groups, or incorporating bedding or electronic sow feeders). Some effects of gestation housing may be long-term, emerging only after sows have occupied a system for several parities.
5. Conclusion There were few differences in production, health or behavioural time budget between gilts housed for one pregnancy in groups of four with individual feeding stalls or individual gestation stalls. By the end of pregnancy group-housed animals had higher skin lesion scores and a tendency towards higher gait scores than females that had gestated in stalls. Injuries and lameness were probably related to pen design rather than a consequence of aggression and did not adversely impact performance. Welfare effects of gestation housing will vary with features of the housing system including space allowance, feeding system, enrichment measures, group size and pen design, and might be cumulative, emerging over the course of several parities. While the simplest possible conversion from a stall to a group system might comply with regulations, and allow its inhabitants the freedom of being able to turn around, it might not confer very many other advantages to its inhabitants in terms of improved welfare. Care must be taken in
the design and management of group housing systems to ensure that they achieve their objective of improved welfare for all group members. References Arey, D.S., 1999. Time course for the formation and disruption of social organisation in group-housed sows. Appl. Anim. Behav. Sci. 62, 199 – 207. Barnett, J.L., Hemsworth, P.H., Cronin, G.M., Jongman, E.C., Hutson, G.D., 2001. A review of the welfare issues for sows and piglets in relation to housing. Aust. J. Agric. Res. 52, 1 – 28. Bates, R.O., Edwards, D.B., Korthals, R.L., 2003. Sow performance when housed either in groups with electronic sow feeders or stalls. Livest. Prod. Sci. 79, 29 – 35. Boyle, L.A., Regan, D., Leonard, F.C., Lynch, P.B., Brophy, P., 2000. The effect of mats on the welfare of sows and piglets in the farrowing house. Anim. Welf. 9, 39 – 48. Broom, D.M., Mendl, M.T., Zanella, A.J., 1995. A comparison of the welfare of sows in different housing conditions. Anim. Sci. 61, 369 – 385. den Hartog, L.A., Backus, G.B.C., Vermeer, H.M., 1993. Evaluation of housing systems for sows. J. Anim. Sci. 71, 1339 – 1344. Friend, T.H., Lay, D.C., Bushong, D., 1995. Gestation in group pens improved productivity and adaptation to farrowing crates. Appl. Anim. Behav. Sci. 44, 261 – 262 (Abstr.) Geverink, N.A., Engel, B., Lambooij, E., Wiegant, V.M., 1996. Observations on behaviour and skin damage of slaughter pigs and treatment during lairage. Appl. Anim. Behav. Sci. 50, 1 – 13. Leeb, B., Leeb, Ch., Troxler, J., Schuh, M., 2001. Skin lesions and callosities in group-housed pregnant sows: animal-related welfare indicators. Acta Agric. Scand., Sect. A, Animal Sci. Suppl. 30, 82 – 87. Main, D.C.J., Clegg, J., Spatz, A., Green, L.E., 2000. Repeatability of a lameness scoring system for finishing pigs. Vet. Rec. 147, 574 – 576. Marchant, J.N., Broom, D.M., 1996. Effects of dry sow housing conditions on muscle weight and bone strength. Anim. Sci. 62, 105 – 113. Marchant, J.N., Mendl, M.T., Rudd, A.R., Broom, D.M., 1995. The effect of agonistic interactions on the heart rate of group-housed sows. Appl. Anim. Behav. Sci. 46, 49 – 56. Marchant, J.N., Rudd, A.R., Broom, D.M., 1997. The effects of housing on heart rate of gestating sows during specific behaviours. Appl. Anim. Behav. Sci. 55, 67 – 78. McGlone, J.J., 1985. A quantitative ethogram of aggressive and submissive behaviours in recently regrouped pigs. J. Anim. Sci. 61, 559 – 565. Meese, G.B., Ewbank, R., 1973. The establishment and nature of the dominance hierarchy in the domesticated pig. Anim. Behav. 21, 326 – 334. Mendl, M., Zanella, A.J., Broom, D.M., 1992. Physiological and reproductive correlates of behavioural strategies in female domestic pigs. Anim. Behav. 44, 1107 – 1121. NRC, 1998. Nutrient Requirements of Swine, 10th ed. National Academy Press, Washington, D.C.
M.J. Harris et al. / Livestock Science 102 (2006) 171–179 SAS Institute Inc., 1990. SAS/STATR User’s Guide. Version 6, 4th ed., Volume 2. Cary, NC. Terlouw, E.M.C., Lawrence, A.B., Illius, A.W., 1991. Influences of feeding level and physical restriction on development of stereotypies in sows. Anim. Behav. 42, 981 – 991. Tillon, J.P., Madec, F., 1984. Diseases affecting confined sows. Data from epidemiological observations. Ann. Rech. Vet. 15, 195 – 199.
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USDA, 2001. Part I: Reference of swine health and management in the United States, 2000, National Animal Health Monitoring System. Fort Collins, CO. #N338.0801. Vieuille-Thomas, C., Le Pape, G., Signoret, J.P., 1995. Stereotypies in pregnant sows: indications of influence of the housing system on the patterns expressed by the animals. Appl. Anim. Behav. Sci. 44, 19 – 27.
Short communication
Effects of stall or small group gestation housing on the production, health and behaviour of giltsB M.J. Harris a,*, E.A. Pajor a, A.D. Sorrells a,b,1, S.D. Eicher b, B.T. Richert a, J.N. Marchant-Forde b a
Department of Animal Sciences, Poultry Science Building, Purdue University, 125 S. Russell Street, West Lafayette, Indiana, 47907-2042, USA b Livestock Behavior Research Unit, USDA-ARS, Poultry Science Building, Purdue University, 125 S. Russell Street, West Lafayette, Indiana, 47907-2042, USA Received 11 March 2005; received in revised form 18 November 2005; accepted 19 December 2005
Abstract The effects of housing gestating gilts in groups of four ( G, n = 8) or individual stalls (S, n = 14) on production, health and behavioural time budget were evaluated. Gilts were allocated to a gestation treatment by d 7 after breeding. They were housed in a single room, floors were fully slatted with no bedding, and all conditions except for housing type were identical. Gilts were weighed and their backfat measured at wk 1 (just after moving to gestation housing), 5, 9 and 13 of pregnancy. After farrowing, litter size, sex ratio, piglet weights and mortality percentages were recorded. Skin lesions were scored using a 6-point scale every 2 wk. Gait was scored using a 6-point scale at the end of gestation. Heart rate was assessed at wk 14 to 15 after breeding. Behaviour was videotaped to collect data on body postures and ingestive behaviour for 24 h at wk 4, 6, 9 and 13 of gestation. Apart from at wk 5, when S gilts had higher backfat than G ( P b 0.05), G and S gilts did not differ in body weight or backfat during the study. Reproductive performance did not differ. While skin lesion scores did not differ at wk 1, by wk 13 lesion scores for several regions of the head, face, body, feet and legs were higher in G than S animals ( P b 0.05). There were no differences in heart rate, but gait scores at the end of pregnancy tended to be poorer in G than S gilts ( P b 0.1). As gestation progressed gilts spent less time standing ( P b 0.0001) and more time lying ( P b 0.05), but behavioural time budgets (percentages of time spent standing, lying, sitting, eating and drinking) of animals housed in G and S did not differ. In conclusion, there were few differences detected between gilts housed for one pregnancy in groups of four or stalls. Stalls in this study were relatively spacious, while group pens were relatively small and barren. Effects of gestation housing on sows’ welfare
B Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. * Corresponding author. Department of Clinical Veterinary Science, University of Bristol, Langford House, Langford, North Somerset, BS40 5DU, UK. Tel.: +44 0117 928 9404; fax: +44 0117 928 9582. E-mail address: [email protected] (M.J. Harris). 1 Present address: 513 Parnassus, UCSF-LARC, MRI 325B Box 0564, San Francisco, California, 94117, USA.
1871-1413/$ - see front matter D 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2005.12.004
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may be cumulative, taking several parities to emerge, and care must be taken in the design and management of group housing systems to ensure that they achieve their objective of improved welfare for all group members. D 2006 Elsevier B.V. All rights reserved. Keywords: Pig; Gestation; Housing; Production; Behaviour; Welfare
1. Introduction Housing pregnant pigs in individual stalls is a controversial practice. Stalls allow for easy management, individual feeding, and reduce aggressive encounters between individuals. However, freedom of movement is severely restricted, and confined sows have been shown to have reduced cardiovascular fitness (Marchant et al., 1997), reduced muscle weight and bone strength (Marchant and Broom, 1996), increased morbidity (Tillon and Madec, 1984), and engage in more unresolved aggression (Broom et al., 1995). Confinement in stalls, in conjunction with feed restriction, has been implicated in the development of oral stereotypies, repetitive, apparently functionless behaviours that probably indicate reduced welfare (Terlouw et al., 1991; Vieuille-Thomas et al., 1995). Welfare concerns have led to gestation stalls being banned or phased out in several European countries, and from 2013 the use of stalls will be restricted to the first four weeks of gestation throughout the European Union. However, stall housing is common in North America: at the time of the study approximately twothirds of sows in the United States spent their pregnancy in stalls (Barnett et al., 2001; USDA, 2001). The simplest method of converting stall housing to groups is to remove the back from gestation stalls, continuing to use the stalls for feeding and adding a communal area. Where complete re-fitting is not an option, this is likely to be the method of first choice adopted by farmers changing from stall to group gestation. While this practice might meet with the letter of legislation it is unclear whether or to what extent it would improve sow welfare, since this type of small group system offers increased freedom of movement but is otherwise rather barren. Broom et al. (1995), in the UK, compared the effects of straw-based group gestation systems with unbedded gestation stalls over four parities, finding more welfare problems in stalls than groups. By sows’ fourth parity, those housed in stalls weighed less but there were no differences in reproductive performance over all four
parities. North American sows are of different genotypes from those in the United Kingdom, and housing designs differ. Bates et al. (2003), in Kansas, compared the performance of sows housed in groups with electronic sow feeders (ESFs) with those in stalls, reporting a similar or improved performance in sows that gestated in ESF groups. In another American study, Friend et al. (1995) compared productivity of sows housed during their first three parities in groups of 3–5, comprising an indoor straw-bedded area and an outdoor area, with those in unbedded stalls. Culling rates were greater in the stall-housed than grouphoused sows and sows from stalls produced fewer liveborn piglets. No published North American study has directly compared the effects of small group and stall gestation housing under controlled conditions. The present study was designed to evaluate the effects on production, health and behavioural time budget of housing gilts for one gestation in either individual stalls or groups of four with feeding stalls. It was part of a larger, multidisciplinary examination of the effects of gestation housing on the welfare of domestic sows and their piglets.
2. Materials and methods 2.1. Facilities and animals The study was conducted at the Purdue University Swine Research and Education Center between October 2000 and March 2001. The Purdue University Animal Care and Use Committee approved all procedures. Forty-eight crossbred Yorkshire Landrace gilts were bred to crossbred Hampshire Duroc boars and allocated to either one of eight groups ( G) of four (pens measured 3.94 2.44 m and included four, 2.21 0.61 m, individual feeding stalls without backs and a rear communal area measuring 2.44 1.73 m) or 16 individual stalls (S, 2.21 0.61 m) by d 7 after breeding. Animals were allocated to a G or S based on availability and groups were composed of
M.J. Harris et al. / Livestock Science 102 (2006) 171–179
unrelated, unfamiliar females. Gilts were introduced into the housing systems in two blocks, one month apart. Within each group, a paint mark across the animals’ back or shoulders was applied to facilitate individual identification during videotaping. Individuals that returned to estrus were not re-bred but remained in gestation accommodation; only data from pregnant females were included in analyses. The single gestation room contained 8 group pens and 16 stalls. Natural lighting was provided via several windows and supplemented by fluorescent lights, which were turned on for approximately 8 h each day. Four, 25 W red lights facilitated night-time videotaping. Floors were fully slatted concrete with no bedding. Gilts were fed 1.8–2.3 kg once per day of a standard corn and soybean meal-based gestation diet, the amount dependent on stage of gestation. Temperature in the gestation room averaged 18.0 8C (range 9.3 to 27.7 8C) and relative humidity averaged 37.3% (range 24.8% to 90.6%), but both temperature and humidity fluctuated with time of day and outside weather conditions. The same stockpersons cared for all animals. Herd veterinarians checked the health of all animals monthly. No animals were removed from the study because of illness. Approximately 5 d before they were due to farrow, gilts were loaded onto a trailer and transported 100 m to the farrowing unit. Farrowing accommodation comprised two interconnected rooms, each of which contained 12 standard farrowing crates. Temperature in the farrowing rooms was set at 21 8C, with supplemental heat pads and heat lamps provided for piglets. Pre-partum gilts in the farrowing room were fed approximately 2.3 kg, once per day, of a standard corn and soybean meal-based lactation diet; intake was increased gradually to ad libitum after farrowing. Both gestation and lactation diets were formulated to meet or exceed NRC (1998) requirements for all nutrients. Farrowing was not artificially induced. If a female exhibited signs of difficulty at farrowing, she was first examined manually by a stockperson, followed if necessary by the administration of oxytocin (1 cc IM) to aid the delivery of piglets. 2.2. Production Gilts were weighed approximately 1 wk after breeding, and again at wk 5, 9 and 13 after breeding.
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On each occasion that they were weighed, gilts’ backfat was measured at the 10th rib site, 2.5 cm from the midline on the right and left sides of the body, and the mean of these two measurements recorded. Piglets from each gilt were counted within 24 h after birth, and numbers of stillborn and mummified piglets recorded. Lung floatation was used to distinguish stillborn piglets from those that had died soon after birth. Piglet deaths up to the age of weaning were noted, and stockpersons recorded the probable cause of death. Within 72 h after birth piglets were individually weighed, their sex noted, their tails were docked, needle teeth clipped, ears notched for identification, an iron injection given, and males were castrated. After weaning at 21 d, numbers of sows culled, reasons for culling and days taken to return to estrus were recorded. 2.3. Health Skin injuries were evaluated every 2 wk throughout gestation, starting 1 wk after breeding, using a scoring system adapted from Arey (1999) and Boyle et al. (2000). Seven regions of the head and body (the head, ears and face; shoulders and neck; mid-body; udder; rump; tail; and vulva) and six regions of the feet and legs (the elbows; carpal joints; fetlocks; accessory digits; hocks; and tarsa–metatarsal joints) were visually inspected and given a lesion score between 0 and 5 (Table 1). The same person (MH) assigned scores at each session. Cardiovascular function was assessed by measuring heart rate at wk 14 to 15 after breeding. At this stage, any cardiovascular effects of gestation housing would have had time to develop. Gilts were fitted with Polar Vantage NV (Polar Electro Oy, Kempele, Finland) monitors (see methodology in Marchant et al., 1995), set to record and store data Table 1 Six-point scoring system used to evaluate skin lesions for seven regions of the head and body, and six regions of the feet and legs Score
Head and body
Feet and legs
0 1 2 3
Normal (no blemish) Some reddening or callus Less than 10 scratches Less than 5 cuts or small wound 10 or more scratches 5 or more cuts or large wound
Normal (no blemish) Alopecia or callus Redness Wound or swelling
4 5
Severe wound Severe wound and severe swelling
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Table 2 Six-point scoring system used to evaluate gait (adapted from Main et al., 2000) Score
Standing posture
Gait
0
Stands squarely on all four legs
1 2
Stands squarely on all four legs Uneven posture
3
Uneven posture. Will not bear weight on affected limb Affected limb elevated off floor Will not stand unaided
Even strides. Caudal body sways slightly while walking. Able to accelerate and change direction rapidly Abnormal stride length. Movements no longer fluent. Pig appears stiff. Shortened stride. Lameness detected. Swagger of caudal body when walking. No hindrance in agility Shortened stride. Minimum weight-bearing on affected limb. Swagger of caudal body while walking. Will still trot and gallop May not place affected limb on floor while moving Does not move
4 5
averaged every 5 s, and both heart rate and behavioural data collected over a 1 h period in mid-afternoon. Gait was scored by a single observer (MH), using an adaptation of a 6-point lameness scoring system described by Main et al. (2000; Table 2), as each animal walked down the corridor during transfer to farrowing. 2.4. Behaviour During wk 4, 6, 9 and 13 of gestation, time-lapse videotape recordings were made of gilts’ behaviour. A time-lapse videocassette recorder (Panasonic AG6540P; Panasonic Video Imaging Systems Company, Secaucus, NJ), multiplexer (Panasonic WJ-FS216) and black and white video cameras (Panasonic WVBP330) were used to make a 24 h recording for all gilts. One camera was used to film one group of gilts or four stall-housed individuals. Due to technical difficulties during wk 9, for three groups of gilts and eight stalls, data from wk 8 of gestation were substituted. Preliminary observations showed that very little activity occurred in either group-housed or stall-housed animals during hours of darkness (98% of time was spent lying). Therefore behavioural observations were confined to daylight hours. From 0600 to 1800, instantaneous samples were made of each gilt’s behaviour at 10 min intervals, recording ingestive activity (eat; drink) and, when not eating or drinking, postural behaviour (stand; lie; sit).
interaction of block and housing treatment (df = 1) and time (df = 3) on body weight, weight gain, backfat and behavioural measures of activity were analysed using a repeated measures analysis of variance (Proc GLM; SAS Institute Inc., 1990), using means per group for G gilts and individual measures for S gilts. Skin lesion scores and gait scores for S and G animals were compared using Wilcoxon one-way analyses of variance (Proc NPAR1WAY; SAS Institute Inc., 1990), using mean scores per group for G females and individual scores for S females. Heart rate data were analysed to determine mean heart rates for each sow in different postures and compared between treatments using two-sample Student’s t-tests. For farrowings where intervention had taken place, percentages of piglets stillborn were removed from reproductive performance data prior to analysis, although outcomes did not differ if these data were not removed. Effects of block and housing treatment on reproductive performance were measured using analysis of variance (Proc GLM; SAS Institute Inc., 1990). Chi-square analysis was used to compare the effects of housing treatment on numbers of sows culled after weaning, and time taken to return to estrus (3–5 d; 6–8 d; 20 d or longer).
3. Results 3.1. Production
2.5. Statistical analysis All percentage data were transformed using the arcsine prior to analysis to achieve an approximately normalized distribution. The main effects of block (df = 1), gestation housing treatment (df = 1), the
Seven individuals returned to estrus, five from G and two from S; this difference was not significant. Unsurprisingly, all pregnant gilts gained weight ( P b 0.0001; Fig. 1) and their backfat measurements increased ( P b 0.0001; Fig. 2) over the course of
M.J. Harris et al. / Livestock Science 102 (2006) 171–179
3.2. Health Tables 4 and 5 show skin lesion scores from wk 1 to wk 13 of gestation for the head and body (Table 4)
210
Group Stall
Body weight (kg)
200 190 180
2.70
Group Stall
2.50 Backfat (cm)
gestation. Gilts allocated to groups or stalls did not differ in body weight or backfat at entry to gestation. During pregnancy, body weight did not differ with housing type. From wk 1 to 5 of gestation, S animals gained more backfat than those housed in G ( P b 0.01), and at wk 5, S females had higher backfat measurements than G ( P b 0.05; Fig. 2). Animals housed in G tended to gain more weight than those housed in S from wk 5 to 9 ( P b 0.1); similarly, from wk 5 to 9, G animals tended to gain more backfat than S ( P b 0.1). One female that had been G housed during gestation died in the farrowing house before giving birth, leaving data from 40 (26 G, 14 S) farrowings. There were no differences in reproductive performance between G and S gilts (Table 3). Four out of fourteen gilts that had gestated in S (28.6%) and nine out of 26 former G occupants (34.6%) were culled after their first farrowing, because of poor health, litter problems, difficulty at farrowing or failure to return to heat. Differences in numbers culled were not significant (chi-square = 0.17; df = 1). The mean weaning to re-breeding interval for previously G females bred at their first postweaning heat was 4.8 d, compared to 5.6 d in previously S females. Differences in weaning to rebreeding intervals were not significant (chi-square = 0.92; df = 2).
175
2.30
*
2.10 1.90 1.70 Week 1
Week 5
Week 9
Week 13
Time after breeding * Means differ (P<0.05)
Fig. 2. Backfat measurements (least squares means F standard error) for group-housed and stall-housed gilts, at wk 1, 5, 9 and 13 after breeding.
and feet and legs (Table 5) of G and S gilts. There were no significant differences between gilts allocated to G and S at the time of transfer to gestation. From wk 3 after breeding (2 wk after entry to gestation housing), skin lesion scores for six of the seven regions of the head and body were higher in G than S gilts (Table 4). Lesion scores for the seventh body region, the vulva, did not differ between G and S gilts, either at wk 1 ( G mean score = 0.09; S mean score = 0.31) or at any time during gestation. At wk 13 the feet and legs of gilts housed in G were in significantly poorer condition (as evidenced by higher lesion scores) than those of S animals for all regions except the hocks (Table 5). There were no differences between treatments in basal heart rates, i.e. heart rates while lying inactive with eyes closed ( G = 95.0 beats per minute [bpm]; S = 97.9 bpm), or in heart rates while standing ( G = 115.6 bpm; S = 118.7 bpm) or sitting ( G = 105.9 bpm; S = 107.0 bpm). The mean gait score for G gilts tended to be worse than that for S gilts (group mean score = 0.67; stall mean score = 0.29; P b 0.1).
170
3.3. Behavioural time budget
160 150 140 Week 1
Week 5
Week 9
Week 13
Time after breeding
Fig. 1. Body weight measurements (least squares means F standard error) for group-housed and stall-housed gilts, at wk 1, 5, 9 and 13 after breeding.
Groups in which all individuals were pregnant (n = 4), or less than all members were pregnant (n = 4) did not differ in percentages of time spent standing, lying or sitting by pregnant gilts (all statistical comparisons were non-significant). As gestation progressed, gilts spent less time standing (23.3% during
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Table 3 Reproductive performance data (least squares means F standard error) for gilts housed during gestation in groups or stalls Variable
Group
Gestation length (d) Litter size (total no. piglets) Live litter size (no. piglets born live) Percentage of piglets stillborn Litter sex ratio (males / (males + females)) Piglet weight at birth (kg) Litter weight at birth (kg) Percentage preweaning mortality (of piglets born alive)
115.30 F 0.31 9.01 F 0.66
115.33 F 0.41 9.56 F 0.86
7.81 F 0.71
8.90 F 0.93
12.6 F 5.0 0.518 F 0.043
12.0 F 6.2 0.590 F 0.057
1.687 F 0.053 15.18 F 0.93 18.1 F 4.1
1.732 F 0.071 16.83 F 1.25 13.4 F 5.5
those of Friend et al. (1995) who reported fewer liveborn piglets in stall-housed sows, and Bates et al. (2003) who observed higher birth weights and weaning weights in ESF-fed group-housed sows. Broom et al. (1995) found that sows in small or large groups, though initially lighter in weight than stallhoused individuals, were heavier by their fourth pregnancy. Grouped gilts in our study were, on average, 20% heavier than stall-housed gilts by the end of pregnancy, though this difference was not significant. While there were no differences in backfat by the end of pregnancy, our group-housed gilts gained less backfat in the first four weeks, an effect which might have been due to the social stress of mixing leading to higher energy expenditure (Mendl et al., 1992). It is possible that the relatively low numbers of gilts used in this study contributed to our finding of few production differences. Almost every gilt in the study developed calluses on several areas of her feet and legs, perhaps due to the condition of the slatted floor, which was uneven in places. Leeb et al. (2001) suggested that the opportunity to move around reduces the incidence of callosities, but we found no greater incidence of calluses in stall-housed animals. However, callused areas did not appear to cause pain or impair mobility. By the end of gestation grouped gilts had higher skin lesion scores than stalled animals. Unfamiliar sows fight when first mixed, but in a stable group aggression declines as dominance ranks are established (Meese and Ewbank, 1973). Although aggression was not systematically recorded in this study, informal observations suggested that fighting oc-
Stall
All differences are non-significant.
wk 4 vs. 15.1% during wk 13; P b 0.0001) and more time lying (66.3% during wk 4 vs. 72.6% during wk 13; P b 0.05). Percentages of time spent sitting, eating and drinking did not change over time. On average, gilts spent 5.3% (range 3.7% to 6.9%) of their time sitting, 3.9% (range 3.8% to 4.1%) eating, and 2.2% (range 1.3% to 3.2%) drinking. Time spent standing, lying, sitting, eating and drinking did not differ between the housing treatments.
4. Discussion There were few differences in production or reproductive performance between the two gestation housing treatments. These findings are in accordance with those of Broom et al. (1995), but differ from
Table 4 Skin lesion scores (least squares means) and probability values ( P) for group-housed ( G) and stall-housed (S) gilts, for six regions of the head and body, at wk 1 to 13 after breeding Region
Head, ears and face
Week
G
S
P
G
S
P
G
S
P
G
S
P
G
S
P
G
S
P
1 3 5 7 9 11 13
1.91 1.25 1.47 1.28 1.94 1.84 2.22
1.88 1.00 0.88 0.69 1.06 1.00 1.25
ns ns *
2.50 1.53 1.50 1.44 1.94 2.09 2.03
2.88 0.25 0.38 0.25 0.13 0.50 0.00
ns *** ** *** *** ** ***
1.81 1.38 1.25 1.53 2.13 1.78 2.50
1.63 0.00 0.13 0.00 0.00 0.38 0.25
ns *** *** *** *** ** ***
0.81 0.38 0.03 0.34 0.78 1.28 2.06
0.63 0.00 0.06 0.00 0.00 0.00 0.13
y
1.66 1.69 1.59 2.03 2.41 2.41 2.69
1.63 0.06 1.00 1.06 1.00 1.06 1.13
ns *** *** *** *** *** ***
0.19 0.56 0.63 0.59 0.91 0.84 0.91
0.50 0.69 0.25 0.19 0.69 0.19 0.25
ns ns * *** ns * **
y
y
* y
*
Shoulders and neck
Mid-body
Udder
Rump
*** ns * *** *** ***
Tail
Within a row and region, means differ ( P b 0.1); *within a row and region, means differ ( P b 0.05); **Within a row and region, means differ ( P b 0.01); ***within a row and region, means differ ( P b 0.001).
M.J. Harris et al. / Livestock Science 102 (2006) 171–179
177
Table 5 Skin lesion scores (least squares means) and probability values ( P) for group-housed ( G) and stall-housed (S) gilts, for six regions of the feet and legs, at wk 1 to 13 after breeding Region
Elbow
Week
G
S
P
Carpal joint G
S
P
G
S
P
G
S
P
G
S
P
G
S
1 3 5 7 9 11 13
0.63 1.06 1.09 1.00 1.25 0.97 1.31
1.06 0.88 1.25 0.56 1.00 0.25 0.88
ns ns ns
1.28 1.13 1.02 1.00 1.00 1.19 1.09
1.00 0.88 1.13 0.81 1.00 0.94 1.00
ns ns ns ns ns * *
0.88 0.97 1.22 1.06 1.06 1.06 1.16
1.44 0.94 0.69 0.56 0.88 0.88 0.69
ns ns
0.99 0.81 1.00 0.78 1.19 1.06 1.09
1.25 0.44 0.75 0.63 1.13 0.88 0.88
ns ns ns ns
0.78 1.00 1.06 0.88 1.06 1.50 1.31
0.81 1.13 1.00 0.81 0.81 1.13 1.25
ns ns ns ns
0.84 1.28 1.16 0.97 1.22 1.19 1.38
1.25 0.81 0.75 0.69 0.94 0.88 1.06
y
ns ** *
Fetlock
Accessory digit
y
* ns ns **
Hock
y
ns *
Tarsa–metatarsal joint
y y
ns
P ns y y
ns ns ns **
y
Within a row and region, means differ ( P b 0.1); *within a row and region, means differ ( P b 0.05); **within a row and region, means differ ( P b 0.01).
curred after mixing, but aggression quickly declined to very low levels. Had skin lesions in the groups resulted primarily from aggression, injuries such as cuts, scratches and bites would have been expected to appear soon after mixing followed by an improvement in skin health as aggressive interactions declined. However, in this study, lesion scores increased progressively throughout the course of gestation suggesting that injuries might have been inflicted in other ways such as by contact with pen fittings or flooring, or non-agonistic interactions between individuals such as gilts stepping on one another. This seems particularly likely in the case of the feet and legs, since aggression-related injuries are usually concentrated around the head, shoulders and torso (McGlone, 1985; Geverink et al., 1996). Gilts housed in groups had more opportunity to move around, and thus increased opportunity to sustain minor injuries, than did stall inhabitants. An exception to this finding was the lack of evidence of injuries such as bites or scratches to gilts’ vulvas. Vulva biting, a problem behaviour exhibited by sows in some group systems (den Hartog et al., 1993), was not apparent during this study, perhaps because the simultaneous stall feeding system discouraged queuing. The poorer condition of grouped gilts’ feet and legs was reflected in a tendency for higher gait scores at transfer to farrowing. Gait was not scored before gilts were allocated to gestation housing treatments, and therefore we cannot rule out the possibility that it could have differed at the start of the study. However, since animals were similar in genetic background, age, weight and experience, they probably did not differ initially. Pen design features and the opportunity
for increased locomotion on uneven slatted flooring probably contributed to the development of lameness in grouped animals. Since non-pregnant sows remained in groups, mounting by estrus sows might also have contributed. Heart rate did not differ between treatments, in contrast to a previous study in which stalled sows had higher heart rates than group-housed sows (Marchant et al., 1997). In the study of Marchant et al. the group system was straw-based and provided more space, factors which both probably encouraged higher levels of activity than were seen in the current study. We also used gilts as opposed to multiparous sows, and thus the effects of increased space had less time to exert any influence on cardiovascular fitness. The reduction in time spent standing and corresponding increase in lying time over the course of gestation reflects pregnant gilts’ increasing body weight and probable consequent reduction in ease of mobility. We observed no differences in time spent standing, lying, sitting, eating or drinking. Our behavioural observations did not include locomotion; group inhabitants obviously have more opportunity to walk than gilts housed in stalls, and time spent in locomotion would almost certainly have differed between the two housing treatments. These findings suggest that stalls confer no advantage over small groups in terms of production or reproductive performance. Higher skin lesion scores and higher gait scores did not lead to reduced production or reproduction. Skin lesions were probably uncomfortable — but the assessment of such potentially aversive sensation was not within the scope of this study. Behavioural time budget did not
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differ between group-housed and stall-housed animals. The lack of differences between the two housing treatments is perhaps not surprising. Stalls used in this study were relatively spacious, particularly for gilts whose bodies are smaller than those of mature sows. Groups provided increased opportunity for social interaction and more freedom of movement, but were otherwise rather barren, with no bedding or other environmental enrichment and little environmental complexity. Nutritional intake, which can differ between group and stall housing systems due to differences in feeding method or the opportunity to ingest bedding material, was very similar for females in our two housing treatments. Housing effects are dependent on the design of the housing system, and aspects including space allowance, feeding system and enrichment measures (for both stalls and groups), group size and group design will affect the outcome. The results of this study might not generalise to other group systems (such as those for large and/or dynamic groups, or incorporating bedding or electronic sow feeders). Some effects of gestation housing may be long-term, emerging only after sows have occupied a system for several parities.
5. Conclusion There were few differences in production, health or behavioural time budget between gilts housed for one pregnancy in groups of four with individual feeding stalls or individual gestation stalls. By the end of pregnancy group-housed animals had higher skin lesion scores and a tendency towards higher gait scores than females that had gestated in stalls. Injuries and lameness were probably related to pen design rather than a consequence of aggression and did not adversely impact performance. Welfare effects of gestation housing will vary with features of the housing system including space allowance, feeding system, enrichment measures, group size and pen design, and might be cumulative, emerging over the course of several parities. While the simplest possible conversion from a stall to a group system might comply with regulations, and allow its inhabitants the freedom of being able to turn around, it might not confer very many other advantages to its inhabitants in terms of improved welfare. Care must be taken in
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