Livestock Production Science 66 2000 47–55 www.elsevier.com locate livprodsci
The effect of space allowance on performance, aggression and immune competence of growing pigs housed on straw deep-
litter at different group sizes
a,b , a
a c
S.P. Turner , M. Ewen , J.A. Rooke , S.A. Edwards
a
Scottish Agricultural College , Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen, AB21 9YA, UK
b
Scottish Agricultural College , Sir Stephen Watson Building, Bush Estate, Penicuik, Midlothian, EH26 0PH, UK
c
Department of Agriculture , University of Aberdeen, King Street, Aberdeen, AB24 5UA, UK
Received 29 June 1999; received in revised form 29 November 1999; accepted 17 December 1999
Abstract
Legislation controlling minimum floor space allowances for pigs rarely allows flexibility for variations in the physical and social environment. The space requirement of pigs housed in large groups and on deep-straw bedding has not been
2
adequately addressed. Pigs, housed on deep-straw for 6 weeks in groups of 20 or 80, were provided with a low 50 kg m
2
or high 32 kg m space allowance in an experiment of 2 3 2 factorial design replicated four times. Low space allowance,
irrespective of group size, did not influence average daily gain ADG, but tended to improve efficiency of growth P , 0.1.
Groups of 80 pigs had a lower ADG than groups of 20 0.684 vs. 0.732 S.E.D. 0.0142 kg day, P , 0.01. Within pen
variation in ADG was similar for each treatment. Number of skin lesions were elevated by low space allowance 10.1 vs. 8.5 s.e.d. 0.68 lesions per pig for low and high space allowance respectively, P
, 0.05. The humoral response to an antigen challenge Newcastle disease virus was lower when provided with small space allowance P
, 0.01. Since the main effects did not interact, the poorer ADG of large groups, and the higher lesion score and suppressed immune response of pigs
provided with lower space allowance, suggest that these conditions may independently compromise productivity and welfare.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Pig; Space allowance; Group size; Deep-litter, Performance; Immune response
1. Introduction the severity of this limitation often fail to consider
aspects of the housing conditions such as the ambient In commercial housing systems, space is a re-
temperature and floor type Edwards et al., 1988. source which is limited in the interests of efficiency
The majority of experiments to date have been of building utilisation. Recommendations governing
carried out in housing with fully slatted floors or minimal bedding. In deep-litter systems, it might be
predicted that a greater space allowance will be
Corresponding author. Tel.: 1 44-131-535-3200; fax: 1 44-
required for the maintenance of satisfactory pen
131-535-3121. E-mail address
: s.turnered.sac.ac.uk S.P. Turner.
conditions due to the increased level of activity
0301-6226 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 3 0 1 - 6 2 2 6 0 0 0 0 1 5 9 - 7
48 S
.P. Turner et al. Livestock Production Science 66 2000 47 –55
Lyons et al., 1995, lack of a clearly differentiated was carried out to measure the performance, aggres-
lying and excretory area and infrequent removal of sion and immune competence of pigs housed on
excreta from within the pen. deep-straw bedding in either a conventionally sized
No differential legislation or national codes exist group 20 pigs pen or a large group 80 pigs pen
regarding the space requirements of pigs housed in when provided with a space allowance representative
deep-straw bedded systems and values recommended of the upper or lower quartile of the range of space
by different UK Quality Assurance schemes vary. allowances used in commercial practice for deep-
However, a value of 15 square feet per growing or litter housing.
finishing pig housed on deep-straw has been rec- ommended widely in the UK based on commercial
experience A.T. Smith, Agricultural Development
2. Materials and Methods
and Advisory Service, personal communication; S.A. Edwards, Scottish Agricultural College, personal
2.1. Experimental design and treatments communication. Expressed in terms of liveweight
per square metre of floor space, this equates to a A total of 800 Large White X Landrace growing
2 2
mean stocking rate of 43 kg m , allowing 22 kg m pigs start weight: 29.7 S.E. 0.16 kg were housed on
2
at the beginning of the growing phase and 64 kg m deep-straw, and assigned, for 6 weeks, to one of four
at the end of the finishing phase. For weaner pigs, a treatments. A 2
3 2 factorial arrangement, replicated value of eight square feet has also been suggested
four times, of two group sizes and two space P.I.C., 1994, which translates to a stocking rate at
allowances, was used. The group sizes were 20 and
2 2
the end of the weaner phase of 40 kg m . However, 80 pigs, and the space allowances were 50 kg m
2
no critical experiments have been carried out on low and 32 kg m high. The groups of 20 were
which to base such recommendations, and they are formed by mixing pigs from three smaller pens, and
greatly in excess of current legislative requirements the groups of 80 from 12 pens, such that the mean
EC Council Directive 91 630. number of pigs taken from each original pen was
To the list of factors which might influence space consistent. All animals experienced the same man-
requirement may also be added the effect of varia- agement procedures and similar social and physical
tions in the social environment. Although the in- environments before introduction to the experiment.
fluence of variables such as group size have been The space allowance was maintained by a weekly
studied in association with space allowance for many assessment of mean liveweight and the movement of
years, the two factors have rarely been considered a partition to extend the pen length accordingly. The
independently of each other Krider et al., 1975; ratio of pigs to drinkers 10 pigs per bite drinker and
Mitchell et al., 1983; Kornegay and Notter, 1984. feeder space 61 mm trough length per pig was
Where these factors have been differentiated, the maintained constant. The percentage of males to
group sizes adopted have consistently been small females was similar in each pen 54.2 S.E. 0.02
Bryant and Ewbank, 1974; Brumm, 1996. The males and did not significantly vary across treat-
social environment in large groups of pigs has not ments. Dry pelleted feed was offered ad libitum
been sufficiently described Edwards and Turner, 19.5 crude protein, 5 crude fibre, 1.15 lysine,
2000, and the implications of this for space require- 13.3 MJDE kg. The experiment was performed
ments are unknown. The applicability of current between May and December and ambient tempera-
legislation and recommendations regarding space ture was recorded daily for each treatment. Bedding
allowance is therefore questionable under these was replaced at 4-week intervals and fresh straw was
conditions. Since, for reasons of mechanisation of provided daily.
straw and manure handling, it is very common for deep-litter systems to operate with large group sizes,
2.2. Performance it is necessary to evaluate whether this factor will
modify space requirements. Individual liveweight was recorded on the day of
To address these issues, the present experiment mixing and again after 2, 4 and 6 weeks. The pen
S .P. Turner et al. Livestock Production Science 66 2000 47 –55
49
mean average daily feed intake ADFI and feed and the amount of rabbit anti-pig IgG bound to the
conversion ratio FCR were calculated from records pig IgG coating each well was measured following
of the weight of feed offered and that refused. the introduction of peroxidase-conjugated anti-rabbit
IgG antiserum. The absorbence value was inversely 2.3. Activity
related to the quantity of IgG present in the serum sample.
Fifteen pigs, five each of heavy 34.9 kg S.E. Anti-Newcastle IgG in pig serum was measured
0.21, medium 29.6 kg S.E. 0.17 and light 24.5 kg using a modification of the Flockscreen
E non-com- S.E. 0.18 start weight, were selected from each pen.
petitive ELISA assay for chicken serum Guildhay The activity, classified as active running, walking,
Ltd., Surrey, UK, kit number V120; alkaline phos- standing, sitting or inactive lying was recorded for
phatase-conjugated donkey anti-chicken IgG was each of these 15 pigs at weeks 0, 2, 4 and 6. Sixteen
substituted with alkaline phosphatase-conjugated rab- recordings were made at 15-min intervals, with eight
bit anti-pig IgG. Alkaline phosphatase activity was observations being performed on each of two con-
measured at 550 nm using phenolphthalein mono- secutive days during these weeks. A single observer
phosphate as substrate. Amounts of porcine anti- therefore made 64 recordings per animal.
Newcastle IgG were expressed as arbitrary absorb- ence values. The ELISA assay utilised a highly
2.4. Aggression purified viral sub-unit antigen selected for its high
specificity towards paramyxovirus serotype 1 organ- The skin lesion score of the sample pigs used for
isms and which would not cross-react with organ- the assessment of activity was recorded at 4 days
isms of paramyxovirus serotypes 2 and 3. post-mixing, and at the end of the first and all
subsequent weeks. Fresh cuts, scratches and abra- 2.6. Statistical analysis
sions were counted by a single observer throughout. All parameters were assessed using pen means as
2.5. Immune competence the statistical unit by analysis of variance on the
Minitab computer program Minitab Inc., PA, USA, Six pigs per pen, two each of heavy, medium and
incorporating as factors, replicate, space category light weight classes, were randomly selected from
and group size and their interaction. The influence of the sample pigs used for the activity analysis. A
treatment on immune competence was also analysed blood sample was taken via jugular venepuncture
by a repeated measures analysis of variance using as after 2 weeks on trial and was immediately followed
factors, replicate, space category, group size, week of by an intra-muscular injection of 2 ml inactivated
sampling and the interactions. The effect of treat-
Newcastle disease virus Nobilis Newcavac, Inter-
ment on different focal pig weight categories was vet UK Ltd., Cambridge, UK. After 4 weeks on
examined using analysis of variance on each weight trial, a blood sample was taken and again followed
category independently. The number of animals by a second injection of Newcastle disease virus. A
removed from the experiment due to ill health was third blood sample was collected after 6 weeks on
compared across treatments by a chi-squared test. trial. Following centrifugation, serum samples were
analysed for total IgG concentration and Newcastle virus specific IgG.
3. Results
