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
Total IgG mg ml was measured using a com- petitive ELISA technique Varley et al., 1985. To
3.1. Ambient temperature ELISA plates coated with a known amount of
porcine IgG, a known amount of rabbit anti-pig IgG When treatments were pooled, the mean minimum
and either 0.12 ml or porcine serum diluted 1:300 daily temperature was 13.8
8C, and the mean maxi- or porcine IgG standards were added to each well.
mum temperature was 17.4 8C. The daily minimum
Following a 2-h incubation, the plate was washed temperature tended P
, 0.1 to be slightly higher in
50 S
.P. Turner et al. Livestock Production Science 66 2000 47 –55
pens housing groups of 80 pigs than groups of 20 weight was categorised into quartiles, and the ADG
14.2 vs. 13.4 S.E.D. 0.29 8C, but no difference was
of pigs in the lower and upper quartiles examined apparent in the daily maximum temperature.
individually. This indicated a suppression of growth for all pigs, regardless of initial weight, when in a
3.2. Performance large group, rather than a continuous divergence in
performance between light and heavy individuals. Neither the start weight or coefficient of variation
C.V. of start weight varied across treatments. Start 3.3. Health
weight, assessed as a covariate, did not significantly influence any of the performance parameters, and
Rectal prolapse six cases and hind-leg lameness was therefore excluded from the analysis. No inter-
due to a chronic Mycoplasmal infection 11 cases actions between group size and space were recorded,
were the principal reasons for the removal of animals so main effects only are presented in Table 1. Space
from the experiment. The number of pigs removed allowance did not significantly influence the average
from the experiment due to ill health was not daily gain ADG, but pigs in the smaller space
significantly influenced by treatment. allowance tended to consume less feed, and therefore
grow more efficiently lower FCR P , 0.1. The
ADG for the 6-week trial period was significantly 3.4. Activity
depressed in groups of 80 compared to 20 pigs, irrespective of space allowance 0.684 vs. 0.732
The percentage of the 64 recordings of activity S.E.D. 0.0142 kg day, P
, 0.01. This effect was not where the focal animal was recorded as lying was
significant during the first 2 weeks post-mixing, but, not significantly affected by treatment mean all
over this period, the C.V. of ADG tended P , 0.1 to
treatments 34.7 S.E. 2.23 of observations the pig be higher in the larger groups. Within each pen, start
activity was recorded as lying.
Table 1 Performance parameters for the two space allowances and group sizes
Treatment S.E.
Significance 20 pigs
20 pigs 80 pigs
80 pigs Group
Space size
2 2
2 2
32 kg m 50 kg m
32 kg m 50 kg m
Start weight kg 28.9
29.9 29.1
29.6 0.05
NS NS
C.V. start weight 13.3
11.9 13.4
14.0 0.85
NS NS
ADG kg pig per day:
Weeks 0–6 0.719
0.745 0.682
0.685 0.0142
NS Weeks 0–2
0.591 0.537
0.545 0.504
0.0368 NS
NS C
.V. ADG Weeks 0–6
14.6 13.4
15.4 14.3
1.21 NS
NS Weeks 0–2
20.0 21.5
27.5 29.6
3.20 P
, 0.1 NS
ADG weeks 0 –6 :
Lower quartile Start weight
0.656 0.677
0.624 0.622
0.0152 NS
Upper quartile Start weight
0.805 0.809
0.744 0.743
0.0206 NS
a
Food intake kg pig per day 1.73
1.63 1.72
1.65 0.032
NS P
, 0.1
a
FCR kg feed:kg gain 2.46
2.20 2.53
2.43 0.083
NS P
, 0.1
a
Start weight included as covariate.
S .P. Turner et al. Livestock Production Science 66 2000 47 –55
51 Table 2
Lesion score values for pooled sample pigs and for differentiated weight classes Treatment
S.E. Significance
20 pigs 20 pigs
80 pigs 80 pigs
Group Space
size
2 2
2 2
32 kg m 50 kg m
32 kg m 50 kg m
Weeks 0 –6 :
All pigs 8.0
10.5 8.7
9.0 0.59
NS Heavy pigs
8.3 10.6
9.0 11.8
0.89 NS
Medium pigs 6.6
9.4 9.1
7.3 0.69
interaction Light pigs
9.2 11.5
8.1 7.9
0.96 NS
Day 4 :
All pigs 17.3
15.7 17.4
13.0 3.19
NS NS
Heavy pigs 20.7
20.2 21.7
21.0 5.38
NS NS
Medium pigs 12.7
13.8 18.3
10.1 2.54
NS NS
Light pigs 18.6
13.3 12.4
7.8 3.84
NS NS
3.5. Aggression when in a small group and given the more generous
space allowance P , 0.01, while light weight pigs
When treatments were pooled, heavy pigs had had the lowest lesion score when in a group of 80
significantly more lesions than either medium or 8.0 vs. 10.4 S.E.D. 0.68 lesions pig for group sizes
light weight pigs on the 4th day post-mixing of 80 and 20 respectively, P
, 0.05. 20.8
611.29, 13.765.48 and 13.067.60 lesions per pig respectively, P
, 0.05. Considering the mean 3.6. Immune competence
lesion score for the total 6 week period, a trend was still apparent P
, 0.1. Overall, a larger space Total IgG concentration did not change between
allowance was associated with a lower lesion score weeks 2, 4 and 6 and was unaffected by treatment.
8.4 vs. 9.8 S.E.D. 0.42 lesions per pig, P , 0.05,
Anti-Newcastle virus IgG concentration increased Table 2. The lesion score of the heavy, medium and
significantly following each of the two challenges light weight pigs were also considered separately,
0.25 60.046, 0.7860.198 and 1.03960.215 absorb-
during both the full 6-week period and after 4 days ence at 550 nm in weeks 2, 4 and 6 respectively,
on trial Table 2. Heavy pigs displayed the fewest P
, 0.001. The basal titre of serum anti-Newcastle lesions when given the more generous space allow-
IgG, before injection of the antigen, was significantly ance over the 6 weeks 8.6 vs. 11.2 S.E.D. 0.63
higher in the groups of 80 than 20 Table 3. The
2
lesions pig for 32 and 50 kg m , respectively. week 2 value was therefore included as a covariate in
Medium weight pigs displayed the fewest lesions the assessment of the week 4 and 6 titres. Week 4
Table 3 Treatment effects on concentration of anti-Newcastle IgG absorbence at 550 nm
Week Treatment
S.E. Significance
20 pigs 20 pigs
80 pigs 80 pigs
Group Space
size
2 2
2 2
32 kg m 50 kg m
32 kg m 50 kg m
2 0.22
0.22 0.26
0.29 0.021
NS
a
4 0.85
0.75 0.85
0.67 0.043
NS
a
6 1.04
0.95 1.14
1.03 0.081
NS NS
a
Week 2 value included as a covariate.
52 S
.P. Turner et al. Livestock Production Science 66 2000 47 –55
response to injection of Newcastle virus was sig- ing phase 80 kg, the current UK legislation stipu-
nificantly poorer in pens with the lower space lates a minimum acceptable area which is over 2.5
allowance P , 0.01. Alternative analysis by re-
times smaller than that recommended for the same peated measures analysis of variance also showed a
animal on deep-litter. The extrapolation of space significant effect of space allowance P
, 0.05. requirements calculated for pigs housed on slatted
When treatments were pooled, there were no associa- flooring to those on deep-litter is inappropriate with
tions between liveweight category and total IgG or current evidence.
anti-Newcastle IgG concentration during any sam- Spoolder et al. 1997 have examined the effects
pling period. No clear interactions existed between of providing fully slatted, solid flooring without
pig weight class and treatment for either total IgG or bedding, and straw bedded ‘Straw Flow’ flooring to
anti-Newcastle IgG, suggesting that no environment finishing pigs maintained at the minimum space
disproportionately compromised the immune system allowance accepted in the Welfare of Livestock
of a given weight class of pig. Regulations 1994. No differences in performance,
weight of adrenal glands or stomach or heart abnor- malities were apparent between treatments. Skin
4. Discussion damage was lower in animals housed on solid floors
