Group Formation And Mixing Times For Gestating Sows - Dr. Jennifer Brown, from the 2015 Allen D. Leman Swine Conference, September 19-22, 2015, St. Paul, Minnesota, USA. More presentations at http://www.swinecast.com/2015-leman-swine-conference-material

1. Group formation and mixing
times for gestating sows
Jennifer Brown, PhD
Prairie Swine Centre
Saskatchewan

2. Outline
• Introduction: sows in groups
• When to mix?
– Early vs late
• Group composition
– Uniform vs mixed parities
• Other considerations…
– Socialization, group size, electronic data

3. WHO LET THE SOWS OUT???

4. Introduction
• Increasing regulation of gestation housing
– EU: 2013 stall use permitted up to 4 weeks
– Netherlands: stall use up to 5 days
– UK, Sweden: no stall housing
– Canada: stall use limited in new or renovated
barns (2014), added restrictions in 2024
• Voluntary changes- incentives for branded
products
• Packer and retailer demands

5. When to mix?
• Aggression commonly occurs when sows are mixed
• Concerns over aggression: effects on sow welfare &
productivity (Einarrson et al, 2008; Soede et al, 2007)
– Injury & lameness
– Disruption of estrus expression
– Impact of stress on conception rate, litter size
• Implantation (1-4 weeks)
– sensitive time for mixing

6. Mixing: Post-breeding
• Sows commonly mixed at confirmation of
pregnancy (21-35 days)
- Stall use allows close management from breeding to implantation
- Monitor estrus, feed consumption, breeding, preg checking
- Mixing aggression delayed until after implantation
But:
• Potential for impact on pigs in the pre-natal environment?
• What if stall use becomes more restricted?

7. Mixing: At Weaning
• At weaning
- Mixing aggression resolved before estrus/implantation
- Evidence that early mixing helps to bring sows onto heat (Pearce and
Hughes, 1992)
- Sow-to-sow contact may help to synchronize estrus
Concerns:
• Estrus behaviour (mounting) may lead to injury & lameness
• Mixing aggression may disrupt return to estrus, or inhibit estrus expression (eg in
subordinate sows)
• Added work- concerns re handling sows at breeding

8. Mixing study
Methods:
• Three treatments, tested over six replicates:
– Early Mixing (EM): Sows mixed directly at weaning
– Late Mixing (LM): Sows mixed 35 d after breeding
(Control treatment)
– Pre-socialization (PS): Sows mixed at weaning for
48hrs, then put in stalls for breeding
– Remixed at 35 d
• Collaboration with Dr. Y. Li,
University of Minnesota

9. Housing system
16
stalls
16
stalls
• Free-access stalls- 14 sows/pen
• Gilts and mixed parity sows
• 24 ft2/sow (in loafing area)
• Stalls used for feeding- otherwise locked out
Study pen

10. Data Collection
• Behaviour at mixing
– Days 1, 2: Aggressive encounters, threats (12h/day)
– Days 1-4: Sexual behaviour (EM treatment)
• Sow condition and injury
– Body condition score (1-5), weight, back fat
– At weaning, weeks 5 and 16
– Skin lesion score, gait score (0-3)
– Before & 48h after mixing
• Sow productivity
– Wean-to-service interval
– Conception rate (%)
– Farrowing performance

11. Aggression at mixing
Treatment
Behavior EM PS1 LM P
Frequency of aggressive
interactions (days 1 and 2) 208 213 212 0.993
Percentage (%) of time in
aggression (day 1) 3.20 2.54 3.55 0.637
Percentage (%) of time in
aggression ( days 1 and 2) 2.09 1.89 2.34 0.853
Aggressive interactions, days 1 and 2 (per group of 14 sows)

12. Saliva cortisol
EM PS LM
n 24 24 24
Baseline 6.54 ± 2.58 5.46 ± 0.94 5.21 ± 0.45
24hrs 7.48 ± 2.96 6.87 ± 2.21 .
72 hrs 7.76 ± 3.48 5.66 ± 1.07 .
24hrsWk5 . 5.51 ± 1.09 6.96 ± 3.10
72hrsWk5 . 7.11 ± 5.38 6.88 ± 2.41
nmol/L ±SD, four sows/group

13. Conception rate (%)
50
55
60
65
70
75
80
85
90
95
100
Early Mixing Late Mixing Pre-socialization
b
a
b
98 87 94
• LM sows had significantly lower conception
• No difference in returns or sow removals

14. Performance
• Fewer stillborn piglets in EM treatment
Treatment
Item Early Mixing Pre Socialization Late Mixing P val
Total born 15.2 ± 0.4 15.6 ± 0.4 15.5 ± 0.4 0.700
Born Alive 13.7 ± 0.4 13.3 ± 0.4 13.2 ± 0.5 0.691
Stillborn 0.95a ± 0.12 1.54b ± 0.16 1.58b ± 0.16 0.003
Mummies 0.47 ± 0.09 0.44 ± 0.09 0.53 ± 0.09 0.766
n = 84 sows/ treatment

15. • Under PSC conditions– early mixing did not affect sow
performance
• Better conception in EM and PS vs LM Control
– Clearer estrus expression/more pronounced heat?
• Fewer stillborn piglets in EM sows
– Benefits of early mixing?
Multiple options:
• Producers can select the option that suits their system
• Early mixing can reduce space requirements for barn
conversions
• Mixing post-insemination: study ongoing- common in ESF,
combined with automated heat detection
Sow mixing conclusions

16. • Within ESF systems, low-ranking sows are
known to:
– Receive more aggression and injuries
– Have poorer productivity
– Feed later in the daily feeding cycle
– Be more frequently displaced from the entry
• Already common to house gilts separately
during gestation
Grouping sows in ESF

17. Grouping sows in ESF
• Objective: Study sow groupings in a static ESF to
assess effects on feeding behavior, sow injury and
production
– Collaboration with Dr L. Greiner, Innovative Swine
Solutions, Illinois
– 6,000 sow herd
– Nedap feeding stations
– Static groups: 60 sows per group
– Recovering from PRRS outbreak

18. Grouping sows in ESF
• Four treatments
– (six replicates x60 sows= 1440 total)
• Sows distributed among treatments each week:
1. Mixed parity –Control (parities 2-7)
2. Low parity (parities 1- 3)
3. Medium (parities 3-7)
4. High parity (parities 4-8)

19. Feeding behavior
ESF stations can (theoretically) provide individual
sow data on:
• Entry order
• Feeding time, duration
• Recycling- repeated visits per day
• Example: younger sows eat later in the cycle
(Strafford et al. 2008)
• Potential for study of social dynamics, effects of
hierarchy

20. Time spent feeding
0:10:00
0:12:00
0:14:00
0:16:00
0:18:00
0:20:00
0:22:00
Mixed Low Medium High
DailyFeedingDuration(min)
Early
Mid
Late
*
Feeding time (min per sow) in early, mid, and late gestation

21. Production
Variable
Treatment
PMixed Low Medium High
Stillborn 0.63a 0.40b 0.55ab 0.81a <0.005
Piglet
mortality 1.19a 1.14a 1.51ab 1.83b <0.001
Full value
weaned 9.92a 10.22a 10.00ab 9.37b <0.005
• High parity groups had poorest reproduction
• Reflects effects of parity, not necessarily treatment
• Sows most productive between parities 3 to 6
• Treatments did not significantly affect reproduction

22. Backfat (change wks 5-15)
-5
-4
-3
-2
-1
0
1
2
3
1 2 3
changeinsowbackfat(mm)
Parity score
Mixed
Low
Medium
High
*
*
Interactions within parity score (n = 262)
Young sows in Mixed treatment lost 4mm

23. Sow lameness
Observation
period
Treatment
P
Mixed
(control) Low Medium High
Pre-mixing
to day 3 0.228 a 0.068b -0.015bc -0.09c <0.01
Pre-mixing
to day 7 0.173a 0.039b 0.001b 0.055b 0.05
• Highest lameness in Mixed parity treatment
• Negative values indicate a reduction in lameness
• Medium and High had improved locomotion day 3
Change in lameness following mixing (Score: 0 to 4)

24. Lesion score
Observation
period
Treatment
P
Mixed
(control)
Low Medium High
Premixing to
day 5
5.84b 6.90a 6.52ab 3.83c <0.001
Change in lesion scores following mixing
• Younger sow groups displayed more aggression, received
more skin injuries

25. Conclusions: Sow grouping
• It is already a common practice to house gilts
separately during gestation
• Low parity sows can also benefit from
segregation
– Increased backfat
– Reduced lameness after mixing

26. Other considerations…
• Mixing post insemination
– Integrates well with ESF systems
– Reduce stall space requirements
– Repeats can be detected automatically
• Large groups
– Flexible: Static or dynamic, batch farrowing
– Space to avoid conflict
– Sows adopt more passive social behavior

27. Automation…

28. Acknowledgements
• Specific project funding provided by:
National Pork Board
• Strategic funding provided by:

29. Questions?

30. Parity Score
SEM P
1 2 3
Treatment Treatment Treatment
Mixed Low Mixed Low Medium High Mixed Medium High
-4.12a 0.22bc -0.45bc 0.99c 0.87c 0.50bc 0.17bc 1.99bc -0.64b 1.29 <0.05
Changes in sow backfat (mm) from entering the gestation pen (5 weeks) to 15 weeks,
showing interactions among treatments within parity score (n = 262).
Within parity score, where superscripts differ, P<0.05
Backfat (change wks 5-15)