Group formation and mixing times for gestating sows

Jennifer Brown, PhDPrairie Swine Centre

Saskatchewan

Outline

• Introduction: sows in groups• When to mix?– Early vs late

• Group composition–Uniform vs mixed parities

• Other considerations…– Socialization, group size, electronic

data

WHO LET THE SOWS OUT???

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

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

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?

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

Mixing studyMethods:• 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

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

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

Aggression at mixing

  Treatment  Behavior EM PS1 LM P

       Frequency of aggressive interactions (days 1 and 2) 208 213 212 0.993Percentage (%) 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)

Saliva cortisol  EM PS LMn 24 24 24Baseline 6.54 ± 2.58 5.46 ± 0.94 5.21 ± 0.4524hrs 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 ± 3.1072hrsWk5 . 7.11 ± 5.38 6.88 ± 2.41

nmol/L ±SD, four sows/group

Conception rate (%)

Early Mixing Late Mixing Pre-socialization50

55

60

65

70

75

80

85

90

95

100

b

a

b

98 87 94

• LM sows had significantly lower conception• No difference in returns or sow removals

Performance

• Fewer stillborn piglets in EM treatment

TreatmentItem 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

• 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

• 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

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

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)

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

Time spent feeding

Mixed Low Medium High0:10:00

0:12:00

0:14:00

0:16:00

0:18:00

0:20:00

0:22:00

EarlyMidLate

Dai

ly F

eedi

ng D

urat

ion

(min

) *

Feeding time (min per sow) in early, mid, and late gestation

Production

Variable

Treatment

PMixed Low Medium High

Stillborn 0.63a 0.40b 0.55ab 0.81a <0.005Piglet mortality 1.19a 1.14a 1.51ab 1.83b <0.001Full 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

Backfat (change wks 5-15)

1 2 3

-5

-4

-3

-2

-1

0

1

2

3

MixedLowMediumHigh

Parity score

chan

ge in

sow

bac

kfat

(m

m)

*

*

Interactions within parity score (n = 262)

Young sows in Mixed treatment lost 4mm

Sow lameness

Observation period

Treatment

PMixed

(control) LowMediu

m HighPre-mixing to day 3 0.228 a 0.068b -0.015bc -0.09c <0.01Pre-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)

Lesion score

Observation period

TreatmentPMixed

(control)

Low Medium High

Premixing to day 5 5.84b 6.90a 6.52ab 3.83c <0.00

1

Change in lesion scores following mixing

• Younger sow groups displayed more aggression, received more skin injuries

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

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

Automation…

Acknowledgements• Specific project funding provided by:

National Pork Board

• Strategic funding provided by:

Questions?

Parity Score  SEM

 P

1 2 3Treatment Treatment Treatment

Mixed Low Mixed Low Medium HighMixe

d 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)