Preweaning Management of Replacement Gilts and Boars

W.L. Flowers

North Carolina State University

Raleigh, N.C.

Developmental Period

The period just prior to birth through weaningis an active period of development for boththe testicles and ovaries.

WeaningBirth

Most of the follicles are present at birth, but during the first 30days they begin to acquire their functional components.

WeaningBirth

McCoard et al., 2003

Very active period of Sertoli cell proliferation and testiculardevelopment occurs during the first 30 days of life.

1. Pre-weaning management of replacement gilts and sow longevity

2. Pre-weaning management of replacement boars and sperm production and fertility as adults.

Effect of Neonatal Litter Size on Sow Longevity

• Study was conducted with 1820 gilts in an 80,000 sow commercial production system.

• Only used litters that had between 10 and 14 pigs born alive.

• Litter size was adjusted after birth to either < 7 pigs (n=899) or > 10 pigs (n=921).

• All sows in the study had pigs fostered on and off.

Effect of Neonatal Litter Size on Sow Longevity

• After weaning, all females were managed similarly in that they were housed in the same barns during the nursery and finishing phases

• Study also had a boar exposure component.

• All sows were bred for the first time ~ 240 days of age and then monitored through 6 parities.

Effect of Neonatal Litter Size on Sow Longevity

• Farm management made culling decisions.

• Any female that did not rebreed within 10 days of weaning or failed to farrow after insemination was considered an experimental failure in terms of longevity.

< 7 pigs nursing> 10 pigs nursing

Fe

ma

les

rem

ain

ing

in p

rod

uctio

n (

%)

E = EntryB = Breeding - gilts F = FarrowingR = Rebreeding

Effect of Neonatal Lactation Litter Size on Sow Longevity

90

(Flowers et al., in press)

80

70

60

50

40

30

20

10

F1

100

0

R1 F2 R2 F3 R3 F4 R4 F5 R5 F6E B

Production phase

p < 0.05*

** * * * * * *

**

< 7 piglets

> 10 piglets

Fa

rrow

ing

ra

te (

%)

Effect of Neonatal Lactation Litter Size on Farrowing Rate

(Flowers et al., in press)

90

80

70

60

2

100

0

3 4 5 61

Sow Parity

> 10 piglets (83.3%)< 7 piglets (88.7%) p < 0.05*

Nu

mb

er

Bo

rn A

live

Effect of Neonatal Lactation Litter Size on Number Born Alive

(Flowers et al., in press)

11

10

9

2

12

0

3 4 5 61

Sow Parity

> 10 piglets (10.5 + 0.2)

< 7 piglets (11.0 + 0.1) p < 0.07*

How does the preweaning environment of replacement gilts influence their longevity?

LH, FSH

Estrogens

+

WeaningBirth

Most of the follicles are present at birth, but during the first 30days they begin to acquire their functional components.

0 5 10 15 20 25 30 35 40 45 50 55 60

Num

ber

of G

ilts

in E

stru

s 50

40

30

20

10

0

Days from Onset of Boar Exposure

Estrus Response of Crossbred Giltsgiven Boar Exposure at 140 days of age

LateResponders

EarlyResponders

Effect of Neonatal Environment on Female Response to Early Boar Exposure

Neonatal Environment

Variables < 7 pigs > 10 pigs

Proportion of gilts in estrus 77.0 53.028 days after exposure (%)

Average number born 11.3 10.8alive – early responders

Average number born 10.3 10.2alive – late responders

(Flowers et al., in press)*

*

†

†

p < 0.08p < 0.05

Fe

ma

les

rem

ain

ing

in p

rod

uctio

n (

%)

E = EntryB = Breeding - gilts F = FarrowingR = Rebreeding

Effect of Neonatal Lactation Litter Size on Sow Longevity

90

(Flowers et al., in press)

80

70

60

50

40

30

20

10

F1

100

0

R1 F2 R2 F3 R3 F4 R4 F5 R5 F6E B

Production phase

p < 0.05*

** * * * * * *

**

< 7 piglets

> 10 piglets

22%

How does the preweaning environment of replacement gilts influence their longevity?

Possibly, by affecting how efficiently they pro-duce and/or respond to reproductive hormones.

Gilt

s ex

hib

itin

g vu

lvar

sw

elli

ng (

%)

Neonatal Litter Size and Response to Low Dose of PG600

80

60

40

20

100

100

0

120 140 16080

Age of gilts (days)

> 10 piglets

< 7 piglets

p < 0.05

*

* *

*

1. Pre-weaning management of replacement gilts and sow longevity

2. Pre-weaning management of replacement boars and sperm production and fertility as adults.

WeaningBirth

McCoard et al., 2003

Very active period of Sertoli cell proliferation and testiculardevelopment occurs during the first 30 days of life.

Spring-Born(n=20)

40 boars

>9 pigs/litter

(n=10)

Fall-Born(n=20)

6 pigs/litter

(n=10)

> 9 pigs/litter

(n=10)

6 pigs/litter

(n=10)

1 day of age

2 years

Farrowing

20 weeks

8 weeks

Individual PensIndividual Pens

Pens of 10Co-mingled

Pens of 10Co-mingled

Pens of 4Co-mingled

Pens of 4Co-mingled

Weaning(3 weeks)

1 day of age

Boars - ~90 weeks of age

Litter of 10Litter of 6

Effect of Lactation Litter Size on Reproductive Parameters

Parameter 6/litter >9/litter P value

Total spermatozoa/ 98 + 3 86 + 4 0.01ejaculate (x 109)

Motility/ejaculate (%) 87 + 5 83 + 5 0.39

Normal morphology/ 89 + 6 83 + 4 0.47ejaculate (%)

Normal acrosome 90 + 5 83 + 6 0.49morphology (%)

Griffith et al., 2006

Parameter 6/litter >9/litter P value

Acrosin activity (%) 95 + 5 93 + 4 0.36

Normal capacitation (%) 84 + 6 75 + 7 0.26

Seminal plasmaproteins/ejaculate 17 + 2 10 + 2 0.11 (relative units)

Proportion of pigletssired in heterospermic 69 + 4 31 + 6 0.02matings

Griffith et al., 2006

Effect of Lactation Litter Size on Reproductive Parameters

Developmental Period

Relative Importance of Pre-weaning Growth Characteristics on Sow Longevity

Variables R2 P value

Pre-weaning gain 21.0 < 0.05

Weaning weight 15.3 < 0.05

Birth weight 5.1 < 0.10

Other variables 58.6

(Flowers et al., in press)

Control ~ 40 days of ageFSH ~ 40 days of age

Summary

• Strategic cross-fostering of litters with potential replacement animals appears to have a positive effect on adult reproductive performance.

• In sows, it might enhance their ability to respond to or produce reproductive hormones (sensitivity)

• In boars, it increases testicular size and sperm output.

What We Don’t Know

• At the present time, it is not known how much of a reduction in litter size is needed to effectively improve in each of these situations.

• The answer to this question could be related to a piglet’s birth weight.

0.24

0.20

0.16

0.12

0.08Org

an W

eigh

t (lb

s)

0 1.0 2.0 3.0 4.0

Birth Weight (lbs)

Relationships between Piglet Birth Weights and Organ Weights

0.00

(Adapted from Foxcroft et al., 2009)

Small Intestines

Liver

Brain

151413121110

98

0

Num

ber

Bor

n A

live

10 20 30 40 50

Litter Birth Weight (lbs)

Relationship between Number Born Aliveand Litter Birth Weights

151413121110

98

0

Num

ber

Bor

n A

live

10 20 30 40 50

Litter Birth Weight (lbs)

Relationship between Number Born Aliveand Litter Birth Weights

3 lb averageBirth weight

Replace-ment gilt or boarcandidates

151413121110

98

0

Num

ber

Bor

n A

live

10 20 30 40 50

Litter Birth Weight (lbs)

Number Born Alive and Litter Birth Weights

1.5 lb averagebirth weight

Market animals

Replace-ment gilt or boarcandidates

3 lb averagebirth weight

Strategiccross-fostering

Developmental Period

Early Responders(for gilts)

Birth WeightsWeaning Weights

Graduate Students Undergraduates

Dr. Kara Stewart Nikhol GarbacikDr. Kyle Lovercamp Stefani GarbacikSara Crowell Kristy KinneyFrancis Turner Lisa ThompsonJennifer Griffith Allison Collins

Piglet Birth Weights ReproductivePerformance > 3.6 lbs 2.0 - 2.8 lbs

Age at puberty 170 + 10 184 + 6(days)

Ovulation rate 15.3 + 0.7 12.9 + 0.7

Embryo survival 83 + 7 68 + 7(%)

Effect of Birth Weight on Parity 1 Characteristics

Flowers, unpublished

8 weeksBirth 12 weeks 40 weeks3 weeks

Possible Mechanisms

Development of pigletsfrom small litters

not limited as much

NutrientAvailability

Sow’s milklimits piglet

growth

Increasedresponsiveness

of gonads & brain

8 weeksBirth 12 weeks 40 weeks3 weeks

Possible Mechanisms

Pigs from small littersconsume more milk

and these compounds

Mitogensin Milk

Gut closure inpigs still notcomplete by3 to 4 days

Increasedfunction of

gonads & brain

Birth Weights of Replacement Gilts

• Significant increase in litter size in highly prolific sow lines has occurred.

• There is a well established inverse relationship between litter size and piglet birth weight.

• There is evidence that as birth weight decreases so does organ development.

1 2 3 4 5 6 7 8

13

12

11

10

9

8

0

Sow Parity

Nu

mb

er

bo

rn a

live

Typical Relationship between Productivity and Longevity in Sows

1 2 3 4 5 6 7 8

13

12

11

10

9

8

0

Sow Parity

Nu

mb

er

bo

rn a

live

Typical Relationship between Productivity and Longevity in Sows

Annual cullingrates for sowsare 40 – 60%.

Of this, highestproportion is afterparity 1.

Effect of Neonatal Environment on Growth

> 10 pigs/litter

< 7 pigs/litter

80

9

Bo

dy w

eig

ht (

kg)

SpringFall

*

*

*

Age (weeks)

12 15 180

*

9 12 15 180

*

*

60

40

20

0

100