Dr. Billy Flowers - Managing gene X environment interactions on reproductive performance of...
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Preweaning Management of Replacement Gilts and Boars
W.L. Flowers
North Carolina State University
Raleigh, N.C.
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Developmental Period
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The period just prior to birth through weaningis an active period of development for boththe testicles and ovaries.
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WeaningBirth
Most of the follicles are present at birth, but during the first 30days they begin to acquire their functional components.
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WeaningBirth
McCoard et al., 2003
Very active period of Sertoli cell proliferation and testiculardevelopment occurs during the first 30 days of life.
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1. Pre-weaning management of replacement gilts and sow longevity
2. Pre-weaning management of replacement boars and sperm production and fertility as adults.
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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.
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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.
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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.
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< 7 pigs nursing> 10 pigs nursing
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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
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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*
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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*
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How does the preweaning environment of replacement gilts influence their longevity?
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LH, FSH
Estrogens
+
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WeaningBirth
Most of the follicles are present at birth, but during the first 30days they begin to acquire their functional components.
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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
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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
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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%
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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.
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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
*
* *
*
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1. Pre-weaning management of replacement gilts and sow longevity
2. Pre-weaning management of replacement boars and sperm production and fertility as adults.
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WeaningBirth
McCoard et al., 2003
Very active period of Sertoli cell proliferation and testiculardevelopment occurs during the first 30 days of life.
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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
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Boars - ~90 weeks of age
Litter of 10Litter of 6
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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
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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
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Developmental Period
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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)
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Control ~ 40 days of ageFSH ~ 40 days of age
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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.
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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.
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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
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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
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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
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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
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Developmental Period
Early Responders(for gilts)
Birth WeightsWeaning Weights
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Graduate Students Undergraduates
Dr. Kara Stewart Nikhol GarbacikDr. Kyle Lovercamp Stefani GarbacikSara Crowell Kristy KinneyFrancis Turner Lisa ThompsonJennifer Griffith Allison Collins
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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
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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
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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
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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.
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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
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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.
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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