Managing gene X environment interactions on reproductive performance of replacement gilts and boars through pre-weaning management at multiplication level is this a reality? - Dr. Billy Flowers, NCSU, from the 2011 The Allen D. Leman Swine Conference, September 17-20, 2011, St Paul, MN, USA.

1. Preweaning Management of
Replacement Gilts and Boars
W.L. Flowers
North Carolina State University
Raleigh, N.C.

2. Developmental Period

3. The period just prior to birth through weaning
is an active period of development for both
the testicles and ovaries.

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

5. Very active period of Sertoli cell proliferation and testicular
development occurs during the first 30 days of life.
McCoard et al., 2003
Birth Weaning

6. 1. Pre-weaning management of replacement gilts
and sow longevity
2. Pre-weaning management of replacement boars
and sperm production and fertility as adults.

7. 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.

8. 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.

9. 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.

10. > 10 pigs nursing < 7 pigs nursing

12. Effect of Neonatal Lactation Litter Size on Sow Longevity
100 p < 0.05
*
Females remaining in production (%)
90
80
*
70 *
60 * < 7 piglets
50 * *
* * *
40
**
30
E = Entry
20 B = Breeding - gilts
10 F = Farrowing
R = Rebreeding > 10 piglets
0
E B F1 R1 F2 R2 F3 R3 F4 R4 F5 R5 F6
Production phase (Flowers et al., in press)

13. Effect of Neonatal Lactation Litter Size on Farrowing Rate
100 < 7 piglets (88.7%) * > 10 piglets (83.3%) p < 0.05
90
Farrowing rate (%)
80
70
60
0
1 2 3 4 5 6
Sow Parity (Flowers et al., in press)

14. Effect of Neonatal Lactation Litter Size on Number Born Alive
12 < 7 piglets (11.0 + 0.1) * p < 0.07
> 10 piglets (10.5 + 0.2)
Number Born Alive
11
10
9
0
1 2 3 4 5 6
Sow Parity (Flowers et al., in press)

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

16. +
LH, FSH
Estrogens

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

18. Estrus Response of Crossbred Gilts
given Boar Exposure at 140 days of age
50 Early Late
Number of Gilts in Estrus
Responders Responders
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60
Days from Onset of Boar Exposure

19. 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* 53.0
28 days after exposure (%)
†
Average number born 11.3 10.8
alive – early responders
Average number born 10.3 10.2
alive – late responders
† p < 0.08
* p < 0.05
(Flowers et al., in press)

20. Effect of Neonatal Lactation Litter Size on Sow Longevity
100 p < 0.05
*
Females remaining in production (%)
90
80
*
70 *
60 * < 7 piglets
50 * *
* * *
40
**
30
E = Entry 22%
20 B = Breeding - gilts
10 F = Farrowing
R = Rebreeding > 10 piglets
0
E B F1 R1 F2 R2 F3 R3 F4 R4 F5 R5 F6
Production phase (Flowers et al., in press)

21. 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.

22. Neonatal Litter Size and Response to Low Dose of PG600
Gilts exhibiting vulvar swelling (%) 100 *
80
* < 7 piglets
> 10 piglets
60
* *p < 0.05
40
20
0
80 100 120 140 160
Age of gilts (days)

23. 1. Pre-weaning management of replacement gilts
and sow longevity
2. Pre-weaning management of replacement boars
and sperm production and fertility as adults.

24. Very active period of Sertoli cell proliferation and testicular
development occurs during the first 30 days of life.
McCoard et al., 2003
Birth Weaning

25. 40 boars
Fall-Born Spring-Born
Farrowing (n=20) (n=20)
1 day
1 day 6 pigs/ >9 pigs/ 6 pigs/ > 9 pigs/
of age
of age litter litter litter litter
(n=10) (n=10) (n=10) (n=10)
Weaning
(3 weeks) Pens of 10 Pens of 10
Co-mingled Co-mingled
8 weeks Pens of 4 Pens of 4
Co-mingled Co-mingled
20 weeks Individual Pens Individual Pens
2 years

26. Boars - ~90 weeks of age
Litter of 6 Litter of 10

27. Effect of Lactation Litter Size on Reproductive Parameters
Parameter 6/litter >9/litter P value
Total spermatozoa/ 98 + 3 86 + 4 0.01
ejaculate (x 109)
Motility/ejaculate (%) 87 + 5 83 + 5 0.39
Normal morphology/ 89 + 6 83 + 4 0.47
ejaculate (%)
Normal acrosome 90 + 5 83 + 6 0.49
morphology (%)
Griffith et al., 2006

28. Effect of Lactation Litter Size on Reproductive Parameters
Parameter 6/litter >9/litter P value
Acrosin activity (%) 95 + 5 93 + 4 0.36
Normal capacitation (%) 84 + 6 75 + 7 0.26
Seminal plasma
proteins/ejaculate 17 + 2 10 + 2 0.11
(relative units)
Proportion of piglets
sired in heterospermic 69 + 4 31 + 6 0.02
matings
Griffith et al., 2006

29. Developmental Period

30. 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)

31. FSH ~ 40 days of age Control ~ 40 days of age

32. 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.

33. 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.

34. Relationships between Piglet Birth Weights and Organ Weights
Small
0.24 Intestines
Liver
Organ Weight (lbs)
0.20
0.16
Brain
0.12
0.08
0.00
0 1.0 2.0 3.0 4.0
Birth Weight (lbs)
(Adapted from Foxcroft et al., 2009)

35. Relationship between Number Born Alive
and Litter Birth Weights
15
Number Born Alive
14
13
12
11
10
9
8
0
10 20 30 40 50
Litter Birth Weight (lbs)

36. Relationship between Number Born Alive
and Litter Birth Weights
3 lb average
Birth weight
15
Number Born Alive
14 Replace-
13 ment gilt
12 or boar
11 candidates
10
9
8
0
10 20 30 40 50
Litter Birth Weight (lbs)

37. Number Born Alive and Litter Birth Weights
Market animals 1.5 lb average
3 lb average
birth weight
birth weight
15
Number Born Alive
14 Replace-
13 ment gilt
12 or boar
11 candidates
10
Strategic
9
cross-
8 fostering
0
10 20 30 40 50
Litter Birth Weight (lbs)

38. Developmental Period
Birth Weights
Weaning Weights
Early Responders
(for gilts)

39. Graduate Students Undergraduates
Dr. Kara Stewart Nikhol Garbacik
Dr. Kyle Lovercamp Stefani Garbacik
Sara Crowell Kristy Kinney
Francis Turner Lisa Thompson
Jennifer Griffith Allison Collins

40. Effect of Birth Weight on Parity 1 Characteristics
Piglet Birth Weights
Reproductive
Performance > 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
(%)
Flowers, unpublished

41. Possible Mechanisms
Nutrient
Availability
Birth 3 weeks 8 weeks 12 weeks 40 weeks
Sow’s milk Increased
limits piglet responsiveness
growth of gonads & brain
Development of piglets
from small litters
not limited as much

42. Possible Mechanisms
Mitogens
in Milk
Birth 3 weeks 8 weeks 12 weeks 40 weeks
Gut closure in Increased
pigs still not function of
complete by gonads & brain
3 to 4 days Pigs from small litters
consume more milk
and these compounds

43. 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.

44. Typical Relationship between Productivity and Longevity in Sows
13
12
Number born alive
11
10
9
8
0
1 2 3 4 5 6 7 8
Sow Parity

45. Typical Relationship between Productivity and Longevity in Sows
13
Annual culling
rates for sows
12
are 40 – 60%.
Number born alive
11 Of this, highest
proportion is after
parity 1.
10
9
8
0
1 2 3 4 5 6 7 8
Sow Parity

46. Effect of Neonatal Environment on Growth
100 Fall Spring
*
*
80
*
Body weight (kg)
60
*
40
*
*
20 < 7 pigs/litter
> 10 pigs/litter
0
0 9 12 15 18 0 9 12 15 18
Age (weeks)