Breeding and genetics

1. Department of Animal Science Wageningen University Adaptation Physiology Aquaculture and Fisheries Breeding and genetics Cell Biology and Immunology Nutrition Experimental Zoology

2. Intermittent suckling: possibilities to establish pregnancy during lactation & benefits to piglets Marieke Berkeveld Rosemarijn Gerritsen Pieter Langendijk In cooperation with Veterinary Faculty in Utrecht

3. Weaning-induced growth check weaning after Weary et al., 2002

4. Feed intake shortly after weaning Many piglets hardly eat after weaning Bruininx et al., 2002

5. Weaning related problems, due to • age at weaning • not familiar with dry feed • … • Possible solution: • Make pigs familiar with dry feed before weaning

6. Intermittent suckling: Suckling inhibited for 12 h per day from D14 of lactation

7. Feed intake before and after weaning Eat before weaning = eat after weaning Kuller et al., 2000

8. Feed intake before and after weaning Kuller et al., 2000

9. Distribution of feed intake during lactation Intermittent suckling increases feed intake during lactation Kuller et al., 2000

10. Intermittent suckling increases feed intake during lactation, But weaning at conventional age still induces a growth check Possible solution: Also extend lactation without postponing next pregnancy

11. Growth in the IS model

12. Feed intake in the IS model

13. Relative growth from milk and dry feed

14. Conclusions • Intermittent suckling results in better adaptation to weaning: • Feed intake at weaning is considerably higher than normally • There is hardly any growth check at weaning • If sow is mated, lactation can be extended • Consequences for reproduction ?

15. Past experience with IS

16. Litter separation Number of sows with estrus: VARIABLE Occurrence of estrus: ASYNCHRONISED Important factors Stage of lactation Duration of separation Boar contact Parity Breed … Past experience with IS

17. Intermittent suckling model Intermittent suckling from D14 (or later) of lactation: Suckling inhibited for 12 h: IS12: 0800-2000 IS6: 0800-1400 and 2000-0200 Weaning at 6 w of lactation Reference: continuous lactation and weaning at 21 d Dalland sows

18. LH secretion during IS regime START IS 614 B LO D6.5 LH (ng/ml) Day 1 20:00 20:00 4:00 8:00 period of suckling

19. Cortisol secretion during IS regime Total separation more effective in triggering LH release and increased chance of estrus N=6 N=5 * * * * TOTSEP: sows taken away from farrowing unit PHYSEP: sows only separated physically from piglets *treatment effect

20. Estrus and ovulation *2 of 4 sows ovulated and developed cystic follicles

21. Follicle development during IS regime

22. Peri-ovulatory endocrine changes

23. Estradiol

24. Pre-ovulatory LH surge *

25. Post-ovulatory progesterone rise * * * * *

26. Cystic sows

27. LH surge and progesterone after ovulation are lower in the IS regime This does not seem to influence the number of sows ovulating and showing estrus Although IS6 sows seem to run a higher risk of developing cysts, and have delayed LH surge, estrus, and ovulation What about pregnancy?

28. Conception a,b different superscripts in one row P<0.05

29. Embryo development a,b different superscripts in one row P<0.05, c,d different superscripts in one row P<0.10

30. Lactational estrus/ovulation easily induced in IS12 model Ovulation IS6 sows seems affected Pregnancy rate (?) and early embryonic survival not affected in IS12 Placental characteristics, embryonic development seems affected by IS6 But: LH surge? – stage of lactation Progesterone output? – LH surge, feed intake, growth factors All breeds? Conceptus development during later stages of gestation? Preliminary conclusions

31. Feed intake afer ovulation and progesterone High/low feed intake from O to 6d after ovulation, subsequently weaning High: fed to requirements Low: High – 2.5 kg

32. Restoration of preovulatory LH centre in Hypothalamus. Bevers et al. 1981

33. LH surge and luteal function

34. New experiment Stage of lactation influences LH surge and luteinisation? 3 treatments: 1. IS starts at D14 2. IS starts at D21 3. Control weaned at D21

35. IGF around weaning weaning

36. IGF and luteal function 2004: IS model 2005: IS model 1997: weaned, primiparous sows

37. New experiment Stage of lactation influences LH surge and luteinisation? 3 treatments: 1. IS starts at D14 2. IS starts at D21 3. Control weaned at D21 Wean at ovulation or 30d after

38. IS in a different breed IS12 model, using Dutch Landrace x Yorkshire Boar contact 3x/d, from start of IS (D14) *Of the 21 anovulatory sows, 3 sows were removed from the experiment before treatment with PG600 Sows with ovulation showed estrus, whereas anovulatory sows did not

39. Estradiol ovulation no ovulation cystic

40. Follicle development max min

41. Estradiol in relation to follicle growth

42. IS model is promising, but room for improvement Timing of start of IS – luteinisation Timing of weaning – developing conceptus Breed differences Conclusion

43. Thank you !

46. Nutrients and villous atrophy UW unweaned SMH sow milk high WD weaned on dry feed SML sow milk low Day 4 ME intake 1470 589 557 kJ/BW0.75 The drop in nutrient supply is a major cause of intestinal atrophy Van Beers-Schreurs, 1998

47. SISP – small intestine segment perfusion test Kuller et al., 2002

48. Feed intake and absorptive function Piglets that eat already during lactation have better intestinal absorptive function post weaning Kuller et al., 2002

49. Intermittent suckling From 2 weeks of lactation, sows and piglets are separated for 12 h per day