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Early life programming of stress responses in the farrowing sow - AW0125
Currently we do not know the correct balance of factors to optimise sow and piglet welfare at farrowing. Thus either the sow has to be restrained in a farrowing crate to protect the piglet OR piglet mortality increases when farrowing sows are given greater behavioural freedom.
One area that has recieved little attention is how the gilt or sow's early life experiences might modify her later behavioural and physiologiocal responses to the farrowing environment. This is currently an area of considerable fundamental scientific interest. The single most relevent and compelling lne of evidence suggests that brief early life experiences can cause significant changes in the stress response system and emotionally that persist into adulthood. Current thinking is that early experiences have these effects through 'programming' the sensitivity of one of the body's main stress response systems, the hypothalamic-pituitary-adrenal (HPA) axis, to stressors where programming refers to the ability of a factor, acting during a defined developmental 'window', to exert organisational effects that persist into later life. Early experiences are believed to programme later HPA (stres) sensitivity by altering the effective feedback on the HPA axis. Evidence is emerging that: the phenomenon of early life HPA programming is found in a variety of mammalian species; that it is possible to programme the HPA axis in both a positive and a negative direction; and that the species triggers for the programming are probably species-specific.
The aim of the current proposal is to extend the study of early life programming of the HPA axis to the specific problems associated with the farrowing sow. This research will differ from previous work funded by MAFF on the effects of early experience in pigs in a number of ways: (a) it will focus on the effects of brief early post-natal experiences as opposed to longer and later exposures to diferent environments. (b) It will not focus on aspects of the physical environment (e.g. environemntal enrichment), but initially on the effects of weaning age and latterly early habituation to human contact, a selection based both on scientific considerations and practical implications. (c) Finally we wil apply molecular techniques (e.g. in situ hybridisation; receptor binding studies) in collaboration with the University of Edinburgh. We will combine these measures with behavioural and physiological measures in order to test specific hypotheses about the effects of these early life experiences on brain stucture and function and behaviour. In addition that use of these molecular techniques in this contect will be important in the continuing development of 'markers' for stress and welfare in farm animal studies.
PHASE 1 (0-12 months)
Objective 1 (0-12months): To verify the existence of early life programming of the HPA axis in pigs:
Objective 2 (0-12 months): To investigate the conditions that give rise to beneficial and deleterious programming of the HPA axis in early post-natal life:
Both Objective 1 and 2 will be achieved within a single experiment conducted in Year 1 of the study.
The objectives of the experimental part (0-7 months) of Phase 1 will be:
(1) To establish protocols for applying a selected early life experience (variation in weaning age) to neonatal pigs;
(2) To record behavioural responses of individual pigs in response to a brief exposure to human contact in order to type individual behavioural styles before applying early experience treatments;
(3) To apply the early experience in a balanced design, and to collec data to measure responses of both the piglets and sows to the early experience treatments;
(4) To apply a common set of conditions (e.g. maintenance in litter groups) to the experimental animals once the application of the early experiences ceases;
(5) To test the behavioural and physiological responses of the pigs in relation to their early experiences using 2 behavioural tests ((a) human presence and (b) physical restraint) at 35-40 kg (approx 80-90 days of age);
(6) To euthanase pigs and rapidly collect brain tissue prior to and after the restraint test.
The objectives of the data analysis part of Phase 1 (6-12 months) will be:
(1) To analyse data from initial exposure to human contact using qualitative and quantitative methodologies to provide a typology of individual behavioural styles;
(2) To analyse behavioural and physiological data collected during exposure to the early experience treatments and to include in this analysis both the piglets and the sows responses; these analyses will confirm: (a) if the piglets responded appropriately to the putatively negative (early weaning age) treatment? (b) if the sows` behaviour is affected by the treatments and whether variation in sow behaviour is involved in mediating the effect of the early experience;
(4) COnduct baseline in situ hybridisation analysis of brain tissue for CRH mRNA expression in the PVN regions of the brain;
(5) Conduct baseline saturation GR binding studies of the hippocampal region;
(6) Analyse separate behavioural, physiological and neural data in relation to the experimental design; with the objective of answering the following questions: (a) Do the behavioural and physiological responses to the tests at 35-40kg indicate that weaning age has resulted in more and less stress sensitive individuals respectively? (b) Do the responses to the behavioural tests show consistency indicating that the effects of these early experiences are general and not specific to a single test? (c) Do the results of the analysis of brain structure and funstion indicate that the early experiences have programmed HPA responsiveness in a way similar to that described in the rodent literature (i.e. that the positive handling and later weaning age treatments result in up-related GR binding sites in the hippocampus, that receptor affinity has not been affected by treatment, and that CRH m RNA is reduced in the hypothalamic PVN; with opposite effects in the negative (early weaned and non-handled) treatments? (d) Do the individual behavioural typologies made at the start of the experimental period predict individual differences in reposne to the early experience treatments?
(7) Report to MAFF and review data on the effectiveness of the treatments in modifying HPA sensitivity.
Phase 2 (12-36 months):
The precise nature of the work in Phase 2 will depend on results from Phase 1. Here we have assumed that early weaning has had a measurable and negative impact on HPA responsiveness; we plan therefore to combine early weaning (12 and 42 days) with an early handling treatment in a factorial design (Appendix B gives alternative options id early weaning is found not to influence HPA responsiveness).
Objective 3: (12-26 months): To investigate the longer-term effects of early post-natal experiences on the behavioural and physiological responses of farrowing sows:
Objective 3 will be achieved in a single experiment conducted in Years 2 and 3 of the project.
The specific objectives of the experimental part of Phase 2 will be:
(1) To collect data on behavioural typologies as for Phase 1;
(2) To apply the early experiences in a balanced design to a larger sample of female pigs;
(3) To record behavioural and physological responses to the treatments to confirm their effect;
(4) To apply constant conditions from weaning to all pigs;
(5) To apply the 2 tests and collect behavioural and physiological data at 35-40 kg in order to be anle to examine consistency of response at different stages of development;
(6) To maintain gifts under common conditins (including maintenance in litter groups) through to service;
(7) To serve in litter groups using Al;
(8) To maintain in litter groups under constant conditions hrough pregnancy;
(9) To operate on a selection of gilts prior to parturition to implant jugular catheters; we will contrast the behaviour and parturition performance of catheterised and non-catheterised gilts as catheterisation invloves a greater amount of handling of the animals;
(10) To expose gilts toe ither farrowing crates or to farrowing pens in a balanced deign that allows analysis of the interation between early experience and farrowing environment;
(11) To collect behavioural and physiological data of the gilts responses to the farrowing and also of piglet neonatal viabilty.
The objectioves of the analysis of Phase 2 will be:
(1) To analyse behavioural and physiological data to produce individual typologies and to confirm the effects of the arly experience treatments as for Phase 1;
(2) To analyse data from the tests at 35-40 kg;
(3) To analyse behavioural and physiological data from the farrowing period;
(4) To perform on overall analysis of the dtat to answer the following questions: (a) Do the behavioural and physiological responses to the farrowing environment indicate that the early life experiences have programmed HPA activity as predicted and altered the adaptive capacity of the gifts to the farrwoing environment? (i.e. we would predict that the early handled and later weaned gilts would show reduced behavioural and physiological responses to the farrowing environemnt, faster parturitiions, increased viability of piglets, reduced aggression to piglets; opposite effects would be expected in the control and maternally deprived groups); (b) Is there individual consistency between the responses at 30-40 kg and the later reponses to the farrowung environemnt? (c) Do the initial individual typologies predict individual resposnes to the treatments and at later stahes of development?
(5) To report to MAFF the overall results of the work with a clear indication of the efficacy of brief and early life experiences in programming the HPA axis and in adjusting the later sensitivity of the developing pig to potentially stress or fear inducing environmental challenges and specifically to the farrowing environment.
Final Report : Early life programming of stress responses in the farrowing sow.
Time-Scale and Cost
Contractor / Funded Organisations
University - Scottish Agricultural College
Fields of Study