Fibres from a variety of sources are a common constituent of pig feeds. They provide a means to utilise locally-produced plant materials which are often a by-product of the food or drink industry. The value of a high fibre diet in terms of producing satiety has long been recognised. However the addition of fibre can reduce feed intake, which is clearly detrimental during stages of the production cycle when nutrient needs are high, for example in growing piglets and during lactation. More recently, fibre has been found to promote novel benefits to pig production systems, particularly given the reduction in antimicrobial use world-wide, concern for the welfare of animals fed a restricted diet and the need to ensure that such systems are more environmentally friendly. For example, inclusion of dietary fibre can alter the gut microbiota in ways that could reduce the need for antibiotics, while controlled addition of certain fibre types may reduce nitrogen losses into the environment and so reduce the environmental cost of pig production. Of particular potential value is the opportunity to use crude fibre concentrates as ‘functional’ feed additives to improve young pig growth and welfare. Perhaps the greatest opportunity for the use of high fibre diets is to improve the reproductive efficiency of pigs. Increased dietary fibre before mating improves oocyte maturation, prenatal survival and litter size; providing a consumer-acceptable means of increasing the amount of saleable meat produced per sow. The mechanisms responsible for these beneficial effects remain to be elucidated. However, changes in plasma and follicular fluid concentrations of key hormones and metabolites, as well as effects of the hypothalamic satiety centre on gonadotrophin secretion and epigenetic effects are strong candidates.

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This study reports a proteomic analyses on porcine follicular fluid (FF) obtained from a previous nutritional trial, where oocytes from gilts fed a high-fibre (HF) diet for the first 19 days of their third oestrous cycle produced blastocysts with more cells following in vitro maturation (IVM) and IVF compared with oocytes from control-fed (CON) pigs. Oocytes were matured in TCM-199 supplemented with LH and FSH at 0.5 μg mL–1 and 10% of the animals’ own pooled FF. Following IVF, resultant embryos were cultured in NCSU-23 medium for 6 to 7 days. We hypothesize that FF protein composition is altered by the HF diet and that this confers the reproductive benefits previously observed. The FF had previously been stored at –80°C after the IVF trials and was thawed for the current study, which compared the protein composition of pooled Day 19 FF from 12 CON pigs and 12 HF pigs. These gilts were a subset of the pigs described above with the largest FF volumes. The protein composition of pooled FF from 6 CON pigs whose oocytes produced blastocysts was compared with FF from 6 CON pigs whose oocytes did not produce blastocysts. The same analysis was carried out with the 6 HF pigs that produced blastocysts and the 6 HF pigs that did not produce blastocysts. Equal numbers of samples from animals were selected for experimental balance. The proteomic study was carried out in duplicate. Abundant proteins were depleted from FF by Proteominer enrichment. Samples were labelled by isotopic di-methylation, where in each analysis, one sample was labelled with a heavy methyl group, the other with a light methyl group. Proteins were detected by liquid chromatography tandem mass spectrometry. Protein identifications were filtered using a 1% false discovery threshold and a requirement for two or more peptides detected for each protein. Differentially expressed proteins (DEPs) were identified as having heavy/light ratios greater than 1.2 or less than 0.8, which are recognised cut-off points for differential expression in proteomics. Over 140 DEPs were detected between CON and HF samples, indicating a nutritional influence on FF protein composition. Over one-third (37%) of these DEPs were also differentially expressed in the blastocyst versus no blastocyst analyses, suggesting that the altered FF protein composition may affect IVF outcome. DEPs were submitted into Ingenuity Pathway Analysis to highlight associated canonical pathways and upstream regulators. Top ranking canonical pathways detected included coagulation system, acute phase response, and LXR/RXR activation pathways. Potential upstream regulators detected by IPA included transforming growth factor beta, tumour protein P53, and beta-oestradiol. These pathways and upstream regulators could serve as potential avenues for elucidating the mechanism(s) by which the HF diet results in the reproductive benefits and could lead to the refinement of IVM and IVF culture conditions. This study was funded by AHDB Pork and BBSRC.