Develop strategies to augment non-immune system based defence mechanisms against gastrointestinal diseases in the pig
The use of antibiotic growth promoters is not permitted in organic and most “low input” conventional pig and poultry production systems (EC Regulation 1804/1999). However, the therapeutic use in pig production of antibiotics to treat diarrhoea caused by enteric pathogens (including strains of E. coli, Campylobacter and Salmonella spp.) is common in both organic and conventional production systems and has raised concerns about resistance development in livestock pathogens and about transfer of resistance to potential human pathogens.
A range of studies has shown that probiotic treatments based on Lactic Acid Bacteria (LAB e.g. Lactobacillus, Pediococcus and Bifidobacterium spp.) can reduce the risk of gastrointestinal infections and diarrhoea caused by enteric bacterial pathogens. A protective LAB-dominated microbial population is thought to establish spontaneously in the piglets gut and to persist in piglets prior to weaning. However, overall probiotics were shown to be less efficient then antibiotics in preventing diarrhoea. Important reasons for this are thought to be (i) the reduction in LAB cfu in the acidic environment of the stomach and (ii) the decline in LAB-population density in the upper intestine during weaning; a developmental stage when pigs are highly susceptibility to gastrointestinal diseases. It is therefore essential to identify LAB strains and/or formulations which facilitate (i) increase survival rates during stomach transfer (ii) high population densities in the intestine post-weaning. Unlike other bacteria (e.g. Lactobacillus spp.) investigated as intestinally active probiotics, Bifidobacterium strains are part of the natural intestinal microflora of adult animals including pigs and thus will initially multiply in the intestine when applied as probiotic treatment.
The addition of certain compounds (e.g. oligosaccharides, lactose containing whey) was shown to increase the competitiveness and population density of LAB in the intestine after weaning, by providing selective nutrient sources for LAB. Such “nutribiotics” are thought to improve the establishment of probiotic inocula when added in combination to the feed of newly weaned pigs. However there is little quantitative information on the effect of nutribiotics on the population density of Bifidobacterium based probiotic inocula in the pig intestine.
Survival of Lactic Acid Bacteria (LAB) as they transit the stomach to the intestine may also be improved through specific formulation methods developed for human life attenuated vaccine and probiotic treatments. Some of these formulations (e.g. those based on micro-crystals of cellulose) have a low enough cost to be used in pig production. However, there is little information on the formulation protocols required for Bifidobacterium spp. and their suitability in pig production systems.
Apart from probiotics, diets containing significant amounts of nitrate and/or isothiocyanate (e.g. green plant materials, Brassicas and/or Cassava) have recently been shown to increase the antimicrobial activity of the stomach acid and thereby the resistance of monogastric animals to bacterial pathogens. The mechanism may be exploited in organic and many “low input” pig production systems by increasing the access to forage (which contains substantial amounts of nitrate and is already encouraged in organic farming systems is some EU-countries) and by utilising oil seed rape protein or Brassica processing waste.
To address the technology requirements and deficiencies in knowledge described above we will carry out the following studies (sub-workpackages):
WP 4.3.1 Effect of probiotic inocula and/or nutribiotics on the population density of lactic acid bacteria in the upper intestine (animal studies)
WP4.3.2Effect of novel formulation technologies on the survival of probiotic inocula during transfer through the stomach (in vitro tests)
WP4.3.3 Effect of including feedstuff with a high nitrate and/or isothiocyanate (grass-clover pellets, Brassia processing waste, cassava flakes) content on the antimicrobial activity in the stomach (animal feeding study).
WP4.3.4 Effect of integrating management practices developed under WPs 4.1, 4.4 and treatments developed under WPs 4.3.1., 4.3.2 and 3.3.3 to control diarrhoea in pigs and improve meat quality (field trials on eed study replicated in farms with different rearing systems).
Environmental and sustainability audits and cost/benefit analyses on novel strategies developed under WP4.3.3 selected will be carried out as part of Horizontal activity 1 & 2. The studies under WP4.3 will provide important data/deliverables for SPs 5 & 6 (see graphics).