Integrity of gastric mucosa in reared piglets – effects of physical form of diets (meal/pellets), pre‐processing grinding (coarse/fine) and addition of lignocellulose (0/2.5 %)

Abstract

The aim of the present study was to investigate the potential effects of different particle fractions in non-pelleted (meal) and pelleted diets on the development of pre-ulcerative gastric alterations. Furthermore, the effect of increased crude fibre supply (lignocellulose) on the integrity of gastric mucosa were investigated. For that purpose, 49 piglets were divided into eight feeding groups and fed pelleted diets differing in grinding intensity (very coarse/coarse/fine/very fine) and addition of lignocellulose (0/2.5%) for 6 weeks. A coarsely ground meal was used as control diet. Mucosal integrity of the pars non-glandularis was characterised by macroscopical and histological score and basal epithelial conductance. Feed structure was assessed by sieve analysis (wet/dry). The use of coarsely ground meal (25% >2 mm, 29% <0.4 mm) had almost no negative effects on the gastric wall: three of seven pigs had slight histological and none had macroscopical lesions. Irrespective of the original grinding intensity before pelleting, offering pelleted diets led to mucosal changes similar in severity (one out of seven pigs fed coarsely ground and pelleted diets had no macroscopical alterations, whereas all pigs fed finely ground and pelleted diets showed altered tissues). Increasing the proportion of coarse particles in the pellet (from 25 to 29% >2 mm) did not show any ulceroprotective effect. An increase of crude fibre content (42-54 g/kg dm) by adding lignocellulose did not result in a decreased ulcerogenity. Unpelleted diets are recommended as more favourable for alleviating the problem of gastric ulcers in pigs as the pelleting process is equal to a secondary grinding process. According to our results, an upper level of fine particles seems to be reasonable (a minimum level of coarse particles is not ulceroprotective). In this study, an amount of 30% <0.4 mm resulted in higher risks for ulcerations.

How to assess particle size distribution in diets for pigs?

“…Moreover, the definition of a certain level of coarse particles concerning ulceroprotection does definitively not make sense, whereas the definition of an upper level of fine particles is necessary. As shown in the study of Grosse Liesner et al (2009), the "critical amount" of fine particles (b0.4 mm) is situated between 20% (no mucosal lesions) and 36% (already damage of mucosal integrity). The investigated pelleted/crumbled diets showed not seldom a micro-milled structure; most of these samples were sent in Table 1 Effects of the analysis method (dry or wet sieve analysis) on the particle size distribution of a meal diet (%; mean ± SD).…”

Effects of diet's physical form (grinding intensity; meal/pellets) on morphological and histological parameters (e.g. ratio of neutral to acid mucins) of the gastrointestinal tract in weaned piglets

“…Feeding a coarsely ground meal diet can reduce Salmonella prevalence in pork production (Visscher et al, 2009), whereas a finely ground diet has a strong impact on the incidence of gastric ulcers in pigs (Grosse Liesner et al, 2009).…”

Ulcerogenic risk assessment of diets for pigs in relation to gastric lesion prevalence

“…According to the different mesh sizes of the eight-sieved tower, four qualitative ranks were identified: coarse particles (% ≥1.4 mm); medium particles (0.8 mm ≤% <1.4 mm); fine particles (0.4 mm ≤% <0.8 mm); and very fine particles VFP (% <0.4 mm). Cut off levels of VFP mass of diets were assessed [8]: over 29% of particles <0.4 mm, microscopic mucosal lesions; over 36% particles < 0.4 mm, macroscopic gastric lesions. On this basis, three classes of ulcerogenic risk of diets were therefore assessment:…”

“…Among the parameters screened for during quality assessment and the composition of samples, grinding intensity is routinely checked in pelleted feed, as it is an issue in animal welfare [8] and public health [9,10] concerns.…”

“…Recently, advances in the etiology and pathogenesis of pigs’ gastric lesions have supplied significant tools to support veterinary practitioners in the evaluation of risks associated with the diet. These can be listed as follows: 1) the practice of increasing the proportion of coarse particles in the diet gives no ulceroprotection when the very fine particle (VFP) proportion is also greatly represented [8] and, especially in pelleted feed, coarser particles contribute to making the pellet prone to instability [14]; 2) the particle size distribution should be examined after the pelleting process as it represents a second milling [14]: as a matter of fact, the grinding phase of the manufacturing process, before pelleting, concurs to the particle size of the pellet, but the pelleting phase finalize it. Thus, the pigs could ingest higher proportions of fine particles with the pelleted diets than set in the grinding phase of the production line; 3) the VFP (<0.4 mm) proportion has been identified as a “decisive factor” and that experimental evidence suggests we should focus on this proportion of particle mass in relation to the potential ulcerogenic role exerted by the diet [8-10,15].…”