Effect of grinding intensity and crude fibre content of the feed on growth performance and gastric mucosa integrity of growing-finishing pigs

The influence of the interaction between crude fibre content and grinding intensity of the diet on performance results and gastric mucosa integrity was studied in a 2×2 factorial trial. Therefore, the 4 treatments were: low fibre-finely ground, low fibre-coarsely ground, high fibre-finely ground and high fibre-coarsely ground. Ninety-six pigs were allotted to 16 pens, with 3 barrows and 3 gilts per pen. Each pen was randomly assigned to 1 out of 4 treatments, leading to 4 pens per treatment. The low fibre diet contained 4% crude fibre, and the high fibre diet 9%. The higher fibre content was achieved by including beet pulp and alfalfa in the diet and using soybean meal with a lower protein content. The finely ground feed was produced using a hammermill with a screen of 1.5mm for grinding the ingredients, the coarsely ground was produced with a screen of 6mm. Three-phase feeding was applied and within each phase, diets were formulated to be identical in net energy, crude protein, digestible lysine, methionine+cystine, threonine and tryptophan content. No significant interaction between grinding intensity and crude fibre content on performance was observed, although, during the second feeding phase (40-70kg), a small effect on feed intake was noticed. Performance results were not significantly affected by grinding intensity. While crude fibre content did not affect the growth performance during the first or second feeding phase, an adverse effect on feed conversion ratio was noticed during the third feeding phase. Possibly, the net energy content of the high fibre diet was overestimated in the third phase. Macroscopic lesion scores of the pars oesophagea of the stomach were not affected by grinding intensity or crude fibre content exclusively. However, animals on the coarsely ground high fibre diet showed lower macroscopic lesion scores, indicating a synergistic effect of grinding intensity and crude fibre content on preventing lesions in the gastric mucosa.