Growth and slaughter performance, nitrogen balance and ammonia emission from slurry in pigs fed high fibre diets

The aim of the work was to determine digestibility, nitrogen balance and ammonia emission from excreta, in the typical Italian heavy pig during the last phase of growth, when fed diets with a high fibre content. In comparison with a traditional control diet (C), two diets with 12 and 24% wheat bran (WB12 and WB24) and two other diets with 12 and 24% dried beet pulp (BP12 and BP24) were tested. Totally 76 Landrace x Large White fattening barrows, from 45 to 170 kg live weight distributed in 16 pens, were utilized in the trial. Thirty pigs were allocated to 6 metabolic cages in 5 consecutive periods in order to have 6 observations per treatment. For diets C, WB12 and WB24 daily weight gain (DWG), feed conversion ratio (FCR) and slaughtering performances were also registered, on 20 pigs per dietary treatment. Growing and slaughter performances were similar for pigs fed C and WB12 diets, whilst diet WB24 determined a significant (P<0.05) decrease in performances (growth and feed conversion) in the first period of fattening and a lower dressing percentage at slaughter (85.5, 84.4 and 82.5% for C, WB12 and WB24, respectively). Comparing the diets with the same level of inclusion of the fibrous feeds, WB diets had a lower OM and energy digestibility, while BP diets registered a lower protein but a higher fibre digestibility. Consistently with other experiments, BP diets determined an increase of faecal and a reduction of urinary N, as a percentage of the intake N, as well as a decrease of ammonia emission from the slurries (-16.6 and -25.3% for BP12 and BP24, in comparison with C diet). For the WB diets the reduction of urinary N and the increase in faecal N were less marked and a reduction of ammonia emissions was not registered.