Ensiled citrus pulp as a by-product feedstuff for finishing pigs: nutritional value and effects on intestinal microflora and carcass quality

Abstract

Forty pigs of 76.8 ± 4.2 kg body weight were fed four different diets varying in ensiled citrus pulp (ECP) inclusion level (0, 50, 100, and 150 g of ECP/kg of diet on dry matter base). The trial lasted 5 weeks. During the last week, faecal samples were obtained to calculate apparent nutrient digestibility; also volatile fatty acids (VFA) content in faeces was determined. The digestible energy and protein of ECP was estimated by regression analysis. During the trial faecal samples were collected to determine enterobacteria and lactobacilli counts. At slaughter, carcass characteristics were registered. The inclusion of ECP in the diets decreased energy digestibility but increased neutral and acid detergent fibre digestibility linearly (p<0.05). The estimated digestible energy and protein of ECP were lower than expected (7.0 MJ/kg dry matter (DM) and 33.8 g/kg DM, respectively). Total VFA production in faeces was not affected by the diet. Both enterobacteria and lactobacilli counts were lower (p<0.01) with than without ECP inclusion at the end of the study. Carcass yield decreased linearly (p<0.05) and backfat at gluteus medius increased quadratically (p<0.05) with the inclusion of ECP in the diet. The polyunsaturated fatty acid content of the internal subcutaneous fat layer decreased quadratically (p<0.05) with the inclusion of ECP. Thus, the nutritive value of ECP for finishing pigs is low and levels of 150g/kg can negatively affect carcass yield. However, including up to 100 g of ECP/kg in finishing pig diets did not affect nutrient digestibility, carcass yield and subcutaneous fat FA profile. Additionally, increasing ECP levels in diets decreases faecal enterobacteria and lactobacilli counts in faeces.