The inclusion of ensiled citrus pulp in diets for growing pigs: Effects on voluntary intake, growth performance, gut microbiology and meat quality

Citrus pulp was evaluated as an alternative feedstuff in diets for growing-finishing pigs. Three diets were formulated on an iso-nutrient basis to contain 0 (C), 50 (PM) or 100 (PH) g of ensiled citrus pulp per kg on a dry matter basis (DM). At 56.7 ± 7.1 kg of body weight, 72 pigs were allocated into 3 groups according to the citrus pulp level in the diet. Body weight and voluntary feed intake (VFI) were recorded on days 0, 29 and 55. Backfat thickness (BF) and loin depth (LD) were measured at P2 using ultrasounds. Faecal samples were taken directly from the rectum and cultured for Enterobacteriaceae and Lactobacillus counts. At slaughter, carcass weight, BF at gluteus medius and meat colour was recorded. Also fatty acid profile in subcutaneous fat was determined. Pigs fed citrus pulp showed a lower (P<0.05) VFI on a DM basis and, consequently, a lower (P<0.05) weight gain (ADG) compared to C pigs during the first 4. weeks of study. Thereafter, no differences were found between groups. At the end of the study, C pigs showed a greater level of BF at P2 than PM and PH. The inclusion of citrus pulp significantly reduced (P<0.05) Enterobacteriaceae in faeces, not affecting Lactobacillus population. The inclusion of citrus pulp lead to no differences in BF at gluteus medius and meat colour but tended (P<0.10) to decrease carcass yield and increase oleic acid percentage in subcutaneous fat. It was concluded that growing pigs can adapt their gastrointestinal tract to citrus pulp as a source of high-fermentable carbohydrates without detrimental effects on growth performance and meat quality, and potential benefits on gut microbiology. © 2010 Elsevier B.V.