The inclusion of ensiled citrus pulp in diets for growing pigs: Effects on voluntary intake, growth performance, gut microbiology and meat quality☆
Introduction
Alternative feedstuffs are nowadays becoming increasingly important in animal nutrition because of its availability at competitive prices. By-products of citrus processing are a major concern in the Valencia Community (Spain) which is a major citrus producing area. Citrus pulp is the residue generated by pressing fresh citrus fruits, mainly oranges, for juice extraction. During this process, 45 to 60% of their weight remains in the form of peel, rag and seeds. Fresh citrus pulp is characterized by high contents of moisture (greater than 800 g/kg; Martinez Pascual and Fernandez Carmona, 1980), soluble carbohydrates and pectins together with a low level of crude protein. With almost no starch, it is comparable in composition to sugar beet-pulp. Due to its composition and the perishable nature of this by-product, it ferments and sours easily generating environmental problems when stored. Animal nutrition could contribute to solving the environmental problem linked to its elimination. The use of citrus pulp in ruminant nutrition has been extensively documented, but little is known about its acceptability or nutritive value for pigs. According to O'Sullivan et al. (2003), dried citrus pulp may be included up to 50 g/kg in the diet of growing pigs; inclusion of 100 g/kg depressed pig performance.
In the present work, the potential use of this by-product in pig nutrition was studied in terms of growth performance, gut microbiology and meat quality.
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Materials and methods
Seventy-two pigs, barrows and females were weighed, individually identified and assigned to eighteen pens (4 pigs per pen). From 56.9 ± 6.90 kg body weight until slaughter (105.4 ± 9.97 kg) pigs were fed two diets according to their age (60 to 80 kg and 80 kg to slaughter). Within each age period, 3 dietary treatments were formulated to contain 0 (C), 50 (PM) and 100 (PH) g of ensiled citrus pulp per kg on a dry matter basis (DM). Diets with citrus pulp (PM and PH) were a mixture of C feed with the
Growth performance
Initial weights for C, PM and PH pigs were 58.1, 56.1 and 55.7 (SEM = 1.68; P > 0.05) kg. At the end of the study, pigs fed 10% citrus pulp tended to be lighter than C and PM pigs (C: 107.6, PM: 104.3 and PH: 103.2 kg; SEM = 1.31, P = 0.087). Pigs fed 5 and 10% ensiled citrus pulp in the diet showed lower ADG and ADFI when compared to C pigs (Table 2) according to O'Sullivan et al. (2003) when feeding dried citrus pulp. But, data from the present study suggest that the lower performance was due to a
Conflict of interest
The authors declare not having a conflict of interest.
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This paper is part of the special issue entitled “11th International Symposium on Digestive Physiology of Pigs”.