Prickly Pear By-Product in the Feeding of Livestock Ruminants: Preliminary Investigation

SIMPLE SUMMARY: The question of sustainability of animal nutrition has become a popular topic. The gains made by recycling safe, yet otherwise valueless, by-products and wastes from human food and fiber production (green feeds) may lessen the competition between humans and animals for crops and decrease the environmental impact of food production. In this context, prickly pear by-product, which results from Opuntia ficus-indica (L.) Mill. fruits processed for juice extraction, could be an optimum by-product to ruminant feeding. This study evaluates the nutritional characteristics and its stability during storage using potassium metabisulfite as a preservative agent. This preliminary investigation showed this by-product could represent, for its chemical composition, an interesting and suitable feeding source to be used to increase the environmental and economic sustainability of ruminant livestock. On the basis of the results, the use of preservative was able to slightly slow down the early phase of the acidification process and limit the presence of spoilage microorganisms after a three-week storage period. The high content of soluble sugars in the prickly pear by-product suggests that a likely storage technique could be ensiling the mass with straw. ABSTRACT: In Sicily, the current increasing cultivation of Opuntia ficus-indica corresponds to an availability of prickly pear by-product (PPB) that results from fruit processing for juice extraction. This investigation aims to evaluate the nutritional traits of PPB for ruminant feeding and its stability during a 21-day outdoor storage, using potassium metabisulfite (PMB) as a preservative agent, added to the PPB mass at different doses (0, 50, 100, and 150 g/kg). The fractioning of PPB showed that it included 28% of peel and pulp and 72% of seeds on a dry matter (DM) basis. On the whole, this by-product was low in crude protein (5.32% DM), high in fiber content (51.38%, 41.15% and 14.64% DM for NDFom, ADFom and ADL respectively), non-fiber carbohydrates (NFC, 29.68% DM), and soluble sugars (13.3% DM), with a moderate level of net energy for lactation (4.59 MJ/kg DM). Storage was the main factor of alteration of PPB chemical composition with the exception of ether extract. A decline of NFC and soluble sugars, due to microbial fermentation, was observed with all PMB treatments, especially during the first week of storage, probably due to evolution of both coccus (M17) and rod LAB (MRS), which increased their loads at the seventh day of storage.