Italy is the third largest producer of Opuntia fruits in the world after Mexico and the United States, and 97.72% of these fruits produced by Italy are grown in Sicily. The use of prickly pear fruits or juice leads to a high production of by-products. In this study, ensiling was chosen to preserve prickly pear peels (PPPs) and “pastazzo” (PPS) mixed with 12% wheat bran.
PPP silage presented a lower DM than PPS silage (20.03 vs. 41.37%; p < 0.01), as well as aNDFom (25.31 vs. 66.66% DM; p < 0.01), but had the best protein content (12.02 vs. 9.55% DM; p < 0.01). For both by-products, fermentation proceeded rapidly with increasing temperature, with the temperature for PPS (38 ◦C) being higher than that for the PPP (30 ◦C). Mesophilic LAB (lactic acid bacteria) were detected at higher levels than thermophilic LAB, and rod counts were higher than cocci counts.
The detected organic acids and silage pH indicate an optimal fermentation process for these by-products. PPP silage had a higher polyphenol content than PPS silage (30.24 vs. 24.22 mg GAE/g DM; p < 0.01) and, consequently, also higher antioxidant activity. The results of this study on the mineral composition and macro- and micro-nutrients in silage highlight that these by-products are sources of minerals, with high levels of potassium, calcium, and magnesium.
Prickly pear by-products are characterized by low dry matter content, a fact that could be a negative factor for the ensiling process. However, the results found in this study highlight how PPP and PPS silages are suitable low-cost feeds for ruminant nutrition.
The silages had an optimal pH and organic acid contents, with high levels of beneficial LAB counts and without the presence of spoilage or pathogenic bacteria. The total content of the polyphenols was found to be high compared to the other prickly pear by-products analyzed in other countries; consequently, the antioxidant capacity was found to be high in both the by-products and the silage, highlighting its persistence during ensiling.
Additionally, the minerals, including both macro-elements and micro-elements, highlighted that these by-products are a source of minerals, particularly potassium, calcium, and magnesium. The differences found between the nutritional characteristics of the PPP and PPS silages highlight better results for the PPP silage, which is also richer in polyphenols and, consequently, has greater antioxidant activity; furthermore, its richness in macro- and micro-elements makes PPP silage a mineral supplement without toxicity problems for sheep.