Improve nutritive value of silage based on prickly pear peel by-products

Prickly pear (Opuntia ficus-indica L. Mill) is widely cultivated in arid regions of every continent for its nutritious fruits and various commercial applications, cactus pear cladodes are used as forage in the most arid regions, while recently prickly pear by-products are studied as ruminant feed. They are characterised by a high moisture and sugar content; therefore, it is necessary to study suitable conservation methods. The aim of this study was to verify the effectiveness of silage to preserve prickly pear peels (PP) in a mixture with other by-products at different inclusion levels (5% straw and 6% or 12% wheat bran). For each treatment, six under vacuum micro-silos were prepared and, after 40 d of storage, the state of preservation was evaluated. Subsequently, the aliquots were analysed for chemical composition and incubated with sheep rumen fluid to evaluate the fermentation kinetics. The use of wheat bran and straw added to PP resulted in an increase in dry matter (DM); PP silage with wheat bran was found to have higher protein content and nutritional value. The greater presence of lactic acid was found in PP, such as acetic acid, therefore the lactic/acetic ratio was 2.33, significantly lower than silages with the addition of wheat bran. Silage with 5% straw showed the lowest level of organic matter disappearance (OMD) and the cumulative volume of gas (OMCV) produced during the incubation. The PP showed the fastest fermentation rate achieved after 12 h of fermentation, while those containing wheat bran, presented a higher maximum fermentation rate (Rmax), which need longer time to be achieved. Canonical discriminant analysis (CDA) showed clear discrimination of different silages based on their chemical characteristics and parameters detected during in vitro incubation. Overall, the silages with the addition of wheat bran can be considered the best and, of the two, those produced with the addition of 12% bran. Finally, ensilage represents a conservation technique suitable for preserving the nutritional characteristics of PP.