Alternative foods for small ruminants in semiarid zones, the case of Mesquite (Prosopis laevigata spp.) and Nopal (Opuntia spp.)

This paper provides a summary of studies conducted in our laboratory to evaluate several alternative supplements for goats in semiarid regions. Nutritional characterization was obtained for mesquite pods (Prosopis laevigata) and cacti (Opuntia ficus indica). An initial evaluation was based in comparing the size (or stage of maturity) of the cacti pads (cladodes) of O. ficus indica var. Copena. Different varieties of wild cacti (O. megacantha, O. hyctiacantha, O. robusta and O. streptocanta) were chemically analyzed. Composition of cacti pads varied from 8 to 15% DM, 5 to 7% crude protein (CP), with 10 to 30% of total N represented by CP-ADF, and ash content (7.23%) was highest (P<0.001), whereas O. streptocanta had the highest (P<0.001) Ca content. The mature cladodes had the highest organic matter (OM) digestibility (P<0.01). The intake of cacti cladodes decreased drinking water consumption (P<0.01), but increased total water consumption (drinking and food water). Small cladodes had higher effective degradation of DM (P<0.01), but less effective degradation of CP and neutral detergent fiber (NDF). Mesquite pods had a high content of soluble protein and anti-nutritional factors, which were reduced by roasting the pods. In this experiment the pods were roasted at 150°C during 45min. The roasted mesquite pods resulted in changes (P<0.01) in the OM, CP, NDF and ADF contents; the increase in fiber content appeared to be due to the formation of protein complexes with cell wall carbohydrates. Whereas the CP content was relatively high (12%), the Ca and P contents were low. Both, the mesquite pods and cacti cladodes had low Se and Co concentrations. Roasting decreased effective degradation (P<0.05) of DM, CP and NDF. Digestibility of DM, OM, CP, and NDF contents were above 60%. Roasting did not affect (P>0.05) digestibility or modified the content and activity of anti-nutritional factors. In conclusion, cacti and mesquite pods can be used as supplements for goats in semiarid regions considering their acceptable nutritional characteristics and their capacity to grow under scarce water conditions.