Quality of fermented cactus pear (Opuntia spp.) and its effect on liveweight gain of Dorper lambs
The high-water (85%) and low protein (5%) content of cactus cladodes (Opuntia spp.) reduce the amount of dry-matter consumed by ruminants. The objective of this study was to use protein enrichment technology to increase Opuntia protein content and to feed Dorper lambs, comparing the Opuntia protein enrichment and the basal diet in the liveweight gain. The experiment was carried out for 60 days, using a biodigester (100 kg of cactus) -Title No. 2641- IMPI. The process was based on the daily aerobic semisolid fermentation of Opuntia by applying yeast of the Sacharomyces cereviceae (1%) type, urea (1%) and ammonium sulfate (0.1%) during 20 h (1 h of movement and 1.5 h of rest) recycling the yeast for a week. Unfermented Opuntia cladodes were used as the control. The enriched Opuntia was provided in the final stage in two treatments in a completely randomized design with three replications: 1) Basal diet (control), and 2) Basal diet + fermented fresh Opuntia. The liveweight of each animal was recorded weekly. Analysis of variance and comparison of means were performed (Tukey HSD p=0.05 and orthogonal contrasts p?0.05). The results of the fermentation showed that fermented Opuntia significantly (p?0.01) decrease carbohydrates content (48.9 to 26.4%); increased crude protein content (5.64 to 33.17%) and energy (2.26 to 2.67 Mcal kg-1) compared with unfermented Opuntia. However, on the seventh day of fermentation, these values decreased significantly, because of the temperature decrease. At the end of the experiment, the live-weight increased significantly 11.62 ± 0.99 kg animal-1 month-1 in groups of four lambs fed with enriched Opuntia, while the liveweight of animals fed with the basal diet only increased 8.42 ± 1.69 kg animal-1 month-1, showing a difference in the liveweight gain of 800 g lamb-1 week-1 fed with fermented Opuntia cladodes.