| Experiment 1: Study of preparation optimization for fermented feed of fungus chaff pleurotus nebrodensis based on response surface methodology(RSM)The present research boosted crude protein in fungus chaff of pleurotus nebrodensis through fermentation with Candida albicans and Lactobacillus acidophilus, and then with crude protein of the fermented fungus chaff as the response value, Plackett-Burman design(PBD) and response surface methodology(RSM) were applied to identify the numerous variables influencing the fermentation process and to screen the essential factors. Based on Plackett-Burman design, Box-Behnken Central Composite Design method was adopted following a slope-climbing test on the direction and magnitude of the main effect factors to optimize these crucial factors and thus establish a model for fungus chaff of pleurotus nebrodensis fermentation. A forecast model is built using RSM and generalized regression neural network(GRNN) to find the optimal levels and interactions of the significant factors as 19.1:1 for the mass ratio of fungus chaff of pleurotus nebrodensis to corn flour, 7.0:1 for the volume ratio of Candida albicans to Lactobacillus acidophilus, 7.1% for the inoculation of bacteria solution, 2.1:1 for the ratio of material to water, and 5.0 for the initial PH value. Under these optimized conditions, the predicted value of crude protein and crude fibre were 15.70% and 16.49%, while the observed experimental results were 15.41% and 15.85% respectively. The observed and predicated values were regarded to be relatively close. The fermented fungus chaff presented an increase of 78.6% in crude protein content and a drop of 54.85% in crude fibre. The maximum viable count of Candida albicans and Lactobacillus acidophilus reached 8.7×109cfu/mL. The viable count stood at 9.8×107cfu/mL after storage at room temperature for 60 days, with mycotoxin content within the national limit of feed safety. Results obtained in this study offer a reference for the industrial production of safe mushroom fungus chaff feeds. Experiment 2: Mechanism study on the effects of fermented feed of fungus chaff of pleurotus nebrodensis on the growth performance of meat rabbitDifferent proportions of grass meal contained in meat rabbits’ basal diet were replaced by fermented feed of fungus chaff of pleurotus nebrodensis to study the effects on the growth performance of meat rabbit and its mechanism. Ninety 75±2-day-old commodity meat rabbits with similar weight were randomly assigned to five groups, with three replications per group, six meat rabbits(50% female and 50% male) in each replication. Basal diet was fed to the rabbits in the control group and residue diet was fed to the rabbits in experimental groups Ⅰ,Ⅱ, Ⅲ and Ⅳ with 40%, 60%, 80% and 100% fermented fungus chaff of pleurotus nebrodensis in the basal diet respectively. The results have revealed a remarkable increase of feed conversion efficiency and nutrient digestibility in group Ⅳ(P<0.05), suggesting a best growth performance. The results have shown a gradually increased anti-oxidation capacity and entero-enzyme activity in serum with the increase of the proportion of fungus chaff of pleurotus nebrodensis in meat rabbits’ basal diet. Immune organ index as well as quality of muscle and fur were not significantly(P>0.05) influenced. The research showed that a proper amount of fungus chaff of pleurotus nebrodensis addition is beneficial to the growth performance and physiological function of meat rabbit, and the best feed results were obtained in group Ⅳ under the conditions of this experiment. Thus, it is suggested that 100% of grass meal in meat rabbits’ basal diet be replaced by fungus chaff of pleurotus nebrodensis. |
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