Preparation And Performance Of Olive Leaf Extracts For Feed Additives And Its Application In Broiler Feeding

Antibiotic-induced bacterial resistance and drug residues have caused widespread concern,and it is necessary to find feed additives that replace antibiotics.Olive leaves contain a variety of active ingredients,such as polyphenols,flavonoids,carbohydrate,organic acids,saponins,and terpenoids,etc.Based on this,this paper mainly studie d the preparation and application of olive leaf extract,compared the effects of different extraction methods on the extraction yield of active ingredients of olive leaves,studie d the physicochemical properties,bacteriostatic properties and stability of extract powder,test ed its effects on the growth of broilers through feeding experiments.The specific research contents were as follows:Active substances of olive leaf were optimized by subcritical water,the effects of the solid-liquid ratio,extraction temperature and extraction time on extraction yield of the total polyphenols,the total flavonoids and oleuropein were investigated.Antibacterial activities of the olive leaf extract to Staphylococcus aureus,Bacillus subtilis,Streptococcus pneumoniae,Staphylococcus epidermidis were measured,and the main phenolic substances in the extract were also analyzed.The results showed that the optimal extraction parameters were determined as follows: extraction temperature 120 ?,extraction time 20 min,solid-liquid ratio 1:40 g/m L,extraction pressure 2 MPa.Under this operational condition,the total flavonoids content was 0.90% ± 0.01%,the total polyphenols content was 4.00% ± 0.12% and the oleuropein yield was 3.42% ± 0.08%.At the same time,the effects of different extraction techniques on the extraction yield were compared,the result shows that the content of olive leaf phenolics prepared by microwave assisted extraction and hot reflux extraction was higher than that of subcritical water extraction.The total polyphenol contents of hot extraction were 1.20 times of subcritical extraction,the total flavonoids were 1.16 times.The scale-up of hot reflux extraction of active components from olive leaves was studied,and the related kinetics were evaluated by Exp Dec1 model.The results showed that they were fitting well in general,specifically the higher ethanol concentration,the slightly better the fitness effect.Afterwards,the extracts were spray dried at inlet temperature 150 ? and feeding rate 15 m L/min,and crude extracts were purified by AB-8 macroporous resin,the content of total polyphenols increased from 9.68% to 31.65%,the content of total flavonoids and oleuropein increased to 10.98% and 20.38%.Some physicochemical properties of the extract powder were determined,the moisture content,density and porosity were not much different,the water extracts had better water solubility,and 80% ethanol had better active substance content.At the same time,the content of total polyphenols,total flavonoids and oleuropein and the physicochemical properties such as moisture content,hygroscopicity,water solubility,oxidation resistance and bacteriostatic properties of the commercially available olive leaf extracts were tested,the three olive leaf extract products had low water content and low moisture absorption,and exhibit better antioxidant capacity.The antibacterial activity of the homemade olive leaf extracts and the commercially available olive leaf extracts against Staphylococcus aureus,Bacillus subtilis,Streptococcus pneumoniae and Staphylococcus epidermidis were compared,that of commercially available olive leaf extracts had better antibacterial effect than that of homemade olive leaf extracts.The stability evaluation of the olive leaf extract preparation was carried out,the changes of active substance content in light,high temperature,high humidity and accelerated test were investigated.The results showed that the olive leaf extract of 30% total polyphenols had better water solubility,antioxidant capacity and bacteriostatic performance.The results of stability study showed that the effect of light on the content of active substances in extracts was small,the loss of active substances was below 5%,and the effect of humidity on the content of active substances in olive leaves was significant.In the detection of three active substances,total flavonoids were more susceptible to high temperature and high humidity,and the loss was larger than total polyphenols and oleuropein.The three-dimensional diffusion model was used to analyze the degradation kinetics of oleuropein content,and the shelf life and half-life of the product were predicted according to the degradation kinetics.To determine the effect of olive leaf extract on the growth of broilers,added olive leaf extract containing 30% total polyphenols to the basal diet of broilers.The addition amounts were 0.1%,0.2%,0.3%,0.4%,and 0.5%.720 broiler chickens of similar age were selected and randomly divided into 6 treatment groups,namely control group,experimental group I(0.1%),experimental group II(0.2%),experimental group III(0.3%),experimental group IV(0.4%)and experimental group V(0.5%),for a 42-day feeding experiment.The results showed that the low added amount of olive leaf extract promoted the growth of broilers.When the added amount exceeded 0.4%,the olive leaf extract affected the eating capacity of the broiler,which led to the decrease of the weight of the broiler and the inhibition of the growth of the broiler.The feed conversion rate of the experimental group was higher than that of the control group without the addition of olive leaf extract,indicating that the olive leaf extract improved the utilization rate of the feed.By measuring the index of immune organs such as bursa,spleen and thymus,it is known that olive leaves increased the thymus index.Considering the growth performance and immune organ index,the basal diet supplemented with 0.1% olive leaf extract had better feeding effect.