| China is a large country in pig breeding and pork consumption.With the improvement of people’s living standards,the production of high-quality pork has become one of the key issues to be solved in the development of pig industry in China.Fat deposition has a very important effect on pork quality.Schizochytrium sp.belongs to marine fungi heterotrophic organisms and is an oil-producing microalgae that rich in polyunsaturated fatty acids such as docosahexaenoic acid（DHA）,which can supplement necessary fatty acids in animals,moreover,it contain active substances such as squalene and astaxanthin,which possess multiple biological functions.The schizochytrium sp.grows fast and can be produced on a large scale,and its biomas and DHA content can be effectively improved by adjusting the nutrient components of culture medium.This study aimed to investigate the effect of Schizochytrium sp.on growth performance and meat quality of finishing pigs and optimize its production process.Firstly,the effect of Schizochytrium sp.as a functional additive was clarified by supplementing Schizochytrium sp.into the diet of finishing pigs to understand its effects on growth performance,slaughter performance and meat quality.Furthermore,the single factor experiment was used to screen the key factors for biomass and oil accumulation of Schizochytrium sp.and the optimal culture condition was determined by orthogonal test,in order to provide reference for its large-scale production.In the first experiment,36 Duroc×Landrace×Landrace boars with initial body weight of 100 kg were randomly divided into two groups with six replicates and three boars in each replicate.The control group was fed with a basal diet,while the Schizochytrium sp.group was fed with a basal diet containing 0.3%Schizochytrium sp.powder for a pre-feeding period of 3days and a trial period of 37 days.The results showed that:（1）Dietary supplementation of Schizochytrium sp.significantly increased the terminal weight of finishing pigs（P<0.05）,and the average daily gain showed an increase trend（P=0.059）;（2）Supplementation of Schizochytrium sp.significantly reduced the triglyceride（TG）content in the longissimus dorsi muscle（P<0.05）,but had no significant effect on carcass traits,meat quality and main nutrient components in muscle of finishing pigs.（3）The contents of monounsaturated fatty acid,polyunsaturated fatty acid and n-3 polyunsaturated fatty acid in the longissimus dorsi muscle of finishing pigs were significantly increased by supplementation of Schizochytrium sp.（P<0.05）;（4）Serum levels of TG,total cholesterol（T-CHO）and low density lipoprotein（LDL）of finishing pigs were significantly decreased by supplementation of Schizochytrium sp.（P<0.05）;（5）Total antioxidant capacity（T-AOC）and superoxide dismutase（SOD）activity of the liver were significantly increased by supplementation of Schizochytrium sp.（P<0.05）.In the second experiment,the optimal range of glucose,yeast extract,tryptone,seawater crystal and inoculation amount on the biomass and oil content of Schizochytrium sp.was firstly determined by single factor test.Then the addition of exogenous additives such as citric acid,ammonium sulfate,potassium dihydrogen phosphate and magnesium sulfate was selected for the L27（38）orthogonal design through orthogonal test.According to the results of orthogonal test,the optimal combination of medium for biomass was:glucose 110g/L,yeast extract 5 g/L,tryptone 6.5g/L,haijing 17g/L,citric acid 2.5 g/L,ammonium nitrate 4.5 g/L,potassium dihydrogen phosphate 2.5 g/L and magnesium sulfate 4.5 g/L.The biomass could reach 45.54g/L.The optimal medium combination for DHA content was:glucose 110 g/L,yeast extract 5g/L,tryptone 6 g/L,haijing 17 g/L,ammonium nitrate 2.5 g/L,citric acid 4.5 g/L,potassium dihydrogen phosphate 2.5 g/L,and magnesium sulfate 4 g/L.The content of DHA was 6.17g/L,and DHA accounted for 51.77%of intracellular lipids.In conclusion,dietary suplementation of Schizochytrium sp.can enhance the growth performance of finishing pigs,improve serum lipid level and fatty acid composition in muscles.The accumulation of biomass and DHA in Schizochytrium sp.can be increased by adjusting the composition of the culture medium.These results can provide a theoretical basis for the application of Schizochytrium sp.in pig production and its large-scale production. |
