| This experiment was conducted to investigate the effects of lowering dietary metabolizable energy level and adding Lysolecithin(LPC)supplementation on growth performance,lipid metabolism and liver health of broilers,to provide theoretical basis for the rational application of LPC in broiler breeding industry.A total of 240 1-day-old AA broilers with similar body condition and body weight were selected,they were randomly divided into4 treatment groups with 6 replicates per group and 10 chickens per replicate.Treatment 1,basal diet group,was fed normal basal diet;Treatment 2,energy-lowering diet group,the basal diet reduced ME by 90 kcal/kg;Treatment 3,300 mg/kg LPC was added to the base diet;Treatment 4,300 mg/kg LPC was added to the energy-lowering diet.The experiment used a 2 × 2 design,the experimental period was 42 days.Growth performance was measured at 21 and 42 days of age,one chicken was randomly selected from each replicate for subwing vein blood collection,liver and ileal terminal chyme were slaughtered at 42 days of age after blood collection,and various indexes were determined.The test results were as follows:(1)Growth performance aspects: Basal dietary metabolizable energy level significantly decreased the ratio of feed to gain of broilers aged from 1 to 21 days(P < 0.05);LPC supplementation had a trend of increasing the ratio of feed to gain of broilers aged from 1 to42 days(P < 0.05).(2)Slaughter performance aspects: LPC supplementation tended to increase the slaughter percentage of broilers at 42 days of age(P = 0.083),significantly decreased abdominal fat percentage and liver index(P < 0.05);lower dietary metabolizable energy level tended to decrease abdominal fat percentage and liver index of broilers at 42 days of age(P = 0.083,P= 0.065).There was significant interaction between dietary metabolizable energy level and LPC on liver index of broilers at 42 days of age(P < 0.05).(3)Apparent digestibility of nutrients aspects: LPC supplementation significantly increased the apparent digestibility of dry matter at the end of ileum of broilers at 42 days of age(P < 0.05),and tended to increase the apparent digestibility of crude protein(P = 0.065).(4)Liver fat indicators aspects: LPC supplementation tended to increase liver lipase content of broilers at 42 days of age(P = 0.092);there was an interactive trend between dietary metabolizable energy level and LPC on liver triglyceride content of broilers at 42 days of age(P = 0.059).(5)Serum biochemical indicators: LPC supplementation significantly decreased serum free fatty acid content of broilers at 21 days of age(P < 0.01),significantly decreased serum triglyceride content of broilers at 42 days of age(P < 0.05),and significantly increased serum high-density lipoprotein content of broilers at 42 days of age(P < 0.05).Significantly decreased serum free fatty acid content at 42 days of age(P < 0.01);lower dietary metabolizable energy level had a tendency to decrease serum triglyceride content of broilers at 42 days of age(P = 0.055).(6)Serum transaminase indicators: LPC supplementation significantly decreased serum alanine aminotransferase content of broilers at 21 days of age(P < 0.05),and had a tendency to decrease serum aspartate aminotransferase content of broilers at 42 days of age(P = 0.066);lower dietary metabolizable energy level significantly decreased serum aspartate aminotransferase content of broilers at 42 days of age(P < 0.05);There was significant interaction between dietary metabolizable energy level and LPC on serum alanine aminotransferase content of broilers at 21 days of age(P < 0.01).(7)Antioxidant indicators: LPC supplementation tended to increase serum glutathione peroxidase content of broilers at 21 days of age(P = 0.080),significantly increased serum glutathione peroxidase content of broilers at 42 days of age(P < 0.05),and extremely significantly decreased liver malondialdehyde content of broilers at 42 days of age(P < 0.01),the expression of CAT gene in liver of broilers was significantly up-regulated(P < 0.05),and the expression of SOD in liver of broilers tended to be up-regulated(P = 0.070);there was significant interaction between dietary metabolizable energy level and LPC on liver malondialdehyde content of broilers at 42 days of age(P < 0.05).(8)Immunization indicators: LPC supplementation significantly decreased the serum endotoxin content of broilers at 42 days of age(P < 0.01),significantly decreased the content of interleukin 6(P < 0.05),and significantly increased the liver immunoglobulin A content of broilers at 42 days of age(P < 0.01);lowering dietary metabolizable energy level significantly decreased serum endotoxin content of broilers at 42 days of age(P < 0.05),and significantly increased serum and liver immunoglobulin A content of broilers at 42 days of age(P < 0.05);dietary metabolizable energy level and LPC had significant interaction on serum interleukin-6content of broilers at 21 days of age(P < 0.05),and had significant interaction on serum endotoxin content and liver immunoglobulin A content of broilers at 42 days of age(P < 0.05).The interaction was significant in liver immunoglobulin G content of broilers at 42 days of age(P < 0.01).In summary,300 mg/kg LPC can improve the growth performance of broilers,reduce the content of blood lipid,up-regulate the expression of CAT genes in liver,enhance the immune capacity of broilers,and have certain positive effects on the maintenance of liver health.To a certain extent,reducing dietary ME level can improve body fat deposition,decrease serum transaminase and improve immunoglobulin A content,but it can reduce feed conversion efficiency of broilers aged 1 to 21 days.There were significant interactions between dietary metabolizable energy level and LPC in improving immune ability and reducing liver damage of broilers;According to the economic benefit of the broiler production assessment,the best economic benefit was achieved by adding 300 mg/kg LPC to the lower metabolizable energy level diets. |
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