| Dietary aromatic amino acids(tryptophan,phenylalanine and tyrosine)play an important role in animal growth and metabolism,but they are also the main precursors of indoles,phenols and other odorous compounds.The results showed that dietary stachyose significantly reduced the production of cecal odor compounds in broilers.This experiment was conducted to investigate the effects of dietary digestible aromatic amino acids(d AAA)level,stachnose and their interaction on performance and cecal odor compound concentration of broilers and the mechanism of action,so as to provide scientific reference for rational diet formulation and odor compound abatement.A 3×2 two-factor factorial design was used to prepare 6 experimental diets with low,medium and high d AAA levels(1.40%,1.54% and1.68%),and each level was supplemented with 0 and 0.5% stachyose.A total of 36021-day-old broilers with an average body weight of 914.86 g(male and female)were randomly divided into 6 groups with 6 replicates per group and 10 broilers per replicate.The experiment lasted for 21 days,respectively.The test results show that:(1)Growth performance: Average daily gain(ADG)of broilers at 1.54% d AAA level was significantly higher than that at 1.40% and 1.68%d AAA level,and the ratio of feed to gain(F/G)was significantly decreased(P < 0.05);Stachyose supplementation significantly increased the ADG of broilers(P < 0.05);There was significant interaction between dietary d AAA level and stachyose on ADG of broilers,the ADG of 1.54%d AAA group supplemented with stachyose was significantly higher than that of other groups(P < 0.05),and the F/G of1.54%d AAA group without stachyose was significantly lower than that of other groups(P <0.05).(2)Nutrient apparent metabolic rate: the dry matter apparent metabolic rate of broilers at1.68% d AAA level was significantly higher than that at 1.40% and 1.54%d AAA level(P <0.01);The apparent metabolic rates of protein,fat and energy in 1.54% d AAA groups were significantly higher than those in 1.40% and 1.68%d AAA groups(P < 0.05).Dietary d AAA level significantly affected the apparent metabolic rates of lysine,methionine,tyrosine,aspartate,glutamate,valine,isoleucine,leucine,tryptophan,arginine and proline(P < 0.05).The apparent metabolic rates of fat,protein,tryptophan and lysine of broilers were significantly increased by stachyose supplementation(P < 0.05).There were significant interactions between dietary d AAA level and the apparent metabolic rates of protein,fat,tryptophan and methionine of broilers,and the apparent metabolic rates of protein,fat,tryptophan and methionine of broilers supplemented with stachyose at 1.54%d AAA level significantly increased the apparent metabolic rates of protein,fat,tryptophan and methionine of broilers(P < 0.05).(3)Serum biochemical indices: The concentrations of total protein and tryptophan in serum of broilers with 1.54% d AAA were significantly higher than those in 1.40% and1.68%d AAA groups(P < 0.01);The serum total protein and albumin levels were decreased by stachyose supplementation(P < 0.01).The concentration of phenylalanine was increased(P < 0.05).1.54% d AAA level Serum concentrations of tryptophan,phenylalanine and tyrosine in stachyose group were significantly higher than those in other groups(P < 0.01).(4)Cecal odor compounds: With the increase of dietary d AAA level,the concentrations of indole,skatin,p-methylphenol and butyric acid in cecal contents of broilers were significantly increased(P< 0.05);The concentrations of indole,skatin,phenol,p-methylphenol,acetic acid and propionic acid in cecum were significantly decreased by stachyose supplementation(P < 0.05).The concentrations of indole,phenol and p-methylphenol in cecal of broilers were significantly decreased by stachyose supplementation at 1.40%d AAA level(P < 0.05).(5)Cecal microflora structure: Dietary d AAA level had no significant effects on ACE,Chao1,Shannon index,Simpson index and coverage rate of cecal microflora of broilers(P >0.05).Stachyose supplementation significantly decreased ACE and Chao1 index of cecal microflora(P < 0.05).Dietary d AAA level and stachyose had no significant effects on cecum microflora(P > 0.05).The relative abundance of Phascolarctob genus in cecum of broilers in1.40%d AAA level diet group was significantly higher than that in 1.68%d AAA level group(P< 0.05),and the relative abundance of ruminae and Faecalis genus in cecum of broilers in1.40%d AAA level diet group was significantly higher than that in 1.68%d AAA level group(P< 0.05).There was no significant interaction between d AAA level and stachyose on cecal microflora of broilers(P > 0.05).Conclusion: Adding stachyose at 1.54%d AAA level can increase ADG and decrease F/G of broilers.The metabolic rate of protein,fat,lysine,tyrosine and aspartic acid was increased.1.At 40%d AAA level,stachysaccharide was more beneficial to reduce the caecal indole,phenol and p-methylphenol concentrations of broilers.In conclusion,under the conditions of this experiment,the supplementation of 0.5% stachyose had the best effect when the d AAA level was 1.54%. |
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