| The assessment of the nutritional value of feed ingredients is the basis for accurate nutrition,but there is currently no dedicated feed nutrition database for laying hens in China,making it impossible to achieve accurate dosing for laying hens,resulting in poor feed utilisation and serious wastage of feed resources in actual production.In this thesis,the standardised ileal digestibility(SID)of the 18 amino acids in soybean meal was evaluated using different physiological stages of laying hens,and on this basis,the correlation between the main nutrients in soybean meal and the SID of amino acids and the predictive regression model were analysed to provide a reference for the rational allocation of rations for laying hens.This study was conducted to provide a reference for the rational allocation of rations in egg production and to accumulate basic data for a database on the nutritional value of egg feeds.In this study,44 representative soybean meal feed ingredients were first collected from different parts of China,and the conventional chemical composition and amino acid content were examined by using international common operating procedures and standardized determination methods,and 10 representative soybean meal feed ingredients were selected for testing based on conventional chemical components and origin,etc.The available amino acids of commonly used soybean meal feed ingredients for laying hens were precisely assessed.The results of the study showed that: 1)there were large differences between the conventional chemical components measured by Near infrared spectra(NIR)scanning of 44 soybean meal samples collected from different regions of China,among which the coefficients of variation(Coefficient of variation)of crude fat,crude fiber,neutral detergent fiber,acid detergent fiber and starch were all within 10%.2)The 10 soybean meal samples used for the test were screened according to principal component analysis and factor analysis,and the differences between the conventional chemical composition measured by wet chemical method were large,among which crude fiber,crude ash,acidic detergent fiber coefficient of variation was more than 10%,and the maximum variation of acidic detergent fiber content was 24.58%.The large differences in proline and tyrosine among 18 amino acids may be the main reason for the significant differences in their amino acid digestibility.The crude protein content of SBM2 Shandong Rizhao was the highest at 47.52%,and the crude protein content of SBM1 Beijing was the lowest at 42.70%.The mean values of the 18 amino acids ranged from 0.73%to 7.95%,with the highest mean value of glutamic acid content and the lowest mean value of methionine content.Experiment 1 aimed to investigate the effect of different sources of soybean meal on ileal amino acid digestibility of laying hens during peak egg production.In this experiment,198 healthy,uniformly weighted 35-week-old peak laying hens were selected from the pre-fed flock under conventional feeding management conditions and randomly divided into 11 treatment groups(10 groups on soybean meal diet and 1 group on nitrogen-free diet),with 6replicates of 3 hens each.The test groups were fed 10 different sources of soybean meal and the control group was fed a nitrogen-free diet to determine ileal amino acid digestibility.Soybean meal was the only source of protein in the test diets,and 0.5% titanium dioxide was added to the diets as an exogenous indicator.The ileal meal was collected on the 5th day of slaughter for the determination of the standard ileal amino acid digestibility of laying hens after a 7-day pre-feeding period and a 4-day test period.The results showed that: 1)The source of soybean meal had a significant effect(P < 0.05)on the AID of tryptophan,alanine,threonine and proline of the 18 amino acids in peak laying hens,and no significant effect(P >0.10)on the SID of threonine,tryptophan,alanine and proline of the 18 amino acids in peak laying hens;the source of soybean meal had a significant effect(P < 0.05)and no significant effect on other amino acids(P > 0.10).2)Crude protein,crude fat,crude fiber,crude ash,acidic detergent fiber and neutral detergent fiber content of soybean meal can be considered as better predictors of amino acid AID and SID regression equations for peak laying hens.The best prediction models between amino acid AID and SID of soybean meal for peak laying hens and their conventional nutrient contents were as follows:(1)The best predictive equation for the amino acid AID of soybean meal for peak laying hens:Of the essential amino acids: AID Thr=30.249-3.357CF+3.809Ash+0.949 NDF,R2=0.905.Of the non-essential amino acids: AID Ser=106.052-0.926CP+4.770EE+3.357CF-4.851 ADF,R2=0.987.(2)The best predictive equation for the amino acid SID of soybean meal for peak laying hens:Of non-essential amino acids: SID Pro=56.185+18.923EE-1.698 ADF,R2=0.671.Experiment 2 was designed to investigate the effect of different sources of soybean meal on ileal amino acid digestibility in late laying hens.In this experiment,198 healthy,uniformly weighted 65-week-old late laying Jing Fan No.1 hens were selected from the pre-fed flock under conventional feeding management conditions and randomly divided into 11 treatment groups(10 groups on soybean meal diet and 1 group on nitrogen-free diet),with 6 replicates of 6 hens per treatment and 3 hens per replicate.The test diets were the same as test 1.The pre-feeding period was 7 days,the test period was 4 days,and the ileal meal was collected on the 5th day of slaughter for the determination of amino acid digestibility of the standard ileum of laying hens.The results showed that: 1)The source of soybean meal had a significant effect(P < 0.05)on the AID of all 18 amino acids in late laying hens.Except for isoleucine,tryptophan,cystine,serine and tyrosine,soybean meal source had significant effects(P < 0.05)on the SID values of all amino acids in late laying hens.2)Crude fat,crude ash and acidic detergent fiber content of soybean meal could be considered as better predictors of amino acid AID and SID regression equations in late laying hens.The best prediction models between the amino acid AID and SID of soybean meal for late laying hens and their conventional nutrient contents were as follows:(1)The AID best prediction equation for soybean meal for late laying hens:Of the essential amino acids: AID Thr=-75.538+59.930EE+4.460 Ash,R2=0.770.Of the non-essential amino acids: AID Ala=-93.320+71.333EE+5.207 Ash,R2=0.827.(2)The best predictive equation for the SID of soybean meal for late laying hens:Of the essential amino acids: SID Thr=-34.401+41.134EE+6.319 Ash,R2=0.704.Of the non-essential amino acids: SID Ala=-50.017+25.461EE+4.850 Ash,R2=0.875.The results of test 1 and test 2 showed that except for methionine and alanine,age of week had a significant effect(P < 0.05)on the AID of all other amino acids in laying hens;except for aspartic acid,age of week had a significant effect(P < 0.05)on the SID of all other amino acids in laying hens,and the SID values of all other amino acids in laying hens at 35 weeks of age were significantly higher(P < 0.05)than at 65 weeks of age.Except for isoleucine,lysine,arginine,aspartic acid,glutamic acid and serine,there were significant reciprocal effects of soybean meal source and age on the AID of other amino acids in laying hens(P < 0.05);and there were significant reciprocal effects of soybean meal source and age on the SID of methionine,threonine,valine,tryptophan,alanine,glycine and proline in laying hens(P < 0.05).In conclusion,there are great differences in conventional chemical components of soybean meal samples collected from different areas of our country,and there is little difference in amino acid content.There were significant differences between AID and SID of amino acids in soybean meal from different sources.The SID of most amino acids in soybean meal decreased with the increase of weekly age of laying hens.There was an interaction effect between the source and weekly age of soybean meal on AID and SID of amino acids of laying hens.The contents of crude fat,ash and acid detergent fiber in soybean meal could be regarded as good predictors of amino acid AID and SID regression equations in peak and late laying period.The above results can provide theoretical basis for efficient utilization of soybean meal feed and rational diet formulation in laying hens. |
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