| Protein and lysine are essential nutrients for the growth and development of poultry,and the crude protein and lysine requirements of poultry with different varieties and ages are different.This experiment was conducted to study the effects of dietary crude(CP)protein and lysine(Lys)levels on growth performance,slaughter performance,meat quality,serum biochemical indices and gut microbiota of Beijing You chicken(BYC)in brooding and growing period,so as to provide a theoretical basis for meeting BYC’s nutritional needs and further improving the technical regulations of BYC feeding and management.Effects of dietary CP and Lys levels alone and in interaction on growth performance and serum biochemical indices of BYC during brooding period in experiment 1.A total of 1350one-day-old BYC mixed chicks were randomly allocated to 9 groups with 5 replicates per group and 30 chicks per replicate,half male and half female.A 3×3 factorial design was adopted,according to the recommended dietary CP and Lys levels of BYC in “Technical regulations of feeding and management of Beijing You Chicken”(DB11/T1378-2016),CP and Lys levels were adjusted up and down.Dietary CP levels were 17%,18% and 19%,and Lys levels were 0.85%,1.0% and 1.15%,respectively.Growth performance from 0 to 6 weeks was measureded,blood samples were collected at six weeks and serum biochemical indicators were measured.The results showed as follows:1)Dietary crude protein level had a significant effect(P < 0.05)on the average weekly feed intake(AFI)of chicks from 0 to 6 weeks of age,with an increasing trend with increasing crude protein level.Lys level significantly affected BWG and F/G of chicks(P < 0.05).The BWG of 0.85% Lys group was significantly lower than that of 1.0% and 1.15% groups(P < 0.05),and the F/G was significantly higher than that of these two groups(P < 0.05);the BWG was significantly affected by dietary CP and Lys levels in interaction(P < 0.05);when dietary CP is 19% and Lys is 1.15%,the BWG is the highest.2)Serum uric acid(UA)content of chicks aged from 0 to 6 weeks was affected by CP levels(P < 0.05),and the UA content in the 19% CP group was higher than the other two groups(P < 0.05).Serum albumin content was affected by Lys levels(P < 0.05),and when Lys level was 1.15%,albumin content increased significantly(P < 0.05).To sum up,it is recommended that the CP level and lysine level of 0～6 weeks old Beijing Fatty Chicken should be 19% and 1.15% respectively.Experiment 2 aimed to study the effects of dietary CP and Lys levels alone and in interaction on performance,slaughter performance,meat quality,serum biochemical indexes and gut microbiota of BYC in the growth period.A 3×3 factorial design was adopted,according to the recommended dietary CP and Lys levels of growing period BYC in“Technical regulations of feeding and management of Beijing You Chicken.”(DB11/T1378-2016),CP and Lys levels were adjusted up and down.Dietary CP levels were16%,17% and 18%,and Lys levels were 0.69%,0.84% and 0.99%,respectively.A total of540 healthy 9-week-old BYC with similar weight were selected,and 9 treatment groups were set up,with 60 chickens in each group and 5 replicates,with 3 cages for each replicate and 4chickens in each cage.Growth performance of 9～16 weeks was counted.At the end of 16 weeks,one chicken was selected repeatedly to collect blood from the wing vein.After slaughter,the slaughter performance was counted,and the contents of both pectoral muscles and cecum were collected,and all indexes were determined.The results showed that:1)Dietary CP level had significant effects on AFI and BWG of chickens aged 9-16 weeks(P <0.05),and both of them increased with the increase of CP level.When the CP was 18%,the AFI(473.24g)and BWG(93.99g)were the highest;AFI was significantly affected by dietary CP and Lys levels in interaction(P < 0.05),when dietary CP is 18% and Lys is 0.69%,the AFI is the highest(480.80g).2)Serum total protein(TP)content was affected by CP levels(P< 0.05),and the TP content in the16% CP group was lower than the other two groups(P <0.05).3)Chest muscle weight and chest muscle rate were affected by CP levels(P < 0.05),when the CP level was 16%,the chest muscle weight and chest muscle rate were significantly lower than those of the other two groups(P < 0.05).4)The shear force of pectoral muscle was affected by CP levels(P < 0.01),and the shear force increased with the increase of CP level.5)CP level had significant effects on crude lipid content in breast muscle(P < 0.05).6)Dietary CP level significantly affected the contents of free amino acids(FAA)such as threonine,serine,glutamic acid,valine,methionine,leucine,tyrosine,phenylalanine and arginine in chest muscles(P < 0.05),Lys level affected methionine(P < 0.05)and arginine content(0.05< P < 0.1).The contents of glutamic acid,citrulline and arginine in the interaction between them were significantly different(P < 0.05),and the contents of threonine,methionine and fresh and sweet amino acids were affected(0.05 < P < 0.1).7)There were significant differences in C24:1 content in pectoral muscle between dietary CP and Lys level(P < 0.05),and Lys level had significant effects on C20:3n6 content(P < 0.05).The contents of C16:1,C20:2,polyunsaturated fatty acid(PUFA)and essential fatty acid(EFA)in pectoral muscle were significantly different(P < 0.05),and increased with the increase of CP level.8)Dietary CP level and Lys level had no significant effects on Alpha diversity of cecum microflora of You chickens(P > 0.05).The CP level and Lys level and their interaction had no significant effects on the relative abundance of the top 5 dominant bacteria of phylum and genus in cecum microorganisms(P > 0.05).In conclusion,dietary 18% CP level and 0.99% Lys level during growing period can significantly improve the growth performance of young chickens,which is beneficial to improve the meat flavor of young chickens,but has a certain negative effect on the diversity of intestinal flora of BYC. |
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