Studies On Soybean Meal Reduction In Broiler Diets

Reduction of soybean meal content in broiler diet was investigated in the current study.Two approaches either by using insect meal or reduction of dietary crude protein level were adopted in three experiments in the current dissertation.Experiment 1 investigated the efficacy of the housefly maggot meal as an alternative protein source to replace the soybean meal in the broiler diet.A total of 720 1-day-old male broiler chicks were divided into three groups and fed diets formulated with housefly maggot meal to replace soybean meal at the rate of 0%,4%,and 8%.Feed conversion ratio increased linearly(1~21 d)in starter or quadratically(22~42 d)in the grower phase.Housefly maggot meal non-significantly increased the feed intake and body weight during the grower phase.Slight changes were observed for the decrease of blood biochemical indices in the platelets(d 21),and alkaline phosphatase and lysozyme(d 42),and increase for red blood cells,packed cell volume,total protein and uric acid on d 42,however,the fluctuations were within the physiological range.Non-significant effects were observed for carcass composition,and meat quality,except that the housefly maggot meal numerically reduced the shear force of breast muscle(linear,P=0.058).This experiment demonstrated that housefly maggot meal could be used as an alternative protein source at 8% in broiler chick's diet without any adverse effect on chick's performance.Experiment 2 was conducted on a yellow mealworm meal as a protein feedstuff in the broiler diet.A total of 700 one-day-old Ross 308 male broiler chicks were assigned to five dietary yellow mealworm meal treatments containing 0%,2%,4%,and 8% dried MWM or 10.48% fresh mealworm(corresponding to 4% dried yellow mealworm meal).Yellow mealworm meal significantly increased BW and ADG(linear and quadratic,p < 0.05),and FCR was best at 4% yellow mealworm meal inclusion level(quadratic,p < 0.10)for broiler chicks during the starter phase.A fresh 10.48% mealworm diet significantly reduced the blood lysozyme for the grower.Broiler chicks fed on fresh 10.48% mealworm had a significantly reduced abdominal fat percentage compared to the 4% dried yellow mealworm meal counterparts.Yellow mealworm meal did not significantly affect meat quality.Taken together,yellow mealworm meal inclusion in a broiler diet is acceptable as a protein feedstuff,and a 4% level could stimulate early growth in the starter phase.Experiment 3 investigated the reduction of protein level with glycine supplementation.Responses of broiler chicks to dietary protein reduction were investigated in the presence of glycine and cysteine inclusion at the marginal deficiency of sulfur-containing amino acids.A total of 864 broiler chicks were allotted to 12 dietary treatments;SP1 is standard protein diet with 100% total sulfur amino acids(TSAA),SP2 is standard protein diet with 85% TSAA,RPC is reduced protein diet with cysteine supplementation at 0%,0.05%,0.1%,0.15%,and 0.2% respectively while RPGC is also cysteine supplemented reduced protein diet with 1% glycine addition for starter phase and 1.15% for grower phase.In this study,4.5% protein is reduced in diets;thus,17.5% CP for starter phase and 15.5% CP for the grower phase.Broiler chicks fed standard protein diet SP2 had significantly higher ADFI(P<0.05)for the grower and entire feeding period compared to the broiler chicks fed SP1 diet.Cysteine supplementation curbs the adverse effects of the reduced protein and significantly improved the BW(P<0.05),ADG(P<0.05)and ADFI(P<0.05)compared to the reduced protein diet without any supplementation;however,0.2% cysteine in diet badly affected the growth performance.Glycine supplementation in the diet also abated the inimical effects of reduced protein and cysteine;broiler chicks fed reduced protein with 0.1% cysteine and 1 % glycine supplemented diet improved the BW(P<0.05),ADG(P<0.05),ADFI(P<0.05),FCR(P<0.05)in the starter,grower and entire feeding period.Broiler chicks fed on reduced protein diet with 0.1% cysteine and 1% glycine diet showed equivalent ADFI in starter phase,ADFI and FCR in the grower phase and better ADG(P<0.05)in the grower phase to the chickens fed on the SP2 diet.Hematological characteristics showed that broiler chicks fed on 0.2% cysteine supplemented diet significantly reduced the UA(P<0.05)and GLU(P<0.05),and increased BUN(P<0.05)level;however,Glycine fortification in reduced protein diet with 0.1% cysteine reduced the ALB(P<0.05).Metabolites analysis showed that reduced protein downregulated the 54 metabolites;however,glycine fortification upregulated the benzamide,6-Phospho-D-gluconate,D-gluconate,Diethyltoluamide,Gamma-Glutamylcysteine,NCarbamylglutamate,Pro-Ser,and Val-Met metabolites.Free amino acids results showed that broiler chicks fed on standard protein diet SP2 decreased the asparagine(P<0.05),glutamine(P<0.05),alanine(P<0.05),valine(P<0.05),cysteine(P<0.05),methionine(P<0.05),isoleucine(P<0.05),leucine(P<0.05),tyrosine(P<0.05),phenylalanine(P<0.05),glycine(P<0.05),? aminobutyric acid(P<0.05),histidine(P<0.05),ornithine(P<0.05)and proline(P<0.05)compared to broiler chicks fed SP1 diet.Cysteine supplementation increased the threonine(P<0.05),phenylalanine(P<0.05),histidine(P<0.05)and ornithine(P<0.05),and decreased citrulline(P<0.05)and ? aminobutyric acid(P<0.05)compared to the standard or reduced protein.Glycine supplementation in diet increased the threonine(P<0.05),serine(P<0.05),glycine(P<0.05),histidine(P<0.05),ornithine(P<0.05),and decreased the phosphoethanolamine(P<0.05),methionine(P<0.05),tyrosine(P<0.05),?-aminobutyric acid(P<0.05)compared to the standard or reduced protein.Carcass quality showed that reduced protein diet with cysteine supplementation reduced the leg percentage(P<0.05);however,increased the abdominal fat percentage(P<0.05).Glycine fortification in 0.2% cysteine diet reduced the dressing percentage(P<0.05)and breast percentage(P<0.05).Nitrogen digestibility was higher in the diet containing 0.1%(P<0.05)in the starter phase and diet without any supplementation(P<0.05)in the grower phase.The current experiment demonstrated that protein content could be reduced by 4.5% with 1% glycine and 0.1% cysteine fortification in diet,which has the potential to inhibit the adverse effect of cysteine and attain the standard growth performance as well as reduced the nitrogen emission.In conclusion,housefly maggot meal and yellow mealworm meal have the potential to partly replace soybean meal without any effect of chicken's health.Protein level could be successfully reduced by 4.5%,and the negative effect of reduced protein diet could be overcome with optimal inclusion of glycine and cysteine.