Peripheral and Central Impact of Methionine Source and Level on Growth Performance, Circulating Methionine Levels and Metabolism in Broiler Chickens

Assessment of the dietary amino acid profiles and the relative biomarkers for amino acid balance in the low-protein diets for broiler chickens

BACKGROUND

Research on low-protein-level diets has indicated that even though the profiles of essential amino acids (EAAs) follow the recommendation for a normal-protein-level diet, broilers fed low-protein diets failed to achieve productive performance compared to those fed normal diets. Therefore, it is imperative to reassess the optimum profile of EAAs in low-protein diets and establish a new ideal pattern for amino acid balance. Furthermore, identifying novel sensitive biomarkers for assessing amino acid balance will greatly facilitate the development of amino acid nutrition and application technology. In this study, 12 dietary treatments [Con(+), Con(-), L&A(-), L&A(+), M&C(-), M&C(+), BCAA (-), BCAA(+), Thr(-), Thr(+), Trp(-) and Trp(+)] were established by combining different EAAs including lysine and arginine, methionine and cysteine, branched-chain amino acid (BCAA), threonine, and tryptophan to observe the growth and development of the broiler chickens fed with low-protein-level diets. Based on the biochemical parameters and untargeted metabolomic analysis of animals subjected to different treatments, biomarkers associated with optimal and suboptimal amino acid balance were identified.

RESULTS

Growth performance, carcass characteristics, hepatic enzyme activity, serum biochemical parameters, and breast muscle mRNA expression differed significantly between male and female broilers under different dietary amino acid patterns. Male broilers exhibited higher sensitivity to the adjustment of amino acid patterns than female broilers. For the low-protein diet, the dietary concentrations of lysine, arginine, and tryptophan, but not of methionine, cystine, or threonine, needed to be increased. Therefore, further research on individual BCAA is required. For untargeted metabolomic analysis, Con(+) was selected as a normal diet (NP) while Con(-) represented a low-protein diet (LP). L&A(+) denotes a low-protein amino acid balanced diet (LPAB) and Thr(+) represents a low-protein amino acid imbalance diet (LPAI). The metabolites oxypurinol, pantothenic acid, and D-octopine in birds were significantly influenced by different dietary amino acid patterns.

CONCLUSION

Adjusting the amino acid profile of low-protein diets is required to achieve normal growth performance in broiler chickens fed normal-protein diets. Oxypurinol, pantothenic acid, and D-octopine have been identified as potentially sensitive biomarkers for assessing amino acid balance.

Methionine Source and Level Modulate Gut pH, Amino Acid Transporters and Metabolism Related Genes in Broiler Chickens

This study determined the effects of two methionine (Met) sources at three total sulfur amino acids (TSAA) to lysine ratios (TSAA/Lys) on gut pH, digestive enzyme activity, amino acid transporter expression, and Met metabolism of broilers. The birds were randomly assigned to a 2 × 3 factorial arrangement with Met sources (dl-Met and dl-2-hydroxy-4-(methylthio)-butanoic acid (OH-Met)) and TSAA/Lys (0.58, 0.73, and 0.88) from 1 to 21 days. The results demonstrated that dl-Met and OH-Met supported the same growth performance, but high TSAA/Lys ratio reduced the feed intake and body weight (P < 0.05). OH-Met reduced the crop chyme pH and enhanced the jejunal lipase activity (P < 0.05). ATB0,+ expression decreased with increased dl-Met levels in the duodenum; the low TSAA/Lys ratio induced a stronger mRNA expression of basolateral Met transporters. OH-Met resulted in an increase of cystathionine β-synthase expression in the liver and a decrease in serum homocysteine levels at middle TSAA/Lys ratio compared with dl-Met treatment (P < 0.05). In conclusion, two Met sources support the same growth, but OH-Met acidified the crop chyme. The investigated transporter transcripts differed significantly along the small intestine. At the middle TSAA/Lys ratio, OH-Met showed a higher metabolic tendency of the trans-sulfuration pathway compared with dl-Met.

In ovo feeding of methionine affects antioxidant status and growth-related gene expression of TETRA SL and Hungarian indigenous chicks

Methionine (Met) plays a substantial role in poultry due to its involvement in several pathways, including enhancing antioxidant status and improving growth performance and health status. This study examined how in ovo feeding of Met affects hatching performance, antioxidant status, and hepatic gene expression related to growth and immunity in the TETRA-SL LL hybrid (TSL) commercial layer and Hungarian partridge colored hen (HPC) indigenous genotypes. The eggs were injected with saline, DL-Met, and L-Met on 17.5 days of embryonic development. The results showed that the in ovo feeding of DL-Met significantly increased the hatching weight and ferric reducing the ability of the plasma (FRAP) compared with L-Met. The in ovo feeding of either Met source enhanced the liver health and function and hepatic antioxidant status of the chicks. The genotype's differences were significant; the TSL genotype had better hatching weight, an antioxidant defense system, and downregulated growth-related gene expression than the HPC genotype. In ovo feeding of either Met source enhanced the chicks' health status and antioxidant status, and DL-Met improved the hatching weight of the chicks more than L-Met. Genotype differences were significantly evident in the responses of growth performance, antioxidant status, blood biochemical parameters, and gene expression to Met sources.