Growth Performance of Broilers as Influenced by Different Levels and Sources of Methionine Plus Cysteine

Simple Summary

The current work evaluated the utilization of different sources of methionine either from DL-methionine (DL-Met) or L-methionine (L-Met) using different concentrations of dietary methionine plus cystine (Met + Cyst) in broiler chickens. Results showed that a better edible meat yield could be obtained by supplementing Met + Cyst at the rate of 80% of the digestible lysine.

Abstract

The objective of this work was to evaluate the utilization of methionine from DL-methionine (DL-Met) and L-methionine (L-Met) with different levels of dietary methionine plus cystine (Met + Cyst) in broilers. The experimental diets were formulated by using three levels of Met + Cyst, i.e., 74%, 77% and 80% of digestible lysine. Met + Cyst was provided either from DL-Met or L-Met. A total of 450 day-old broilers were divided into six groups (five replicates of 15 birds each) in a 3 × 2 factorial arrangement under completely randomized design. Weight gain (WG), feed intake (FI) and feed conversion ratio (FCR) was determined. At the end of the experiment (35 days), two birds from each replicate were slaughtered to determine carcass characteristics and serum homocysteine. Results indicate that the combined effect of L-Met and DL-Met significantly affected (p < 0.05) the WG in the starter period and FI in the finisher period. Neither source nor level of methionine influenced (p > 0.05) the FI, WG and FCR of broilers during the starter, finisher or overall phase of growth. The interaction between sources and levels of methionine did not influence (p > 0.05) the feed intake, weight gain and FCR during the overall phase of growth. Source of methionine had no (p > 0.05) effect on carcass characteristics. Methionine levels had a significant effect (p < 0.05) on carcass weight, chest weight and thigh weight. The interaction between sources and levels of methionine had a significant (p < 0.05) effect on the liver weight. The sources of methionine had significant (p < 0.05) effects on the liver and heart weight, while methionine levels significantly influenced (p < 0.05) the liver and gizzard weight. Finally, it was concluded that if DL-Met and L-Met are included in feed at a standard level, they are equally effective as a source of methionine for broilers.

Dietary methionine source and level affect hepatic sulfur amino acid metabolism of broiler breeder hens

A study was carried out to investigate the effects of dietary methionine source and level on plasma free amino acids patterns and the expression of genes involved in hepatic methionine metabolism in broiler breeders. A total of 2184 broiler breeders were assigned to 13 dietary treatments, with eight replicates per treatment. The 13 treatments included one control group and 12 additional treatments employing two sources and six levels (0.05, 0.10, 0.15, 0.20, 0.25 and 1.00%). Higher plasma methionine concentration was measured for DL-methionine (DLM) treated hens. Plasma alanine concentration was linearly increased as DLM or 2-hydroxy-4-(methylthio) butanoic acid (HMTBA) supplementation level increased. There was a linear increase in concentrations of tyrosine, valine, glycine and serine as dietary DLM supplementation level increased. Hens treated with DLM had higher relative expression of ADA than those fed HMTBA. The expression of MS, ADA, SAHH and MAT2A changed quadratically as HMTBA supplementation level increased, while the expression of GNMT and SAHH changed quadratically as DLM supplementation level increased. In conclusion, the effects of HMTBA on plasma free amino acid patterns and the expression of hepatic genes involved with methionine are different from DLM.