Effects of DL and L-Methionine on Growth Rate, Feather Growth, and Hematological Parameters of Tetra-SL Layers from 1–28 Days of Age

Simple Summary Methionine is the first limiting amino acid and plays an important role in the growth and health status of chicks. Animal health status was easily detected by examining the hematological parameters. This study aimed to investigate the influence of methionine sources (L-methionine and DL-Methionine) at different supplementation levels (10% deficit, 100% and 10% surplus of the recommended) on growth performance and health status of chicks. The results of the feeding trial found no differences in the chicks’ growth performance and feather growth on neither methionine sources nor methionine levels. However, most of the hematology parameters were affected by the methionine sources and/or methionine levels, as well as their interaction being significant in some cases. Therefore, this trial showed that varying methionine by ±10% of the requirements does not adversely affect growth performance and feather growth. Abstract The study was carried out to determine whether sources or levels of methionine (Met) affect the health status of Tetra-SL (TSL) chicks by examining growth performance, feather growth, and hematological parameters. A total of ninety-six (96) day-old (44.2 ± 0.18 g lw) TSL chicks were randomly allotted to six treatment groups (three levels for each DL and L-Met source) with four replicates of four chicks each. Chicks were fed ad libitum diets supplemented with 90, 100, and 110% of methionine requirements for four weeks after hatch. The parameters examined are bodyweight (BW), average daily gain (ADG), feather length (FL), and hematological parameters, including: red blood cell (RBC) count, hemoglobin (Hb) concentration in the blood, hematocrit (Ht; %), number of white blood cells (WBC), platelet count, mean corpuscular volume of red blood cells (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), lymphocyte (LYM), mid-range (MID), and granulocyte (GRAN). There was no significant effect of Met sources and levels on BW, ADG, and FL of TSL chicks for the first four weeks of rearing. The RBC, Hb, Ht, WBC, LYM, MID, and GRAN values of TSL chicks were statistically influenced by dietary Met sources and Met levels (p < 0.05). Among the treatment groups, the number of white blood cells (WBC) on 90% DL–Met was the lowest. WBC, RBC, Hb, and Ht were higher from chicks that received 100% DL-Met than all other levels, regardless of the Met sources. The MCV, MCH, and MCHC values were not affected by either Met source or levels or their interactions. Met source and level interactively affected the Ht, WBC, LYM %, and GRAN values of TSL chicks (p < 0.05). The platelet number was affected by Met source only (p < 0.05) with chicks receiving L-Met source having more than twofold higher platelet values than DL-Met source. In conclusion, varying Met levels by ±10% of the requirement does not adversely affect the growth performance, feather growth, and hematological parameters of TSL chicks reared for up to four weeks of age. DL-Met increased the body weight and improved the white blood cells, red blood cells, and hematocrit at 28 days after hatch. DL-Met showed similar biological efficacy as L-Met for body weight and feather growth but not for the hematological parameters.