Evaluation of methionine sources on performance and carcass traits of broilers at different dietary sulfur amino acid levels under northern European and middle Eastern conditions

DL-Methionine (DL-Met, 99%) and liquid DL-2-hydroxy-4-methylthio butanoic acid (methionine hydroxy analogue-free acid, MHA-FA, 88%) are often used in commercial poultry feeds to meet the requirements for Methionine+Cysteine (M+C). However, differences in chemical properties and absorption decrease the relative bioavailability value (RBV) of MHAFA, which corresponds to 65% of DL-Met for performance .

This study aimed to confirm that MHA-FA can be replaced with DL-Met at a weight-to-weight ratio of 100 to 65 under different rearing conditions. In total, 720 (Trial 1: Finland, 5 treatments with 9 replicates and 16 males per replicate, wheat soybean based feeds) or 2500 (Trial 2: Jordan, 5 treatments with 10 replicates and 25 males and 25 females per replicate, corn-soybean based feeds) day-old Ross 308 broilers chicks (~41 g) were used.

In both trials, broilers received a basal diet (BD) formulated to meet the nutritional requirements except for additional Met sources (60-66% of M+C requirements), or BD supplemented with MHA-FA or DL-Met (added at 65% of MHA-FA, w/w), to reach 75% (75MHA-FA, 75DL-Met) or 100% (100MHA-FA, 100DL-Met) of M+C requirements. Broilers were fed ad libitum a 3-phase program during day (d) 0-35 (Trial 1) or d 0-32 (Trial 2) under standard housing conditions. Bodyweight (BW), feed intake (FI), daily feed intake (DFI), bodyweight gain (BWG), daily weight gain (DWG) and feed conversion ratio (FCR) were measured in Trials 1 and 2. Carcass (CY) and breast (BY) yields were measured on d 32 in Trial 2. Data was analyzed using one-way ANOVA with GLM procedure of SAS (ver. 9.4).

Significances were considered if P< 0.05 (Tukey test). In Trials 1 and 2, MHA-FA and DL-Met improved (P< 0.01) FI, DFI, BW, BWG, DWG and FCR compared to BD, without any differences between MHA-FA and DL-Met groups within each M+C level. In trial 1, the 100% M+C groups had higher BW (+4.68%, P< 0.01), DWG (+4.76%, P< 0.01) and lower FCR (-4.04%, P< 0.01) than 75% M+C groups, while DFI did not differ between 75% and 100% M+C levels during d 0-35.

In Trial 2, the 100% M+C groups had higher (P< 0.01) BW (+4.27%) and BWG (+4.34%), and similar FI (P> 0.1) compared to 75% M+C groups, whilst FCR was only lower (-3.54%, P< 0.01) in 100MHA-FA vs. 75MHA-FA groups. There was no difference in CY and BY between MHA-FA and DL-Met groups within each M+C level. Breast yield was higher (P< 0.01) in 100% and 75% M+C vs. BD groups (+16.62%, +8.40%) and in 100% M+C vs. 75% M+C groups (+7.58%), whilst CY was only higher (+3.44%, P< 0.01) in 100% M+C vs. BD groups. In conclusion, the results confirm that 100 units of MHA-FA can be substituted by 65 units of DL-Met for broilers at the same M+C level, regardless of the regional differences.

Keywords: Nutrition, poultry, amino acids, performance, methionine

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