An optimal duck performance on growing and feathering with 100% efficient methionine sources: OHMethionine or DL-Methionine

The objectives of the trial described in the article were (i) to compare the effects of OH-Methionine compared to DL-Methionine on growth performance and feather growth of Cherry Valley ducks fed from 0 to 42 days and (ii) to determine the bio-efficacy of OH-Methionine (OH-Met) relative to DL-Methionine (DL-Met).

The trial was published by Zhao et al.2018 in Poultry Science: Efficacy of 2-hydroxy-4-methylthiobutanoic acid compared to DL-Methionine on growth performance, carcass traits, feather growth, and redox status of Cherry Valley ducks.

The study was performed on 630 Cherry Valley ducks reared from 1 to 42 days in China (Huazhong Agricultural University). Birds were randomly allocated to 9 treatments with 7 replicates of 10 birds each. Diets were based on corn, wheat and soybean meal and formulated according to NRC (1994) recommendations. Treatments consisted in a basal diet deficient in Total Sulfur Amino Acids (TSAA) and eight supplemented treatments with either DL-Methionine or OH-Methionine. For the supplemented treatments, equimolar doses of methionine added to the basal diet from 0 to 21 d (0.04, 0.12, 0.16 and 0.20%) and from 21 to 42 d (0.0.2, 0.06, 0.10 and 0.14%). Birds had free access to feed and water during the whole experimental period. Feed intake, body weight, feed conversion ratio, carcass weight and breast meat weight were recorded. Downs and plumages were collected for analysis on d 21 and d 42.

Growth performance is presented Table 1.

No significant difference of feed intake was found between DL-Met (5927 g) and OH-Met (5916 g). However, it increased with the dose of methionine. Body weight and body weight gain were significantly improved with methionine addition. DL-Met and OH-Met lead to similar growth performance, respectively 3019 g and 3007 g of body weight gain on the 0-42 d period. However, unexpectedly, feed conversion ratio (FCR) increased with methionine addition. This was also observed by Kluge et al., (2016) on the 0-21 d period. Total amino acids recommendations for ducks are poorly documented and only some of the amino acids’ requirements are known. Given that our diets were formulated according to NRC (1994), there might be another amino acid limiting in the feed. According to Baeza (2016), methionine, lysine, threonine and tryptophan are the most limiting amino acids in ducks’ practical diets. However, it appears that threonine level in our basal diet (Table 2) is lower than the recommendations of Grimaud Frères (2015). In addition, the dietary energy levels of the experimental diets were slightly lower than the recommendations (Baeza, 2016; Grimaud Frères Company, 2015). Altogether, these slight differences might explain the lack of improvement of FCR for supplemented treatments in comparison to the basal diet. Therefore, there is a need to update the amino acids recommendations for ducks.

In addition, methionine efficacy determined as the extra methionine intake per extra weight gain shows similar values between DL-Met and OH-Met. The exponential modeling of the growth rate as function of the TSAA intake takes in consideration the difference of feed intake and allows to determine the actual bio-efficacy of OH-Met relative to DL-Met. The body weight gain follows the same exponential response for the two sources and shows no significant difference between the two methionine sources (P = 0.88). The bio-efficacy calculated as steepness coefficient ratio is of 99% with a confidence interval of [86%; 112%]; thus, confirming that DL-Met and OH-Met have the same bio-efficacy on body weight gain.

Carcass yields and feather weights are presented Table 3. Carcass weight and breast weight increased with methionine addition. Results observed with the basal diet are significantly different from the supplemented treatments. This is consistent with other studies which showed a degradation in breast yield with methionine (Conde-Aguilera et al., 2016) and lysine deficiency (Tesseraud et al., 2001;). DL-Met and OH-Met similarly improved carcass and breast weights. However, the carcass and breast weights expressed relative to the body weight (respectively, carcass yield and breast yield) were not affected by treatments. However, a linear regression model performed on the breast meat yield indicated that it increased linearly with methionine addition (P = 0.001). The absence of plateau in the breast yield response to methionine dose might also indicate that all amino acids requirements are not met yet; thus, confirming the observations made with the FCR. The comparison of slopes indicated no significant difference of breast yield between DL-Met and OH-Met (P = 0.47), thus confirming the bioequivalence of the two methionine sources.

Additionally, feather weights were measured at d 21 and d 42. No significant difference was observed in feather weight or yield at d 21. At d 42, results indicated a significant difference of feather weight between the basal diet (150 g) and the DL-Met supplemented treatments (172 g, P = 0.003) on one hand and between the basal diet and OH-Met supplemented treatments (174 g, P = 0.001) on the other hand. No significant difference of feather weight or yield was observed between DL-Met and OH-Met independently to the age. The two methionine sources promote feather growth in the same way.