Data interpretation raises risk for performance depression in broiler production - Reply.

We disagree with the letter to the editor entitled “Data interpretation raises risk for performance depression in broiler production” (Lemme and Mack, 2021). The Ross 308 performance objectives at 10, 23, and 35 days of age are 321, 1142, and 2235 grams for the body weight and 0.947, 1.240, and 1.473 for FCR, respectively (Aviagen, 2019a). The birds in the cited trial fed first or second inclusion level of L-Met (see Table 3 in Millecam et al., 2021) achieved performance comparable with the Ross 308 objectives. Better performance was achieved at the recommended level of L-Met plus Cys, indicating no risk to broiler production using the recommended level of L-Met plus Cys. The performance data left no doubt about other nutrients becoming limiting.

Data presented by Millecam et al. (2021) is measuring L-Met plus Cys requirements in 3 broiler growth phases. Each phase used new birds to allow accurate measurement of L-Met plus Cys requirements by age while avoiding carry over effects of lack of a nutrient deficit from previous phases. In the absence of a feed grade L-Met, Met plus Cys recommendations have been developed using DL-Met. Fickler et al. (2016) recommends 0.92, 0.81, and 0.76 dig Met plus Cys for starter, grower and finisher phases in male broilers (in line with the Aviagen (2019b) recommendation.). Millecam et al. (2021) suggests an optimal dig Met plus Cys of 0.69, 0.66, and 0.62%, respectively. Despite the lower requirements achieved by using L-Met, Millecam stated “the deviation might be attributed to some extent to a higher bioavailability of L-Met than DL-Met. Other factors cannot be excluded in the present study”. The authors did not compare bioavailability of L-Met with DL-Met. It is focused on L-Met plus Cys requirements of broilers and describes why eventually their data should be lower than available table values which are based on DL-Met. The basal diets contained 0.60, 0.55, and 0.50 dig Met plus Cys in the starter, grower, and finisher periods (0.30 below the known recommendations). The protein levels in feed were also in line with common practice. Raw materials and feed samples of all treatment groups have been analyzed for major nutrients including amino acids at CBA GmbH (Boehlen, Rötha, Germany). We reject the speculation about the inconsistency of analytics because Fickler et al. (2016) used calculated values only. Millecam et al. (2021) reported lab based analytical results of raw materials as well as all the individual feeds (see Supplementary Materials in Millecam et al., 2021).

There is no current official recommendation for Gly plus Ser (Aviagen, 2019b) thus it is not common to keep a minimum level in formula. Nevertheless, Millecam et al. (2021) reported Gly plus Ser contents of the feed. At very low crude protein levels, non-essential amino acids Gly plus Ser might become a limiting factor but conclusions based on multiple research studies have been variable. Both Gly and Ser can be derived also from threonine, betaine and choline metabolism (Hofmann et al., 2020). Further research is needed before Gly and Ser can be applied in feed formulations.

DISCLOSURES

B. Saremi and D. R. Khan are employees of CJ Europe GmbH. All other authors declare that they have no conflict of interest.