Partial Explanation for Difference in Response of Hens Fed Diets Formulated Based on Lysine vs. Protein

Previous studies have indicated that hens fed diets formulated based on protein (FBP) produced more and heavier eggs compared with diets formulated based on lysine (FBL). It was hypothesized that this beneficial effect may be due to higher lysine or other amino acids rather then just protein per se. To test this hypothesis, fish meal (FM) which contains more lysine and has different amino acid ratios than soybean meal, was used to determine if the decline in performance associated with hens fed diets FBL could be prevented. Fish meal was used in diets FBL to supply the same quantity of TSAA and protein but more lysine (0.02 and 0.04%) than diets FBL. Three levels of FM (0, 2.5 and 5%) with three TSAA levels (0.65, 0.72 and 0.81%) were used to obtain the 9 dietary treatments. Three diets were also FBP to compare results. A total of 96 replicates of 16 hens each (n = 1536) were randomly assigned to 12 dietary treatments. Egg production (EP), feed consumption (FC), egg weight (EW) and egg specific gravity (ESG) were evaluated to determine hen performance. Hens fed diets FBP produced more (1.4%) and heavier (0.6g) eggs than hens fed diets FBL. Inclusion of FM (lysine) to diets FBL prevented the drop in EP and there was no significant difference (P > 0.05) in EP of hens fed diets FBP (90.4%) and hens fed diets FBL using FM (90.4%). However, FM (lysine) did not improve EW equal to hens fed diets FBP. Although FC was not influenced by FM (lysine), a TSAA effect was observed. Hens fed the higher TSAA levels consumed more feed than those fed the lower level. These results indicate that the difference in performance of hens fed diets FBP and FBL were not due to protein per se but at least partially due to lysine and other non-sulfur containing amino acids.