Effect of the exclusion of synthetic amino acids and potentially GMO-protein sources in vegetable diets for laying hens

From week 21 to week 66, four vegetable diets were formulated on a base of 11,5 MJ ME and 0,41% methionine per kg feed. In comparison to the control d iet (diet A), soybean meal and maize gluten as potentially genetically modi fied (GMO-)protein sources were excluded in diet B and synthetic amino acid s (SAA) from diet C. Exclusion of both protein sources (GMO, SAA) was combi ned in diet D. Due to the fine structure, the experimental diets had to be crumbled. Feed and water were available ad libitum during the whole trial. A flock of 1800 white laying hens of H & N-hybrid was divided into ten unit s of 180 animals. The hens were kept in a floor system. Diets A and B were fed to three units each whereas diets C and D were given to two units each. Formulating diets without possible transgenic components was followed by a small reduction of egg production (-1,3%), whereas feed consumption per day and per egg as well as feed conversion rate were increased by 3,6, 5,0 and 5,6%, respectively. Due to the exclusion of SAA, crude protein content had to be increased from 18% in diets A and B to 19% in diets C and D (base: 0,41% methionine). The refore, nitrogen content in dry matter of feces (+14,0%) as well as daily n itrogen excretion per hen (+9,0%) were higher for diets C and D. Without di etary SAA, an increase in mortality rate (4,4 vs. 3,1%) was observed over t he whole trial, from which only a small part was due to cannibalism (0,6 vs . 0,0%). The exclusion of both protein sources (GMO, SAA) was followed by a signific ant reduction in egg weight (-1,0 and -2,0%, respectively). This effect cou ld also be seen in a higher percentage of eggs smaller than 53 grams (11,5 vs. 8,9%). Due to the exclusion of SAA, feather scores were worsened mainly in the sec und half of the trial. Effects of the exclusion of soybean and maize gluten as potentially GMO-protein sources on plumage condition were small and not significant. It can be concluded from this trial, that further limitations of available protein sources for vegetable layer diets can be followed by considerable e ffects on performance, plumage condition and feed structure as well as on a spects us ecology, animal health and animal protection. Therefore, these ar guments should also be considered in future discussions about additional re strictions on protein sources.