Abstract
Two consecutive growth experiments with meat-type chickens (Ross 308) were conducted in order to quantify the age-dependent amino acid (AA) content in the whole body protein of male and female birds based on experimental data of the feather and feather-free body protein fractions. Birds were reared under uniform housing and feeding conditions (floor pens, 15 pens per gender, 5 birds per pen) during the starter (day 1 to 22) and grower period (day 22 to 36). Both the starter and grower diet based on corn, wheat, soybean meal, soybean protein concentrate and feed amino acids was formulated to ensure an equal feed protein quality close to the ideal amino acid ratio by adjusting a constant mixture of the feed proteins. At start of the experiment and further on weekly up to the end of the 5th week, 15 birds per gender (each 3 pens of 5 birds) were selected and fasted for 24 h, to emptying of gastro-intestinal tract, respectively. Subsequently, birds were euthanized and the feathers were manually removed. Nitrogen (N) and AA content were determined both in the feather and feather-free body fraction. The concentration of individual AAs in both of body protein fraction is varying considerably. Explicitly higher Cys, Ser and Pro but importantly lower Met, Lys and His concentrations were found in the feather protein. Furthermore, significant differences (p for nearly all AAs of the studied body protein fractions and the whole empty body protein dependent on age of birds were observed. Especially high deviations were obtained during the first week of age and at the end of the experiment. According to this observed variation of AA concentrations must be concluded that the body AA composition of meat-type chickens during growth is not constant. The detected gender-specific differences for several AAs in the feather and body protein of male and female birds were rather low and with very low variation.
Highlights
Body composition data of modern fast growing meat-type broiler chickens provide important information for further optimization of nutrient supply
Two consecutive growth experiments with meat-type chickens (Ross 308) were conducted in order to quantify the age-dependent amino acid (AA) content in the whole body protein of male and female birds based on experimental data of the feather and feather-free body protein fractions
In addition to our experimental data including both the age and gender dependent proportions of the feather and feather-free body fraction including their protein partitioning [28] [29], the present study aimed to provide detailed results about the AA composition of the whole body protein based on weekly analyses of feather and feather-free body fractions from male and female meat-type chickens during the entire growing period up to market weight
Summary
Body composition data of modern fast growing meat-type broiler chickens provide important information for further optimization of nutrient supply. Different assumptions exist regarding the age and gender dependent body AA composition. Constant AA contents in feather and feather-free body protein were applied as reference data for assessing AA requirement data [6] [7]. This assumption is invalid according to influencing factors like genotype [8] [9] [10], gender [11] [12] and age [11] [13]-[18]. An increased accuracy in estimations of the adequate dietary AA supply could be achieved if substantial body protein fractions are initially investigated separately
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