Age and Gender Dependent Amino Acid Concentrations in the Feather, Feather-Free and Whole Empty Body Protein of Fast Growing Meat-Type Chickens

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.

Age and Gender Dependent Nutrient Composition of Feather and Feather-Free Body Fractions in Meat-Type Chickens

The objective of this research was to update current results about the nutrient composition of broiler chickens during the growth period up to market age. Two growth experiments were conducted for assessing the nutrient content of feathers and feather-free body of meat-type chickens (Ross 308). Both male and female birds were reared under uniform management conditions (floor pens;15 pens per gender;5 birds per pen). Experimental diets both for the starter (day 1 to 22) and the grower period (day 22 to 36) were based on corn, wheat, soybean meal, soybean protein concentrate and well balanced with feed amino acids. The feed protein quality was adapted to the ideal amino acid ratio and equated within both of the feeding periods by adjusting a constant mixture of the feed proteins. Each 15 birds per gender (3 pens of 5 birds) were selected and subsequently fasted for 24 h before quantitative de-feathering both at start of the experiment and further on weekly up to the end of the 5th week. Nutrient content was determined in representative samples of the feather and feather-free body fraction. In the feather dry matter (DM) very high crude protein (CP) concentrations (>96%) with low age-dependent and insignificant gender-specific differences were observed. In spite, a relatively high variation of CP content in the DM of feather-free body was found. Depending on age, the body CP significantly decreased with increasing age, but male birds yielded higher (p < 0.001) CP content. The crude lipid content of the feather-free and whole empty body significantly increased with age and was higher in female as compared to male birds (p < 0.001). Depending on age and gender, the crude ash content both in feathers and feather-free body of modern fast-growing chickens was rather low and with very low variation.

An Elevated Dietary Cysteine to Methionine Ratio Does Not Impact on Dietary Methionine Efficiency and the Derived Optimal Methionine to Lysine Ratio in Diets for Meat Type Chicken

Optimal dietary methionine (Met) to lysine (Lys) ratio in presence of elevated dietary cysteine (Cys) levels was derived for meat type growing chicken. Twelve averaged weighed Ross 308 birds (each 50% of male and female per dietary treatment) were utilized in N balance trials. During starter (d10 - 20) and grower period (d25 - 35) five dietary treatments were used. Diets based on uniform mixtures of maize, wheat, soybean meal, potato protein and fish meal were supplemented with crystalline amino acids (AA). In diets 1 - 3, the dietary Cys to Met ratio was set as 85, 95 and 105 to 100, respectively. Diet 4, at a Cys to Met ratio of 105 to 100, was additionally supplemented with betaine (BET) as methyl group donor. Diets 1 - 4 were limiting in Met, diet 5 without L-Lys·HCl addition was limiting in Lys. Individual N-balance data per treatment were utilized for assessing protein quality and efficiency of dietary Met (Diets 1 - 4) or Lys (Diet 5) based on “Goettingen approach”. Elevated dietary Cys supply and supplemented BET failed to improve both dietary protein quality and Met efficiency. The established optimal Met to Lys ratio was on average 34 to 100 for growing chicken during starter and grower period, respectively.

Relative Bioavailability of DL and L-Methionine in Broilers

Studies on the relative bioavailability (RBV) of DL-Methionine (DL-Met) to L-Methionine (L-Met) have produced variable results. An experiment was conducted to determine the RBV of DL to L-Met. A total of 2268 1-day old male chicken were housed in 54 floor pens (42 bird/pen). There were 9 treatments (6 repetitions) including the basal diet (BD). The BD was deficient in Met content with 0.27, 0.26 and 0.25 in the starter, grower and finisher periods respectively. Four levels of experimental diets for each DL-Met and L-Met were created by supplementing 0.05%, 0.10%, 0.15% and 0.20% of DL- or L-Met to the BD. The feeding program consisted of starter (0-14 d, 21% CP and 2900 kcal ME/kg), grower (15 - 28 d, 20% CP and 3000 kcal ME/kg) and finisher period (29 - 37 d, 18.5% CP and 3050 kcal ME/kg). Chickens and feed were weighed at the end of each age period. Regression coefficients of a common plateau asymptotic regression were used to calculate RBV. Birds responded to gradual increase in Met levels, BW, FCR and ADG were significantly (P 0.05) higher in treatment groups as compared to control. Through the study period (37 d), the RBVs of DL-Met for BW and FCR were 89 and 77 respectively.

Age and Gender Depending Growth of Feathers and Feather-Free Body in Modern Fast Growing Meat-Type Chickens

Two growth experiments with fast growing meat type chickens (Ross 308) were conducted to assess the growth of feathers and feather-free body dependent on age and gender (male:female ratio = 1:1). Birds were reared under uniform management 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). Diets were based on corn, wheat, soybean meal, soybean protein concentrate and balanced with feed amino acids to ensure an equal feed protein quality close to the ideal amino acid ratio by 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 24 h fasted before quantitative de-feathering. Both feather and feather free body fractions were significantly increased with increasing age of the birds (p < 0.001). Feather percentage as related to the empty body weight increased non-linearly from approximately 2% at the end of the first week to about 4% at the end of the experiment. Feather percentage and dry matter content of the feather-free body was significantly higher in female birds (p < 0.001) as compared to males. Further investigations will show how this varying proportions impact on nutrient deposition of modern meat-type chickens dependent on age and gender, respectively.