Two concurrent assays were conducted with the objective of evaluating the bioequivalence and determining the relative bioavailability value (RBV) of L-tryptophan biomass 60% for laying hens. In both assays, L-tryptophan 98% was used as the reference source. A total of 216 hens were used in the two assays. The first assay was performed using the direct comparison method to assess bioequivalence between the sources. In the second assay, the slope ratio method was used to determine the RBV. The variables analyzed were feed intake, tryptophan intake, egg production, egg weight, daily egg mass, feed conversion ratio, feed efficiency, yolk weight, shell weight, albumen weight, albumen height, eggshell thickness, Haugh unit, body protein weight, body lipid weight, body water weight, and body ash weight. The data from both assays were submitted to analysis of variance, and we only applied linear regression to variables from the data obtained using the slope ratio method that were significant at 0.05. The results obtained via the direct comparison method showed no significant difference (p > 0.05) between the L-tryptophan sources when using ANOVA. In the slope ratio method, the treatments only affected the egg production and daily tryptophan intake responses of the hens and linear equations were adjusted. No differences (p > 0.05) were found for egg quality. When we applied the slope ratio in adjusted equations, we found that the RBV = 100%. The results showed that the utilization of L-tryptophan biomass 60% in the diet of laying hens was bioequivalent.

The present research was defined to evaluate the residual feed intake (RFI) of white and brown groups of aged layers, between 85 to 90 weeks of age. A completely randomized design was used, with two treatments and 15 replicates, of one hen per replicate, for individual control. The treatment consisted of two genetic groups, brown and white (W-80), from Hy Line. Performance, egg quality, biometry visceral, body composition, energy partition, RFI, and residual metabolizable energy intake (RMEI) were evaluated. The results showed that egg weight was the main factor responsible for the difference between genotypes, affecting the production of the egg mass, yolk weight, and eggshell weight, as well as measures related to utilization efficiency (p < 0.05). The size of the uterus + vagina was larger for white layers (p < 0.05). The values obtained for RFI and RMEI were lower (p < 0.01) for white layers. While brown layers did not present hens with low RFI, 64.3% of the hens were classified as high RFI. The differences shown in this research between white and brown layers are smaller than in the past and show a tendency towards similarity; however, the economic impacts of the current differences are significant and must be considered.

This study aimed to assess the nutritional value of whole corn germ (WCG) in the diet of chickens. Amino acid digestibility, fatty acid digestibility, and metabolizable energy were evaluated. A metabolism assay was conducted using the precise feeding method on roosters. A completely randomized design was used, with two treatments and ten replications per rooster in each experimental unit. The treatments were as follows: WCG1, precise feeding with WCG; and WCG2, fasting birds to determine metabolic and endogenous losses in energy and fat. The variables analyzed were coefficients for amino acids in corn germ meal and fatty acid digestibility. The results showed that the standardized digestibility coefficients for amino acids in corn germ meal were (in g/kg) as follows: Lys, 920; Thr, 780; Met + Cys, 800; Arg, 910; His, 890; Ile, 950; Leu, 970; Phe + Tyr, 870; Val, 980; Gly + Ser, 740; Ala, 960; Asp, 870; and Glu, 930. The average fatty acid digestibility and AMEn were 850 g/kg and 4934 kcal/kg, respectively. Corn germ meal, which showed high digestibility of nutrients and energy, is considered an interesting ingredient for diets requiring high energy concentration.

This research evaluated levels of peanut meal inclusion in diets for laying hens. A total of 200 Hisex White hens, 72 weeks of age, were used in a completely randomized design with five treatments and ten replicates of four hens each. Treatments consisted of replacing soybean meal with peanut meal at 0, 25, 50, 75, and 100%. Over a 70-day period, feed intake, egg production, egg weight, egg mass, feed conversion, and internal and external egg quality were evaluated. Economic analyses of diets and estimates of the carbon footprint were also conducted based on life cycle assessment data of the ingredients. Total replacement of soybean meal with peanut meal did not significantly affect productive performance or egg quality (p > 0.05). Increasing levels of peanut meal inclusion linearly reduced feed cost, providing savings of up to US$ 41.81 per ton. In addition, a progressive reduction in the carbon footprint of the diets was observed, reaching a decrease of 26.37% in CO₂ equivalent emissions. Peanut meal can fully replace soybean meal in laying hen diets without compromising productive performance or egg quality while reducing feed costs and environmental impact.