Abstract: Exogenous phytase could influence dietary protein availability by variation in using dose. The objective of the present study was to determine if incremental dosing of an evolved E.coli 6-phytase would lead to improvements in lysine availability through evaluating performance and bone status in Bovans White layers. A total of 182 layers were placed in individual cages and distributed to 13 treatments: a 3 × 4 factorial arrangement with three levels of digestible lysine (dLys - 0.67, 0.77, and 0.87 %) and four doses of phytase (0, 300, 1 200, and 4 800 FTU/kg) in 0.12 % available P (avP) diets. Additionally, one phytase-free control treatment was included with 0.25 % avP and 0.87 % dLys. Productive parameters were recorded for 25 weeks, from 39 week-old. At the end, abdominal fat deposition and the tibia were sampled; in bone was determined breaking strength and bone ash. Layers fed 1 200 FTU/kg phytase increased egg production percentage (F3,169= 2.01, p = 0.111), abdominal fat deposition (F3,169= 2.52, p = 0.059), bone breaking strength (F3,169= 4.29, p = 0.006) and bone ash weight (F3,169= 3.62, p = 0.014) compared with non-phytase inclusion. Furthermore, 1 200 FTU/kg phytase decreased incidence of broken eggs and soft-shell eggs (F3,169= 2.9, p = 0.036). Phytase and dLys levels influenced egg mass and bone ash concentration (F12,169= 1.86, p = 0.043). FCR and body weight loss was reduced with phytase inclusion (respectively: F12,169= 2.43, p = 0.006, and F12,169= 2.24, p = 0.012). Phytase-free control diet increased egg weight (F12,169= 3.70, p < 0.001), but gave greater BW loss (F12,169= 17.79, p < 0.001), less abdominal fat content (F12,169= 5.85, p < 0.001), and no effect on other variables (p > 0.07). In conclusion, 1 200 FTU/kg of phytase improved productive performance and preserved body weight and bone status, without equivalence of phytase inclusion for dLys level, even with higher doses.

Two experiments were conducted to evaluate the nutritional quality of two sources of low-oil distiller's dried grains with solubles (DDGS) and their pigmenting ability for broiler chicken skin and egg yolks. In Experiment 1, 360 Bovan-White hens between 69 and 77 weeks of age were randomly assigned to five dietary treatments with 6 replicates of 12 hens each. In Experiment 2, 375 Ross 308 broiler chickens were randomly assigned to five treatments with three replicates of 25 birds each. The chickens were fed the experimental diets from one to 42 d of age. In both experiments, treatments consisted of a basal diet with no DDGS, and diets with 6% or 12% inclusion of DDGS from two sources. In Experiment 1, no significant differences in performance were detected among treatments (p> 0.05). Egg yolk pigmentation, according to CR-400 Minolta Colorimeter redness (a) and yellowness (b), linearly increased (p<0.05) with DDGS inclusions. In Experiment 2, no significant differences (p>0.05) were detected among treatments in growth performance, carcass yield, or abdominal fat at 42 d of age. Yellowness linearly increased (p<0.05) in the skin and abdominal fat of the birds that consumed diets with DDGS. The results of the current study indicate that feeding two sources of low-oil DDGS to broiler chicks or laying hens does not negatively affect egg production or growth performance while improves egg yolk and skin yellowness.

There is little information on the use of low-protein diets with the ideal protein profile for laying hen. An experiment was conducted to evaluate the layer performance of hen with low crude protein diets with the ideal protein profile. 240 hens Hy-Line W36 were used from 26 to 44 weeks of age, and the treatments were distributed among the experimental units in four treatments with five replicates of 12 birds each. The experimental design was completely random. The hens were fed sorghum plus soybean meal diets and synthetic amino acids formulated to 13, 14, 15 and 16% crude protein with similar levels of digestible amino acids lysine 0.725% (100), 0.596% methionine and cystine (82), threonine 0.509% (70) and tryptophan 0.179% (25). The variables studied were feed intake, egg production, egg weight, egg mass per bird d-1 and feed conversion. An analysis of repeated observations and a regression analysis with quadratic transformation was determined with each level of crude protein. Furthermore, we calculated the value of protein to maximize performance using the derivative of the regression formula. There was a quadratic effect (P ≤ 0.05) for egg production, egg weight, egg mass ave d-1 and feed consumption. The data analysis suggests that for better bird egg mass d-1 of laying hen Hy-Line W36, 15.3% crude protein is required in the diet. The relationship lysine-arginine and lysine-valine could be limiting for diets with 13% crude protein.

Existe poca información del uso de dietas reducidas en proteína con perfil de proteína ideal para gallina, por esto se llevó a cabo un experimento para evaluar el comportamiento productivo de gallinas con dietas bajas en proteína con perfil de proteína ideal. Se usaron 240 gallinas Hy-Line W36 de 26 a 44 semanas de edad, los tratamientos se distribuyeron entre las unidades experimentales en cuatro tratamientos con cinco réplicas de 12 aves cada una. El diseño experimental fue completamente al azar. Las gallinas se alimentaron con dietas sorgo + pasta de soya y aminoácidos sintéticos formuladas a 13, 14, 15 y 16% de proteína con niveles similares de los aminoácidos digestibles lisina 0,725% (100), metionina + cistina 0,596% (82), treonina 0,509% (70) y triptófano 0,179% (25). Las variables estudiadas fueron consumo de alimento, porcentaje de postura, peso del huevo, masa de huevo por ave d-1 y conversión alimentaria. Se realizó un análisis de observaciones repetidas y un análisis de regresión con transformación cuadrática con cada nivel de proteína. Además, mediante la derivada de la fórmula de regresión se calculó el valor de la proteína que maximice la producción. Hubo un efecto cuadrático (P ≤ 0,05) para porcentaje de postura, peso del huevo, masa de huevo ave d-1 y consumo de alimento. El análisis de los datos sugiere que para una mejor masa de huevo ave d-1 de gallinas Hy-Line W36, 15,3% es la proteína requerida en la dieta con los principales aminoácidos sintéticos presentes en el mercado. La relación lisina-arginina aparenta ser limitante para dietas con 13% de proteína así como la relación de lisina-valina.