RESUMEN
Low crude protein (CP) diets can reduce nitrogen (N) excretion and costs by increasing N utilization efficiency. Exogenous proteases may further improve protein digestibility in low CP diets. This study first evaluated in vitro the efficacy of a multiprotease on amino acid (AA) release from feedstuffs and broiler feed. Later, a broiler study evaluated the effect of feeding corn-soybean meal diets containing 3 CP levels (17, 19, and 21% CP) with supplementation on top of 0 or 2,400 U/kg multiprotease on chicken growth performance, total tract CP, and ileal AA digestibilities, and energy utilization. Ross 708 male chickens were placed in 42 cages and assigned to 6 treatments resulting from a 3 × 2 factorial arrangement. Three isocaloric basal diets were formulated to reduce CP, but all diets maintained digestible Lys:CP in 5.47% and the same ideal protein profile. Data were analyzed in a completely randomized design. On average, the multiprotease increased (P < 0.05) in vitro free AA release by 27.81% in most feedstuffs evaluated compared to the control. For broiler feed, 1,200 U/g multiprotease addition improved (P < 0.001) in vitro free AA release by 18.90%. This multiprotease showed interaction effects (P < 0.05) on chicken FCR, energy, and CP digestibility. As expected, BW at 24 d, BW gain, and FCR (8-24 d) worsened (P < 0.001) as dietary CP reduced from 21 to 17%, and multiprotease addition did not improve (P > 0.05) these parameters. BW gain decreased by 12.9% when N intake was reduced from 49.32 to 38.49 g/bird. Multiprotease supplementation improved (P < 0.01) AMEn by 71 kcal/kg, CP digestibility from 59.45 to 63.51%, ileal AA digestibility, and DM digestibility from 67.08 to 73.49%, but only in the 21% CP diet. No differences in ileal AA digestibility due to CP level (P > 0.05) were detected, except for Cys digestibility (P < 0.01). In conclusion, low CP diets reduced growth performance and improved N utilization but negatively affected energy utilization efficiency. Exogenous multiprotease supplementation improved AME, AMEn, protein, ileal AA, and DM digestibility in the 21% CP diet without significantly affecting growth performance.
Asunto(s)
Aminoácidos , Alimentación Animal , Fenómenos Fisiológicos Nutricionales de los Animales , Pollos , Dieta , Proteínas en la Dieta , Suplementos Dietéticos , Digestión , Metabolismo Energético , Animales , Pollos/fisiología , Pollos/crecimiento & desarrollo , Alimentación Animal/análisis , Dieta/veterinaria , Masculino , Aminoácidos/metabolismo , Fenómenos Fisiológicos Nutricionales de los Animales/efectos de los fármacos , Metabolismo Energético/efectos de los fármacos , Digestión/efectos de los fármacos , Suplementos Dietéticos/análisis , Proteínas en la Dieta/metabolismo , Proteínas en la Dieta/administración & dosificación , Distribución Aleatoria , Nutrientes/metabolismo , Péptido Hidrolasas/metabolismo , Péptido Hidrolasas/administración & dosificación , Relación Dosis-Respuesta a DrogaRESUMEN
Egg consumers worldwide have increased their concerns about laying hens' welfare and its impact on final egg product quality. This study compared the egg quality parameters under the conventional cage (CC) and cage-free (CF) egg production systems in the tropics. The study was conducted on a commercial farm in Colombia using Hy-Line Brown pullets, reared under the same conditions for the first 15 wks. At 16 wks, the hens were distributed into two housing systems, CC and CF, on the same farm. The hens were fed the same diet for each phase in both systems and feed intake varied slightly. Egg samples were collected every six wks, from 22 to 82 wks of age. A total of 3960 eggs were analyzed at 11 sampling times. Parameters such as albumen height, egg weight, yolk color, eggshell thickness, eggshell strength, and Haugh units were determined using a DET-6000 machine. At 22 and 82 wks, screening for Salmonella spp. status was conducted using environmental and egg samples. Additionally, at 34, 64, and 82 wks, yolk samples were obtained for fatty acid profiles and crude protein (CP) analysis. The data were analyzed in a completely randomized block design with repeated measures (11 times): mean separation by Student's t-test yolk pigmentation, Haugh Units, and albumen height (p < 0.001) were higher in the CF compared with the CC between 38 and 69 wks of age, and eggs at 63 and 82 wks (p < 0.05) were heavier in the CF compared to the CC. Likewise, eggs from the CC had better eggshell strength from 57 to 82 wks. In the egg yolk fatty acid profile at the 34th wk, the pentadecanoic, palmitic, and heptadecanoic acids had higher concentrations in the CF systems than the CC. At the 64th wk, the egg yolk fatty acids-lauric, myristic, and heptadecanoic-had higher concentrations in the CF; likewise, at the 82nd wk, egg yolks from the CC had higher concentrations of lauric, heptadecanoic, and nervonic fatty acids than the CF. The eggs and environmental samples were negative for Salmonella spp. throughout the whole production phase. These results indicated that the production system might impact internal and external egg quality measures, potentially due to various stressors, including environmental factors or behavior restrictions.
RESUMEN
Stress factors during poultry production can evoke changes in gene transcription and protein synthesis in the hen oviduct and could affect the internal and external egg quality. Studies of relative gene expression require the identification of the most stable reference genes for the quantitative polymerase chain reaction (qPCR) to investigate the reproductive tissues' response in laying hens kept in different production systems. The objective of this study was to determine the most stable reference genes of the magnum tissues of laying hens housed in two different production systems. Hy-Line Brown hens were reared under the same sanitary conditions until 15 weeks of age. Later on, they were transferred into two different production systems, conventional cage (CC) and cage free (CF), up to 82 weeks of age. At 50 and 60 weeks, a total of six hens from each production system were euthanized, and magnum samples were collected. The qPCR was used to determine the RNA transcription level of five reference genes, ACTB, 18S, GAPDH, MSX2 and HMBS. These genes were evaluated for transcript expression in magnum tissues by NormFinder, BestKeeper, geNorm and RefFinder software. The results indicated that the most stable gene in the CF housing system was HMBS in three of the algorithms and in the CC housing system was the 18S, and the best combination of reference genes was HMBS/GAPDH in CF and 18S/HMBS in CC. In conclusion, HMBS, 18S and GAPDH genes could be used together as reference genes for the normalization of the magnum tissues transcript expression of hens in CF and CC housing systems.