Energy values and metabolizability coefficients of maize kernels with different specific gravities / Valores energéticos e coeficientes de metabolizabilidade de grãos de milho com diferentes densidades específicas

The aim of this study was to examine the influence of the specific gravity of maize kernels on physicochemical traits, energy values, and metabolizability coefficients. Pearson's correlations were evaluated between specific gravity (kg/m3) and crude protein (%); ether extract (%); crude fiber (%); gross energy (%); presence of fumonisins (ppb) and aflatoxins (ppb); and kernel quality (good, rotten, weevil-damaged, broken, and shriveled kernels, %). A metabolism trial was conducted with diets containing maize fractions of different specific gravities for male broilers from 14 to 21 days of age. Apparent metabolizable energy (AME), nitrogen-corrected AME (AMEn), and the metabolizability coefficients of dry matter (MCDM), crude protein (MCCP), ether extract (MCEE), calcium (MCCa), and phosphorus (MCP) were evaluated. The experiment consisted of five treatments (reference diet and diets with 40% replaced with maize at five specific gravities (740, 740, 760, or 800 kg/m3). Eight replications were used, totaling 400 broilers chickens. The Scott-Knott test was applied and regression equations were fitted to compare the treatments. Specific gravity had moderate correlations with good and broken kernels and low-magnitude correlations with chemical parameters. Increasing specific gravities caused AME and AMEn to increase linearly when analyzed on an as-is basis; and to respond quadratically when expressed on a dry-matter basis. The specific gravity of 780 kg/m3 provided the lowest MCDM, MCCP, MCCa, and MCP values, whereas the lowest MCEE, was found at the lowest density. It was not possible to determine the best nutritional composition or the best metabolizability coefficients.(AU)

Objetivou-se avaliar a influência da densidade do grão de milho sobre características físico-químicas, valores energéticos e de metabolizabilidade aparente. Avaliou-se a correlação entre a densidade específica (kg/m3) e os parâmetros: proteína bruta (%); extrato etéreo (%); fibra bruta (%); energia bruta (%); presença de fumonisinas (ppb) e aflatoxinas (ppb); umidade (%); grãos bons, quebrados, chochos, carunchados e ardidos, em Percentagem. Um ensaio de metabolismo com dietas contendo diferentes densidades específicas do grão de milho, para frango de corte, no período de 14 a 21 dias de idade, foi conduzido para avaliar a energia metabolizável aparente (EMA) e a corrigida pelo balanço de nitrogênio (EMAn), os coeficientes de metabolizabilidade: matéria seca (CM_MS), proteína bruta (CM_PB), extrato etéreo (CM_EE), cálcio (CM_Ca) e fósforo (CM_P). O experimento foi composto por cinco tratamentos (dieta referência e dietas substituindo 40% desta com milhos de densidades específicas: 740 kg/m3, 760 kg/m3, 780 kg/m3 e 800 kg/m3), com oito repetições, totalizando 400 frangos machos. As médias foram comparadas pelo teste de Scott-knott e estimada as equações de regressão nas diferentes densidades específicas das frações de milho. As correlações entre a densidade específica e grãos bons e quebrados foram de moderada magnitude e com os parâmetros químicos foram de baixa magnitude. Com o aumento da densidade específica para EMA e EMAn na matéria natural obteve-se resposta linear decrescente, enquanto na matéria seca, foi quadrático. Para CMMS, CMPB, CMCA e CMP a densidade de 780 kg/m3 apresentou os menores valores, enquanto para CMEE, o menor valor foi para a menor densidade específica. Não foi possível determinar a fração de milho com melhor composição nutricional e melhores coeficientes de metabolizabilidade.(AU)

Performance of brown layers fed reduced dietary protein levels in two rearing systems

An experiment was conducted aiming to evaluate the effect of different levels of crude protein, based on the ideal protein concept and two rearing systems, on productive performance of brown laying hens. A total of 400 Hisex Brown laying hens between 30 and 45 weeks of age were distributed in a completely randomized design and a 2×4 factorial arrangement, with main effects including two rearing systems (cage and floor) and levels of crude protein (140, 150, 160, and 180 g kg−1), totalizing eight treatments. Five replicates with 10 birds each were used per experimental unit. The following parameters were evaluated: egg production, feed intake, body weight gain, feed conversion ratio, and quality traits such as dirty, cracked, or broken eggs. No interaction effect was observed between dietary protein levels and rearing systems for body weight gain, feed intake, egg production, egg weight, and feed conversion ratio. Feed intake and egg production were higher in the floor rearing system. Feed conversion ratio (kg/dz) was improved in birds reared in the cage system. The rate of cracked and broken eggs was higher in the cage system. The layers reared in the floor system produced a higher percentage of dirty eggs. The dietary protein level did not affect the evaluated parameters. Thus, we conclude that a floor rearing system is an option for layers, and the dietary protein level can be reduced up to 140 g kg−1 for Hisex Brown hens from 30 to 45 weeks of age.(AU)