Tilapia (Oreochromis niloticus) is the most cultivated fish species in Brazil. Studies have shown that fish consumption is related to the prevention of cardiovascular diseases due to its high contents of polyunsaturated fatty acids, as omega-3 (n-3) and omega-6 (n-6). In this sense, a new method to determine omega-3 and omega-6 by near-infrared (NIR) spectroscopy and multivariate calibration based on partial least squares (PLS) was proposed. Spectra of fillets of Nile tilapias packed under vacuum were obtained and compared to the reference method (gas chromatography) used for quantification of fatty acids. The outliers were evaluated in the models that were validated by calculation of the parameters for model performance estimation, showing promising results. The appropriate values achieved for accuracy, limits of detection and quantification, indicate that the NIR/PLS models can be an alternative to chromatography in the determination of omega-3 and omega-6 in fillets of Nile tilapia. Furthermore, the spectra acquisition on the vacuum-packed fillet contributes to the NIR/PLS method in terms of cost and quickness.

RESUMO Objetivou-se, com este trabalho, avaliar as características produtivas e químicas do capim Marandu fertilizado com esterco de galinha com ou sem uso de escarificador, no período de 210 dias. O experimento foi realizado em Latossolo Vermelho distrófico de textura arenosa utilizando-se o delineamento em blocos casualizados com 4 repetições em esquema fatorial 6 x 2 (0; 1,037; 2,074; 4,148; 6,222) t ha-1 de esterco e tratamento adicional com adubação química baseado em 2,074 t ha-1, sem e com escarificação. O manejo de corte do capim foi realizado entre a interceptação luminosa de 95% do dossel e a altura de resíduo, de 0,15 m. O esterco de galinha proporcionou o aumento na produção de forragem com o aumento de número de cortes (NC). Com o modelo linear a quantidade do esterco aplicado é refletida na massa seca acumulada (MS), colmo + bainha (CB) e material morto (MM). Constatou-se interação entre doses de esterco e o manejo edáfico para lâmina foliar acumulada (LF), com maiores variações sem escarificação do solo. Na avaliação química da planta houve redução nos teores de Ca, Mg, N, S, Mn e Zn, com aumento de dose de esterco de galinha talvez pelo aumento no número de cortes. O esterco de galinha alterou de forma positiva a produção do capim Marandu.

ABSTRACT The objective of this study was to evaluate the productive and chemical characteristics of Marandu grass fertilized with poultry manure with or without the use of soil chiseling, during a period of 210 days. The experiment was conducted in a Dark-Red Latosol (Haplustox) of sandy texture, in a randomized block design with 4 replicates, in a 6 x 2 factorial scheme (0, 1.037, 2.074, 4.148, 6.222 t ha-1 of poultry manure and an additional treatment with chemical fertilizer based on 2.074 t ha-1, with and without soil chiseling). Grass-cutting management was performed between 95% of light interception by the canopy and the residual height of 0.15 m. The application of poultry manure resulted in an increase of forage production with higher number of cuts (NC). A linear model described the effect of the applied manure doses on dry matter accumulation (DMA), stems + sheaths (SS) and dead material (DM). There was significant interaction between manure doses and soil managements for leaf blade (LB), with greater variations in the treatment without soil chiseling. For plant chemical evaluation, a negative effect of poultry manure was observed on the contents of Ca, Mg, N, S, Mn and Zn, which may be due to the increased number of cuts. Poultry manure positively changed the production of Marandu grass.