The consumer's profile has changed, and in recent years, there has been a greater concern for the nutritional quality of meat, especially in relation to fat that compose it. The meat fat composition can contribute to the onset of cardiovascular disease. On the other hand, fat is an essential component in the human diet, as well as providing energy; it contains essential fatty acids (FAs) that must be present in food. The meat nutritional properties are largely related to its fat content and fatty acid composition. In addition, fat gives flavor to food, helps in the absorption of vitamins, and plays an important role in the immune response, for humans, and animals. The fat nutritional and sensory quality in meat that is determined by the fatty acid composition can affect the degree of fat saturation, the storage stability, and flavor. There are several factors that can influence the fatty acid composition, such as animals' species, breed, sex, and diet, causing various changes in carcass, as well as in tissues and chemical meat composition.

-The objective of this work was to investigate adjustments of the Gompertz, Logistic, von Bertalanffy, and Richards growth models, in male and female chickens of the Cobb 500, Ross 308, and Hubbard Flex lines. Initially, 1,800 chickens were randomly housed in 36 pens, with six replicates per lineage and sex, fed ad libitum with feed according to gender, and bred until 56 days of age. Average weekly body weight for each line and sex was used to estimate model parameters using the ordinary least squares, weighted by the inverse variance of the body weight and weighted with a first-order autocorrelated error structure. Weighted models and weighted autocorrelated error models showed different parameter values when compared with the unweighted models, modifying the inflection point of the curve and according to the adjusted coefficient of determination, and the standard deviation of the residue and Akaike information criteria exhibited optimal adjustments. Among the models studied, the Richards and the Gompertz models had the best adjustments in all situations, with more realistic parameter estimates. However, the weighted Richards model, with or without ponderation with the autoregressive first order model AR (1), exhibited the best adjustments in females and males, respectively.Index terms: autocorrelated errors, autoregressive model, poultry science, homogeneity of variance, mathematical model, weighting structures. Ajuste de modelos de crescimento em frangos de corteResumo -O objetivo deste trabalho foi investigar os ajustes dos modelos de crescimento Gompertz, Logístico, von Bertalanffy e Richards em frangos fêmeas e machos das linhagens Cobb 500, Ross 308 e Hubbard Flex. Foram inicialmente utilizados 1.800 frangos, alojados aleatoriamente em 36 unidades experimentais, com seis repetições por linhagem e sexo, alimentados à vontade com ração, de acordo com o gênero, e criados até 56 dias de idade. A partir do peso vivo médio semanal de cada linhagem e sexo, realizou-se a estimação dos parâmetros dos modelos, por meio dos mínimos quadrados ordinários, ponderados pelo inverso da variância do peso e ponderados com estrutura de erros autocorrelacionados de primeira ordem. Modelos ponderados e modelos ponderados com autocorrelação apresentaram valores diferentes dos parâmetros comparados aos modelos não ponderados, mudando o ponto de inflexão da curva e de acordo com o coeficiente de determinação ajustado, e o desvio padrão do resíduo e os critérios de informação de Akaike apresentaram os melhores ajustes. Entre os modelos estudados, os de Richards e Gompertz resultaram nos melhores ajustes em todas as situações, com as estimativas mais reais dos parâmetros. Porém, o modelo ponderado de Richards, com ou sem ponderação com o modelo autorregressivo de primeira ordem AR (1), apresentou os melhores ajustes em fêmeas e machos, respectivamente.Termos para indexação: erros autocorrelacionados, modelo autorregressivo, avicultura, homogeneidade da variância, modelos matemáticos, estruturas de ponderação.

ABSTRACT. Effects on diets with reduction of crude protein and methionine + cystine (RCP) and protease supplementation (PRO) for laying hens at different ages and their influence on the internal quality of eggs at different conditions (STO) and storage times (TM) are evaluated. Four hundred and twenty eggs from commercial Hy-Line W36 laying hens collected at 32, 44 and 58 weeks of age were used. Experimental design was completely randomized in a factorial scheme 3 x 2 x 2 x 2: RCP (control, enhancement of one and two times the enzyme protease), PRO (with and without protease), STO (room temperature and refrigerated) and TM (14 and 28 days), with seven replications of one egg per experimental unit. The factorial scheme 3 x 2 x 2 was used at 58 weeks of age, because TM could not be evaluated. The percentages of egg weight loss, Haugh unit, albumen percentage, percentage and yolk index were evaluated after each storage time. RCP and PRO had no effect on internal egg quality whereas eggs under refrigeration preserved their internal quality regardless of the different storage periods.Keywords: egg yolk, egg white, enzyme, Haugh unit, nutrition, poultry.Qualidade interna de ovos de poedeiras leves alimentadas com protease em diferentes condições de armazenamento e estocagem RESUMO. O objetivo desse estudo foi avaliar os efeitos da redução de proteína bruta e metionina + cistina (RPB) e suplementação de protease (PRO) em dietas de poedeiras comerciais em diferentes idades, e sua influência sobre a qualidade interna de ovos armazenados em diferentes condições (ARM) e períodos de estocagem (EST). Foram utilizados 420 ovos das poedeiras comerciais da linhagem Hy-Line W36 colhidos com 32, 44 e 58 semanas de idade. O delineamento experimental foi inteiramente ao acaso em esquema fatorial 3 x 2 x 2 x 2 sendo os fatores: RPB (controle, valorização de uma e duas vezes da enzima protease), PRO (sem e com protease), ARM (ambiente e refrigerado) e EST (14 e 28 dias), com sete repetições de um ovo por unidade experimental. Com 58 semanas foi utilizado o esquema fatorial 3 x 2 x 2, pois não foi possível analisar o fator EST. Após cada período de estocagem foram avaliadas as características de perda de peso do ovo em porcentagem, Unidade Haugh, porcentagem de albúmen, porcentagem e índice de gema. A RPB e PRO não apresentaram efeitos na qualidade interna dos ovos. Ovos mantidos sob refrigeração tiveram a qualidade interna conservada, independente dos diferentes períodos de estocagem.

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The goal of this study was to evaluate the performance and the carcass traits of Nelore cattle progenies from bulls selected by contrasting traits for precocity, growth and muscularity, through the Expected Progeny Difference (EPD). One hundred and five Nelore bulls (initial weight of 350kg±15kg) and 20 months of age were confined and fed with same diet (73% of concentrate). Thirty-two animals were selected to create the contrasting groups for precocity, growth and muscularity (16 animals assigned as a low EPD group - LEPD and 16 animals assigned as a high EPD group - HEPD), based on the EPD of their parents. The ribeye area and backfat thickness were performed by ultrasonography of 12–13th rib fat thickness and longissimus muscle area (LMA), as well as rump fat thickness (RF) measurements. Animals were harvested after 100 days and during the deboning, meat cuts were weight for cutting yield. The animals selected for the HEPD group had greater average daily gain (P = 0.006), which can be explained by the higher feed intake (P = 0.006). However, there are no difference between groups for the final body weight (P = 0.254) and feed efficiency (P = 0.715). The LEPD group presented higher dressing percentage (P = 0.028). Although the groups evaluated did not presented difference in LMA (P = 0.329) and weight of longissimus muscle (P = 0.480), the weight of rump displayed heaviest in the HEPD (P = 0.037). There was no difference between groups for RF (P = 0.086). Nevertheless, backfat thickness was higher in HEPD group (P = 0.006). The present study indicates that Nelore cattle progenies, with parents displaying higher potential for precocity, growth, and muscularity, show greater backfat thickness and weightiest of rump than the other genetic backgrounds. Thanks to FAPESP for the scholarship (Grant # 2017/02349–1).