The use of nitrogen fertilization in tropical grasslands is a strategy that may reduce the pressure of livestock production on biome areas with humid forests. The objective of this study was to assess the use of different doses of nitrogen in Guinea grass (Megathyrsus maximus (Jacq.) con. Mombasa) cultivated in the humid tropics. Doses of 0, 10, 20, 30, 40, and 50 kg of N ha⁻¹ application⁻¹ were applied during two consecutive years in experimental plots. The experimental area is located in the northeast of Pará, Brazil, with a predominantly tropical climate according to the Köppen classification. The morphogenic, production, and qualitative characteristics of the forage were evaluated. The morphogenic variables, rate of leaf appearance and rate of leaf elongation, in addition to daily accumulation of forage and crude protein content, increased with increasing doses of nitrogen. The morphological structure of the pasture was not modified. The number of cuts increased, whereas the number of days of recovery decreased, in the rainy season with increasing doses of nitrogen. The use of nitrogen fertilization does not alter the structure of the pasture; however, it improves the morphogenic, production, and chemical characteristics of Guinea grass.

Nitrogen fertilization is one of the main management strategies for continuous pasture management with high productivity. We examined the effects of nitrogen fertilization on the morphogenic, structural, and tillering dynamic characteristics of Tanzania grass in the Amazon region in the state of Pará, Brazil. The study was conducted using a randomized block design with six treatments (0, 100, 200, 300, 400, and 500 kg N ha⁻¹ year⁻¹) and five replicates. The treatments were performed during the rainy season in 2016 and 2017 using urea as the nitrogen source. The leaf elongation rate was increased by 68.5% compared with that of the control treatment (p < 0.01). The leaf appearance rate and number of alive leaves increased with higher doses of nitrogen (p < 0.01, each). The regrowth period was reduced by approximately 13 days under 500 kg N ha⁻¹ (p < 0.01), thus providing more production cycles. Nitrogen fertilization was also associated with a higher tillering rate (p < 0.01); however, the rate of this increase decreased with increasing nitrogen dose. Higher nitrogen doses thus improved the development of Tanzania grass; however, this became less pronounced at doses < 300 kg N ha⁻¹.

The nutritional composition of bovine liver, particularly in terms of vitamins E, β-carotene, and cholesterol concentration, is significantly influenced by the cattle-rearing system and diet. This study aimed to elucidate the impact of four predominant cattle-rearing systems in the Eastern Amazon region on the vitamin E, β-carotene content, and cholesterol levels in bovine liver during the rainy season. Liver-tissue samples were collected from 48 cattle, with twelve specimens representing each rearing system. The systems encompassed two native pastures located in flood-prone areas, cultivated pastures on upland terrain and a confinement-rearing system. Our findings indicate that, when considering all rearing systems collectively, there were no significant differences in the levels of vitamins and cholesterol in the liver tissues (p > 0.05). However, a marked disparity in cholesterol levels emerged when comparing intensive rearing systems to extensive ones, with the former demonstrating notably higher concentrations (p = 0.01). Additionally, the intensive rearing system was associated with elevated levels of β-carotene (p < 0.01), α-tocopherol (p = 0.01), and β-tocopherol (p = 0.01) relative to the extensive systems. No significant variations were observed amongst the different extensive systems (p > 0.05). These results suggest that, while all rearing systems yielded liver tissues with typical concentrations of vitamins and cholesterol, the intensive rearing system led to a higher accumulation of certain vitamin compounds. This study highlights the substantial nutritional implications of different cattle-rearing systems in the Eastern Amazon and provides valuable insights for developing dietary strategies to optimize the nutritional quality of bovine liver. Therefore, the generated results are groundbreaking in the Eastern Amazon, Brazil, and inspire the development of new research projects to address other demands in this field and achieve additional outcomes.

The scientific literature currently lacks studies that evaluate the nutritional composition of the tissues of cattle raised in different systems, so that the nutritional effects can be known and used to enhance consumption and use in the diet. The aim was therefore to assess whether the mineral content of muscle tissue (longissimus lumborum) in cattle finished during the rainy season in the Eastern Amazon is influenced by different farming systems. The treatments consisted of four systems (three pasture production systems and one feedlot system). 1. native wetland pasture in Santa Cruz do Arari (Mesoregion of Marajó); 2. native wetland pasture in Monte Alegre (Mesoregion of Baixo Amazonas); 3. cultivated dryland pasture in São Miguel do Guamá (Mesoregion of Nordeste Paraense); and 4. Confinement in Santa Izabel do Pará (Metropolitan Region of Belém). The analyses were carried out on samples of the longissimus lumborum muscle tissue of 48 male, castrated, crossbred Nelore cattle, twelve per breeding system, from commercial farms, destined for meat production, finished during the rainiest period of the year (between January and June). In systems 1 and 2, the animals were slaughtered in licensed slaughterhouses; the animals in systems 3 and 4 were slaughtered in commercial slaughterhouses. Food sampling and chemical analysis, soil sample collection and analysis, longissimus lumborum muscle tissue collection, sample preparation and digestion, and inductively coupled plasma optical emission spectrometry were evaluated. The experimental design was completely randomized in a linear model with four rearing systems and one period (rainy). The data was compared using the Statistical Analysis Systems (SAS) program. All analyses were carried out considering a significance level of 0.05. Samples of the diets offered (pasture and concentrate) were also collected. The Amazon systems influenced the macro- and micromineral content in the muscles of cattle (p < 0.05). The interaction between pasture systems vs. confinement showed differences in the minerals calcium (Ca), magnesium (Mg), phosphorus (P), copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) (p < 0.05). However, there was no difference in the values of sodium (Na), potassium (K), and sulfur (S) between the rearing systems (p > 0.05). By contrast, the cultivated pasture system vs. extensive pasture showed differences in all the elements evaluated (p < 0.05). The rearing systems of the Eastern Amazon influenced the mineral content of beef, which continues to be an excellent source of macro- and microminerals and can compose the human diet.

This study aimed to investigate the relationship between rearing systems and seasonality (rainy and dry seasons) on the fatty acid (FA) composition in cattle. Samples of the Longissimus lumborum muscle were obtained from carcasses of 96 castrated Nelore cattle. The samples were lyophilized, and the FA composition was determined by the direct transesterification method and analyzed by gas chromatography. The rearing systems comprise two native pastures (extensive grazing), one cultivated pasture (intensive grazing) and one feedlot. Data were analyzed using generalized linear models, including the fixed effects of production system, season, and their interaction. Regarding polyunsaturated fatty acids (PUFAs), linoleic acid (C18:2n‐6), arachidonic acid (C20:4n‐6), and α‐linolenic acid (C18:3n‐3) were the most abundant in all systems. C18:2n‐6, C18:3n‐3, and C20:4n‐6 were higher in pasture systems than in the feedlot, especially in intensive grazing during the rainy season. In the dry season, the scenario was reversed; C18:2n‐6 and C20:4n‐6 showed a higher concentration in the feedlot system compared to pasture systems. The study demonstrated that pasture production, such as traditional extensive systems, promoted a better ratio of n‐6/n‐3, contributing to a healthier lipid composition in the meat, when compared to the feedlot. Although the feedlot system has a lower concentration of saturated fatty acids (SFAs), the analysis shows that the extensive system offers a more balanced and healthy FA composition.

Bovine liver is a food that is known to be nutritious and easily accessible to consumers. The nutritional quality of this food can be influenced by several factors, such as the rearing system. The objective of this study was to characterize the fatty acid profile in the liver tissue of cattle raised in the Brazilian Eastern Amazon, taking into account the effect of the rearing system and seasonality. Liver tissue samples from cattle raised in native pastures, in flooded areas, in cultivated pastures, in highlands and in a confinement, system was evaluated. The liver tissue from the extensive systems showed ( p < 0.05) a higher proportion of saturated fatty acids (C16:0 and 17:0) and a higher proportion of monounsaturated fatty acids compared with the confinement liver tissue. The sum of polyunsaturated fatty acids was higher for the hepatic tissue of the feedlot system compared with the pasture system; however, the tissue of animals from the pasture system showed much higher percentages of long‐chain PUFA′s such as EPA, DHA, DPA, and their precursor, alpha‐linolenic acid. The information gathered is important for optimizing the production of beef and its offal with desirable nutritional properties for promoting human health.