Unique stomach physiology allows ruminants to utilise any form of dietary nitrogen (N) as a protein source. Ruminant N requirements can be divided into N requirements for microbial fermentation and host requirements for amino acids. Ruminant diets often contain non-protein nitrogen (NPN) compounds, a group of components that are not proteins but can be converted to proteins by rumen microbes. Therefore, NPN compounds in ruminant diets serve as alternative sources of ammoniacal nitrogen (NH3-N), which is necessary for the synthesis of microbial protein (MCP) in the rumen. MCP is an important component of metabolizable protein for ruminants and, under certain production conditions, may be the only amino acid source for synthesis of tissues and products. In this manner, ruminants utilise NPN compounds without having enzymes for their degradation. The use of NPN compounds in ruminant nutrition allows for an increase in feed consumption and utilisation, as well as the substitution of protein supplements, which in turn leads to more cost-effective production. However, abrupt supplementation or excessive consumption of NPN could negatively affect MCP synthesis, feed digestion, and animal production. On the other hand, it may lead to animal poisoning and the release of large amounts of N into the environment. Knowledge of N metabolism in the rumen, as well as optimization of its utilisation, sets the conditions for the presumed beneficial effects of NPN compounds in ruminant diets, without adverse effects on animal health and the environment. Therefore, the aim of this study was to summarize the recent literature data on the metabolism and utilisation of NPN compounds in ruminants.

The problem of the erosion of animal genetic resources is evident in certain local donkey breeds, and their long-term sustainability can be achieved by economically repositioning them. To develop alternative and sustainable commercial programs, the meat and milk production characteristics of Istrian donkey and Littoral Dinaric donkey breeds were investigated. The meat production characteristics were examined in mature males, whose carcasses were dissected, and meat composition was determined using NIT spectrophotometry and gas chromatography. Milk yield and milk composition were determined in jennies in second or subsequent lactations by measuring milk volume and using infrared spectrometry and gas chromatography. Compared to the Littoral Dinaric donkey, the Istrian donkey has a higher carcass weight and dressing percentage (p < 0.001). The share of boneless meat in relation to live weight was 28.27% in the Istrian donkey and 26.18% in the Littoral Dinaric donkey. The absolute masses of primal cuts of meat in E, I, and II classes were significantly greater in Istrian donkeys than in Littoral Dinaric donkeys (p < 0.01), although the differences in the proportions of primal cuts were not significant. The breed did not have a significant impact on the color, pH, or meat composition. A significant influence of breed on milk yield, lactose, protein, and the fat content of milk was observed (p < 0.01). A significant influence of breed on the ratio of n-6/n-3 PUFA fatty acids in donkey milk was observed (p = 0.002). The values of the atherogenic and thrombogenic indexes were favorable, considering potential beneficial effects of donkey milk and meat on consumer health. The findings of this research suggest that local donkey breeds hold significant potential for meat and milk production, focusing on the uniqueness and quality of their products rather than the quantity of meat and milk they can produce.

Gestational diabetes mellitus (GDM) is a public health problem with increasing prevalence. Analyses of metabolic and immune profiles have great potential for discovering new markers and mechanisms related to the development of GDM. We monitored 61 pregnant women during the first and third trimesters of pregnancy, including 13 pregnant women with GDM, 14 pregnant women with elevated glucose in the first trimester and 34 healthy pregnant women. A number of metabolic and immunological parameters were measured, including glucose, insulin, lipid status, fatty acids, lymphocyte profile, adiponectin, IL-6, IL-10 and TNF-a. A higher number of T-helper lymphocytes and a higher ratio of helper/cytotoxic lymphocytes was found in the control group in the first trimester of pregnancy. Pregnant women whose glucose threshold values were measured in the first trimester, but who did not develop GDM, showed a higher percentage of neutrophils and a lower percentage of lymphocytes in the third trimester. Differences in polyunsaturated fatty acids levels were observed between healthy pregnant women and those with glucose metabolism disorders in the first trimester of pregnancy. The results of this pilot study demonstrate that there are differences in the profiles of T lymphocytes, NK cells and polyunsaturated fatty acids between the examined groups of pregnant women, which can serve as a direction for future research.