The hazelnut skin is waste biomass rich in bioactive compounds that may affect lipid rumen metabolism, ruminant performance, and products’ quality. Therefore, we investigated the effect of dietary hazelnut skin on milk production and composition and on rumen fatty acids in ewes. During 28 days, 20 Comisana lactating ewes received alfalfa hay ad libitum plus 800 g/head/day of pelleted concentrate containing 36% dried beet pulp (CTRL group; n = 10) or 36% hazelnut skin (HS group; n = 10). The protein percentage was lower in HS milk. Milk fatty acids (FA) partially reflected those of rumen content. Total saturated FA (SFA), odd and branched-chain FA, and n-3 polyunsaturated FA (PUFA) were greater in CTRL milk. Total monounsaturated FA (MUFA) and 18:1 trans were greater in HS milk; moreover, HS milk showed a double percentage of oleic acid than the CTRL group. Individual SFA were greater in CTRL milk except for 18:0. Differing from the rumen content, total PUFA, n-6 PUFA, and 18:2 n-6 were comparable between groups. Vaccenic and rumenic acid were greater in HS milk. To conclude, dietary HS slightly reduced milk protein percentage but improved atherogenic index and healthy FA in milk. The content of the somatic cells suggested a healthier udder in the HS group.

The aim of this study was to examine the influence of the level (1, 3, and 5 mg I/kg) and source of iodine (KI, Ca(IO₃)₂, and KIO₃) on thyroid hormone and immunoglobulin concentrations in the blood serum of laying hens alongside a histological picture of the thyroid. In the first, birds were fed grain–soybean meal mixtures, and in the second, two kinds of diets based on corn–soybean or corn–soybean–rapeseed meal were applied. In the experiments, we determined the levels of the blood serum thyroid hormones fT₃ and fT₄, as well as the morphological structure of the thyroid gland. In the second experiment, the concentration of immunoglobulins in blood serum was assayed. In both experiments, no influence of iodine source on thyroid hormone concentration was observed. However, increasing the iodine level in the full mixture and adding rapeseed meal in both experiments caused an increase in fT₃ concentration. Increasing I-addition in both experiments led to a decrease in thyroid gland follicle diameter. Rapeseed meal inclusion (at a level of 10%) to the complete hen mixture led to an increase in thyroid gland follicle diameter. Applying KIO₃ as an iodine source in both experiments caused a decrease in the thyroid gland height of follicle epithelial cells. Immunoglobulin concentrations in the serum were not affected by experimental factors. The results suggest that the methodologies of studies on the bioavailability of minerals and the corresponding analytical methods require unification. The lack of such standardization makes it impossible to engage in a satisfactory discussion of the results and exchange experiences.

An in vitro experiment was conducted to determine the impact of silage produced from selected varieties of sorghum on the microbial fermentation profile of cows’ ruminal fluid. To determine the main microbial fermentation products, ruminal fluid samples were obtained from Polish Holstein–Friesian cows. Serum bottles were filled with 80 mL of ruminal samples, and 1 g of one of the following substrates was added: corn silage (CS), grass silage (GS), rye silage (RS), sorghum silage (sweet) (SS1), sorghum silage (grain) (SS2) or sorghum silage (dual-purpose) (SS3). The serum bottles were flushed with CO₂ and fermented for 8 and 24 h at 39 °C. After incubation, the obtained gas and rumen fluid were then analysed to determine the methane and volatile fatty acid (VFA) contents using gas chromatography. The use of sorghum silage (SS) resulted in a decrease in the total concentration VFA concentration in the ruminal fluid compared with the use of other silages, especially GS. Moreover, the ruminal fluid contained a lower molar proportion of propionic and butyric acids when SS was used compared with CS. The butyric acid proportion was higher in SS samples than in RS samples. The differences in chemical composition between sorghum varieties did not influence the rumen VFA concentration or profile. A decrease in gas production, but without effects on methanogenesis, was observed when SS was used compared with GS and CS. The analysis demonstrates the physiological processes of fermentation in the rumen, as evidenced by the products of microbial fermentation. The main advantage is that the addition of SS, irrespective of the plant variety, reduced fermentation gas production in the ruminal fluid compared with CS. The silage of the analyzed sorghum varieties may be used in the diets of dairy cows as a substitute for corn and grass silages.

In recent years, edible by-products (including the liver) have gained growing popularity among consumers. That is why the study aimed to assess the energy value, chemical composition, and mineral content of broiler chicken livers after including wheat germ expeller (WGE) in the feed of the broilers. Liver samples were obtained from 32 Ross-308 chickens (8 individuals per treatment). The control group received a basal diet, whereas the remaining treatments (EX5, EX10, and EX15) were characterized by a partial substitution of ground wheat with 5%, 10%, and 15% WGE. The WGE inclusion did not influence liver weight or chemical composition. However, livers from the CT group showed a higher energy value (p ≤ 0.05) than the EX15 group. Sodium and calcium contents were higher in CT and EX5 livers than in EX10 and EX15. No differences were observed in micronutrient levels between groups. A 100 g portion of EX15 livers provided the highest NRV coverage for phosphorus, iron, zinc, and copper, while EX5 livers were richest in calcium and magnesium, and CT livers in manganese. Total Hazard Quotients for Fe, Zn, Cu, and Mn in chicken livers were below 1, suggesting no potential health risk to consumers. These findings indicate that livers, also from WGE-fed broilers, may serve as a valuable dietary source of minerals for people.

Mineral homeostasis in horses is traditionally attributed to the coordinated regulation of the intestine, kidneys, skeleton, and endocrine system. Emerging evidence suggests the gut microbiota also shapes this process by modifying the intestinal environment where mineral absorption occurs. Despite the growing interest in host–microbiota interactions, the mechanisms linking the equine gut microbiota to mineral metabolism remain poorly understood and have not been comprehensively synthesized. This review integrates current knowledge of equine gastrointestinal physiology, gut microbial ecology, and mineral metabolism to examine how the gut microbiota influences mineral homeostasis, focusing on microbial fermentation, bioactive metabolite production, luminal pH regulation, epithelial barrier integrity, modulation of intestinal mineral transporters, and interactions with endocrine and immune pathways. The assessment of macro minerals such as calcium, phosphorus, and magnesium, along with trace minerals like iron, zinc, copper, selenium, and manganese, was conducted with a critical approach. This evaluation differentiates between results derived from equine research and those inferred from studies on other species. However, direct mechanistic evidence in horses remains limited, highlighting the need for future research. Advancing equine microbiome research through integrated microbiome profiling, metabolomics, molecular biology, and mineral balance studies will improve our understanding of host–microbiota interactions and support microbiome-informed nutritional strategies to enhance mineral utilization, gastrointestinal health, skeletal function, and long-term equine health and performance.