*3.2. Mineral Profile*

The changes in feeding are manifested in blood serum mineral profile [45]. Minerals perform a number of important physiological functions, such as the effect on acid-base balance, osmotic pressure, adrenal function, normal heart function, but also the metabolism of proteins or carbohydrates [46–48]. The difference in the P content after the GP was not statistically significant (Table 5). However, average P concentrations were higher than the upper limits in comparison as previously reported [48–51]. On the other hand, Jelinek et al. [52] found in rams similar blood serum P content from 2.49 to 2.92 mmol/L (depending on age). Identically, Chedea et al. [25] did not describe a statistically significant effect of dried GP (15% concentrations) in dairy cows on blood serum P content. The Ca content was similar, after feeding of all examined diets and in the interval according to Merck [51] (2.88–3.20 mmol/L). Ca concentrations were also comparable with data reported by Dias et al. [20] and Kovacik et al. [37], but higher in comparison with Schweinzer et al. [53]. Similarly, Chedea et al. [25] reported an effect of dried GP on Ca content in dairy cows (diet contained 15% dried GP). Iannaccone et al. [26] also reported in Fresian calves (10% proportion of dried GP meal in concentrate) a significant effect on the content of Ca. A similar ratio of Ca:P 1.07:1 (C, GP1) and 1.13:1 (GP2) was found which is in consent with previously reported data [48]. Concentrations of Mg in experimental groups were higher than upper limits 1.10 mmol/L found by Tschuor et al. [50] and 1.31 mmol/L Merck [51]. Simpraga et al. [21] determined the content of Mg 1.30–1.60 mmol/L, which was similar to GP2. The GP addition did not affect the content of Mg, which was also confirmed by Chedea et al. [25]. The Na+ content was after the addition of GP lower in comparison with control variant but its content was in the interval 130.00–155.00 mmol/L reported by Vrzgula et al. [48]. However, the analyzed Na+ values were lower than determined by Kovacik et al. [37]. The intake of GP decreased non-significantly the K+ content. According to Merck [51], the reference range for K+ is 3.90–5.40 mmol/L. The values found in our experiment were in the range reported by Tschour et al. [50] (4.60–6.50 mmol/L). The ratio of Na and K 23.81:1 (C), 24.04:1 (GP1), 26.53:1 (GP2) was found, thus similar compared to the recommendation of Vrzgula et al. [48]. The 2% GP intake increased the concentrations of Cl− (*p* < 0.05), which we do not consider a negative effect, because the main problem for chlorides is mainly a decrease, which can cause digestive disorders [48]. However, in all groups, the Cl− concentrations in blood serum were in physiological range according to Vrzgula et al. [48] and Tschour et al. [50], but higher compared to Merck [51]. Kovacik et al. [37] found higher concentrations of Cl− compared in their study. The main factor that can influence the reduced mineral absorption in this type of dietary supplement is increased fiber intake [54], which is not confirmed by animals' in vivo studies, similar to our study.


**Table 5.** Biochemical wether blood parameters.

C: control, GP1: 1% addition of dried grape pomace from daily dry matter intake (DMI), GP2: 2% addition of dried grape pomace from daily DMI, GLU: glucose, CHOL: cholesterol, TG: triglycerides, TP: total protein, ALB: albumins, GLB: globulins, AST: aspartate aminotransferase, ALT: alanine aminotransferase, ALP: alkaline phosphatase, GGT: gamma glutamyl transferase, different letters in row indicate statistical differences (Tukey test, *p* < 0.05); data are presented as mean ± SD.
