# The Housing System Contributes to Udder Health and Milk Composition
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Traits**} & \multicolumn{3}{c}{**Housing System (HS)**} & \multicolumn{3}{c}{**SCC Class (ths mL\({}^{-1}\))**} & \multicolumn{3}{c}{\(p\)**-Value**} \\ \cline{2-10}  & **Tie-Stall** & **Free-Stall** & \(\leq\)**200** & **201–400** & **401–1000** & **\(>\)1000** & **SE** & **HS** & **SCC** & **HS\(\approx\)SCC** \\ \hline C 4:0 (BA) & 2.74 & 2.65 & 2.77 & 2.63 & 2.46 & 2.51 & 0.025 & 0.197 & 0.064 & 0.121 \\ C18:1 t10 + 11 (TVA) & 1.43 \({}^{\text{A}}\) & 1.13 \({}^{\text{B}}\) & 1.25 & 1.34 & 1.30 & 1.33 & 0.024 & 0.000 & 0.743 & 0.893 \\ C 18:1 c9 (OA) & 22.74 & 22.35 & 22.56 & 22.55 & 22.49 & 21.42 & 0.326 & 0.745 & 0.783 & 0.877 \\ C 18:2 (LA) & 1.91 & 1.88 & 1.87 & 1.88 & 1.96 & 1.95 & 0.034 & 0.937 & 0.523 & 0.521 \\ C 18:3 (LNA) & 0.53 \({}^{\text{A}}\) & 0.39 \({}^{\text{B}}\) & 0.47 & 0.46 & 0.49 & 0.48 & 0.014 & 0.000 & 0.556 & 0.434 \\ C18:2 c9 (ILA) & 0.63 & 0.59 & 0.63 & 0.60 & 0.58 & 0.62 & 0.012 & 0.389 & 0.509 & 0.173 \\ C 20:4 (AA) & 0.14 \({}^{\text{B}}\) & 0.16 \({}^{\text{A}}\) & 0.14 \({}^{\text{B}}\) & 0.14 \({}^{\text{B}}\) & 0.16 \({}^{\text{B}}\) & 0.18 \({}^{\text{A}}\) & 0.003 & 0.000 & 0.007 & 0.064 \\ C 20:5 (EPA) & 0.07 & 0.07 & 0.07 & 0.07 & 0.07 & 0.07 & 0.002 & 0.204 & 0.643 & 0.067 \\ C 22:5 (DPA) & 0.11 & 0.12 & 0.11 \({}^{\text{b}}\) & 0.10 \({}^{\text{b}}\) & 0.12 \({}^{\text{b}}\) & 0.14 \({}^{\text{a}}\) & 0.003 & 0.494 & 0.015 & 0.291 \\ C 22:6 (DHA) & 0.034 \({}^{\text{a}}\) & 0.030 \({}^{\text{b}}\) & 0.03 & 0.03 & 0.04 & 0.04 & 0.001 & 0.013 & 0.145 & 0.115 \\ \hline \end{tabular}
\end{table} 
Table 6: The effect of the housing system and udder health on the concentrations of functional fatty acids in milk fat. In the current experiment, an increase in SCC was accompanied by a decrease in the proportion of LCFAs and an increase in the proportion of MCFAs in milk. This could be explained by the alteration of milk fat globule membranes by leukocyte lipases or plasmin through lipoprotein hydrolysis, which may enhance lipolysis [35]. In a study by [PERSON] et al. [16], an increase in SCC induced a considerable decrease in OA (C18:1) concentration. A similar relationship was noted in this study. In turn, [PERSON] and [PERSON] [36] reported that SCC had no significant effect on the proportions of fatty acids in cows' milk. However, the maximum SCC value in milk analyzed by the cited authors was 400,000 per mL, which corresponds to SCC groups I and II in the present study. In the current experiment, the percentages of PUFAs, including LA, AA, and DPA, increased with deteriorating udder health. These results partially corroborate the findings of other authors. [PERSON] et al. [37] found that higher SCC values were accompanied by increased transport of bioactive compounds from blood to milk in cows with mastitis. Lipids present in feed undergo hydrolysis by microbial enzymes, followed by biohydrogenation that converts UFAs (C18:3, C18:2) to SFAs (C18:0) [38]. The fatty acid profile of milk can be altered by feed additives and the type of diet fed to animals [39]. In the evaluated herd, the cows did not receive lipid supplements and were fed similar roughages, including maize silage, grass silage, and meadow hay. In comparison with maize silage, grass silage contributes to a greater increase in the proportions of fatty acids that deliver health benefits to milk consumers [39]. Maize silage is richer in linoleic acid than grass silage, because maize grain, which represents 30-40% of silage, comprises ca. 60% linoleic acid [40]. Apart from the type of forage, i.e., the source of fatty acids, the feeding strategy is also an important consideration [40]. In our study, the method of feeding was the same in both housing systems. Mixing all feed components thoroughly and feeding them as a ration (PMR) could promote the access of microorganisms to lipids, thus decreasing the proportion of UFAs in total fatty acids in milk.