## 3 Results  
Table 1 shows the changes in daily milk production and basic milk composition over the course of the experiment. Daily milk production increased over successive weeks of lactation, while the casein, protein, and fat levels in the milk decreased. The greatest changes in the basic composition of milk were seen between the first (days 5-7 of lactation) and second (days 8-14 of lactation) intakes, with a 1.27% decrease in fat, 0.37% decrease in protein, and 0.18% decrease in casein. The highest increase in milk production, i.e., 2.15 kg, occurred between the second (days 8-14 of lactation) and third (days 15-21 of lactation) collections. Table 2 contains data on the content of selected milk fatty acids per 100 g of fat, which were sourced during the experiment. The results indicated that the highest selected milk fatty-acid content was registered for C18:2 n-6 (LA); the next highest content was C18:1 trans11 (TVA), followed by CLA9 and CLA10. From the results, it was evident that there was an increase in the TVA and LA acid content due to the fact that the first increase in TVA content occurred between the second (days 8-14 of lactation) and third (days 15-21 of lactation) intakes; however, in the case of LA, the increase was observed throughout the experiment. In relation to the CLA isomers, the situation looked different. The CLA9 content decreased in the second week compared to the first week of lactation, but in the third week, there was an increase in this acid content. CLA10, as with TVA, remained at the same level during the first two weeks of lactation, while its content decreased in the third week, in contrast to TVA. Table 3 shows the results of the average \(\beta\)-hydroxybutyric acid (BHBA) content. This acid is one of the markers for diagnosing diseases of metabolic origin. The BHBA content in \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Component**} & \multicolumn{4}{c}{**Treatment Effect**} & \multirow{2}{*}{**SEM**} \\ \cline{2-2} \cline{4-5}  & **1** & **2** & **3** & \\ \hline Milk yield [kg] & 28.15  & 28.71  & 30.86  & 1.596 \\ Casein [\%] & 2.73  & 2.45  & 2.39 ,c & 0.036  \\ Protein [\%] & 3.36 ,B & 2.99 ,c & 2.85 ,c & 0.046  \\ Fat [\%] & 5.23 ,B & 3.96 ,C & 3.62 ,C & 0.196 ,C \\ Fat/Protein & 1.56 ,B & 1.32 ,C & 1.27 ,C & 0.121 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition and daily milk production. Data were presented as least-squares means with the standard error of the mean. Treatment effect: 1 st week of lactation; 2 nd week of lactation; 3 rd week of lactation. Means marked with the same letters differ significantly at lowercase letters, \(p\leq 0.05\); uppercase letters, \(p\leq 0.01\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Fatty Acid**} & \multicolumn{4}{c}{**Treatment Effect**} & \multirow{2}{*}{**SEM**} \\ \cline{2-2} \cline{4-5}  & **1** & **2** & **3** & \\ \hline C18:1 trans11 & 1.01  & 1.01  & 1.12 ,b & 0.044 \\ C18:2 n-6 & 2.11  & 2.14  & 2.17 ,b & 0.46  \\ C18:2 cis9, trans11 & 0.51  & 0.44  & 0.46  & 0.019 \\ C18:2 trans10, cis12 & 0.04 & 0.04 & 0.03 & 0.004 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Content of selected fatty acids [g/100 g fat]. Data were presented as least-squares means with the standard error of the mean. Treatment effect: 1 st week of lactation; 2 nd week of lactation; 3 rd week of lactation. Means marked with the same letters differ significantly at lowercase letters, \(p\leq 0.05\); uppercase letters, \(p\leq 0.01\). the blood of animals that participated in the experiment varied, though it was characterized by the first week of lactation having the highest level (days 5-7 of lactation), followed by a decrease in content value, which then remained at a similar level during the second and third weeks of the experiment, indicating that there was no problem related to metabolic diseases in the herd.