The Effect of Supplementation Using a Mixture of Fish Oil and Linseed on the Level of Immunomodulatory Components in Bovine Colostrum

**Background:** Calves are born with only non-specific immunity due to the syndesmochorial placenta preventing transfer of immune proteins. Passive humoral immunity depends entirely on ingestion of high-quality colostrum, which contains immunoglobulins, lactoferrin, lysozyme, fatty acids, and fat-soluble vitamins. Colostrogenesis begins approximately 21 days before calving, making the transition period a critical window for nutritional intervention. Over 60% of colostrum samples have reduced immunological quality, particularly in high-yield Holstein-Friesian cows. This study aimed to determine whether supplementing rations with a mixture of fish oil (rich in n-3 PUFAs) and linseed (rich in ALA) during the three weeks before calving could improve the immunomodulatory component levels in bovine colostrum.

**Methods:** The experiment was conducted on a high-input farm with 350 Polish Holstein-Friesian cows. Twenty multiparous cows (2nd or 3rd lactation) with body condition score 3–3.5, three weeks before scheduled calving, and without multiple pregnancies or metabolic diseases were selected. Cows were divided into two groups: experimental (FOL, n=10) received the standard ration enriched with 150 g fish oil and 250 g golden linseed daily for approximately 21 days until calving; control (CTL, n=10) received the standard ration for dry cows. Colostrum samples were collected up to two hours after calving, then twice daily on days 1 and 2 of lactation (1a, 1b; 2a, 2b), and once daily from days 3 to 5 (3, 4, 5). Basic chemical composition was determined using MilkoScan FT 120. Whey proteins, immunoglobulins (IgG, IgA, IgM), and fat-soluble vitamins were determined by RP-HPLC chromatography. Fatty acid methylation was performed per EN ISO 5509, and individual fatty acids were identified using an Agilent 7890A GC. Statistical analysis used multivariate analysis of variance by least squares method with SPSS 22 software.

**Key Results:** Supplementation significantly increased colostrum protein content (FOL: 8.55% vs CTL: 6.61%, p ≤ 0.01) and fat content (FOL: 5.67% vs CTL: 4.27%, a 32.73% increase). IgG concentration was significantly higher in the FOL group for first and second intakes (59.358 g/L and 48.78 g/L, respectively) compared to CTL (46.011 g/L and 27.889 g/L, respectively) (p ≤ 0.01). Average IgG was 41.86 g/L for FOL vs 24.80 g/L for CTL. IgA was significantly higher in FOL first intake (11.476 g/L) vs CTL (8.895 g/L) (p ≤ 0.01). IgM was significantly higher in FOL first intake (6.319 g/L) vs CTL (4.898 g/L) (p ≤ 0.01). Lactoferrin content was significantly higher in FOL (average 3.39 g/L) vs CTL (average 2.31 g/L) (p ≤ 0.01). Lysozyme content was lower in FOL (average 643.86 mg/L) vs CTL. Vitamin A content nearly doubled in FOL (1.35 mg/L) vs CTL (0.70 mg/L). Vitamin D was 23.63% higher in FOL. DHA content more than doubled in FOL (peak 0.207 g/100 g fat) vs CTL (p ≤ 0.01). CLA content was 57.42% higher in FOL (peak 0.777 g/100 g fat) (p ≤ 0.01). AA and LA contents decreased by 38.68% and 12.06%, respectively. The n-3:n-6 ratio improved to 1:4 in FOL vs 1:5 in CTL. ALA content was 8% lower in FOL. No significant effect was observed on EPA content.

**Clinical Implications:** This study demonstrates that supplementing dairy cow rations with a mixture of fish oil and linseed during the three-week transition period before calving can significantly improve colostrum quality. Colostrum from supplemented cows met the threshold of IgG ≥ 50 g/L for high immunological quality (intakes 1a and 2a), whereas control colostrum fell below this threshold. The improved n-3:n-6 fatty acid ratio and increased CLA content may reduce oxidative stress and inflammation in newborn calves, as supported by prior research showing that flaxseed- and fish oil-enriched colostrum reduces oxidative stress in calves. The increased lactoferrin and immunoglobulin concentrations enhance passive immunity transfer, which is critical during the first hours of life when intestinal absorption of intact proteins is most efficient. The study is limited by its small sample size (n=10 per group) and single-breed focus on Holstein-Friesian cows. Future research should examine dose-response relationships, effects on calf health outcomes, and applicability to other breeds and production systems.