Nutritional intervention and its effects on colostrum fatty acids and amino acids profile in lactating yaks in first week of lactation

This experiment aimed to explore the effects of nutritional intervention on the composition and content of routine nutrients, amino acids, and fatty acids in the colostrum of lactating yaks. Twenty yaks in the late pregnancy stage with the same parity and similar body conditions were selected as and randomly divided into two groups (n = 10). The control group were allowed to graze freely from 8:00 to 18:00, and treatment (TR) group, yaks were supplemented with 3.0 kg of oat hay and 1.0 kg of concentrate feed per day. The experimental period lasted for 28 days, including 21 days before parturition and 7 days after parturition. From 1–7 days after parturition, colostrum was collected daily to determine the routine nutrients, amino acids, and fatty acids profile of colostrum. The results showed that the colostrum protein, non-fat colostrum solids, and lactose contents were extremely significantly higher (P < 0.01) in the TR group. The lysine content in the TR group increased significantly (P < 0.05), additionally the prolongation of lactation time, the ratio of essential to non-essential amino acids increased significantly (P < 0.05) higher in colostrum of lactating yaks. The C_{18:1 n-9t}, C_{18:3 n-3}, and polyunsaturated fatty acids (PUFA) contents extremely significantly increased (P < 0.01) with supplementation in the TR group. Compared to day 1, the contents of C_6:0 and C_10:0 increased extremely significantly on day 7 (P < 0.01). In contrast, the contents of C_14:1, C_{18:2 n-6c}, and PUFA decreased significantly (P < 0.05), and the content of C_16:1 decreased extremely significantly (P < 0.01). Colostrum protein content was significantly positively correlated with methionine content (P < 0.05), and lactose content was significantly negatively correlated (P < 0.05) with C_4:0 and C_18:0 contents. The non-fat colostrum solids content was extremely significantly negatively correlated with C_4:0 and C_18:0 contents (P < 0.01), while colostrum fat content was significantly positively correlated (P < 0.05) with C_18:0 content, additionally the colostrum fat content was extremely significantly positively correlated (P < 0.01) with histidine content. Perinatal supplementation with oat hay and concentrate significantly improved yak colostrum quality by increasing protein, non-fat colostrum solids, lactose, lysine, and beneficial fatty acids (C_{18:1 n-9t}, C_{18:3 n-3}, PUFA) contents. Key correlations (protein-methionine, fat-C_18:0/histidine) suggest nutrient interventions regulate fatty acid and amino acid metabolism to enhance colostrum synthesis. This study demonstrates the importance of targeted perinatal nutrition for optimizing neonatal yak health and livestock productivity in high-altitude pastoral systems, and offering a sustainable strategy to address nutritional challenges in grazing-based management.