Milk fatty acids of pure Holstein cows compared with Holstein, Montbéliarde, and Viking Red crossbred cows in commercial dairy herds

The objective of the study was to compare fatty acids (FA) of milk from Holstein (n = 424) cows and crossbred cows composed of Montbéliarde, Viking Red, and Holstein breeds (n = 138) from 2 commercial dairy herds in Minnesota. Total, de novo, mixed, and preformed FA, as well as C16:0, C18:0, C18:1 cis-9 FA in g/100g of milk and g/100g of total FA units from all monthly test-days were provided by Minnesota DHIA (Buffalo, MN) from July 2022 to January 2024. Test-days were grouped into 7 seasons; summer 2022 (July and August 2022), fall 2022 (September through November 2022), and thereafter, every 3 mo to the winter of 2024 (December 2023 and January 2024). Test-day observations were also used to fit the lactation curves of cows during their first 4 lactations. Three test-day samples were required per cow. Lactation curves from Legendre polynomial random regression were compared for 305-d FA production, as well as test-day observations in g/100 g of milk and g/100 g of total FA. For statistical analysis of test-day observations of g/100 g of milk and g/100 g of total FA, fixed effects were breed group, parity group (primiparous and multiparous), herd, calving season (April to August 2022, September 2022 to February 2023, and March to July 2023) nested within herd, season, and the interaction of parity group and breed group and herd and season. Random effects were cow nested within breed group and herd and DIM. For statistical analysis of 305-d FA production, fixed effects were breed group, parity group, herd, calving season nested within herd, and the interaction of parity group and breed group. Random effects were cow nested within breed group and herd. Herd A had higher preformed and C18:0, C18:1 cis-9 FA (g/100 g of milk and g/100 g of total FA) than herd B. However, herd B had higher mixed, and C16:0 FA. Across lactations, de novo and mixed FA peaked during midlactation, and preformed FA were higher in early lactation. The multiparous crossbred cows had higher de novo FA (27.6 vs. 26.9 g/100 g total FA) and lower mixed FA (37.6 vs. 38.3 g/100 g total FA) than multiparous Holstein cows. However, Holstein cows had more 305-d C16:0 production compared with crossbred cows. The C18:0, C18:1 cis-9, and de novo FA may have human health benefits and de novo FA are an indicator of improved rumen health. Crossbred cows may have advantages over Holstein cows for FA profile in high-performance dairy herds.