Soybean Oil vs. Palm Oil Calcium Soap Supplementation: Effects on Milk Yield and Methane Emissions in High-Yielding Dairy Cows
Abstract
This observational field study evaluated the effects of dietary lipid supplementation with soybean oil and palm oil-based calcium soaps on milk yield, composition, in high-yielding Holstein-Friesian dairy cows under real-world commercial conditions representative of intensive European dairy systems. Conducted across four commercial dairy farms, the study assessed four distinct fat supplementation strategies: soybean oil (70 g/kg dry matter [DM]), and palm oil calcium soap at three inclusion levels (150, 210, and 250 g/kg DM). A total of 335 multiparous cows were followed throughout a full 305-day lactation period.
All cows were fed a basal total mixed ration (TMR) formulated in accordance with NRC (2001) guidelines, with fat supplementation incorporated into the concentrate. Milk yield was recorded daily, and samples were analyzed for fat, protein, β-hydroxybutyrate (BHB), milk urea nitrogen (MUN), somatic cell count (SCC), and detailed fatty acid (FA) profiles. Enteric methane emissions were estimated, not directly measured, using the IPCC Tier-2 model with methane conversion factors (Ym) adjusted for lactation status. This approach provides a practical estimation of environmental impact based on dry matter intake and energy conversion, though it does not capture animal-level variation.
Due to the study's observational design and lack of experimental replication—each farm applied a unique supplementation protocol—statistical comparisons were not conducted. Instead, results are presented descriptively and interpreted with caution, reflecting real-world variability in genetics, management, and environment.
Among the tested strategies, moderate supplementation with palm oil calcium soap (150 g/kg DM) achieved a favorable balance between productivity and environmental efficiency, showing intermediate milk yield and the lowest methane emission intensity per kilogram of milk. In contrast, higher levels of palm oil supplementation (210 and 250 g/kg DM) were associated with increased milk yield and fat content, but also higher methane emissions. The soybean oil group exhibited the lowest milk yield but similar methane intensity to the 150 g/kg palm oil group, indicating potential for environmental sustainability despite lower productivity.
Fatty acid analysis revealed that increasing palm oil supplementation led to a higher proportion of saturated and trans fatty acids, while moderate levels favored a more balanced FA profile. Principal Component Analysis (PCA) and Pearson correlation analysis showed clear associations between milk yield, milk fat, trans FA, and methane intensity, suggesting that the type and level of fat supplementation can influence both productive and environmental parameters.
While causal inference is limited, the findings provide practical insights into climate-smart nutritional strategies applicable to commercial dairy systems. Further controlled trials are warranted to validate these associations and optimize fat supplementation protocols for both productivity and environmental sustainability.
