Mitochondrial function and nutrient partitioning in high and low feed efficient multiparous Holstein dairy cows

Area of Science:

• Animal Science
• Nutritional Biochemistry
• Metabolic Regulation

Background:

• Residual Feed Intake (RFI) is a key metric for assessing feed efficiency in livestock.
• Identifying animals with divergent RFI (high vs. low feed efficiency) is crucial for optimizing animal production and sustainability.
• Understanding the physiological underpinnings of RFI variation can lead to targeted breeding and management strategies.

Purpose of the Study:

• To investigate differences in metabolites, hormones, fatty acids, hepatic gene expression, and mitochondrial function between dairy cows with divergent RFI.
• To quantify and compare methane (CH4), carbon dioxide (CO2), and oxygen (O2) consumption and emissions in cows with contrasting RFI.
• To elucidate the metabolic and physiological factors contributing to variations in feed efficiency in dairy cattle.

Main Methods:

• Two 8-week trials involving 64 Holstein dairy cows per trial to measure intake, body weight, and milk production.
• Analysis of blood metabolites, hormones, and fatty acids from tail vessel and mammary vein.
• Measurement of hepatic gene expression, mitochondrial function (oxygen consumption rates), and gas exchange (CH4, CO2, O2).

Main Results:

• Negative RFI (-RFI) cows exhibited greater milk lactose percentage and lower MUN and SCS compared to positive RFI (+RFI) cows.
• Specific fatty acids (e.g., C16:0, C18:0) and insulin concentrations were higher in tail vessel blood of -RFI cows.
• Mitochondrial complex IV showed lower oxygen consumption rates in -RFI cows, and these cows had lower CH4 and CO2 emissions, despite similar hepatic gene expression related to uncoupling, mitochondrial, or TCA cycles.

Conclusions:

• Divergent RFI status in dairy cows is associated with distinct patterns in blood metabolites, fatty acids, and insulin.
• Differences in hepatic mitochondrial function, particularly oxygen consumption, are linked to feed efficiency variations.
• Lower methane and carbon dioxide emissions are observed in more feed-efficient (-RFI) cows, suggesting potential environmental benefits, with variations primarily driven by mitochondrial function rather than hepatic gene expression.