Deletion of arginine from an abomasal infusion of amino acids does not decrease milk protein yield in Holstein cows

Area of Science:

• Animal Nutrition
• Dairy Science
• Biochemistry

Background:

• Arginine (Arg) is an essential amino acid (EAA) crucial for milk protein synthesis.
• Understanding the impact of Arg availability on mammary function is vital for optimizing dairy cow nutrition.

Purpose of the Study:

• To investigate the effects of limited arginine supply on milk production, milk protein yield, and mammary uptake of amino acids (AA) and energy substrates in lactating Holstein cows.
• To determine if arginine supplementation influences mammary uptake and utilization of other nutrients.

Main Methods:

• Six lactating Holstein cows were used in a replicated 3x3 Latin square design.
• Diets met National Research Council requirements for energy and 72% of metabolizable protein.
• Treatments involved abomasal infusions of water (CTL), EAA without Arg (ARG-), or EAA with Arg (ARG+).

Main Results:

• Milk protein yield increased with ARG+ compared to CTL, and Arg deletion (ARG-) did not impair this response.
• Mammary uptake of Arg decreased with ARG- but remained in excess of milk secretion.
• Mammary uptake of other essential amino acids (Ile, Leu, Lys, Val) increased, supporting higher milk protein and lactose yields, particularly with ARG+.

Conclusions:

• Limited arginine supply has minimal impact on milk and milk component yields when other EAAs are adequately provided.
• Adequate supply of other EAAs can compensate for reduced Arg uptake by the mammary gland.
• Group 2 EAAs (Ile, Leu, Lys, Val) play a role in supporting lactose yield responses to EAA infusions in dairy cows.