A new protein requirement system for dairy cows

Area of Science:

• Animal Nutrition
• Dairy Science
• Nutrient Metabolism

Background:

• Accurate prediction of protein requirements for dairy cows is crucial for optimizing diet profitability and minimizing environmental nitrogen (N) impact.
• Existing models for predicting metabolizable protein (MP) requirements for maintenance and lactation require refinement.
• A novel factorial approach was developed to improve the estimation of net protein for maintenance (NP _M) and MP efficiency for lactation (EMP _L).

Approach:

• A meta-analysis of 223 N balance trials was conducted to define and estimate NP _M from endogenous fecal and urinary N excretion.
• The MP efficiency for lactation (EMP _L) was calculated as the proportion of absorbed protein secreted in milk, proposing a fixed value.
• The developed system's accuracy in predicting MP requirements was validated against an independent dataset and compared with established North American and European models.

Key Points:

• The new model accurately estimates NP _M (6.32 ± 0.15 g protein/kg metabolic body weight) with a strong goodness-of-fit (r = 0.91).
• A fixed EMP _L value of 0.705 ± 0.020 was proposed and utilized in the model.
• The developed system demonstrated higher accuracy in predicting MP requirements for lactation and maintenance compared to several leading dairy nutrition models.

Conclusions:

• The proposed factorial approach offers improved prediction of MP requirements for dairy cow maintenance and lactation.
• Further development of predictive models for intestinal digestibility of rumen undegradable protein and microbial protein is necessary to reduce biases.
• This research contributes to more profitable and environmentally sustainable dairy farming practices through enhanced nutritional strategies.