Review: extended lactation in dairy cattle

Area of Science:

• Animal Science
• Dairy Husbandry
• Agricultural Economics

Background:

• Extended lactation (EXT) is a management strategy in dairy cattle with potential impacts on various farm metrics.
• Understanding the multifaceted effects of EXT is crucial for optimizing dairy farm sustainability and profitability.

Purpose of the Study:

• To review the effects of extended lactation (EXT) in dairy cattle.
• To assess impacts on milk production, reproduction, milk quality, lifetime performance, economics, and environmental footprint.

Main Methods:

• Literature review of extended lactation strategies in dairy cattle.
• Analysis of effects on milk yield, persistency, reproduction, milk quality, and cow longevity.
• Evaluation of economic and environmental implications at herd and farm levels.

Main Results:

• Primiparous cows show increased milk yield per feeding day with EXT; multiparous results are variable.
• EXT can enhance lifetime milk production and maintain or improve milk quality.
• Reproductive effects are generally neutral to slightly positive; EXT reduces calvings, diseases, and replacement needs.

Conclusions:

• Extended lactation offers potential benefits for lifetime cow performance, farm economics, and reduced environmental impact, particularly through reduced beef production.
• Optimal EXT durations vary by parity, with modeling suggesting 16 months for first lactation and 10 months for subsequent lactations.
• Further research on cow selection, milking frequency, and feeding strategies is needed to support wider EXT adoption.