Optimizing heifer rearing: balancing efficiency, profitability, and welfare

Professor Ginny Sherwin, Clinical Associate Professor in Farm Animal Medicine, School of Veterinary Medicine and Science, University of Nottingham

Synopsis

How can we ensure that our heifer rearing practices are both efficient and profitable while also supporting longevity and welfare? This lecture delves into various methods to assess and improve the efficiency of heifer rearing on individual farms, with a focus on maximizing profitability and sustaining animal welfare.

Impact of Longevity on Herd Performance

Enhancing cow longevity, particularly reaching the third lactation, can reduce the number of heifer replacements needed, increase the number of beef calves available for sale, and lower annual heifer rearing costs. It also reduces overall methane production, as youngstock can contribute 19-33% of total herd methane emissions (Knapp et al., 2014), and optimizes profitability since cows typically reach peak yield by the fifth lactation. Recent studies suggest that the economically optimal longevity is five lactations, based on factors such as genetic opportunity cost, herd replacement cost, and calf value (De Vries and Marcondes, 2020).

The longevity of dairy cows is increasingly recognized as a crucial metric in evaluating herd performance. It influences not only the economic viability of dairy farming but also the environmental footprint and public perception of the industry. Traditionally, longevity refers to the length of time an animal lives. For dairy cows, while their natural lifespan can extend up to 20 years, the average productive lifespan is much shorter – around 6 years in the UK and 5 years in the USA (Hanks & Kossaibati, 2022; Nowak, 1999). This disparity suggests that management practices significantly influence cows’ productive lifespans, often leading to their early exit from the herd. This trend is concerning, as it reflects inefficiencies that have broad implications for herd economics and sustainability.

Understanding Longevity and Herd Dynamics

Longevity in dairy cows is commonly measured in terms of productive life, defined as the duration from a cow’s first calving to its removal from the herd, either through culling or death. Other metrics include lifetime milk production and the age at which cows are culled. However, these averages can be misleading as they do not account for the variation within a herd. A more accurate measure might be the percentage of cows that achieve the target lifetime yield, adjusted for farm-specific goals such as fat-protein corrected milk output.

Cows leave the herd for various reasons, typically categorized as either voluntary or involuntary culls. Voluntary culls are economic decisions made by farmers, while involuntary or “forced” culls occur when a cow can no longer contribute productively due to health issues or other factors (Fetrow et al., 2006). Understanding the reasons behind culling is essential for managing herd longevity effectively. It can reveal whether cows are being replaced efficiently or if underlying management issues are forcing premature culls.

Rather than relying solely on average statistics, it is more useful to monitor the survival rates of cows at key points in their lifecycle. For example, the survival rate of first-lactation heifers to their second lactation is a critical metric, as approximately one in eight heifers in the UK does not make it to their second lactation. This failure represents a significant economic loss, as the cost of rearing these heifers is not recouped through their milk production. Therefore, improving the survival rates of young cows is essential for enhancing overall herd longevity.

Efficiency of Heifer Rearing

Two key performance indicators (KPIs) are used to evaluate heifer rearing efficiency (Bach et al., 2021):

• Rearing Efficiency: Percentage of heifers born alive that calve by the target age of ≤670 days (target ≥85%).
• Heifer Effectiveness: Percentage of heifers born alive that calve by the target age and complete three lactations (target ≥75%).

Achieving optimal heifer effectiveness depends on survival through calfhood and reaching first calving by 22 months. The median age at first calving (AFC) in the UK is 28 months, with higher AFC linked to increased rearing costs and potential impacts on future survival, productivity, health, and fertility (Bach, 2011; Eastham et al., 2018; Sherwin et al., 2016).

Economic Impacts of Longevity

Herd longevity has a direct impact on the profitability of dairy farms. A longer productive life increases the number of days a cow spends in milk production, thereby improving its lifetime yield and overall efficiency. Research from the Scottish Rural College (SRUC) indicates that the British cattle industry loses over £860 million annually due to inefficiencies such as decreased daily live weight gain (DLWG), mortality, and fertility issues. These losses are compounded by high culling rates, which result in a younger herd with more cows in their first and second lactations – periods typically associated with lower milk yields and higher vulnerability to health issues (Geragthy, 2022).

The economic impact of premature culling is significant. For instance, culling during early lactation can cost farmers between £325 and £650 per cow (Vries, 2013). These losses underscore the importance of managing herd longevity to optimize economic returns. By extending the productive life of cows, farms can reduce the need for frequent replacements, lower rearing costs, and improve overall profitability.

Sustainability Considerations

Longevity also plays a critical role in the sustainability of dairy farming. Dairy cows are a significant source of greenhouse gas emissions, particularly methane, which is produced during rumen fermentation and from manure management (Wolf et al., 2017). Increasing milk yield has been proposed as a strategy to reduce methane emissions per unit of milk produced (Knaus, 2009). However, higher milk yields are often associated with shorter productive lifespans, leading to increased culling rates and a higher demand for replacement heifers, which contribute substantially to a farm’s overall methane emissions.

By extending the productive life of cows, the number of replacement heifers needed can be reduced, thereby lowering the overall greenhouse gas emissions of the herd. This strategy not only benefits the environment but also aligns with the growing consumer demand for more sustainable dairy products (Knapp et al., 2014).

Determining Optimal Longevity

The optimal longevity of dairy cows is a complex issue that depends on several factors, including genetic potential, economic considerations, and herd management practices. Research by Professor DeVries suggests that the ideal productive lifespan for a cow is around five lactations, assuming the cow remains healthy. However, this optimal point can vary significantly between farms and requires careful monitoring and management to achieve (De Vries, 2020; De Vries & Marcondes, 2020).

Key drivers in determining optimal longevity include the genetic opportunity cost of keeping older cows versus introducing genetically superior heifers, the lack of maturity costs associated with younger cows, and the aged cow cost, which considers the reduced productivity of older cows. Balancing these factors is crucial for maintaining an efficient and profitable herd.

Conclusion

Longevity is a vital metric for modern dairy herds, influencing both economic performance and sustainability. Extending the productive lifespan of cows can lead to increased profitability by maximizing lifetime yield and reducing the need for costly replacements. Additionally, improving herd longevity can significantly reduce the environmental impact of dairy farming by lowering methane emissions associated with replacement heifers. Determining the optimal longevity of cows requires a nuanced understanding of both economic and environmental factors, tailored to the specific conditions of each farm. By focusing on longevity, dairy farmers can achieve a more sustainable and profitable operation, aligning with industry trends and consumer expectations.

Bibliography

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