Breeding Worth
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15 min read
Breeding Worth (BW) is an index that ranks cows and bulls on their ability to breed profitable, efficient replacements. This page explains how BW is used to create herds resilient to changes and disease, therefore increasing farm profits. It describes ten traits, split into 'Production Efficiency' and 'Robustness', contributing to a cow's BW score. By understanding BW, you can make informed decisions to improve your herd's profitability. It also introduces the concept of 'reliability', which measures the confidence in a BW evaluation.
What is Breeding Worth?
Breeding Worth (BW) is the index used to rank cows and bulls on their expected ability to breed profitable, efficient replacements. Herds that are more resilient to farm system changes and illness are going to make you more profit as their rates of production vs input are likely to be higher and more reliable. The Breeding Worth Index helps farmers achieve a genetically strong herd and benefit from greater genetic gains faster, which means you can increase your farm profit more and more each year.
Our National Breeding Objective (NBO) in New Zealand is to breed dairy cows that efficiently convert feed into profit. We rank cows and bulls on their ability to meet this objective using the index known as Breeding Worth (BW).
How Breeding Worth is calculated
BW is calculated by combining breeding values with the appropriate economic values for each trait and adding them all together.
Breeding Values (BV): An estimate of a cow or bull's genetic merit for a trait. e.g. Will his or her daughters produce milksolids efficiently, and be robust herd members?
Economic Values (EV): An estimate of the future dollar value of a unit change in each trait to an NZ dairy farmer.
BW is expressed as $ net farm income per 5 tonnes of dry matter. A bull whose BW is $300 is expected to produce daughters that are on average $150 (half of the bull’s BW) more profitable than a bull whose BW is $0. Importantly, animals can be compared using BW across different breeds, herds and ages.
Ten traits included in BW
There are ten traits included in BW that have been identified as having a direct economic value to the NZ dairy sector. These traits can be categorised as either 'Production efficiency' traits or 'Robustness' traits.
The effective emphasis of the ten individual traits within BW are split between 63% production efficiency traits and 37% robustness traits (see pie chart). Updating the liveweight evaluation and adding udders to BW has resulted in a slight reduction in the emphasis on production efficiency traits and an increase in the emphasis on robustness traits.
Production efficiency traits
Milk protein and milk fat yield
Cows that produce more protein and fat will bring in more income for the dairy farm business.
Milk volume
Cows that produce the same quantities of fat and protein but with more volume incur costs to the dairy farm business.
Liveweight
Included in BW as the 'efficiency' part of production efficiency. There is a positive correlation between liveweight and milk production and between liveweight and feed requirements for maintenance and growth. If not included, selection would lead to successive generations getting heavier and the costs to feed these heavier cows would increase.
Robustness traits
Somatic cell
Cows with lower somatic cell counts have better survival, lower costs due to mastitis, and fewer penalties due to bulk somatic cell count being lower.
Fertility
Fertile cows have better longevity and lower empty rates. Higher in-calf rates to high genetic merit bulls through artificial insemination reduces the need for natural mating bulls.
Gestation length
Short gestation length increases the number of days in milk, allows a cow more time to recover from calving and provides an opportunity for a condensed calving period.
Functional survival
Cows that fail for functional reasons such as udder breakdown have reduced longevity and lead to increased costs associated with rearing more replacements. Having more mature cows in the herd (the engine room of the herd) will positively impact profitability.
Body condition score
Cows that maintain condition easily can be dried off later. This increases lactation length and boosts potential production and profit, compared with cows that lose condition easily.
Udder overall
Cows with poor udder conformation add costs to the farm system due to an increased risk of developing mastitis or being culled due to their udder failing.
Reliability
The other number that is reported alongside BW is reliability. Reliability measures how much information has contributed to the BW evaluation for that animal. We show reliability on a scale of 0 to 100%, with reliabilities closer to 100% representing more information on progeny and ancestors being available for that bull.
High-reliability bulls are unlikely to have large shifts in their BW when more daughters are added. In contrast, bulls with lower reliabilities are more likely to have large shifts in their BW as we add more daughters.
Six steps to a high BW herd
Genetic merit sets the foundation for the profitability of your dairy herd. The info below guides you through six steps to enhance your herd's genetic worth. The genetic merit of your herd will set the foundation for the profit you can achieve. Check out the six steps you can take to close that gap. Make these changes to help boost your annual profit.
The national herd improves every year, and the value of this compounds over time. The difference between the genetic merit of the median herd, and a herd in the top 10% is estimated to be worth $25,086 in profit every year.
Step 1: Use high-genetic merit sires
Using high-genetic merit sires can accelerate the rate of genetic improvement within your herd.
View the top bullsStep 2: Keep accurate and detailed records
Calving and mating records are used to assign a mother and a father to your replacement heifers.
Read moreStep 3: Use DNA sire verification
Mix ups with parentage will slow the rate of gain in your herd. Twice as many animals are DNA verified in top-ranking herds, compared to mid-range herds (top range 42%, mid range 24%). DNA sire verification is an effective tool to correct any mistakes.
Read moreStep 4: Measure cow performance
Did you know, 75% of top-BW herds are herd tested at least 3 times/season (compared to 60% of mid-range herds). Using herd testing, weighing, calving and mating records provide valuable information to cow performance.
Read moreStep 5: Use AI over your best heifers
Using AI over your best heifers will give you more choice when it comes to picking heifer calves to rear. It also means calves from those top heifers will be in the herd one year sooner.
Read moreStep 6: Target replacements from top cows
Use BW to help you decide which cows to keep replacement heifers from. Target your top BW cows.
How Breeding Worth impacts your herd value and farm profit
Herd quality has a direct impact on a farmer’s profitability. Herds that are more resilient to farm system changes and illness are going to make you more profit as their rates of production vs input are likely to be higher and more reliable.
The Breeding Worth Index helps farmers achieve a genetically strong herd and benefit from greater genetic gains faster, which means you can increase your farm profit more and more each year.
Your breeding plan will set you up for future seasons and have a lasting impact on your herd. That’s where Breeding Worth (BW) can help you make informed decisions to improve your herd’s profit through genetic gain.
The information you choose to focus on will depend on what your herd objective is. While you won’t see changes immediately in your herd, the decisions you make now will have an impact on your production for several seasons. Knowing you have accurate and meaningful data in Breeding Worth is critical to aid your decision-making.
Choosing the best bull for your herd
No two bulls are the same: Two bulls can have exactly the same BW but will have reached it through very different strengths. The best bull for your herd is one that fits your herd breeding objective.
International dairy sires
Choosing the right genetics is crucial for New Zealand's pasture-based grazing systems. The performance of international bulls’ daughters depends on how similar the environment and farming systems are. This means that how well daughters perform overseas doesn’t always indicate how they’ll do here.
Interbull, an international bull genetic evaluation organisation, generates breeding values for international dairy sires. They collect sire data from around the world and estimate breeding values for New Zealand based on known relationships between our breeding values and other countries estimated breeding values. NZAEL receives these breeding values three times a year after each Interbull Animal Evaluation run.
However, these values have lower accuracy for New Zealand conditions. International bulls aren’t progeny tested here, leading to less data and fewer comparisons. As bulls sire more daughters in New Zealand, their performance data will be gradually included in Interbull’s breeding values, making them more reliable.
When selecting an international sire, consider these two factors:
Fertility: In New Zealand, poor fertility impacts profitability because our cows calve once-a-year. Overseas, cows often calve year-round, reducing the economic impact of poor fertility. Some international bulls can have lower genetic fertility than New Zealand bred bulls, but many still have daughters with good fertility here.
Production efficiency: The ratio of milk solids to mature liveweight is vital for cow profitability in New Zealand. International bulls often sire daughters with higher mature liveweights, increasing feed costs. These cows need to produce more milk to offset the extra feed required.
Choosing the right sire can lead to better performance and profitability on your farm.
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