O que é repetibilidade - Berrante Genética

Summary

In this video, Rodolfo explains the concept of repeatability in animal breeding, which measures the correlation between an animal's past and future production. He discusses how repeatability is influenced by genetic and environmental factors, using examples from cattle, pigs, and poultry. The video highlights the practical applications of repeatability, such as predicting future production, determining the number of observations needed for genetic selection, and estimating the maximum heritability of traits. Rodolfo emphasizes that repeatability is a useful tool for improving animal genetics, especially when parental data is limited.

Takeaways

• 😀 Repetibility is a key parameter used to predict future production levels in animals, such as milk production or the number of offspring.
• 😀 Repetibility can only be applied to characteristics that are repeated over the animal's productive life, such as egg size in poultry or the number of piglets born to a sow.
• 😀 The definition of repetibility is the correlation between two production events in an animal's life, like lactations in cows or piglets born to a sow.
• 😀 Repetibility is expressed through a coefficient, symbolized by 'r', and is derived from a genetic model involving additive genetics and environmental factors.
• 😀 The genetic model used to calculate repetibility differentiates between permanent and temporary environmental effects on production traits.
• 😀 Permanent environmental factors have a long-lasting impact on an animal's production, while temporary factors, like nutrition, influence production in the short term.
• 😀 Repetibility values range from 0 to 1 (or 0% to 100%), and it is influenced by the proportion of genetic vs. environmental factors affecting the trait.
• 😀 The repetibility coefficient can be used to predict future performance, such as forecasting the next lactation of a cow based on previous data.
• 😀 When a characteristic has high repetibility, fewer measurements are required to select genetically superior animals. In contrast, low repetibility traits require more measurements to ensure genetic superiority.
• 😀 Repetibility also helps estimate the maximum value of heritability, as seen in traits like the number of piglets born to a sow, where repetibility is 15%, thus limiting the heritability to the same value.
• 😀 Repetibility is easier and faster to measure than heritability, and it is often used at the beginning of breeding programs to estimate the maximum possible heritability of a trait.

Q & A

What is the concept of 'repeatability' in animal breeding?

Repeatability refers to the correlation between two measurements of the same trait in an animal during its productive life, indicating how consistent a characteristic is over time.

Can you give examples of traits that can be measured using repeatability?

Examples of traits that can be measured using repeatability include egg size or weight in hens, number of piglets born per sow, wool weight of sheep, milk production of cows, milk composition (fat or protein percentage), and the interval between calvings in dairy cows.

How is repeatability calculated?

Repeatability is calculated using a formula based on the variance of genetic additive factors and the variance of permanent environmental effects, relative to the total phenotype variance.

What is the difference between permanent and temporary environmental factors in the context of repeatability?

Permanent environmental factors influence an animal's production permanently, such as long-term changes in health or environment. Temporary environmental factors, like nutrition, affect production temporarily and vary over time.

How does repeatability differ from heritability in genetic evaluation?

While both repeatability and heritability measure genetic influence, repeatability includes the influence of permanent environmental factors in the numerator, whereas heritability does not. This makes repeatability a broader measure of an animal's consistency over time.

What is the range of values for repeatability and heritability?

Repeatability and heritability both range from 0 to 1, or from 0% to 100%. A value of 1 means complete consistency or genetic influence, while a value of 0 means no consistency or genetic influence.

What is the repeatability of traits in dairy cattle, according to the script?

For dairy cattle, repeatability estimates are: 15% for the interval between calvings, 50% for milk production, and 60% for milk fat percentage.

What repeatability estimate is provided for pig breeding?

In pigs, the repeatability of the number of piglets born per sow is estimated at 15%, while the birth weight of piglets in relation to the sow is around 30%.

What repeatability value is mentioned for egg size in poultry?

The repeatability of egg size in poultry is estimated at 95%, indicating a very high level of consistency influenced more by genetic factors than environmental factors.

How is repeatability useful in predicting future performance in animal breeding?

Repeatability helps predict future performance by using past performance measurements to estimate future outcomes, especially when an animal has shown consistent results over time. This is useful in selecting animals with desirable traits.