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UPSC MainsANI-HUSB-VETER-SCIENCE-PAPER-I201120 Marks
Q18.

What calls for the use of information from relatives for selection of breeders ? Discuss and differentiate the family selection and within family selection schemes.

How to Approach

This question requires a nuanced understanding of animal breeding principles, particularly the role of pedigree information. The approach should begin by explaining why family history is crucial for breeder selection. Then, clearly differentiate between family selection and within-family selection, highlighting their advantages and disadvantages. Use a tabular format to compare the two schemes effectively. Finally, briefly touch upon the limitations and modern advancements in these selection methods. A structured response showcasing a grasp of the underlying genetics is key.

Model Answer

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Introduction

Animal breeding aims to improve desired traits in livestock populations, impacting productivity and overall efficiency. Historically, and even presently in many developing regions, breeders rely heavily on information from relatives—the pedigree—to make informed selection decisions. This is because traits often exhibit heritability, meaning they are influenced by genetic factors passed down through generations. Understanding the family history allows breeders to predict the potential of an animal based on the performance of its ancestors, minimizing guesswork and maximizing the likelihood of producing superior offspring. The principles of family and within-family selection are core to this process, and their application can significantly influence breeding outcomes.

Why Utilize Information from Relatives for Breeder Selection?

Information from relatives, or pedigree data, is invaluable in animal breeding for several key reasons:

  • Heritability: Many economically important traits, such as milk yield in dairy cattle or growth rate in poultry, are moderately to highly heritable. This means a significant portion of the variation observed in these traits is due to genetic factors.
  • Predicting Performance: Knowing the performance of an animal's parents, siblings, and other relatives provides a reasonable estimate of its own potential. While environmental factors play a role, genetic predisposition remains a strong indicator.
  • Avoiding Genetic Disorders: Pedigree analysis can help identify and avoid mating animals that carry recessive genes for genetic disorders, preventing their transmission to future generations. For example, identifying carriers of Congenital Hydrocephalus in Brahman cattle.
  • Accelerating Genetic Progress: By selecting animals with superior family performance, breeders can accelerate the rate of genetic improvement in the population.

Family Selection vs. Within-Family Selection

Family selection and within-family selection are two distinct approaches leveraging pedigree information. While both utilize family history, their methodologies and outcomes differ significantly.

Family Selection

Family selection involves evaluating the average performance of a group of related animals (e.g., a sire's daughters or a dam's sons) and selecting the families with the highest average performance for the desired trait. The individual animal is selected based on the overall performance of its family.

  • Advantages: Relatively simple to implement, particularly when individual animal data is limited. Effective for traits with low heritability where the cumulative effect of multiple genes is important.
  • Disadvantages: Less accurate than within-family selection because it considers the entire family, potentially masking superior individuals within a less-performing family. Can lead to selection of animals with undesirable traits if those traits are prevalent within the family.
  • Example: Selecting a bull stud based on the average milk yield of his daughters across multiple farms.
  • Applicability: Commonly used in breeds with limited record-keeping systems or when dealing with traits like disease resistance where family history is a stronger indicator than individual performance.

Within-Family Selection

Within-family selection involves comparing the performance of individuals within a family and selecting the individuals that perform best relative to their siblings. This approach focuses on identifying the superior animals within a group of related individuals.

  • Advantages: More accurate than family selection, as it identifies the best individuals within a family. Effective for traits with moderate to high heritability.
  • Disadvantages: Requires complete data on all members of the family, which can be challenging to obtain. Can be influenced by environmental differences between siblings.
  • Example: Selecting the highest-performing heifer from a group of sisters based on their individual milk production records.
  • Applicability: Favored in breeds with robust record-keeping systems and for traits with a significant genetic component, such as growth rate in swine.
Feature Family Selection Within-Family Selection
Selection Basis Average performance of a family Individual performance relative to siblings
Accuracy Lower Higher
Data Requirement Less extensive More extensive (data for all family members)
Heritability Suitability Low to moderate Moderate to high
Complexity Simpler More complex

Modern Advancements & Limitations

Modern animal breeding has moved beyond simple family and within-family selection. Genomic selection, using DNA markers to predict breeding values, has revolutionized the field. However, pedigree information remains valuable, especially when combined with genomic data. Limitations of family and within-family selection include the potential for inaccurate pedigree records and the influence of environmental factors. The National Livestock Productivity Enhancement Programme (NLPEP), launched in 2014, aims to improve livestock productivity through better breeding practices and data management, which inherently emphasizes the importance of pedigree information.

Case Study: Dairy Cattle Breeding in the Netherlands

The Dutch dairy cattle breeding program is a prime example of how pedigree information, combined with advanced genetic evaluation techniques, has driven significant genetic progress. Initially, family selection was used extensively. As data collection improved, within-family selection became more prevalent. The integration of genomic information in recent years has further accelerated genetic improvement, but the historical reliance on pedigree data laid the foundation for this success. The Dutch system emphasizes rigorous record-keeping and accurate pedigree tracing, highlighting the importance of data quality for effective breeding programs.

Conclusion

In conclusion, utilizing information from relatives, through family and within-family selection schemes, remains a cornerstone of animal breeding programs. While modern genomic technologies offer increasingly sophisticated tools, the foundational principles derived from pedigree analysis continue to be vital. A balanced approach, integrating pedigree information with other data sources and embracing technological advancements, is key to achieving sustainable genetic progress and ensuring the long-term health and productivity of livestock populations. The NLPEP initiative in India exemplifies the continued relevance of these principles in a developing nation context.

Answer Length

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Additional Resources

Key Definitions

Pedigree
A record of an animal's ancestry, including information about its parents, grandparents, and other relatives.
Heritability
The proportion of phenotypic variation in a population that is attributable to genetic factors. A higher heritability indicates that a trait is more strongly influenced by genetics.

Key Statistics

Milk yield in high-yielding dairy cattle breeds has increased by approximately 2% per year through selective breeding over the past several decades.

Source: FAO (Food and Agriculture Organization of the United Nations)

The heritability of milk yield in Holstein cows is estimated to be around 0.3 to 0.4, meaning that 30-40% of the variation in milk yield is due to genetic factors.

Source: Knowledge Cutoff

Examples

Brahman Cattle and Hydrocephalus

Congenital hydrocephalus is a recessive genetic disorder that can affect Brahman cattle. Pedigree analysis is crucial to identify carriers of the recessive gene and avoid mating them to prevent the disorder in offspring.

Frequently Asked Questions

▶Why is pedigree information more important for some traits than others?

Pedigree information is more critical for traits with higher heritability and for traits where genetic disorders are a concern. Traits influenced by multiple genes or environmental factors require a broader perspective than pedigree alone.

Topics Covered

Animal BreedingGeneticsSelection StrategiesGenetic EvaluationPedigree Analysis
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