Progeny Testing | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Introduction

Genetic improvement programs hinge on precise performance measurement across a significant portion of the breeding population. The interplay between heredity and environmental factors influences an animal's performance, emphasizing the need for comparable conditions in performance evaluation.

Environmental Considerations in Performance Measurement

Ensuring that phenotypic expressions are observed under comparable conditions is a critical aspect of performance measurement. Statistical adjustments using conversion or standardization factors prove beneficial when identifying known environmental effects, such as age at calving or lactation milk yields.

Importance of Comprehensive Performance Testing

Performance testing programs should encompass a substantial proportion of the breeding population to establish a robust breed base for selecting breeding stock. The identification of superior individuals is more likely with a larger number of tested animals, providing a solid foundation for stock selection.

Progeny Testing and its Role in Genetic Improvement

Progeny testing, particularly in the context of dairy sires, offers advantages in assessing breeding values. The sex-limited trait of milk production necessitates predicting a male's breeding value from the performance of close relatives and progeny.

Advantages of Dairy Progeny Testing

• Early and reliable indication of a sire's potential based on progeny testing.
• Distribution of sire risks across multiple herds, reducing the impact of poorer sires.
• Reduced likelihood of herd-specific influences on proof, as daughters are scattered across several herds.

Limitations of Dairy Progeny Testing

• High costs associated with holding young bulls awaiting progeny test results.
• Requirement for a sound testing program with cooperation from breeders.

Accuracy in Progeny Testing Programs

The accuracy of progeny testing increases with the number of progeny tested. However, a balance must be struck between the accuracy of assessing each young bull and the selection intensity available post-progeny testing. Striving for a minimum of 50 tested daughters ensures a more reliable progeny test, allowing widespread use of the bull without undue risk. 

Methods of expressing the progeny test

Equal Parent Index: Indexing bulls for production is a good method in the 'selection program of dairy balls. A sire index is a way of expressing what the air's progeny indicates about his heredity It is most needed for characteristics which the sirs cannot show himself like milk and butter-fat. The dairy ball index is the simplest for use in the Equal Parent Index, which places the daughters halfway between the production of their dams and the index of their series

where P = yield of progeny, Saire Index and D = dam's sparage in this index, the milk scends of the cow to which a ball has been mated is converted into some standard basis using conversion factors. The same thing is done with the unselected daughter's records, Then a comparison is made between the daughter's and dam's averages below

305-day, 2x ME Daughter Average:

• While the 305-day, 2x ME Daughter Average is a straightforward method, providing reliable evaluation when the number of daughters is large and consistent feeding and management levels are maintained, it has limitations. 
• This method does not consider the merit of the dam to which a bull was mated, leading early breeders to prefer the daughter-dam comparison. However, changes in herd management over time can significantly influence the daughter-dam difference.

Herd Mate Comparison (HMC):

• Introduced in 1962, HMC aimed to address environmental influences on daughter-dam comparisons. However, it faced criticism due to random sampling of mates, herd mates, and sons of herd males in a bull's summary. 
• Additionally, HMC lacked consideration for genetic trends in the population and exhibited no differential culling among daughters of a bull and their herd mates.

USDA-DHIA Modified Contemporary Comparison (MCC):

• Implemented in 1974 as a replacement for HMC, MCC overcomes its defects by utilizing a contemporary average based on records from a five-month interval. This method includes animals calving before and after the individual daughter, ensuring the same feeding, climatic stresses, and milking personnel. 
• The contemporary comparison is effective when the sire's daughters and contemporaries receive the same opportunities. MCC further reduces the impact of age adjustment inadequacies by grouping daughters into first lactation and second and later lactation categories.

Proven Bull:

• The term "Proven Bull" does not necessarily imply superiority but rather signifies a bull that has been proven for his inheritance.
• The proof is a statement based on the performance of the bull's daughters and their dams, indicating whether the bull is selected as superior or rejected as inferior.