CAL: Animal selection

Question 1

Why does animal selection occur? 4

Answer 1

For desirable characteristics
Against undesirable characteristics
For production indices
For inherent disease resistance

Question 2

What is the role of vets in animal selection? 2

Answer 2

Enhance animal welfare

Increase production/profitability of production animals

Question 3

List some examples of ways genetic merit for production trait are calculated

Answer 3

EBV
Selection indices
Estimated Progeny Difference (EPD)

Question 4

How is heritability defined?

Answer 4

As a percentage
0 = all characteristic is due to environment
1 = all characteristic is due to genetics

Livestock:
0-0.2 = low
0.2-0.4 - medium
0.4-0.6 - high

Question 5

What is spider lamb syndrome?

Answer 5

inherited chondrodysplasia of Suffolk sheep
simple recessive gene
lambs are born with long fine-boned limbs that bend outwards from the carpi (spider-like) and many die young

Question 6

Which dog breed is prone to ceroid lipofuscinosis (an inherited storage disease)?

Answer 6

Border Collies :-(

Question 7

Define EBV

Answer 7

figures indicating how much better/worse a beef animal is in terms of its genetics or breeding value compared with an average animal in the breed born in 1980.

Management/environment effects removed

Question 8

What are indices made up of?

Answer 8

a number of EBVs

Question 9

What are EBVs calculated from?

Answer 9

Performance records - compiled by pedigree breeders and MLC

Updated twice a year (3 times for the 6 major breeds)

Question 10

How are EBVs calculated?

Answer 10

Using a computer program which uses a statistical procedure called BLUP (best linear ubiased predictor) to separate the records of an animal into 2 parts:

1. ) proportion due to the animal’s breeding (i.e. heritability)
2. ) the proportion due to how the animal has been reared (i.e. its environment).

This involves running several hundred simultaneous equations to calculate the EBVs of each animal.

Question 11

How are EBVs made as accurate as possible?

Answer 11

The BLUP program adjusts the EBV according to how much information is available.

Also an accuracy value is calculated for each EBV (dependent on how much information is available).

Multi-trait analysis - the BLUP program takes into account all records relevant to the specifc trait that an EBV is being calculated for.

Question 12

Differentiate EBV and indices.

Answer 12

EBV - measure of how an animal will physcially perform for a specific characteristic.

INDICES - produced to meet a single breeding objective: they take into account the relative economic value of each of the component traits involved by combining several EBVs and assigning them a financial value to derive a single financial benefit/penalty for each animal

Question 13

What EBVs are associated with calving? 3

Answer 13

Gestation length
Calving ease (%)
Birthweight (kg)

Question 14

What is calving ease calculated as?

Answer 14

the percentage change in the number of difficult calvings. Positive values indicate animals whose progeny will be born more easily.

Question 15

What is birthweight used to indicate?

Answer 15

growth weight and carcase potential of the animal

Question 16

List some EBVs associated with growth and carcase quality - 5

Answer 16

200-day weight (kg)
400-day weight (kg)
muscle score (points) - 15-point scale
muscle depth (mm) - measure of the eye depth
fat depth (mm)

Question 17

What is eye muscle depth used for?

Answer 17

greater depth often associate with better overall muscling but remember that carcase conformation is more dependent on the shape of the hindquarter than the depth of the eye muscle

Question 18

List some maternal EBVs

Answer 18

200-day milk (kg)

Question 19

What 2 UK indices are there?

Answer 19

Beef value (£)
Calving value (£)

(within all breeds, a few bulls do have what is ideally required, positive EBVs for both calving value and beef value)

Question 20

How should EBVs be used?

Answer 20

each parent’s EBV should be halved before adding them together to arrive at the expected EBV of the calf.