PMVPH: Population genetics CAL

Question 1

What is PTA

Answer 1

Predicted Transmitting Ability. It indicates the amount of a particular trait an animal is predicted to pass on to its progeny (for example a milk kg PTA can be +1000kg which means that this animal, on average, is expected to pass on an extra 1000kgs to its progeny).

Question 2

What is a genetic base?

Answer 2

This is the standard against which all animals are measured, and from which proofs are expressed as a deviation. Every 5 years this is reset to zero to keep it current (2000, 2005, 2010, 2015).

Question 3

What is the Rel%?

Answer 3

Reliability is a measure of the accuracy of the animal’s evaluation (PTS). The higher the reliability, the more confidence you can have in the figures (low 90&)

Question 4

Is a negative SCC PTA good?

Answer 4

Yes - it indicates the bull will (likely) cause a reduction in SCC

Question 5

How are lifespan PTAs expressed?

Answer 5

Expressed in the number of lactations. Usually +/- 0.5 lactations. Usually relative to the daughters of a bull with a PTA of zero.

Question 6

What is the FI?

Answer 6

The fertility index PTA. These are the latest addition to bull proofs and are expressed as a financial value on the same scale as PIN and PLI. Made up of the principal components: calving interval, non-return rate. Positive proofs indicate the daughter is better than average.

Question 7

What are Type PTAs?

Answer 7

Unlike other PTAs, these are expressed in a standardised form on a scale of +/-3. These standardised scores allow animals to be ranked by how extremem an animal is for a particular trait compared with the population. For example, animals above +2 are in the top 2.5% of the population

Question 8

What is £PIN? What does it include?

Answer 8

It its the Production Profit Index. This is the combination of the PTAs for milk, fat and protein yield into a single financial value indicating the profit expected from per lactation from production alone.

Question 9

What is the £PLI? What does it include?

Answer 9

The Profitable Lifetime Index. This is used as our national ranking index. It is an extension of £PIN so includes the production traits (milk, fat and protein) and other traits where available (lifespan, SCC, locomotion and fertility)

Question 10

Statistics on UK sires.

Answer 10

nearly 700 proven sires are currently on offer in UK (may be just holstein and friesian, not sure), as many as 33 traits and 12 different countries these are offered to.

Question 11

When is accurate interpretation of bull proofs particularly important and why?

Answer 11

where are relatively small number of bulls is used to breed replacements each year, given the large impact they will have on the herd.

Question 12

Why is daughter distribution important?

Answer 12

Example - with only 3% in the herd with the most daughters shows that the proof is not overly affected by the performance in any one herd.

Question 13

What are the important points to remember when reading a bull proof? 5

Answer 13

• appreciate that the figures are only predictions of the traits a bull will, on average pass onto his daughters
• use the figures to compare different bulls, rather than to indicate specific gain
• be more wary of figures with a lower reliability, since these are more likely to change in the future with the addition of more daughter information
• even with a reasonable daughter numbers a poor herd distribution (with a large proportion of daughters in one herd) can lead to proof instability
• the indexes indicate the amount of financial improvement per lactation the bull is, on average, predicted to pass on to his offspring compared to the current Genetic Base.

Question 14

What is a type proof?

Answer 14

This sets out a bull’s Breeding Values for all of the key linear and composite type traits, including overall type merit. It also details the management traits (locomotion, ease of milking and temperament) on the same scale. The reliabiility of the Type Breeding Values (which is invariably different from and generally lower than that of the production PTA’s is included in the type proof, together with details of the number and daughter distribution of the UK classified daughters. Any absence of daughter numbers indicates a bull is proven overseas and yet to be proven on UK cows.

Question 15

What would a good UK Daughter Distribution be?

Answer 15

A good spread of UK daughters in herds for a 1st crop would be around 130+ daughters in 80+ herds.

Question 16

What would a good reliability first crop proof be?

Answer 16

between 85-95%

Question 17

Should you attach greater importance to individual linear trait scores or composite type traits when trying to correct a specific problem?

Answer 17

individual linear trait scores are more important

Question 18

To improve a particular trait, what should the score be?

Answer 18

a score above 2.0+ is likely to be needed, with the exception of the mid-scoring traits

Question 19

What do the standard deviations mean?

Answer 19

refer to the average of the bulls daughters for any particular trait or composite compared to the average of all bulls daughters.
Animals with a -3 or +3 are in the bottom or top 1% of the population
Animals with a -2 or +2 are within the bottom or top 2.3% of the population
Animals with a -1 or +1 are within the bottom or top 16% of the population

Question 20

What data does a bull production proof include? 8

Answer 20

Name of bull, breed code, genetic recessive test codes
Sire and dam
Production PTAs (milk, fat, protein, etc)
Production PTA reliability
Current genetic base
Selection indexes (PIN and PLI)
UK daughter distribution
Lifespan PTA