PTA - Predicted Transmitting Ability
PTAs are expressed for several traits and are an indication as to how much of a particular trait will be passed to an animals offspring. This is not a measure of performance, but predicts the amount of a trait the offspring will, on average, receive from its parents compared with average parents whose base is zero. This base is recalculated every five years.

Genetic Base
The current base is set to PTA2005 and is recalculated every five years. This is to take into account the genetic progress which has been made in those five years, so in essence it is the average of the population which is recalculated. It is this average to which PTAs are compared.

All the production values in a bull proof are taken from milk records of daughters of that bull, hence the importance of our Cornerstone members being officially milk recorded with NMR, CIS or UDF, to generate all this information.

Milk
The PTA will predict how much milk daughters of a bull will produce per lactation. e.g. For a bull with a milk PTA of +500kg, his daughters are predicted to produce 500kg more in a lactation than a bull with a PTA of 0kg.

Fat
The PTA will predict how many kilos of fat, daughters of a bull will produce per lactation.

Protein
The PTA will predict how many kilos of protein, daughters of a bull will produce per lactation.

Persistency
This is derived from milk yield at 280 days as a percentage of yield at 60 days. The PTA is expressed as a percentage and a higher figure indicates a flatter lactation curve.

Somatic Cell Count
Expressed as a percentage, somatic cell counts  PTA has a range of +30 to -30 and predicts the percentage change in the bulls daughters somatic cell counts. Negative values for somatic cell counts are desirable as these indicate a reduction in cell count.

e.g. for a bull with an somatic cell count  PTA of -10% his daughters are predicted to have cell counts 10% lower than daughters of a bull with an somatic cell count PTA of 0%.

Lifespan
Lifespan PTAs are calculated from actual daughter survival information and fall within a -0.5 to +0.5 range and represent how many extra lactations daughters of a bull are predicted to last.

e.g. for a bull with a lifespan PTA of +0.5, his daughters will last half a lactation longer (milk for an extra 150 days) than daughters of a bull with a PTA of 0.

Fertility Index
Fertility Index PTA is a prediction of female fertility. The range of values are from -15 to +15 with every point increase being worth half a day gain in calving interval and 0.5% increase in non return rate. Fertility Index is calculated from insemination data from milk records and calving interval. Where this information is not available, predictions are taken from body condition score and milk yield at 110 days.

The current average for Fertility Index in the Holstein breed is -3.5.

e.g. for a bull with a fertility index PTA of +4, his daughters are predicted to get back in calf 3.5 days sooner than daughters of a bull with an average fertility index PTA.

Genetic Indices with economic weightings

£PIN
Based purely on production PIN calculates the financial increase in revenue per lactation for each daughter. Milk, fat and protein values are put into an equation which also takes into account costs for feed, quota and transporting the extra milk.

£PIN = (Milk kg PTA x -0.027) + (Fat kg PTA x 0.8) + (Protein kg PTA x 1.71)

£PLI
Profitable Lifetime Index (PLI) takes into account other traits as well as production and is the increase in total revenue each daughter will produce in her lifetime. There is a strong influence of health, welfare and fitness traits in PLI reflecting the value of these traits in farm profitability, and in the wider industry as consumers demand higher animal welfare standards.

£PLI= (£PIN) + (Lifespan PTA x 25.4) + (SCC PTA x -0.19) + (Locomotion x 1.13) + (Udder composite x 1.81) + Fertility Index

Reliability
With all genetic information, accuracy and reliability of the information is crucial, to enable to make the best breeding decisions. Cornerstone, the progeny test programme at Genus ABS forms the foundation for Rock Solid genetics:

Rock Solid: 100 daughters in 60 herds

Diamond Sire: ultimate in reliability with over 1,000 milking daughters.

Further detail on genetic indices and heritability values can be found on the Dairyco website: www.dairyco.org.uk