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WORKING
TOGETHER
FOR A HEALTHIER FUTURE...
13
LIVESTOCK MATTERS
D A I R Y C O F E A T U R E
MARCO WI NT E R S
PLI:
what's behind it
and what lies ahead!
Developing a national breeding index
for the UK dairy industry has been a
cornerstone of the DairyCo
breeding+
research strategy for several years.
It has always been considered important
that such an index would represent the
economic benefits a dairy cow could bring
to a business, while also addressing the need
for better health, fitness and welfare standards
to which both farmers and consumers aspire.
To this end, funding has been directed to
both SAC and Edinburgh University, who
have analysed millions of cow records
*
and assessed the relative importance of
different traits under a variety of possible
economic conditions.
The outcome of this work and the economic
assumptions that were made were then
considered by an industry group, on which
breed societies, milk recording organisations,
the AI industry, the milk processing industry
and many practising dairy farmers were all
represented. And the final result of all the
discussions was the development of an index
in which each trait is included in line with
our best estimate of its ongoing economic
importance. That index is the current
Profitable Lifetime Index (PLI).
This PLI is a revision of previous formulae
for the index, but, for the first time, represents
the financial improvement an animal is,
on average, predicted to pass on to its
offspring over its lifetime, rather than for
a single lactation.
As with the previous PLI, it still has strong
emphasis on production - retaining 45 percent
of its emphasis on the milk, fat and protein
traits - but now includes a 55 percent
emphasis on a variety of fitness traits. The
particular traits included are those which have
been proven to be most strongly associated
with the cow's lifetime profitability, full details
of which are given in the Pie Chart.
Since the launch of the current index in
2007, we at DairyCo
breeding+
have been
encouraged and reassured by how positively
it has been received throughout the dairy
industry. Many leading breeders and
commercially successful dairy farmers have
strongly endorsed the index and we have
been able to vindicate their confidence with
some encouraging results, including genetic
improvement across the national herd in
many of PLI's component traits.
Similarly, when we analyse the actual
performance on the farm of animals with
different indexes, we can clearly see that the
genetic prediction is accurately pinpointing
the best animals.
This has been seen in some recent research
undertaken by DairyCo
breeding+
which
shows that daughters of bulls with high
Lifespan indexes (positive scores) live
considerably longer than daughters of bulls
with low Lifespan indexes (negative scores).
The same relationship between the genetic
predictions and daughter performance has
also proven to be the case when other
components of PLI are looked at individually.
Naturally, we don't expect every single dairy
farmer in the UK to religiously select their
AI sires for PLI, although we would highly
recommend that it was the first selection goal.
We know there will be farmers with specific
problems to correct, who may wish to use PLI
as their first screening tool and then focus on
a secondary trait which is important to their
particular situation.
But we can confidently say that if the country
as a whole followed the PLI breeding route,
the national cow population as a whole
would steadily begin to reduce the recent
decline in dairy cow fertility and make
improvements in each of the other traits in
the index. And since genetic improvement
is cumulative, significant improvements can
be built up over the generations.
*
Records analysed in the process of creating PLI are
obtained from the milk records organisations (NMR,
CIS and UDF), and the dairy cattle breed societies.
THE RELATIVE IMPORTANCE OF TRAITS
IN PROFITABLE LIFETIME INDEX (PLI)
KEY FACTS ABOUT PLI
l
The current formula was introduced in
August 2007.
l
45% of the index is based on milk
production (milk, fat and protein).
l
55% of the index is based on health,
welfare and fitness traits.
l
£ value represents improved potential
profitability over a daughter's lifetime.
l
Top bulls have PLIs of over £200.
l
Daughters of top bulls will earn
around £200 more than average
daughters.
l
This is worth £30,000 for a 150
cow herd.
l
The improvements build up over
the generations.
HOW TO USE PLI
Use the highest PLI bull you can without
compromising on any of the other traits
you wish to address. Try to select from
the top 50 percent available, with PLIs
of £70 or more.
HOW TO CHECK A
BULL’S PLI
PLIs are always available on the
DairyCo
breeding+
website at:
www.dairyco.org.uk
Here, it is also possible to re-rank the
top PLI lists to highlight the best bulls for
individual traits such as production,
fertility, lifespan or cell counts.
The current Profitable Lifetime Index (PLI) represents the
culmination of years of research and the interrogation of
millions of cow records. Marco Winters, DairyCo head
of genetics explains why it was considered important to
invest in this index and where it will take the UK dairy
cow population.