How much better are the youngest bulls?

Published 27 August 13

Dairy herds using young Holstein genomic sires over the past 12 months could now have an average Profitable Lifetime Index for their latest crop of calves around £40 greater than their neighbours using conventional bull semen.  And if they’ve used genomic sires for longer, their genetic advantage is likely to be even greater.

Geneticist, Marco Winters, head of DairyCo Breeding+, says that not only will herds using young sires have a worthwhile advantage in terms of PLI, but their genetics will be better for kg milk, fat and protein, and type, as well as some key fitness traits including lifespan and cell counts.

Mr Winters’ confidence stems from two key areas of research he has undertaken on behalf of DairyCo.

In the first, he looked into the correlations between young sires’ genomic indexes in April 2012, and the same bulls’ indexes when their indexes included actual daughters’ performance in April 2013.

This revealed a strong correlation between the two sets of figures, indicating that genomic indexes – calculated from a bull’s own DNA – are an accurate guide to transmitting ability.

“We had confidence in the technology when we launched genomic indexes in the UK in April 2012 as it had been extensively trialled and fine-tuned in North America and by ourselves, here in the UK,” says Mr Winters. “But finding a correlation of 0.89 for Profitable Lifetime Index – where a correlation of 1.0 represents a perfect relationship – gives us even more confidence that young sires’ daughters will perform close to expectations.

“Of course, the fact that the correlation is not perfect and the reliability of genomic indexes is still lower than for daughter-proven bulls, means genomic bulls won’t be the choice for every breeder and certainly not for those who are at all risk-averse,” he adds.

The second piece of research undertaken by Mr Winters reveals that not only are young Holstein bulls likely to perform close to expectations, but they will also perform considerably better than earlier generations.

“A young genomic sire may be marketed from as early as 12 months of age, which means that assuming the AI industry has been doing a good job of sire selection, he’ll represent a huge genetic leap over daughter-proven sires of five or more years old,” he says.

Precisely how much better is shown in the table below based on the latest (August 2013) genetic indexes.

Analysing the indexes, Mr Winters found that the top 100 daughter-proven bulls had an average PLI of £201 while the top 100 young genomic sires had an average PLI of £241.

The young sires were also better for their Predicted Transmitting Ability (PTA) for milk at 693kg (compared with 524kg); fat at 31.3kg (compared with 25.4kg) or protein at 23.9kg (compared with 20.4kg).

However, while young sire Type Merits were better, as too were Somatic Cell Count Indexes and daughter Lifespan Indexes, there was a small difference in both daughter Fertility Index and in milk components in favour of daughter proven bulls, although both sets of bulls display good positive scores for both traits.

“The figures overall are an endorsement of the new generation of genomic sires and I’d suggest that the careful selection of a group of these bulls can improve a herd’s genetic merit,” says Mr Winters. “But just because a bull is a young genomic sire does not automatically mean he is better and breeders should ideally look at every component of a bull’s index to make sure he meets their herd requirements.”

Find out more about how to use genomics in your herd 

Average genetic indexes of top 100 daughter-proven sires and top 100 young genomic sires (August ’13)

 

 

 

 

£PLI

Rel (%)

Milk (kg)

Fat (kg)

Prot (kg)

Fat (%)

Prot (%)

SCC Index

Lifespan Index

Fertility Index

Udder Comp

Legs & Feet Comp

Type Merit

Daughter proven sires

201

83

524

25.4

20.4

0.06

0.04

-14

0.3

3.3

1.19

1.32

1.44

Genomic young sires

241

68

693

31.3

23.9

0.05

0.02

-18

0.4

2.7

2.16

1.9

2.41

Difference

40

-15

169

5.9

3.5

-0.01

-0.02

-4

0.1

-0.6

0.97

0.58

0.97