Sire Selection in the Future Herd

At this time of year many farmers are thinking about sire selection in advance of breeding cows this winter.  Sire selection is an important decision as bulls selected today and used for insemination this winter will determine what cows you have milking in 3 to 7 years time, and potentially longer.  Therefore sire selection is part of a long term strategy for your herd and one that should be taken with the longer term aims of your herd in mind.  Establishing where you currently are is key to this.  The herd genetic summaries available from milk recording and CAFRE’s Dairy Benchmarking and Fertility Benchmarking programmes can help you determine the key breeding goals for your herd.

In Greenmount’s Future Herd the sire selection targets are outlined in Table 1.  The herd production target is to produce 8,000-8,5000 litres/cow/year on a rolling average basis with a butterfat target of 4.10% and protein of 3.50%, and a lifetime yield of 40,000 litres/cow.  The high milk quality targets are based on the fact that 86% of the milk produced in Northern Ireland is used for manufacturing.

Table 1:  Future Herd genetic merit and sire selection targets

Source: DairyCo and Annual Statement of Terminated Lactations.

For farmers who are milk recording and can identify the sires of individual cows in their herd, a herd genetic report is available.  This is available from either DairyCo or your milk recording company, and it forms the basis for sire selection in the Future Herd.  The Annual Statement of Terminated Lactations (available in October each year) lists the PTAs for milk yield, fat yield, protein yield, fat%, protein%, £PLI and inbreeding coefficient of individual cows in your herd.  From this report, it was established that cows in the Future Herd have an average PTA for milk yield, fat% and protein% of +63 kg, 0.13% and 0.06%.  Sires are selected to improve the genetic merit for production and milk quality, but are also selected with positive fertility and negative somatic cell count PTAs in line with herd policy.

Rather than trawling through the sire catalogues of individual companies, sires considered at Greenmount are short listed using the list of available Holstein bulls published on the DairyCo website (www.dairyco.org.uk).  The sire list is available by clicking on the links for Breeding and genetics, DairyCo breeding+ evaluations, selecting the appropriate breed from the Breed Selector and clicking on the list of available bulls.  These can be downloaded as an Excel spreadsheet.  Of the list of around 500 available Holstein bulls in the UK, bulls that fall short of the selection criteria on individual PTAs can be quickly filtered off leaving perhaps around a dozen bulls to choose from.  The selection criteria used for sires at Greenmount this winter were in order of importance:

Three sires are generally chosen for use on the Future Herd each year with the final selection based on both type and pedigree background.  Bulls are generally not used for more than two years to avoid the risk of inbreeding.  Sires selected for use this winter are Kelstein Dynasty, Helhoeve Delta Spencer (both used last winter) and Bidlea Padbury.  These all have a reliability of greater than 80%, are positive fertility, negative somatic cell count and should improve the herd’s milk quality and lifetime performance in the future.

Table 2:  Sires selected for breeding the Future Herd this winter.

To counteract the decreasing levels of cow fertility, increasing somatic cell count and increasing levels of lameness, £PLI was introduced as a Profitable Lifetime Index incorporating management as well as production traits.  This should help to improve the longevity and lifetime performance of dairy cows in the future.  These currently stand at around 3.5 lactations and 27,500 litres per cow in Northern Ireland.

The £PLI index was restructured in 2007 to increase the influence of management traits and improve lifespan.  Production traits now account for just 45% of this index with lifespan accounting for 21%, fertility 18%, somatic cell count 6%, udder 6% and locomotion 4%.  

A sires PTA for lifespan typically ranges from -0.5 to +0.5 and reflects the number of lactations a bull’s daughters are likely to have compared to the breed average of zero.  Therefore daughters of a bull with a lifespan PTA of +0.5 would be expected to survive for half a lactation (150 days) longer than those of a bull with a lifespan PTA of zero.

The PTA for fertility typically ranges from -15 to +15 and is based on calving interval and non-return rate together with a number of indirect traits that are strongly correlated to fertility.  The average bull in the list of available sires in the August 2009 proof run had a fertility index of -3.2 and a milk PTA of +425, but it is possible to select a bull with both positive fertility and a good PTA for milk yield.  Each one point increase in a sire’s fertility index will decrease the calving index of his daughters by 0.5 days and increase their conception rate by 0.5%, on average.  To address the problem of declining dairy cow fertility it is best to select bulls with a positive fertility PTA.

The somatic cell count PTA typically ranges from -30 to +30 and is expressed in percentage terms.  Sires with negative SCC PTAs are desirable as these should reduce the average somatic cell count of their daughters.  Therefore the somatic cell count of daughters of a sire with a SCC PTA of -1% should be 1% less than those of daughters of a bull with a SCC PTA of zero.

When selecting sires for use on your cows this winter, the revised £PLI index which takes account of both production and management traits is a good starting point.  However, if you know the genetic merit of your herd for particular traits and have clear aims for the future direction of your herd, it is advisable to look at the PTAs for individual traits.  It is also advisable to consider sires with positive fertility and lifespan PTAs and a negative somatic cell count PTA to help increase the future longevity of your herd.

Michael Graham (Farm Manager) and David Mackey (Dairying Technologist) reviewing the list of available sires on the DairyCo website (www.dairyco.org.uk).