Using heifer genomic results for sire selection

 

Genomic testing of dairy heifers has now become an important part of some herds’ breeding strategy and replacement policy. Apart from the obvious decisions about which heifers to breed back to dairy, beef or sell as surplus stock, it is now possible to select the most appropriate bull to mate with individuals or groups using the improved reliability of the heifer’s genetic information.

Genotype profiling with 67-70% reliability, will ensure that any corrective mating is done more effectively by carefully selecting a bull to complement both the production and linear profile of the heifer to maximise the genetic gain. Table 1 shows the genomic profile of one heifer ready for bulling at one of the Farming Connect Demonstration Farms. As with all heifers she has strengths and weaknesses depending on the system she will enter after calving, therefore it is critical that any mating fits the farm situation. In the scenario below a brief description of the system and milk contract is given along with the main breeding aims and objectives. We can then highlight any strengths and weaknesses in the profile of the heifer that needs addressing through corrective mating.

Scenario. 380 Holstein Friesians yielding 9200 litres/cow, fully housed 2X day milkers that calve all year round and supply a volume contract. All replacement heifers are reared on farm.

Breeding goals.

  • Increase milk volume
  • Reduce replacement rates to save on rearing costs and be in a position of having surplus youngstock to sell in the future
  • Reduce somatic cell count and cases of mastitis
  • Moderate sized functional animal with good legs & feet and udders to cope with large volumes of milk

Therefore based on the information above and set against firm breeding goals it is now possible to assign strengths and weaknesses to the example heifer in table 1.

Table 1. Genetracker report profile for the example heifer

 

Strengths

  • Fertility index – more likely to get in calf once in the herd
  • Condition score – more likely to hold her condition whilst in milk
  • Minus cell count index – Reduced Somatic cells in the milk

Weaknesses to be improved

  • Lower milk volume with high fat and protein % - more suitable for manufacturing contract
  • Negative score for Mammary composite - could lead to lower herd lifespan
  • Feet & Legs and Locomotion  - higher risk of lameness

From the above strengths and weaknesses we can see three weak points to be addressed giving us our main breeding aims for the example heifer. Trying to correct too many traits in one single mating can be difficult and won’t have the impact of correcting just two or three traits in one generation. This principle will allow the farmer to search for a bull with extreme corrective values, in this example Milk Yield (Kg) along with mammary and feet & legs composite should be focused on to rapidly improve the genetic potential of the heifer’s offspring. Searching through a myriad of brochures and company websites can be both time consuming and confusing as the powers of marketing can often influence the individual’s final decision. This process can be shortened and simplified using independent free to use tools such as the AHDB interactive Dairy Bull list (Fig. 1)and Holstein UK’s Bull selector (Fig. 2)

Fig 1. AHDB Dairy interactive bull list

 

AHDB Dairy support interactive bull lists across most breeds which are updated three times a year during proof runs in December, April and August. It is important to use the most up to date information possible on each bull and the AHDB Dairy breeding and genetics page ensures this data is available and interpreted independently and accurately.

Also by using Holstein UK’s bull selector feature (Fig.2)you can assign minimum and maximum Bull PTA values for production and conformation to the slide bar and then ask the software to list bulls that fall within the desired parameters.

Fig 2. Independent web based sire selection application free from Holstein UK

 

 

Below we see a list (Table.2) of bulls that fall within the specified search criteria along with the company that supplies the semen. We can then click on each individual bull to see a production and type merit proof (Fig. 3).

Table 2. Shortlisted bulls that fall into example criteria

 

The third ranked bull on the shortlist above ‘Peak AltaRecoil’, has good levels of milk production and fertility without losing too much on milk components. Aspects of conformation in the heifer that need improving can also be achieved with the high composite values for both mammary and legs & feet that will be transmitted by the sire.

Fig. 3  Genomic production and conformation proof for Peak AltaRecoil

However one thing to consider when using a young genomic sire is the direct Calving Ease value (dCE). A negative or low positive score can be problematic on heifers, especially if the semen is not female sex sorted. Proven bulls with proven calving ease data and reliability can sometimes be a better option if heifers are to be artificially inseminated. The above sire will reduce somatic cells, increase the fertility index and has average breed values for stature which will further complement the overall breeding aims and objectives.

The potential Parental Average (PA) of the calf born as a result of the above mating can now be calculated for the main traits that need improving from the breeding aims.

Table 3. Potential parental average of resulting calf from mating Peak AltaRecoil with the example heifer

Genomicaly tested Trait

Heifer Genomic Value

Sire Genomic value

Resulting calf Parental Average (PA)

GPLI £

£356

£723

£540

Milk Kg

127

679

403

Mammary composite

-0.28

2.43

1.08

Legs and feet composite

-0.27

2.09

0.91

 

This exercise can be done for an individual heifer or groups of heifers where the average GPTA (Genomic Predicted Transmitted Ability) for the group can be used to select sires. It is recommended that a team of genomic bulls is used to serve a  large group of heifers or cows as it will spread the risk of the lower reliability of the genomic proof compared to using a full daughter proven sire.

Summary and Key Points

  • Key breeding goals should be set appropriately to the system operated.
  • Main Strengths and weaknesses of individuals or groups of heifers should be identified using genomic data and through a visual phenotypic appraisal.
  • Use of independent breeding tools to select sires for corrective mating.