Fine art of selecting bulls

01-07-2010 | Jackie Harrigan

Angus bull breeder Richard Rowe gave a rundown of a few of his tricks for bull selection at a recent Beef Returns Improvement Group day at Hunterville.

Standing in a pen of rising two-year-old Angus bulls bred at his Merchiston stud, Rowe suggested Estimated Breeding Values (EBVs) described the genetics of each bull but advised against telling potential buyers which one was best for them.

"A balance of traits is important for every operation but the mix varies for each commercial farmer; it depends on your breeding objectives," Rowe says.

Farmers producing weaners would be looking for a fast growth-rate sire, and should consider 200-day and 400-day weight EBVs, he says.

Then they need to consider where the weaners are going to be finished - because if they are finished in a longer time frame then they should take into account later growth, out to 600 days weight EBV.

"Producing weaners for the market requires a combination of growth and milk, with a balance of calving ease."

He asked farmers to consider if they really needed a high milk EBV bull, or whether the breed average would give their cows enough milk to produce good weaners.

He believes breed average is plenty enough milk for Angus cows on hill country.

When it comes to fat EBVs, positive fat cows are better at retaining condition through hard times and selecting bulls with negative fat can cause trouble with the fertility of female progeny.

"Cows sometimes have trouble getting back in calf if they don't have the fat, but then too much fat can also create fertility problems," Rowe says.

Drawing attention to the strong correlation between rib fat, rump fat and intramuscular fat (IMF), he says IMF is the last fat to be laid down but also the last fat deposit to be lost.

He cautioned that Australian moves to yearling bull sales have shown it is hard to measure IMF and rib and rump fat at that early stage.

The mature cow weight EBV can be used as a proxy EBV for efficiency, Rowe says, as a smaller mature cow weight tends to equate to a more efficient animal requiring less feed for maintenance.

Selecting bulls with below breed average for mature cow weight EBV would tend to breed lighter daughters with a more moderate frame size, as the frame size of the bull would also tend to be more moderate. The bulls might have more fat compared with other bulls but the cows would tend to be more easy-doing.

To breed early maturing progeny, Rowe suggests a bull with lower fat EBVs and says farmers should look at what stage the weights go up and plateau, as earlier growth leads to earlier maturity.

There is no easy answer to which Birthweight EBV bull to take home for mating to heifers. "It is trial and error within your own herd, starting at the breed average for Birthweight EBV and working around that level," Rowe says.

Using an index selection method is a good way of finding a balance of traits, and a good starting point for many farmers when buying a bull, Rowe advises.

"Choosing on the index figure puts the different pieces of the jigsaw together to see the whole picture - just make sure the index reflects your production system.

"A good way to do it is to rank by the index but pay attention to some of the individual EBVs - choose three or four key EBVs and make sure they are around the breed average at least."

The indexes are reported as dollars of profit per cow mated and take account of the traits affecting the returns for the particular production system as well as tracking the impact of correlations between traits.

The Angus breed has three beef selection indexes. The Self Replacing index (SR) ranks bulls on their ability to generate profit in a self-replacing herd situation in which some females are retained for breeding and some sold for slaughter along with the males.

The main profit drivers included in the index are direct and maternal calving ease, growth, meat yield, cow survival, finishing ability, fertility and cow efficiency. Selection on this index favours production of a cow herd with excellent reproductive efficiency, rearing progeny with moderate to high growth rates and high-yielding carcases.

The Ease of Calving index (EoC) ranks bulls on their progeny's ability to generate profit when crossed with dairy cows and heifers to produce dairy beef progeny. Calving ease is the most important driver in this index along with meat yield, and the index figure can be used as an indicator of a bull's suitability for heifer mating.

The Angus Pure index (AP) targets a similar beef production system as the self-replacing index but has a greater emphasis on higher marbling sires with progeny sold at around 16-17 months.

A sensible way to go about bull selection, Rowe suggests, is for a commercial farmer to do his homework before a sale by identifying around 10 suitable bulls on their EBVs from a catalogue of 35. Then go to the sale (or visit the breeder beforehand) and check all the prospects for structural and breeding soundness. As an example he highlighted how the most attractive bull in the yard on EBVs was not actually suitable for sale as his scrotal circumference was not adequate for the Merchiston catalogue.

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