Ironing out angus index wrinkles
Beef farmers could be led down the wrong path by sire selection indexes, an angus breeder tells Rob Tipa.
The sire selection index system used by Angus New Zealand and available to commercial beef farmers has outlived its usefulness and is no longer robust enough for farmers to make credible decisions.
That is the considered opinion of Neil Sanderson, a North Otago veterinarian, specialist beef breeder and former board member of Angus NZ.
Sanderson believes the Angus Pure (API) and Self Replacing (SRI) indexes are not robust enough to help commercial farmers make credible decisions on sire selection without an in-depth knowledge of estimated breeding values (EBVs), a complex science in itself.
‘‘Indexes should be designed to enable the commercial farmer to use them reliably and be able to trust the outcomes without having to be a genetics expert. The problem with [them] is they are too strongly linked to the schedule price.’’
As the schedule price climbs an animal with high growth rate and carcass weights will by default end up with high indexes as the other traits and important maternal and calving ease traits are simply overwhelmed.
‘‘This gives a very distorted picture of what is driving profit with that animal.’’
The index system was adopted by Angus NZ about 20 years ago and, as chairman of the board’s technical committee, Sanderson was involved with its update about three years ago. ’’The higher the schedule goes, the more uncomfortable I feel about them.’’
Most commercial beef breeders trust the indexes but don’t necessarily understand the complex background behind them, he says.
If breeders base their genetic selection of bulls only on the indexes without looking at EBVs, he says it could lead them down the wrong path by, for example, selecting a sire for its extreme growth rates and large cow size at the expense of calving ease.
In this case, a farmer could theoretically generate more profit from eight live calves out of 10 calves born, despite losing two calves through difficult calving. The eight surviving calves may grow faster and generate more profit than 10 live calves from another sire with the same index but greater calving ease and moderate growth rates.
Sanderson says this scenario is totally unacceptable for a self-replacing herd. He believes the value placed on a premium for marbling (or IMF) in the Angus Pure index is another cause for concern.
The Angus Pure index incorporates a premium to encourage selection for marbling, but this could create distortions if high indexing animals have very poor calving ease and some may have no marbling whatsoever.
Both indexes are promoted as being suitable for beef herds with heifers retained for replacements. ’’At the moment it sits in the index calculation at well over a dollar a kilogram carcass weight for a moderate marbling score. It is highly unlikely that this will be achievable under our current meat industry model for quite some time.’’
Sanderson believes the ‘‘one size fits all’’ indexes have outlived their usefulness. He is a strong advocate for an alternative system of four commercially sub-indexes developed for beef cattle by AbacusBio and Beef + Lamb Genetics to produce the best profits on hill country.
‘‘I think the adoption of this new index model is going to offer a far more transparent, clearer picture for commercial beef breeders because it groups breeding values [EBVs] together related to their economic output.’’
Under the new model, there are four separate sub-index categories. They include growth, calving ease, maternal attributes and carcass eating quality. Cumulatively the four categories make up a single, overall index and are expressed in dollars. They can be presented in the form of a graph that shows rankings within New Zealand.
The growth index only relates to income generated from growth traits by an animal and indirectly correlates to carcass weight. The calving ease sub-index mostly relates to calving ease along with length of gestation, which gives real values related to successful calving outcomes. Dead calves don’t make profits.
The maternal sub-index recognises the real value of cow survival on New Zealand hill country. It penalises cows for high mature cow weight EBVs and for low rib and rump fat EBVs.
In the future Sanderson says this sub-index may incorporate other fertility traits, such as the highly heritable antral follicle counts. It rewards cows for weaning a superior calf.
The eating quality sub-index relates to premiums available for high-value branded beef. It rewards high marbling and penalises carcasses with excess fat cover that require trimming by meat processors.
Sanderson believes the new subindexes would give commercial beef breeders the tools to select herd sires for different purposes. He says the dynamics of the beef industry have changed as beef cows have been steadily displaced by dairy cows on better finishing country.
As a result, farmers have to be smarter about finishing cattle on crops on a smaller area of land.
‘‘If you can look at growth and carcass attributes separately, you can then pick genetics that identify steers and surplus heifers that will make you the most money quickly if you are finishing them, especially on crops like fodder beet which has been quite revolutionary for the beef industry.’’