Dorian Garrick
In any modern farm enterprise, increases in costs and administrative procedures necessitate increases in productivity to maintain profit. Different technology areas can assist such productivity gains. One area with scope for improvement is the biological systems.
This is true of our pastures and forages, of our sheep, and of our beef cattle. Although there are many aspects of the environment and management that can make the biological systems better, the response of animals to better management is often limited by their genetic potential.
Most farming enterprises have the option – provided they can discriminate – to buy improved seed, rams, and bulls.
A small proportion of livestock enterprises make it their business to sell seedstock, and in order to remain competitive, they must effectively apply selection to annually lift the genetic potential of their rams or bulls that will sire the next generation of commercial animals.
The annual lift in genetic potential that results from selection depends upon several factors. The most important are the intensity of selection, the age at which selected animals become parents, and the accuracy of the selection decisions.
Ideally, a ram or bull breeder wants to accurately select animals before puberty, choosing only a small proportion that represent the best of the selection candidates to become parents of the next generation. In a genomic evaluation, accuracy is achieved by participating in an analysis that includes at least tens of thousands of genotyped animals that have phenotypes for the traits of interest to the breeder. In order to choose a small proportion to retain to become parents means that there needs to be a big number of selection candidates.
The early days of ram and bull breeding were mostly characterised by selection within-flock or within-herd. Selecting animals from other breeders was a risky practice, as there was little information to indicate whether the outside animals were likely to be better than the home-bred candidates.
ACROSS-HERD EVALUATION
The situation improved with the shift to across-flock (SIL) or across-herd (Breedplan) evaluation. Provided link sires had been used in common across a number of farms, much more reliable selection decisions could be made in choosing animals bred outside one’s own flock or herd.
In the New Zealand context, most beef cattle breeds soon migrated from a national across-herd evaluation to trans-Tasman evaluations. This would have allowed for more intense selection if a breeder was prepared to use foreign bulls and cows.
The trans-Tasman evaluation could also increase accuracy of evaluating parents if close ancestors had offspring on both sides of the Tasman. Trans-Tasman within-breed evaluations have remained the approach adopted by most NZ beef cattle breeds for the last 20-25 years. But breeders are now looking with some urgency at other opportunities. Several options are available. Some Australasian breed associations have already made a move, and others seem likely to follow soon.
The options are: to join an evaluation including the same breed in another country or region, such as North America or Europe; to pool data from performance-recorded commercial animals that are not pedigree registered; or to join an across-breed evaluation. These options are not mutually exclusive, but some will be more appealing to particular beef cattle breeds than will others.
There are three large-scale national beef-cattle evaluations in North America. The largest is run by International Genetic Solutions (IGS), which comprises a consortium of more than 14 breed associations from a number of countries, but mostly from the United States and Canada. IGS runs weekly single-step genomic evaluations using a pooled pedigree file approaching 20 million animals. Many of the animals in the evaluation are of admixed breed, including crossbred animals sired by purebred Angus bulls. The second largest evaluation is run by Angus Genetics Inc (AGI) and includes US and Canadian purebred black cattle. The third largest analysis is the Pan-American Cattle Evaluation (PACE) which evaluates purebred Hereford and crossbred Hereford-sired animals from US, Canada, Uruguay, and Argentina.
Collaborating in the mixed breed IGS evaluation instead of Breedplan would be an option for routine single-step genomic analysis for all Australasian breeds, except Hereford. Collaborating in the Hereford PACE instead of Breedplan would be an option for NZ and/or Australian Hereford breeders.
In Europe there is an across-country evaluation operated by the International Committee of Animal Recording (ICAR), and known as Interbeef.
It began through a research partnership between Ireland and France, but has now grown to include other countries. It runs evaluations for Angus, Hereford, Simmental, Charolais, and Limousin breeds, and these evaluations include records from crossbred animals sired by bulls in any of those five breeds.
Unlike the Interbull dairy cattle equivalent, Interbeef uses raw phenotypic records, not just the progeny test summaries. The system is designed to enhance but not replace a local national evaluation, and has had an initial focus on weaning weight and calving traits.
NZ DAIRY EVALUATION
In NZ, there has been a recent major focus on upgrading the dairy industry evaluations run by NZ Animal Evaluation Limited (NZAEL), a subsidiary of DairyNZ. The NZ dairy evaluation uses a pedigree of some 30 million animals and represents a highly admixed dataset, including many mixed breed offspring of Holstein, Friesian, Jersey and Kiwi-cross bulls.
In the past, weight records were limited to lactating cows, but in recent years the Dairy Industry Good Animal Database (DIGAD) has annually recorded liveweights on more than 250,000 animals under a year of age, and a slightly lesser number on yearling cattle. This is already about an order of magnitude larger than the number of NZ registered beef cattle performance-recorded for liveweight each year.
Since 1990, Beef and Lamb reports that NZ has 30% fewer beef cows, but 9% more steers slaughtered per year, and harvests 22% more bull beef. Some 57% slaughters from sheep and beef farms are of dairy origin. Some breeds, such as Hereford and Wagyu, already have developed a close association with the dairy industry and have herds breeding for crossbred attributes. Plans are underway by both NZAEL and Beef + Lamb to increase the scope of routine evaluations to better represent the beef value proposition in the dairy industry.
Aligning the data pipelines for pedigree, performance and genotype files with other kindred organisations in order to take part in a larger-scale across-country and/or across-breed evaluations can increase selection intensity and can improve the accuracy of prediction which are the key determinants of the rate of genetic improvement. All these activities incur costs, and the costs need to be considerably less than the benefits to the nation in terms of improved productivity and efficiency that comes from using better bulls. A feature common to selection programmes in pasture, sheep and beef cattle, is that it is most cost-effective to keep the size of the pedigree and performance-recorded nucleus sector that drives the genetic improvement as small as possible relative to the size of the commercial sector that obtains the value from the more productive and efficient offspring.
NUCLEUS AND MULTIPLICATION
Improving the cost-effectiveness of improvement schemes is typically achieved by separating the sire breeding sector into a nucleus, which drives genetic gain, and a multiplication tier, which serves to multiply and disseminate the improved germplasm generated in the nucleus. In the bull-breeding sector, most performance recording herds are multipliers, and only a few are nucleus herds driving genetic gain.
Pedigree analysis can be applied to the breed association data to identify the sources of influential sires in each breed. If those sources mostly represent just a few breeders, those breeders are likely to represent the nucleus.
In the NZ Angus pedigrees, it is apparent that many breeders are multiplying US germplasm. US sources are much more prevalent than Australian sources. This is perhaps not surprising, given the much larger size of the North American Angus population, and the fact that marbling has been an important trait in North America for many years, but has only relatively recently been recognised as being important in Australasia.
The collective dominance of North American sires is also apparent in Hereford and Simmental pedigrees in NZ. Accordingly, North America would be an obvious place to look for data sharing opportunities. These new opportunities to expand the nature and scope of cattle evaluation in NZ are a considerable focus of some bull breeders, but what does it mean for most sheep and beef farmers, who don’t breed bulls but buy them for use as terminal or maternal sires in their commercial cow herds?
It shouldn’t make any difference to the fact that objective information will take the form of EBVs and corresponding accuracies, and that these values may be summarised in the form of index values of multiple trait merit.
It might make a difference in that EBVs could come available on some new traits that have not been available from the Breedplan system. It might make a difference that the accuracy of EBVs are improved, and that selection intensities can be increased, and that will translate to faster rates of progress for those breeders using objective information to select the best animals as parents of the next generation.
- Dorian Garrick is chief scientist at the AL Rae Centre of Genetics and Breeding at Massey University, a Director of Performance Beef Breeders (PBB), on the Scientific Advisory Committee of Interbeef, and a founding partner of ThetaSolutions LLC, whose software has been used under license in beef cattle and dairy cattle genomic analyses including those of ABRI, PBB, IGS, PACE and NZAEL.
