Technology to help boost genetic gain

01-02-2009 | Gerard Hall

Ram breeders have several new breeding tools to assist them deliver the increased rates of genetic gain their clients are demanding of them.

Developed by AbacusBio's Peter Amer they are designed to add further value to current pedigree and genetic evaluation systems.

Dunedin-based Amer says SIL ANI-Mate and ANI-Mate Advanced are two in a suite of services offered as part of the AbacusBio team's Accelerator package.

SIL Ani-mate provides ram breeders with a relatedness table or alternatively ‘ready-to-draft' mating list for selected rams and ewes which increase the likelihood of breeding greater numbers of elite animals and at the same time reduce the impact of inbreeding.

The relatedness tables match each ewe in the stud flock against candidate rams and shows the degree of inbreeding that may result in the progeny from each of the different matings.

Amer say the lists can be used on their own, or alternatively, to fine tune mating groups provided as part of the SIL Ani-Mate mating listings prepared to keep inbreeding to a predefined minimum.

Having ‘ready to draft' mating lists also saves valuable time when sorting up mating groups in the yards and increases the flexibility of the breeding programme.

As a well as controlling all matings between direct relatives, Ani-Mate enables all sire-daughter and parent-progeny matings to be avoided.

Rams are assigned to ewes according to the breeders preferred selection strategy.

This could include mating ‘best-to-best, (high-to-high) or high-to-low using the breeders' choice of SIL indexes or breeding values (BV) or focusing solely on minimising inbreeding in the progeny.

Available in user friendly e-report format, the listings are easy to use and sort through. They can be quickly printed off for use when fine tuning individual matings in the yards or they can be directly viewed from a computer screen at the side of the drafting race.

Breeders simply advise their SIL bureau which rams they intend using and the tag number of any rams they intend to put to particular age groups such as just the ewe hoggets or two-tooth ewes. SIL Ani-Mate then assigns ewes to rams on the basis of minimal inbreeding and the breeder's selection strategy.

A ram usage summary, a backup ram list, a simple ewe mating list and a comprehensive ewe mating list are among the four reports.

Amer says a more customised service, Animate Advance, is now available to cater for those breeders that have specific requirements when planning their mating groups.

It is able to cater for a wide range of situations including large flocks, multiple sire joinings and where complex preferential mating systems are being used.

Ani-Mate Advance develops specific individual and group mating plans by analysing SIL breeding value, index and pedigree data. This creates the opportunity for breeders to increase the likelihood of producing greater numbers of elite animals while reducing the impact of inbreeding in both the short and long-term.

Ani-Mate Advance does this using a number of techniques including assortative (random) or best-to-best mating, the use of tactical and strategic inbreeding controls and relatedness profiling.

Amer says each of the techniques can be used individually or in combination depending on the needs of the individual breeder.

Along with best-to-best and random mating, Ani-Mate applies several inbreeding control strategies that can be put in place to carefully manage the overall relatedness among selected parents while maintaining the highly valuable genetic diversity within a flock.

When purchasing their flock rams, farmers are looking primarily for a good solid team of rams that will on average deliver the increased rates of genetic gain they are now demanding. In a team of four rams, one super star and three duds is not the answer.

Amer says mating ‘best-to-best' increases the spread of breeding values in the next generation so the chance of producing an exceptionally high breeding value animal increases.

However he points out when compared with random mating the average breeding values of the animals in the next generation remains largely unchanged.

Because the highest ranking rams in a flock are more often related to the highest ranking ewes than to the lowest ranking ewes and resulting elite progeny are expected to contribute to future generations, the use of random mating can lead to rates of inbreeding going unnoticed.

As a result Amer suggests best-to-best mating should only be used in tandem with Animate tools that assist in managing rates of in-breeding.

One variation of the best-to-best option allows specific rams to be allocated to groups of ewes with specific characteristics. These may be ewes belonging to a specific breed or cross or those identified with a genetic merit or weakness in a particular trait.

Such a situation may be in a composite flock where the breeder might be looking to identify a ram with high genetic worth for a trait such as growth or number of lambs weaned (NLW) to mate with ewes with the lowest growth or NLW BVs.

Amer says the expected increase in annual rates of genetic gain when using best-to-best mating when compared with random mating can be in the order of 5-10%.

In the long term levels of inbreeding will continue to build up in closed flocks even when tactical strategies are in place to avoid mating closely related animals.

However having in place the appropriate inbreeding controls gives breeders the confidence to select elite individuals and retain elite rams knowing the rate of inbreeding is being managed.

Amer says breeders are achieving this by avoiding matings of animals where the degree of co-ancestry or relatedness exceeds a pre-determined threshold and by identifying teams of rams and ewe replacements so that diversity of family lines is maintained.

Often the decisions to use a stud ram or not may be influenced by how closely it is related to the ewe flock. In this situation Amer says relatedness profiling assists breeders make more informed decisions in the knowledge that they are effectively managing future levels of inbreeding within their flock.

This is achieved by eliminating matings between selected animals where the degree of co-ancestry of relatedness exceeds a threshold and also by identifying teams of rams and ewe replacement so that a diversity of family lines is maintained within the flock.

Amer says not all rams have to be chosen in this manner and recommends breeders maintain a degree of flexibility in the size of their ram mating groups is a key when considering whether to replace a sire in a ram team which if left would contribute greatly to relatedness of selected animals.

In some flocks a large proportion of the ewes may trace back to a small number of sires or family lines. In these flocks genetic gain may be compromised by the increasing degree of relatedness between animals complicating selection and mating of young high genetic-worth rams.

AbacusBio is also able to generate customised selection indexes and breeding values designed to achieve specific changes in levels of genetic merit for a specific trait.

Amer says when deciding which ewe or groups of ewes to join with a specific ram, breeders are often faced with the trade-off increasing relatedness of animals within the stud may have on slowing down rates of genetic gain.

Amer says a review of the science shows both the number of ewes lambing and lamb survival rates drop as levels of inbreeding rise.

Getting the balance right is important as a 10 percentage point increase in the inbreeding-co-efficient can result in a 2% reduction in the performance for each trait.

"Once we have a snapshot of where a breeder is at in terms of their inbreeding, we can work out a programme to reduce any further inbreeding and at the same time maximise genetic gain," says Amer.

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