The Nerstane Breeding Program

At Nerstane we are aware that there are a range of breeding and selection systems used in the Merino industry. Our aim is to maximise genetic progress in achieving our breeding objective. If there is a system available that will do that more efficiently then our current index based system we would be very keen to capitalise on it. We spend a considerable amount of time and effort in keeping up to date with breeding technology and our research to date, combined with the results we have achieved, indicates that our current system is the best available. Feedback from our clients supports this belief.

The Nerstane breeding program is designed to maximise genetic progress and to deliver maximum benefits to our commercial clients. To appreciate the Nerstane breeding system it is necessary to be familiar with the major events that occur during the year leading up to the selection of stud sires, sale rams, stud and flock ewes. The selection system is based on accurate measured data and thorough visual assessments.

The Ram Selection Program

TIMING	SELECTION EVENT
August/September	Lambing - lasts for six weeks; majority born in first three weeks
October	Lamb marking - all lambs tagged and any faults noted
December	Weaning and tip shearing using Bioclip to ensure accurate fleece weights at 12 months
September	Classing at 12 months of age - 20 to 50% are identified as visual culls. All rams are scored for a range of visually assessed traits
September (early)	Hogget rams are shorn and measured for fleece weight and fibre diameter testing (1st Stage Test). All visual culls are also measured and recorded for progeny test purposes. All fleeces are scored for Style and Fleece rot incidence as they come over the table.
October	Body weights recorded
November/December	Faecal samples collected for worm egg count data to be used for selection for worm resistance.
December/January	Ram classing with the aid of fleece measurements; 50 Reserves are selected. Nerstane on-property sale team selected. Sale flock rams are selected and divided into six grades mainly on performance.
February	Flock rams available
February (late)	Reserve Sires are shorn, fleece weighed and fibre diameter tested (2nd Stage Test). Results are used to aid in the final selection of young sires which will be progeny tested.

The use of visual classing combined with measurement of important traits is a feature of the ram selection program. At the classing in September all rams are scored for a range of visual traits. This visual assessment data is recorded on computer and is used at the final classing in December - January in combination with the recorded data on measured traits to provide a full evaluation of all rams, particularly those involved in the progeny testing program. All recorded data for both measured and visually assessed traits can be made available to clients when purchasing rams.

The Progeny Testing Program

The aim of the progeny testing program is to improve the accuracy of the estimation of the breeding value of the young sires which at this stage is based on their own performance as a hogget and pedigree information from sire and dam. While a rams own performance is a reasonable indicator of its breeding value, the performance of his progeny is a true indicator of his genetic value.

Every year at Nerstane nine young sires are selected for evaluation in a progeny testing program. The progeny testing program is also linked to the Central Test Sire Evaluation program by including a sire that has already been evaluated in Central Test or has been used in the stud, ie a proven sire. This ‘linking’ enables the young progeny test rams to be evaluated against rams in the Central Test program and older sires in use at Nerstane.

Progeny tests are designed to determine the breeding value of a ram through the performance of its progeny. It is essential that each ram is individually joined to randomly allocated ewes preferably from the one age group.

Because the ewes are randomly allocated to each joining group, the ewe effect on the test is eliminated. The differences in the progeny will therefore be due to the differences in genetic merit of the rams.

It is also important that environmental or non genetic effects such as management differences do not influence the results. To guarantee this all ewes involved in the progeny testing program are run together except for the four week joining period and lambing period. After the lambs are identified all ewes and progeny receive identical treatment until their performance is measured and assessed.

All introduced sires are subjected to the same progeny testing program and are only used further in the stud if they perform better then the home bred sires.

At Nerstane the progeny testing program is conducted using the 2nd stud ewes. Outside sires are only introduced into Nerstane as semen in the AI program.

The selection of sale rams

After the selection of the potential sires to be progeny tested, the rams required for use in the Nerstane commercial flocks are identified. These rams are only used once in the commercial flock and then offered for sale as 4 tooths.

This is a system that is appreciated by clients as it allows access to more of the high performance rams bred at Nerstane.

The Nerstane on property sale team consists of some of these 4 tooth rams plus top performing 2 tooth rams. The remaining flock rams are sold by private treaty at Nerstane and presented in five grades based on performance ie. Index ranking.

The Ewe Selection Program

All ewes bred in both the stud and commercial flocks are involved in a thorough selection program which is designed to identify the most productive replacements to promote to the ram breeding level.

By having all ewes as candidates for selection, the selection pressure for both visual and measured traits is substantially increased. Details of the program are presented in the following table.

The stud ewe flock of 1800 ewes is divided into two tiers on the basis of measured performance (Index rank) and visual excellence. The top tier (Special Studs) consists of 300 ewes which are joined in single sire joining groups to proven sires identified through the progeny testing program.

TIMING	SELECTION EVENT
August/September	Lambing - lasts for 6weeks with the majority born in first 3 weeks.
December	Weaning and tip shearing using Bioclip to ensure accurate fleece weights at the next shearing.
September (early)	1 year old visual classing and scoring for 10 traits. Approx. 35% identified as visual culls.
September (late)	All ewes shorn, fleece weighed, mid side sampled and scored for style and fleece rot.
February	Final visual classing with the aid of fleece weights and fibre diameters. Stud and flock ewes selected. A further 5% are culled.
March/April	All ewes joined (6 weeks)
April	Stud ewes (1.5yo) shorn again, fleece weighed and fibre diameter tested. (2nd Stage test). This data is used to finalise grade ie. Special stud, stud or flock.

In recent years a corrective mating approach has been trialed with ewes being allocated to particular rams on the basis of visual assessment.

The AI program is also conducted at this level. Semen is purchased from carefully selected rams that have a proven record in the industry. Performance data from Central Test Sire Evaluation programs is highly regarded when choosing AI sires.

The second tier of stud ewes is used to progeny test young sires and selected sires (as semen only) from outside bloodlines.

Stud ewes not involved in the progeny testing program are syndicate joined to the remaining proven Nerstane sires. When the ewe syndicates are selected, the finer ewes are allocated to a separate syndicate (fine stud syndicate).