Stud breeders

The standard model has two levels of stud herds: elite and multiplier herds (Figure 1). 

Elite herds are the top tier. They supply progeny to the multiplier herds and commercial herds. The genetic progress of elite herds is determined largely by their stag selection decisions. Multiplier herds are the next tier. They purchase progeny from elite breeders and sell to commercial herds. The genetic progress of multiplier herds is dictated largely by the stags they purchase from the elite herds.

This is, of course, a simplified model and many real situations may not completely fit this. Whatever stud breeder a commercial farmer selects, the primary consideration should be matching the stud herd their breeding objective with the commercial herd production goals ensure they have a good positive genetic trend for the traits, indexes or BV's that fit those goals. Stud breeders need to be continually improving so the whole industry can improve.

For stud breeders the scale of the breeding programme can be considered at two levels; the industry level and the individual stud herd level. At the industry level, the economically optimal number of recorded hinds is between 2% and 4% of the total hind population, which currently is 13,000 to 26,000 hinds. Note the reference to “recorded” rather than “stud” hinds, based on the assumption that all selection is essentially based on BVs and indices, hence the need for stud breeding stock to be 'recorded' on DEERSelect. 

At an individual stud herd level, the hind herd size needs to be large enough to-

• meet the stag requirements of customers (i.e. market size) in a competitive environment (i.e. where other stud breeders are operating)
• allow sufficient selection of both replacement breeding stags for the stud and sale stags (see How many sires? below)
• spread fixed costs of operating a stud herd over as many sale stags as possible

What are Breeding Objectives?

A breeding objective is the overall production goal that is intended to be achieved by genetic management.  Usually this relates to one of the major products, such as venison or velvet. So the breeding objective will be structured around permanent genetic gains in the per-animal performance for producing that product. Be aware that it is very difficult to structure breeding goals around both products together due to the very different nature of each product in the production system.

The stud breeder’s breeding objectives need to take account of their target customers and their farming operations/production systems, as well as the stud breeder’s own objectives for the stud herd. Primarily there is the need to target the most overall economically beneficial outcomes for the customers’ farming systems. Breeding objectives (or goals) will in many ways define the customer base. 

The main production traits available in Deer Select are Reproduction, Growth, Meat Yield and Carla (immune response to internal parasites) and velvet.

There will of course be other considerations for buyers, for example, reputation, stockman ship, trust and genetic trends. It is important to keep breeding objectives clear, simple and well defined to make maximum progress towards goals. Not only that, but a simple breeding objective is easy to communicate to customers and easy for them to understand.

Once breeding goals are defined then the focus on the traits to measure and record becomes important. BVs and indexes which support selection decisions to achieve the breeding goal are based on accurate measurement of these traits.

What to record?

Different production systems have differing minimum trait recording requirements within DEERSelect. For venison traits, the primary focus is on animal growth (live-weight for age) and carcass traits (muscularity). For velvet production the primary focus is on velvet antler yields by age (particularly 2-year-old production). For replacement females the emphasis is on body mass (live-weight for age and mature live-weight) and reproductive performance (conception date). It is also possible to incorporate measurements related to earlier and better immune response to parasitism, and in future potentially resilience to disease as well as behavior (temperament). Each trait will require its own set of standardized measurements, as defined within DEERSelect. For details on measurements required by DEERSelect for various traits, click here >>

Drivers

For stud herds recording on DEERSelect the number of sires used in the breeding program (within the the limitations of the stud hind herd size) has two drivers:-

• the number of progeny required per sire (to enable selection of offspring for the next generation) 
• the accuracy of the BVs of the progeny. 

Consideration of these factors, along with the size of the breeding hind herd helps to determine the number of progeny weaned per sire.  

Ideally 20-30+ progeny per sire are required for a good assessment for most traits of interest.

Once the number of progeny per sire has been established the type of sires required is next consideration which will determine the number of sires to mate that season. 

Sire types

The first type of sire to consider are link sires, there are two different types of linkage required: between-year and between-herd linkage

Between-year linkage is required to account for year/season environmental effects on performance measures to be accounted for on Deer Select. If no year links are used it is difficult for the genetic evaluations to separate out year/season effects from sire effects. This means that herd BVs would not be comparable across years, leading to poor selection decisions and, probably, erratic genetic trends. Ideally at least 2 sires from the previous year with 20-30+ progeny in each year is required for larger herds, one sire from the previous year with good progeny numbers in small stud herds.

Between-herd linkage, is required to link recorded herds and to correct for environmental effects between herds to be accounted for on Deer Select. As for between-year linkage at least two sires should be used for between-herd linkage with 20-30+ progeny in two or more herds, ideally in the same year. year.

So for a herds recording on Deer Select, for linkage purposes alone, at least two (small stud herd) to four (medium to larger stud) sires are needed. The target for these sires should be to wean 20 to 30 progeny each.

With link sires determined, that leaves the consideration about “optional” or non-linked stags. Using a similar target of 20-30 progeny weaned per sire, the number of non-link stags able to be used will depend on how many hinds are in the breeding herd. Likely conception rates need to be factored into equations when planning your number of progeny weaned per sire (e.g. anticipate less weaned progeny per mating for AI than for natural mating). Sires can be mated to more hinds than required to wean the recommended 20-30 progeny per sire, this will not have any negative impacts in Deer Select. So it is perfectly acceptable to breed more than 20-30 progeny per sire for the non-linked sires, so long as acceptable mating ratios are maintained.

Example:

A 200-hind herd, (assuming 85% hinds mated wean a calf) would expect to use a total of 7 sires (4 link and 3 others)

200 x 0.85 = 170 progeny weaned (about 24 progeny per sire).

A 300-hind herd would expect to use 10 sires (4 link and 6 others).

300 x 0.85 = 255 progeny weaned (about 26 progeny per sire).

The number of 20-30 weaned progeny per sire is an optimized figure, which balances various statistical considerations involved in trait collection, and BV estimation for sires and the accuracy of sire BV's. based on what they passed to progeny. When it comes to accuracy of the progeny BV's, the more half-siblings (half brothers and sisters) produced the greater the accuracy of the BVs. The greater the BV accuracy the better selection decisions on young stock.

Within a recorded stud deer herd parentage is vital information for estimating breeding values for commercial (production) traits. Parentage is the basis behind establishing extended pedigree records and associated genetic links on DEERSelect.

History 

Traditionally many breeders single sire mated their hinds and generally also calved them in single sire groups. This worked well, in that the breeder always knew who the sire of the offspring was. The disadvantage of this system was that there was no linkage between groups (sires) which makes it impossible to adjust for environmental effects to estimate breeding values using DEERSelect.

Before laboratory based pedigree testing known sire mating was determined either by the single sire mating (above) or a combination of known sire mating dates (e.g. AI-10 day gap-follow up stag) and ultrasonic pregnancy scan fetal aging or birth date recording was used to determine the sire. This along with direct observation of suckling behavior (calf to hind matching) assigned parentage to the offspring. Breeders also went to the trouble of tagging calves at birth (i.e. usually within 24 hours of), this was often a risky procedure to all involved.

Currently

Direct observation can still be used to determine hind-calf matches, and, so long as sire is known, parentage.  Direct observation and the linkage issues around single sire mating and associated management issues can make this form of parentage assignment very time consuming. The alternative to this is laboratory-based DNA parentage. Currently only one laboratory in New Zealand delivers this service to the deer industry, Genomnz.  

DNA parentage testing can be completed for around $25.85 - $32.50 per animal, sample number dependant using a range of sample types (hair follicles, ear punch tissue, blood or semen). DNA parentage testing supports optimised farm management practices as well as enhanced DEERSelect genetic analysis, such as adjusting breeding values for environmental effects and sire linkage.  

The farm management practices which become possible (recommended) are: multiple-sire-mating, and mixed group calving, as well as minimising disturbance caused by suckling observation of tagging at birth. With DNA pedigree testing, follow up or chaser stags can be introduced to hinds 3 days after artificial insemination, rather than 10-14 days if the sire needed to be determined by ultrasonic fetal aging or calf birth date, which provides a potential advantage of earlier conception of non-synchronized hinds.

Remember that hinds have breeding values too!  Unlike a commercial herd, where the majority of their genetic gain is from the selection of sire stags, half of the genetic gain of stud breeders comes from the hinds.  From an industry wide perspective the core purpose of the stud herds is to provide improved genetic material to the commercial producer herds. So ideally maximizing the genetic improvement of stud hinds should be a major focus of stud breeders.  

How many replacement hinds?

Replacement rate for a stud breeder is determined by how much selection pressure they consider desirable, that is how quickly to turn over the hind herd and introduce new better genetic stock. Using the formula applied for calculating hind replacement rates for commercial breeding hind herds: 2.5 hinds are required for every replacement female required. So this means the maximum possible replacement rate is 40% (100 / 2.5 = 40), however around 20-30% replacement rate is usual.  

Criteria for selection

The first cut of young hinds should initially be based on basic stockmanship considerations - are they fit, healthy, without any obvious faults or defects (e.g. undershot jaws, poor hooves) and temperamentally suited to your breeding herd?

The next consideration should be are they well grown (i.e. will they achieve live-weights at 15 months to allow them to attain puberty and become pregnant). 

Following that initial level of culling, for recorded herds the main selection criteria for hinds should be based on their economic indexes or BV's. The indexes and breeding values are directly comparable so, older hinds with low values should be replaced with young hinds with higher values. 

This replacement should be ruthless – replace as many of the older hinds as possible with younger hinds with superior values. When older hinds with poorer index and breeding values are retained in the stud breeding herd the opportunity (or potential) for improvement is diminished.  

In Deer Select the 'replacement' index has been specifically designed for selection of replacement hinds in venison focussed systems, so can be used as the only selection requirement when breeding replacement hinds for venison production systems. It rewards early conception, early growth and meat (if recorded) and has a penalty of mature size.

For velvet herds, replacements can be selected on hind velvet breeding values. Hinds velvet breeding values are based on velvet records on all known male relatives. This is particularly helpful as replacements hinds are selected at 1 year of age, prior to any male ½ sibs having 2 year old velvet weights.