The new generation of EBVs ?

(reprinted from a New Zealand Angus newsletter)

Paul Charteris
Institute of Veterinary, Animal and Biomedical Sciences
Massey University

It appears that speculation on the future of agriculture in New Zealand has become a favourite media pass-time in recent weeks, so I'll join in the party and throw in my guesses of what the future of EBVs might be.
Our current beef cattle EBVs comprise the usual stock-in trade values such as the growth and carcass EBVs which are used by most major genetic evaluations world-wide. In addition, fertility EBVs comprising scrotal; size, gestation length and days to calving appear in some genetic evaluations in Australasia and North America. Summing up the total number of different EBVs available on beef cattle around the world would likely reveal more than fifty different measures used (more, if I could interpret French and Belgian catalogues). What will the future hold ?

The future of beef cattle EBVs in New Zealand might develop in either of four ways:

1. Keep the status quo. Keep the EBVs available to us at present and perhaps add or delete a few EBVs over time. The advantages of this approach is that little extra work is required and that breeders and bull-buyers do not need to re-learn a whole new set of values. The disadvantages of this approach are that most of our current EBVs are (at best) predictors of traits influencing farm profit rather than the economically-important traits themselves.
2. Increase the number of EBVs. This seems a likely scenario since the general world trend is toward developing new (but not always more relevant) EBVs. The advantage of this approach is new EBVs are marketable since a breeder (or Breed Society) is seen to be making progress when they deliver a new EBV. On the downside, how many commercial producers have the skills to interpret even the current EBVs, let alone a few extras ?
3. Development of fewer but smarter EBVs. Smarter means more closely related to farm profit and easier to interpret. For example, why persist with publishing EBVs for scrotal size, gestation length, days to calving, birth weight and calving ease (direct and maternal) EBVs when two EBVs namely heifer fertility and sustained cow fertility might cover the entire range. This major shift in use of EBVs would probably require two levels of reporting.
   
   Firstly, presenting bull-buyers with a few highly relevant EBVs which relate to farm profit such as those listed in the table below:
   
   

   Possible new EBV	What it predicts
   Heifer fertility	Probability of a heifer successfully weaning a calf at 2.5 years
   Sustained cow productivity	Probability of cow weaning a calf every year until she has recouped the initial cost of her investment (plus the weaning weight of calves minus cow feed intake).
   Bull fertility	Probability of successfully mating 60 cows per year for five years
   Efficiency of growth to harvest	Genetic merit for growth though to harvest age (say 300 kg steer carcass at 20 months) accounting for feed costs to achieve target carcass weights. Such an EBV would be customisable allowing different target carcass weights or harvest ages to be specified.
   Saleable meat yield	The yield of saleable meat as a percentage of carcass weight
   % Angus Classic	The % of steer or heifer progeny expected to quality for Angus Classic (or any other branded beef price premium).

   
   The second level of reporting (not seen by the bull-buyer) would occur on bull-breeding herds and would require bull-breeders to measure most or all of the traits which influence economically important traits. For example, bull-buyers might only ever see a heifer fertility EBV in a catalogue even though bull-breeders would have measured birth weight, calving ease score, and scrotal size) to predict heifer fertility.
   
   
4. Any combination of (1,2,3) may be incorporated with breeding objectives technology to more accurately weight EBVs according to their effect on farm profit.

Any change in EBVs cannot arise from Boffins within Ivory Towers (or even cold concrete towers located in Palmerston North) but must arise from Angus breeders who are themselves users of EBVs but more importantly are suppliers of genetically more profitable cattle to the commercial beef industry.