Dr Ken Geenty
Ensuring good genetic progress in your beef cattle is one of the easiest and most cost-effective steps you can take. For some homework visiting websites and talking to rural professionals, bull breeders and farming mates, very significant and growing rewards will come.
Spending two or three days a year on these tasks, with appropriate investment in the right bulls, will provide annual benefits of up to 9% in line with the breeder’s genetic trends. Importantly genetic gains, unlike management, are cumulative so can grow with each generation.
Importantly the payoff from genetic improvement is heavily dependent on day-to-day feeding, management and animal health all being up to scratch.
The basis of genetic improvement is estimated breeding values (EBVs) for productive traits. EBVs are derived from a stack of information on heritability, the extent the trait is passed on to offspring, difference from the group average for that animal, adjustment for effects on other important traits and information on relatives. The more of the latter the greater the reliability of EBVs.
The important component of heritability varies in strength widely among production traits. The top bracket in New Zealand beef breeds with medium to high levels include – birthweight, calving ease, liveweight at 200, 400 and 600 days, mature cow weight, carcaseweight and fatness, dressing percent and yield.
Lower-ranking traits more influenced by management and environment are generally those associated with reproduction.
Individual trait EBVs are rarely used on their own but are normally combined in a ready-to-use or customised index. Included are the most influential traits for that index weighted for their relative economic values.
The bottom line is that breeding values work so you can afford to invest time in choosing the EBVs, or using an index, for your bull team.
For example, the Angus Self Replacing Index (SRI) estimates differences in net profitability per cow joined for a self-replacing commercial herd finishing steers around 525kg liveweight at 16 months. For the 2020 sale year the Angus SRI average is +114. An Angus bull with a Group Breedplan SRI of +214 will mean he will contribute $100 more value to his progeny compared to an average 2018- born bull. Remembering only half the genes come from the bull translating to a $50 advantage to offspring adding up to an additional $5000 for 25 calves over each of four seasons.
While this example is for an Angus herd the same process can be applied for any breed recorded on Group Breedplan.
Graph 1 shows dated but useful SRI genetic trends from Group Breedplan in real live herds compared with the breed average. Clearly herd B would be best for a bull buyer averaging 9 percent genetic gain a year. Even an individual bull below the herd B average would be a good choice. Emphasising the importance of selecting the best breeder for your objectives.
Signposts for various indexes by Australian based Group Breedplan, and offered by different breed societies or customised individually using BreedObject, can be found at http://breedplan.une.edu.au/index
These can cater for overall productivity, dairy beef crossing or inclusion of specialized carcase traits like marbling.
Graph 2 shows the key economic traits that are important in the Angus SRI. The different trait emphases reflect the underlying profit drivers in a typical self-replacing commercial operation
Considering the genetic relationship between the key profit drivers and the EBVs that are available, this transposes to the following EBV emphases. The sign indicates the direction of each emphasis. For example, greater 400 Day Weight EBVs and shorter Days to Calving EBVs are favoured. There is some negative pressure on mature cow weight. See Graph 3.
It is argued by many that NZ beef breeding cows have become too heavy and inefficient. Waikato-based AgFirst consultant Bob Thomson says commercial beef breeding cows should weigh around 530kg and wean calves at 200 days weighing 240kg. Currently cows over 600kg inefficiently wean calves around 240kg.
The all-important job of getting out and purchasing bulls for your situation is well outlined by B+LNZ Genetics on their website https://www.blnzgenetics.com/ under the heading ‘Better beef breeding – bull selection tools’.
The five steps listed to find the best bull for your particular operation include – 1. setting your objective; 2. finding a breeder with similar objectives; 3. choosing a bull with the right index to do the job; 4. checking him for structural soundness; 5. settling the bull in at home.
Remembering the key mantra ‘where your breeder goes, you will go’. Emphasising the importance of choosing the right breeder for your situation preferably based on the breeder’s genetic trends available, with the breeder’s permission, from Group Breedplan. You will follow a similar trend in genetic improvement but lag up to two generations behind.
Individual breeders or breed societies can customize their selection index by altering trait weightings using BreedObject to counter this. For example the negative weighting on mature cow weight in the example above could be increased.
Use of the Australian Group BreedPlan system has worked well for NZ beef producers for many years. However, the scheme is used at full cost recovery unlike the producer subsidised New Zealand sheep genetic improvement scheme SIL, currently run by B+LNZ Genetics but soon to become nProve. A shortcoming of Group BreedPlan is an absence of between breed comparisons but the new nProve scheme should supply this if beef cattle are included.
