Friday, March 29, 2024

Seeking ewe efficiency

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The quest for a genetically efficient ewe depends on the individual farmer’s requirements, geneticist Tim Byrne writes. Efficiency is the ability to do things successfully, without waste. In a more general sense, it’s simply getting more from less. In farming it usually means getting more product from the grass consumed. At the Beef + Lamb New Zealand Genetics sheep breeders’ forum where there was quite a bit of discussion about ewe efficiency I was asked “what is being done about a ewe efficiency trait?” So, it’s worth thinking what efficiency means in terms of genetics. Sheep farmers tend to define it in different ways, depending on their production system, farming environment and general view of the world. From a genetics point of view, the same principle holds in that it’s about animals with the genetic make-up to get more output from the inputs they consume, but it is difficult to define this as being the outcome of just one trait.
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In B+LNZ’s SIL genetic evaluation system, animals are assessed for growth, reproductive rate, and adult size, among other things.

When these performance measures are valued in profit terms, some produce net profit and some result in net cost.

When animals are ranked for overall profit, we account for a measure of economic efficiency at the system level, because both profit and cost aspects are included across a range of traits.

For example, the profit captured from increased growth rate is a function of revenue from a heavier carcase at slaughter minus the cost of estimated feed eaten to achieve that heavier carcaseweight.

For ewe liveweight, the evaluation estimates how much feed a ewe of a particular weight needs to eat to maintain her body weight. The evaluation deals with the fact that genetic selection for more growth (profit) in part results in bigger ewes (cost).

Soon, body condition score will be added, which will help to better estimate the cost of maintaining ewes of the same weight, but with very different body condition profiles.

Another economically important trait is ewe longevity, which certainly has an impact on economic efficiency, through its impact on replacement rate.

We don’t yet have routine measurements and evaluations of feed intake, because that is very difficult to measure in NZ’s extensive pasture systems.

Understanding how much individual animals actually eat, rather than relying on estimates from theory, and relating that to their performance would be a nice-to-know.

This is biological efficiency, and is generally measured in only part of the production system – growing animals post-weaning.

It may be a very useful addition to our description of economic efficiency but the goal remains as economic efficiency across the whole system.

Understanding how much individual animals actually eat, rather than relying on estimates from theory, and relating that to their performance would be a nice-to-know.

The problem with trying to define a single ewe efficiency genetic trait is that there are lots of ways to define it and that depends on what you require from your animals and what farming system you are running.

An organic farmer would place significant emphasis on the ability of animals to survive and thrive under parasite burden.

That is surely a different type of efficiency than a summer dry property that needs to sell a large proportion of the lambs at weaning to avoid being hit with a low store market.

Different again is a system that has ample grass in summer and can finish all lambs.

What then defines ewe efficiency in genetic terms? Well, an efficient ewe is one with the right balance of performance across the range of genetic traits that impact the profitability of your farming system.

The SIL genetic evaluation system produces estimates of genetic merit for a whole range of traits from growth to dagginess. These traits are combined into indices designed to rank animals on profit.

With the right combination of traits, these profit indices are the best measure of economic efficiency across the whole production system.

For a breeder, the key is to ensure you are recording, evaluating and improving a relevant set of traits that impact the efficiency and profitability of your ram buyer clients.

Ram buyers need to continually discuss with breeders the things that impact the efficiency and profitability of their business.

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