Choosing the right pig breeding stock
Balanced selection and a pig’s total genetic merit should be considered before purchasing.
The pig breeding stock you purchase directly affects your farm’s financial success. Pig traits such as litter size, growth and feed efficiency are key factors that influence a pig farmer’s balance sheet.
However, there are a number of pig characteristics that are important for the long-term expression of the above traits that are not normally considered. Some examples that are too easily taken for granted include:
● Good temperament and easy to manage
● Adaptable to different temperatures and housing
● Robust and resistant to disease
● Long life
● Easy re-breeding
From a genetics viewpoint, some of these pig traits are difficult to measure phenotypically and financially. On-farm they are not an issue when production is going right, but obvious to everyone when things start going wrong.
Balanced selection is a principle that is important to animal breeding, and in the recent past has had substantial focus from the network of European pig breeding companies. It is equilibrium between a pig’s production and its physiology as measured by its health and welfare, but also between production and secondary traits.
First, through selection emphasis on relatively few pig traits we can make substantial changes using traditional quantitative selection. However, even with quantitative genetics, undue emphasis can be placed on a few pig traits to the detriment of overall genetic merit.
It is overall genetic merit that is of long-term and sustainable commercial importance, for example, balanced selection. Geneticists achieve this by using an index of weighted information that is dynamic as indices of pig breeding stock changes weekly.
But, not everything can be measured easily; for example, some of the secondary traits mentioned above. Part of the solution to this is through the use of well-trained farm selectors who take into account additional information on a pig beyond the index information, such as body and leg structure, temperament and mothering ability.
Recently, several populations have concentrated selection pressure on total numbers of piglets born. There is an often quoted statement, “You can’t improve something unless you measure it.” However, there is a less well known saying, “You get what you measure.”
In animal and pig breeding as in managing people and farms, results can be different from the naive intention. Recent UK press articles have highlighted high numbers of piglets born associated with high pre-weaning mortality levels. As an industry, we have to consider how consumers view such information and how the pig industry views different aspects of animal welfare.
The Danish government, for example, is clearly disturbed by the large numbers of piglets that die daily – reportedly 25,000 piglets/day, according to BPEXExport Bulletin, week 21.
Total genetic merit
When purchasing pig breeding stock, a rounded consideration of total genetic merit is necessary including secondary traits. Prolific sows are only beneficial to pig producers if they are capable of eating sufficient feed intake to produce the quantity of milk required to rear additional piglets, not to mention sufficient teats for the additional piglets.
Recently, for example, concerns were raised about second litter drops indicating that already there is a challenge to maintaining a sow’s body condition. In Demark, they are working hard to reduce the high level of shoulder sores on lactating sows.
Excellent outdoor mothering ability is required to ensure piglet survival with no indoor luxuries like heating. An outdoor sow’s appetite is crucial as there is little opportunity for three time’s day feeding as they do in Denmark. Spontaneous feeding is an option, but with many pig herds in individual farrow paddocks this is not always possible.
For example, sow longevity is three times worse at Danish pig farms compared with UK pig populations. Selection for total born has increased the total number of piglets born. But commercially what is needed is an increase in numbers born alive, not total born. (We are interested in numbers reared, but the heritability is lower and hence genetic response lower).
This has led, belatedly, to selection emphasis moving away from a focus on total piglets born to focusing on piglets born alive, for example, in Denmark “live at 5 days.” Other methods to lessen the emphasis on total born have led to focusing on offspring survival alongside selection for litter size, or using birth-weight alongside selection for litter-size.
New selection tools
We are entering a new area of genetic selection with so-called Genome Wide Selection moving beyond theoretical modeling to commercial reality, at least on a trial basis in the dairy sector. The benefits discussed relate to improvements in genetic rates of response of two times greater than current schemes, with colossal reduction in dairy testing costs.
The benefits to the pig sector are currently believed to be relatively small in contrast to the dairy sector where they have at a stroke removed progeny testing of young bulls which shortens the generation interval and speeds up the annual genetic response.
In pigs, the areas of application are currently perceived to be fewer; relating to traits that are currently difficult to measure or where we have low accuracy (such as female reproduction) or at a crossbred level.
All of this is good news, as along the way we understand more of the biology of livestock animals we work with. The potential danger is that selection emphasis on a few important traits leaves us open to potential negative consequences from selection on other important but difficult to measure traits.
To mitigate the rapid unforeseen consequences of correlated selection necessitates intense and broad recording at the nucleus herd level. The recording of accurately described phenotypes will be essential in the new genomics arena. As the genetic rate of response increases, the necessity to record a greater number of traits increase as a risk mitigation tool.
Rapid rates of genetic response affect rates of change in correlated traits. These rapid rates of response require that genetic merit is measured in a broad sense to ensure that unfavorable correlated changes are mitigated.
Accurate recording of well described phenotypes is increasingly important to the health of the pig population, as well as the productivity and profitability of the pig supply chain.