Selecting for Improved Weaning Capacity

A lot of strides have been made in the improvement of pigs in the past few decades. The advent of the use of BLUP in the early 90's in particular gave a boost to the slow progress seen in those traits with low heritability, particularly reproductive traits. BLUP gave breeders increased accuracy in the estimation of genetic values, and therefore higher reliability of selection decisions. Hence, as will be observed in many breeding programs litter size, a trait that was previously very slow to improve, started going up relatively quickly. Some breeding programs reported annual rates of improvement of as high as 0.3 pigs per sow per year in total piglets born. But with this improvement comes an important question; are there any drawbacks?

Indeed, if the breeding program is not well balanced there can be downsides to this improvement and these have been very well documented. One can cite such problems as reduced birth weight, an increase in the number of unviable piglets, an increase in number of still births, increased piglet mortality, an increase in number of runty pigs in nursery/grower, reduced carcass quality of runty pigs, shorter sow productive life, overall sow weakness, etc. These problems arise when the program fails to take into account the relationships between the different traits that are critical to having a balanced approach. When a breeding program is too heavily weighted towards prolificacy, some of the problems cited occur because litter size is negatively correlated to birth weight and consequently piglet viability. Some of the research done by people like Dr. George Foxcroft has shown that as litter size goes up average birth weight of the piglets regresses.

Another trait that easily gets ignored as programs over-focus on prolificacy is the physical aspects of the selection candidates. Ignoring this aspect will eventually result in a line that lacks physical strength and hence sows that have very poor longevity. A prolific sow that lasts only one parity cannot recoup the investment of its purchase price.

In a survey done in Germany a couple years back pig farmers were asked to rate different genetics available in the German market for various aspects. It was interesting to note that some of the programs that have been known to have decent sows in terms of prolificacy were found lacking in sow physical strength and longevity. Hypor sows were rated as among the best when it came to these two attributes.

In Hypor we understood this and quite some time back adopted the philosophy of breeding for balance. We sought to improve not only total number of piglets born but also to address other traits that in combination create a balance in both the sow and her piglets. The tenets are a prolific sow with good milk production, enough teats to support a big litter and good physical attributes to guarantee longevity. It is also a sow that breeds easily and is robust enough to withstand the rigours of reproduction and production stress in all production environments. This sow in turn produces piglets that are what can be referred to as "value pigs". They are born in decent size litters yet with good enough birth weight to guarantee high survival rates. The sow's high milk production and good mothering ability on these piglets that are already kick-started with good birth weight leads in turn to high weaning weights for big litters. The final product is a sow that consistently produces large litters of heavy piglets and that maximizes the potential of her progeny in the nursery and finishing phases resulting in faster growth, more efficient feed conversion, heavier market hogs and improved carcass quality.

Selecting for balance (Weaning Capacity) requires the development of an index that covers the salient attributes and traits. An example of such an index is shown in Figure 1.

In endeavouring to achieve a sow with optimum longevity we understood that there are various factors that contribute to the removal/culling of sows from a herd; 1) reproductive failure - no heat, failure to conceive, 2) poor performance - small litters, poor milking, 3) feet and leg problems leading to welfare and management problems. These three main reasons can be referred to as voluntary culling. Involuntary culling may be caused by various factors including injury, accidental death, and so on. By genetically improving the traits that lead to culling we indirectly select for improved longevity, which is one of the key components of "Weaning Capacity". On top of the selection for reproductive performance, Hypor lines undergo a rigorous selection process for conformation and physical attributes, an aspect we touched on earlier.

Weaning capacity = balance

This whole breeding focus as described here is what we in Hypor came to call breeding for "Weaning Capacity". By pursuing a balance in the sow, with the view of maximizing both the quantity and quality of pigs weaned, the improvements are gradual for all traits and in so doing we avoid compromising one trait for the sake of another. In some cases, the choices are easy. The point is that by combining several traits, even though some are negatively correlated, we can still progress to a better sow.

The bottom line is that good Weaning Capacity has to be built on the foundation of a good breeding program. The message here was to show that Hyporï¿½s breeding program has been built to address this. As technology advances, there will be more tools available to contribute to this focus, and we in Hypor will be well placed to adopt them to even further enhance the Weaning Capacity philosophy.

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Selecting for Improved Weaning Capacity