Total number of piglets born (or number born alive) is an important economic driver in pig production. However, there is an upper limit to the number of quality piglets that can be produced, meaning more piglets are not always necessarily better. Numerous reports have shown that in general as total number born increases there is a concomitant decrease in average piglet birth weight. A piglet’s birth weight is an important characteristic for its performance later in life; research has shown that heavier piglets are more robust and have better fi nishing performance than lighter ones.
The first graph above shows that average birth weight decreases with increasing number of total born. However, the second graph shows that there is still quite a lot of variation in total birth weight. This indicates that selection for increased litter size in combination with a stable or even increasing birth weight is possible. This calls for a judicious balancing act of the traits in the selection index. However in our balanced breeding approach, where we combine the selection for different traits to improve the total package, selection is not focused at a single trait. If we were to select for only birth weight the increase in average birth weight would be approximately 50-70 grams per generation., This, however, would be at the expense of a number of other traits, most notably total number born, since total number born and birth weights are negatively correlated. Hypor’s goal is to increase total (and live) born while keeping birth weight constant, and at the same time improve survivability, uniformity and finishing performance (growth, lean, efficiency, etc.). Uniformity of birth weight is critical in production because in this era of all-in, all-out, high variability can be a big hindrance to achieving a high proportion of full-value pigs. Lack of uniformity (variability) of birth weights translates to high variability in nursery and finishing. By taking the approach above we ensure that in Hypor products that is not a problem. Genetic trends from the last years in our dam lines show that we have increased total number born without a decrease in average birth weight (see graph below)