Positive action publications

by Egbert F. Knol and Jascha I. Leenhouwers, Topigs, PO Box 86, 5268 ZH-Helvoirt, The Netherlands.
Piglet mortality is high. On average,
Sire line
13% of live born piglets die during lacta-tion. veterinarians, since death can be seen as the ultimate form of disease. Geneticists gers on mortality. In this article we will explain that this fear is not justified. Piglet backfat
Table 2. Realised litter results of a genetically low and a genetically high piglet birth
Some traits show variation that is easy to weight group for a dam line and a sire line. Expected differences in birth weight were
141g and 99g respectively. Bold differences between the groups were significant (P<0.05).
can easily be measured by ultrasonicbackfat measurements. Ultrasonic back- the survival chances for the intrinsically weak piglets quite dramatically. If vitality two piglets with a birth weight of 1400g, one with more vitality than the other.
vitality, thereby realising a ‘not survived’ ences in vitality. Add to this the lack of genetic background. That is the heritabil- ity is 0.5. For survival the situation is vitality will easier escape crushing, dehy- the piglets that are crossfostered to other intrinsic vitality between piglets, but this dration or starvation. A third problem is sows, and it becomes clear that it is very difficult for geneticists to work on mor- problem is birth weight. Piglets differ in vival chances of piglets. Of course this is Extensive Dutch trial
Table 1. Realised litter results of a genetically low and a genetically high piglet survival
group in a dam line and a sire line. Expected differences in survival were 4.97% and 4.08,
respectively. Bold differences between the groups were significant (P<0.05).
started to collect data on various farms tofind out if genetic differences in survival Sire line
tification of all piglets at birth, even the records of some 600,000 piglets thathave been followed until weaning. With this exact registration and with the large genetic analysis. Heritability of survival International Pig Topics — Volume 17 Number 2 variation is very high (a piglet is either In advance, let us try to predict the per- realised survival in the order of the pre- It is quite safe to predict that the high ing survival (the complement of stillbirth) therefore calculated and their predictive compared with the low group. Also, litter It takes some time to digest the results.
Imagine a barn of 200 gestating sows.
results are shown in Table 1. First of all, stored. The future litters of the gestating birth weight of the high group comparedwith the low group is against gut feeling,since common knowledge dictates thatthe single most important factor for sur-vival is birth weight. Genetic factors and survival
This is definitely true at the phenotypiclevel, that is in the barn, in the pigletsyou see. But the influence of birth weighton survival is not true on the geneticlevel. Increasing birth weight geneticallyis relatively easy, the heritability is atleast 0.20. But increasing birth weightgenetically will hardly increase survival(see Table 2). Moreover, it will nega-tively influence litter size. In the litera-ture, there are a number of indicationsthat genetically heavier animals do notnecessarily have a higher survival.
an average birth weight below 1000gwith high survival rates.
lar result. Selection for increased leandeposition in a British selection experi-ment lead to heavier piglets at birth, butat the same time to a decreased survival.
of the breeding values, genetic correla-tions of survival with other economicallyimportant finishing traits were calcu-lated. Additionally we tried to unravelthe underlying biological mechanisms ofgenetic differences in piglet survival. ics and underlying traits of motheringability. All work was and is performed inco-operation between Topigs, DumecoBreeding, and Wageningen Universityand partly financed by STW.
In summary, piglet survival is heritable.
Considerable genetic variation in pigletsurvival exists. Selection for increasedpiglet survival will lead to more uniformpiglets, which will have a much highersurvival chance, especially at lower birthweights. Selection will not increase birthweight. ■ International Pig Topics — Volume 17 Number 2

Source: http://www.topigs.com.mx/demo/documentos/publicidad/Articulo%20(Ingles)%20Vitalidad.pdf