Causes of piglet mortality, and the impact of uterine environment, maternal behavioural traits and their genetic component (218900)

Around 14-15% of the liveborn piglet in each litter die before weaning, and if we add the stillborn piglets, the total loss will be approximately 20%. Most of the liveborn losses are due to crushing or trauma caused by the sow or starvation, and this is particularly the case in larger litters. Our field survey in 52 commercial LY loose housed sow herds spread on three different country regions, revealed that out of 1200 dead piglets from 14 of these herds that were subjected to a post mortem investigation, around 7% was stillborn, and approximately 15 % of the liveborn piglets died before weaning in most cases due to trauma or starvation. Therefore, piglet mortality and the causes of mortality have remained similar during the last 10 years, with the most prominent difference being that the ones dying of trauma are no longer the thinnest and weakest, but the ones that have already received milk might just as well die. The latter could be due to the increased litter size. We investigated the effects of management by the farmer on piglet mortality in the 52 herds, and the management routines were divided into 4 groups with an increasing effort: M1. herds without any particular routines around the time of farrowing, M2. herds where the farmer had contact with sows >2 times per day, M3. herds where the farmer was present at 80-100% of the births, conducted split suckling, systematic cross fostering and dried piglets manually, and M4. Herds where the farmer had sow contact >2 times a day, were present at 80-10% of the births, and conducted all the mentioned routines. The predicted values of mean herd piglet mortality for M1, M2, M3 and M4 were 20.1%, 17.0%, 16.2% and 13.3%, respectively. The farmer`s increased management effort was associated with lower piglet mortality. The farmer`s effort at critical times together with systematic and important routines, and having frequent contact with the sows, thus makes a huge difference for piglet survival. Experiments with different types of nest building material (18 LY sows in each of the three treatments), showed that straw was a more stimulating material for sows in terms of nest building activity and exploration than sawdust or peat. The treatment group with straw also had a lower incidence of stillborn piglets and a lower mortality due to crushing than sows given the two other materials. This may indicate that straw stimulates maternal care in sows. Our study is unique in that there are not to our knowledge any other international studies showing a clear link between nest building and piglet survival. One of the main goals of the project, was to find maternal traits (physical and behavioural) that were directly related to piglet mortality/survival in primiparous and multiparous sows of two Norwegian pure lines (Norsvin Duroc, Norsvin Landrace) and one crossbred line (Norsvin Landrace × Yorkshire). The reason why we included the paternal line breed, Duroc, was that this breed has not been selected for maternal traits such as litter size. The investigation of udder traits (teat pair distance, teat length and diameter), important for teat use/functionality, showed that teat pair distance in the middle and posterior part of the udder was the most important udder trait for teat use and preservation of teat functionally in all breeds. Because of significant variance in teat pair distance among sows, our findings indicate that it is possible to select for this trait and it is most important to record it in the middle and posterior positions of the udder on the first day after birth. Other udder characteristics, such as teat length and diameter, had only minor effects on teat use, without any effect on preservation of teat functionality. Larger litter investment in the Norsvin Landrace were costly for sows, demonstrated by larger losses in their body condition scores and a higher prevalence of shoulder lesions during lactation, especially in gilts. Thus, todays breeding program in the maternal line most likely shift resources toward higher investment in earlier litters, jeopardizing future productivity and longevity. Piglets in larger litters spent more time engaged in teat massage, resulting in shorter nursing intervals. Although more piglets survived to weaning in larger litters, this came at the cost of more frequent termination of nursings prior to letdown, more piglets without access to teats at letdown, an increased risk of mortality due to starvation and crushing, and lower, more variable body weights at weaning. Therefore, selection for larger litter size is an unsustainable future strategy. We developed qualitative scores of maternal care behavioural traits in all three breeds that directly affected piglet mortality and survival until weaning. Sows that spent more time preparing their nest prior to parturition, had lower overall piglet mortality due to less crushing and, thus, a higher numbers of weaned piglets. Furthermore, sows that communicated a lot with thei

Piglet survival is the result of complex interactions between prenatal factors, the state of the piglet, maternal behaviour,physical environment and the management routines around farrowing. The main focus of this project is to study the relationships bet ween maternal, behavioural characteristics, udder morphology and piglet survival, with an ultimate goal to develop a qualitative score that can be used directly in the breeding program. As effects of the physical, farrowing environment and management aro und farrowing has been given a much reserach attention during the last years, this is not emphasized in the present project. The only environmental factor studied in detail is the use of nest building material as this is considered to have major impact on maternal behaviour in sows. The genetic basis for maternal traits is investigated with an ultimate goal of implementing this into the existing breeding program. A future goal is also to improve the sow material in such a way that production efficieny doe s not jeopardize sow welfare and longivity as well as piglet survival. The strength of the present project is that we can combine studies of maternal traits, including uterine environment in different breeds, with more detailed infomation on the causes of mortality. The international network connected to this project will ensure the scientific quality of the work. Since all the main pig organisations in Norway are involved, the results from the present project will not only reach the pig producers directl y, but we can potentially also change the breeding goal in a way that improve piglet survival and welfare for both sows and piglets. Thus, the result from this project is of major importance for other countries as well, since many countries are faced wit h future legislations where sows no longer can be crated.