Differences in Weight, Hierarchy, and Incidence of Lameness between Two Groups of Adult Pigs Derived from Assisted Reproductive Technologies

SIMPLE SUMMARY: More than 90% of the animals in current pig farms have been conceived by artificial insemination (AI). However, it is expected that the number of pigs derived from in vitro fertilization (IVF) will increase in the coming decades since the trade of cryopreserved pig embryos can be a reality soon, as it already is in cattle. Today, nothing is known about the repercussions that IVF could have on animal health, welfare, or food safety because no colonies of study exist yet. We created a small one 4 years ago and the present work shows some data collected from 16 pigs derived from IVF and 14 pigs derived from AI, conceived from the same boar, and housed and fed under the same conditions since they were born. The results point out that the IVF animals showed a lower incidence of lameness and higher weight and occupied more predominant positions in the hierarchy of the herd than the AI animals. Although genetic differences from the maternal line could explain some of these results, it is also possible that the way in which the animals were conceived (AI or IVF) induced better adaptative abilities in the IVF group, explaining the lower incidence of lameness. Nonetheless, more studies with a higher number of animals are necessary to reach consistent conclusions about the phenotype of IVF-derived adult pigs. ABSTRACT: The in vitro production (IVP) and subsequent transfer of embryos (ET) to recipient mothers is not yet an established reproductive technology in the pig industry, as it is in cattle. However, that the trade of IVP-cryopreserved pig embryos is expected to start in the next decades. Society and governments are increasingly aware of the repercussions that IVP could have for animal health, welfare, behavior, or food safety, but proven scientific information for this type of animal does not exist, since no colonies of pigs have been created to this end. We created a small one and studied the differences between 16 IVP-derived pigs and 14 pigs derived from artificial insemination (AI), at 3.5 years of age, conceived from the same boar, and housed and fed under the same conditions since they were born. Incidence of lameness, position in the herd hierarchy, weight, adenosine deaminase activity, and hematological and biochemical analytes were compared between the two groups of animals. The results showed that the IVP animals weighed more, occupied higher positions in the herd hierarchy, and had a lower incidence of lameness. Although genetic differences from the maternal line could explain some of these results, it is also possible that the IVP animals developed better adaptative abilities, but more studies with a higher number of animals are necessary to reach consistent conclusions.