Reduced neonatal mortality in Meishan piglets: a role for hepatic fatty acids?

The Meishan pig breed exhibits increased prolificacy and reduced neonatal mortality compared to commercial breeds, such as the Large White, prompting breeders to introduce the Meishan genotype into commercial herds. Commercial piglets are highly susceptible to hypoglycemia, hypothermia, and death, potentially due to limited lipid stores and/or delayed hepatic metabolic ability. We therefore hypothesized that variation in hepatic development and lipid metabolism could contribute to the differences in neonatal mortality between breeds. Liver samples were obtained from piglets of each breed on days 0, 7, and 21 of postnatal age and subjected to molecular and biochemical analysis. At birth, both breeds exhibited similar hepatic glycogen contents, despite Meishan piglets having significantly lower body weight. The livers from newborn Meishan piglets exhibited increased C18∶1n9C and C20∶1n9 but lower C18∶0, C20∶4n6, and C22∶6n3 fatty acid content. Furthermore, by using an unsupervised machine learning approach, we detected an interaction between C18∶1n9C and glycogen content in newborn Meishan piglets. Bioinformatic analysis could identify unique age-based clusters from the lipid profiles in Meishan piglets that were not apparent in the commercial offspring. Examination of the fatty acid signature during the neonatal period provides novel insights into the body composition of Meishan piglets that may facilitate liver responses that prevent hypoglycaemia and reduce offspring mortality

Heat maps and principal component analysis of fatty acid profiles.

<p>Heat maps and dendrograms visualizing the hierarchical clustering results (average linkage, Euclidean distance metric) of Meishan (A) and commercial piglets (B). Rows correspond to animals and the corresponding age group is indicated by coloured circles. The fatty acid mole percentiles were transformed to a z-score and indicated by a colour code, with red representing low percentiles and green high percentiles. Principal component analysis (PCA) plots of all Meishan (C) and all commercial piglets (D).</p

Body and liver weight with age and breed.

<p>Influence of breed on early growth in Meishan (open bars) and commercial (closed bars) piglets during the first 21 days postnatal life. (A) Changes in body weight, (B) Changes in liver weight and (C) Relative liver weight. A; p<0.05: statistical difference between the Meishan breed age groups, B; p<0.05: Statistical difference between the commercial age groups, C; p<0.05: Statistical difference between the 0 and 7 day old in comparison to 21 days old commercial breed group and *; p<0.05: Statistical difference between the same postnatal age groups. Bar graphs illustrate means ± SEM.</p

Liver composition between age and breed.

<p>The effect of breed and postnatal age in liver composition between Meishan (open bars) and commercial (closed bars) piglets: (A) Triglyceride content and (B) glycogen content. *; p<0.05: statistical difference between the same postnatal age groups. Bar graphs illustrate means ± SEM.</p

Fatty acid profiles.

<p>Differences of the major fatty acids in the livers of Meishan (open bars) and commercial (grey bars) piglets over the first 21 days of postnatal life. (A) stearic acid, (B) heptadecanoic acid, (C) oleic acid, (D) eicosenoic acid (E) arachidonic acid, (F) docosahexaenoic acid. A; p<0.05: statistical difference between the 0 and the other age groups within Meishan breed group. B; p<0.05: Statistical difference between the same postnatal age groups. Bar graphs illustrate means ± SEM.</p

mRNA expression of hepatic metabolic genes between breed and age.

<p>mRNA abundance of <i>FAS</i>, <i>SCD-</i>1, <i>ELOVL</i>-6 and <i>CoA</i> in the liver of newborn Meishan (open bars) or commercial (closed bars) piglets as determined by real time PCR. Bar graph illustrates means ± SEM with statistically significant differences between groups represented by *p<0.05.</p