Isolated Rearing at Lactation Increases Gut Microbial Diversity and Post-weaning Performance in Pigs

Environment and diet are two major factors affecting the human gut microbiome. In this study, we used a pig model to determine the impact of these two factors during lactation on the gut microbiome, immune system, and growth performance. We assigned 80 4-day-old pigs from 20 sows to two rearing strategies at lactation: conventional rearing on sow’s milk (SR) or isolated rearing on milk replacer supplemented with solid feed starting on day 10 (IR). At weaning (day 21), SR and IR piglets were co-mingled (10 pens of 4 piglets/pen) and fed the same corn-soybean meal-dried distiller grain with solubles- and antibiotic-free diets for eight feeding phase regimes. Fecal samples were collected on day 21, 62, and 78 for next-generation sequencing of the V4 hypervariable region of the bacterial 16S rRNA gene. Results indicate that IR significantly increased swine microbial diversity and changed the microbiome structure at day 21. Such changes diminished after the two piglet groups were co-mingled and fed the same diet. Post-weaning growth performance also improved in IR piglets. Toward the end of the nursery period (NP), IR piglets had greater average daily gain (0.49 vs. 0.41 kg/d; P < 0.01) and average daily feed intake (0.61 vs. 0.59 kg/d; P < 0.01) but lower feed efficiency (0.64 vs. 0.68; P = 0.05). Consequently, IR piglets were heavier by 2.9 kg (P < 0.01) at the end of NP, and by 4.1 kg (P = 0.08) at market age compared to SR piglets. Interestingly, pigs from the two groups had similar lean tissue percentage. Random forest analysis showed that members of Leuconostoc and Lactococcus best differentiated the IR and SR piglets at weaning (day 21), were negatively correlated with levels of Foxp3 regulatory T cell populations on day 20, and positively correlated with post-weaning growth performance. Our results suggest that rearing strategies may be managed so as to accelerate early-life establishment of the swine gut microbiome to enhance growth performance in piglets

MECHANICAL CHARACTERIZATION OF PRETERM NEONATE PIG LIVER AS A FUNCTION OF HIGH-DENSITY LIPOPROTEIN (HDL)

ABSTRACT Elastography, a non-invasive imaging modality, utilizes mechanical properties of tissue as markers for disease diagnosis or staging. In the case of liver, there have been a number of studies focusing on the relationship between elastic mechanical properties and underlying disease, i.e. fibrosis and cirrhosis. In summary, these studies indicate the feasibility of elastographic tools in detecting liver diseases such as fibrosis and steatosis. There have not been any studies looking at the mechanical properties of the preterm neonate liver to date, which is important, because preterm neonates are at a greater risk for developing liver complications due to their aggressive dietary needs that are met with total parenteral nutrition (TPN). They use of elastography may be less from the use of elastographic tools since the concerns over noise levels in measurements resulting from abdominal wall thickness may be less influential. Therefore, it is necessary to establish basic preterm neonate liver mechanical properties. In this study, we measured the nonlinear (hyperelastic) mechanical properties of livers from preterm pigs that were fed common neaonatal diets, i.e. colostrum, total parenteral nutrition (TPN). 16 neonate pigs survived the feeding regime. Mechanical evaluation of 15 of these neonatal pigs was achieved with the use of uniaxial compression experiments at 0.01 s -1 strain rate. The livers averaging a weight of 34.7±7.0 (SD), were stored in phosphate buffered saline solution at 4°C until experimentation, which occurred within 30 minutes of the animal sacrifice. A minimum of three specimens from each liver was required for the computation of averaged mechanical properties. In addition to mechanical testing samples, blood serum was also obtained from these animals and common chemical parameters for liver health were measured (bilirubin, ALT, AST, HDL, LDL, etc.) Exponential form of the hyperelastic strain energy function, , where b i are the material parameters and L is the stretch ratio, was utilized to describe the hyperelastic mechanical behavior of the preterm neonate pig livers. With the use of E=6b 1 b 2 , a small-strain regime estimate of the elastic modulus of the neonate liver tissue was also computed. The mean b 1 and b 2 parameters are determined to be 97.00±44.15(SD) Pa and 1.90±0.28(SD) (n=71). The mean elastic modulus exhibited an linear dependence on the HDL values obtained from chemical analysis of the blood serum. Moreover, although relatively weak, the ratio of the HDL over LDL also correlated with the elastic modulus. To our knowledge, this is the only study to date that has focused on the mechanical properties of preterm neonatal pigs and its correlation with liver lipid profile in neonates. Future work will focus on correlating this information with histology and then devising multi-scale material characterization approaches that link underlying neonatal liver structure to its overall mechanical properties