Effect of different protein sources on intestinal crypt cell proliferation and density of macrophages in neonatal piglets
Type of DegreeMaster's Thesis
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Pre-weaning mortality is one of the major concerns for the swine industry since it can negatively affect production efficiency. Since the piglet immune system is not fully developed at birth, they are more likely to suffer an immune challenge. Nutrients necessary for immune system function are redirected from growth and negatively impact growth performance. A randomized complete block design experiment utilizing a 4 × 2 factorial treatment arrangement was conducted. A total of 123 male and female piglets from 5 different farrowing groups were fed 1 of 3 liquid diets: 1) Whey only (MLK), 2) MLK + spray dried plasma (SDP), or 3) MLK + soy protein concentrate (SPC). Piglets were left with the sow for a minimum of 24 h, but not more than 36 h, to ensure adequate colostrum intake. Then, piglets were transferred to Rescue Decks® and reared until tissue collection on experimental d 6, 14, 19, and 25. A 4th group of piglets was left in the farrowing crate and nursed the sow until sampling (SOW). On sampling days, pigs were injected with 5’-bromo-2’-deoxyuridine (BrdU) to label proliferating (BrdU+) cells. One h after injection, pigs were euthanized followed by duodenal (DUO), jejunal (JEJ), and ileal (ILE) tissue collection. Analyses of proportion of proliferating (BrdU+), crypt epithelial cells (PCEC), and enumeration of mitotically active cell (BrdU+), CD172a+ (total) and CD80+ (pro-inflammatory) macrophage populations were performed after cryohistology and immunofluorescence staining. Data were analyzed as a 2-way ANOVA using SAS V9.4 PROC GLIMMIX and treatment means were separated using PDIFF at P ≤ 0.05. Tendencies were declared when 0.0501 < P ≤ 0.10. At d 25, SPC-fed piglets tended to have a higher BWG than all other treatments (P = 0.0699). Jejunum PCEC was greater on SDP-fed piglets than males fed SOW at d 6 (P = 0.0081). At d 6, SOW-fed male pigs had greater populations of pro-inflammatory macrophages (P = 0.0478) and proliferating pro-inflammatory macrophages (P = 0.0040) in the duodenum compared with all others. At d 14, male piglets fed SPC had higher DUO PCEC than those fed SDP (P = 0.0074). In the DUO, at d 19, SDP-fed and male SPC-fed piglets exhibited the highest total macrophage density (P = 0.0025). In the ILE, on d 19, SDP-fed females had the highest pro-inflammatory macrophage density compared with all other groups (P = 0.0465). Macrophage (CD172a+) and total macrophage densities were higher in the duodenum of female piglets fed SDP and male piglets fed SPC compared with female pigs fed MLK and SOW, and male pigs fed SPC and SOW at d 19 (P = 0.0016). The study of the gastrointestinal tract can provide great insight on the activity of immune-related cells which can help to understand how to prevent these dangerous scenarios.