Development of a model to examine developmental changes in intestinal crypt cell proliferation and macrophage densities of neonatal piglets

Young piglets are more susceptible to severe immune challenges because their immune system is not fully developed at birth. A randomized complete block design experiment utilizing a 4 × 2 factorial treatment arrangement was conducted to evaluate the effect of dietary protein source on intestinal crypt cell proliferation and local macrophage populations of neonatal piglets. Male and female piglets (n = 123) from 5 farrowing groups were fed 1 of 3 liquid diets: (1) Whey (MLK) only, (2) MLK + spray-dried plasma (SDP), or (3) MLK + soy protein concentrate (SPC). After receiving sow colostrum, piglets were reared in Rescue Decks® until tissue collection. A fourth group was left in the farrowing crate and nursed the sow until sampling (SOW). Duodenal (DUO), jejunal (JEJ), and ileal (ILE) tissue was collected at 6, 14, 19, and 25 d of age. One hour before euthanasia, pigs were injected with 5′-bromo-2′-deoxyuridine (BrdU) to label proliferating (BrdU+) cells. Proportion of proliferating (BrdU+), crypt epithelial cells (PCEC) and CD172a (total) and CD80+ (pro-inflammatory) macrophage populations was assessed after cryohistology and immunofluorescence staining. At 6 d old, male piglets fed SDP had greater JEJ PCEC compared with SOW males (P = 0.0081). At d 14, male piglets fed SPC had higher DUO PCEC than those fed SDP (P = 0.0074). Females fed SPC tended to have greater JEJ (P = 0.0894) and ILE (P = 0.0793) PCEC than SPC-fed males. At d 6, male SOW-fed piglets had the largest populations of both DUO pro-inflammatory (CD80+; P= 0.0478) and proliferating, pro-inflammatory (BrdU+:CD80+; P = 0.0040) macrophages. 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). These data establish a model to evaluate developmental intestinal innate immunity and indicate that dietary protein source can impact PCEC, which may benefit renewal of the intestinal epithelial barrier.

Key Words: immune system, small intestine, intestinal macro[1]phages, spray-dried plasma.

Presented at the 9th Symposium on Gut Health in Production of Food Animals, St. Louis, USA, 2021. For information on the next edition, click here.