Acute and persistent effects of oral glutamine supplementation on growth, cellular proliferation, and tight junction protein transcript abundance in jejunal tissue of low and normal birthweight pre-weaning piglets

Abstract

Breeding for higher fertility has resulted in a higher number of low birthweight (LBW) piglets. It has been shown that LBW piglets grow slower than normal birthweight (NBW) littermates. Differences in growth performance have been associated with impaired small intestinal development. In suckling and weaning piglets, glutamine (Gln) supplementation has been associated with improved growth and intestinal development. This study was designed to examine the effects of oral Gln supplementation on growth and small intestinal parameters in LBW and NBW suckling piglets. At birth (day 0), a total of 72 LBW (1.10 ± 0.06 kg) and 72 NBW (1.51 ± 0.06) male piglets were selected. At day 1, litters were standardized to 12 piglets, and experimental piglets supplemented daily with either Gln (1 g/kg BW) or isonitrogenous amounts of Alanine (Ala) as control (1.22 g/kg BW) until day 12. Creep feed was offered from day 14 onward. Subgroups of piglets were euthanized at days 5, 12, and 26 for the analyses of jejunal morphometry, cellular proliferation, glutathione concentration and transcript abundance of tight junction proteins. From age day 11 to 21, Gln supplemented LBW (LBW-Gln) piglets were heavier than Ala supplemented LBW (LBW-Ala) littermates (P = 0.034), while NBW piglets were heavier until age day 26 compared to LBW littermates. Villus height was higher in LBW-Gln compared to LBW-Ala on age day 12 (P = 0.031). Sporadic differences among supplementation and birthweight groups were detected for jejunal cellular proliferation, cellular population and glutathione concentration, whereas age was the most dominant factor. These results show that Gln supplementation improved the growth of LBW piglets compared to LBW-Ala beyond the termination of Gln supplementation, but this was not associated with consistent effects on selected parameters of jejunal development.

Fig 1. Jejunal histomorphology and immunohistochemistry of 5-, 12-, and 26-day-old suckling piglets.

(A) Alcian blue pH 2.5 -periodic acid Schiff stained jejunal tissue with stained goblet cells. Different arrows highlight goblet cells containing different mucins: Narrow arrow = acidic mucins (blue stained), wide closed arrow = neutral mucins (magenta stained, wide open arrow = mixed mucins (purple stained); days 5, 12, 26. (B) Representative immunohistochemistry images of CD3, counterstained with hematoxylin, arrows showing positive stained intraepithelial CD3+ cells in villi; days 5, 12, 26. (C) Representative immunohistochemistry images of IgA positive stained cells in lamina propria. No IgA positive cells were detected at age day 5, arrows indicating IgA positive cells; days 5, 12, 26. Abbreviations: AB-PAS = Alcian blue pH 2.5-periodic acid Schiff, CD 3 = Cluster of differentiation 3, IgA = Immunoglobulin A.