| Summary: | 博士 === 國立臺灣大學 === 畜產學研究所 === 87 === Chromium (Cr) is an important factor in nutrient metabolism for mammals. Stressed bovine fed with organic forms of Cr has been reported to improve milk production and immune response. The purposes of the study were to evaluate the optimal dietary Cr from picolinate chromium (CrPic) on growth performance and immunity of weanling pigs, the effects of Cr supplementation on the growth and immunity of weanling pigs under endotoxin stress, and the mechanisms of Cr on the cellular activity of pulmonary alveolar macrophages of weanling pigs.
Four-week-old pigs were randomly assigned to (1) 0, (2) 200, (3) 400, and (4) 800 ppb of Cr supplementation group and fed on diets for 7 weeks. Cr supplementation significantly (P<.01) increased plasma Cr, and 400 ppb of Cr supplementation tended to increase daily gain and feed efficiency during the period of 0-4 week postweaning. The levels of plasma glucose, insulin, cortisol, and insulin/glucose ratio were not influenced by various dietary Cr supplementation. Supplementation of Cr increased anti-Pseudorabies virus (PR) neutralizing antibody titers during weeks 5 and 7 (P<.05) and tended to increase IgG level at week 6 (P＜.15) and overall means of IgM (P＜.07) throughout weeks 2, 4, and 6.
Dietary supplement of 400 ppb of Cr tended to increase IL-2 activity of peripheral blood mononuclear cells on week 4 postweaning and decreased the level of plasma triglyceride on week 6 postweaning, respectively. But plasma TNF-α, cortisol, glucose, and urea nitrogen were not influenced by Cr supplementation after i.v. injection of 1μg/kg body weight of lipopolysaccharide (Escherichia coli; 055: B5, LPS) on week 6 postweaning.
The experiment was performed on two times i.p. injection of 200μg LPS /kg body weight at d 21 and 35, respectively. Plasma samples and rectal temperature were obtained from all piglets before (h 0) and 2 h (h 2), 4 h (h 4), 8 h (h 8), or 24 h (h 24) after LPS injection. The effect of Cr supplementation (400 ppb) on weanling pigs after LPS challenge was also determined. The supplementation of Cr before LPS injection (d 0-21) decreased the feed intake (0.42 vs. 0.34 kg/day) and rectal temperature at d 21 was decreased significantly (P<0.05) about 0.36℃. Supplementation with Cr had no effect on alleviating the growth performance after LPS challenges. The plasma metabolites, hormones, and immune response changed dramatically after the initiation of LPS injection. Supplementation with Cr facilitated the recovery of plasma glucose, triglyceride, and urea nitrogen rapidly. Plasma TNF-α level was reduced and cortisol release was delayed with Cr supplementation after LPS challenge at d 35.
The pulmonary alveolar macrophages were incubated with 0-100μg/L of two Cr salts from chromium chloride (CrCl3) and CrPic for 4 hrs at 37℃. The glucose uptake and superoxide anion () production were increased in the cells incubated with 20μg/L of Cr from CrCl3. The glucose uptake induced by CrPic might be an insulin-dependent manner. Supplementation of Cr from CrPic at a concentration of 100μg/L increased production significantly (P<0.05) regardless of the presence of insulin. In the presence of insulin, the phagocytosis of E. coli by macrophages was enhanced significantly (P<0.05) in medium supplemented with 10-100μg/L of Cr from CrCl3 and CrPic supplementation did not affect the phagocytosis of macrophage regardless of the presence of insulin.
The results suggest that supplemental 400 ppb of Cr from CrPic was beneficial during normal feeding condition and under LPS stress in weanling pigs. Supplementation of CrPic under the cooperated action of insulin enhances the cellular activity of macrophages.
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