Effects of calcium gluconate on the utilization of magnesium and the nephrocalcinosis in rats fed excess dietary phosphorus and calcium

Gluconic acid improves performance of newly weaned piglets associated with alterations in gut microbiome and fermentation

BACKGROUND

Weaning is a critical phase in the pigs' life and gut health might be compromised. Gluconic acid was shown to be poorly absorbed but readily fermented to butyrate in the gut which in turn can improve gut function. Hence, a total of 144 weaning pigs were fed the experimental diets for 42 days. Three treatments were replicated in 8 pens with 6 piglets each: control; low dietary dose of gluconic acid, 9 g/kg; and high dietary dose of gluconic acid, 18 g/kg. After 21 days, one piglet from each pen was sampled for blood haematology and biochemistry, fore- and hindgut digesta characteristics and microbiota, and distal small intestinal histo-morphological indices and gene expression.

RESULTS

Feeding gluconic acid enhanced performance in period d 0-14 post-weaning, in particular feed intake was increased (P = 0.028), though the high dose did not show benefits over the low dose. Regarding d 0-42, feed intake was elevated (P = 0.026). At d 21, piglets fed 18 g/kg gluconic acid showed a trend for lower number of total white blood cells (P = 0.060), caused by particularly lower numbers of lymphocytes as compared to control (P = 0.028). Highly reduced plasma urea was found for groups fed gluconic acid, it amounted to 2.6 and 2.6 mmol/L for the 9 and 18 g/kg level, respectively, as compared to 3.8 mmol/L in control (P = 0.003). Feeding gluconic acid promoted the relative abundance of lactic-acid-producing and acid-utilizing bacteria. In distal small intestine, Lactobacillus amylovorus increased substantially from 11.3 to 82.6% for control and gluconic acid 18 g/kg, respectively (P < 0.05). In mid-colon, the butyrate producers Faecalibacterium prausnitzii (P > 0.05) and Megasphaera elsdenii (P < 0.05) showed highest abundance in gluconic acid 18 g/kg. Consequently, in caecum and mid-colon, increased relative molar percentage of butyrate were found, e.g., 10.0, 12.9 et 14.7% in caecum for gluconic acid at 0, 9, and 18 g/kg, respectively (P = 0.046). Elevated mRNA anti-inflammatory cytokine and survival signalling levels in distal small intestinal mucosa were found by feeding gluconic acid which might be mediated by butyrate.

CONCLUSIONS

Gluconic acid may have potential to alleviate the postweaning growth-check in pigs by altering microbiota composition and fermentation in the gut.

Effect of dietary mineral sources and oil content on calcium utilization and kidney calcification in female Fischer rats fed low-protein diets

We studied the effects of dietary mineral source and oil intake on kidney calcification in 4-wk-old female Fischer rats after consuming the AIN-76 purified diet (AIN-76). A modified AIN-76 mineral mixture was used, although the original calcium (Ca)/phosphorus (P) molar ratio remained unchanged. Rats were fed the modified diets for a period of 40 d before their kidneys were removed on the last day. Ca balance tests were performed on days 31 to 36 and biochemical analysis of urine was also studied. Kidney Ca, P, and magnesium (Mg) in the standard diet group (20% protein and 5% oil) were not affected by the mineral source. Kidney Ca, P, and Mg in the low-protein (10% protein) diet group, were found to be influenced by the dietary oil content and mineral source. In particular, the different mineral sources differentially increased kidney mineral accumulation. Pathological examination of the kidney showed that the degree of kidney calcification was proportional to the dietary oil content in the 10% dietary protein group, reflecting the calcium content of the kidney. The information gathered on mineral sources in this study will help future researchers studying the influence of dietary Ca/P molar ratios, and histological changes in the kidney.

The effects of various organic acids on phytate phosphorus utilization in chicks

Previous research from our laboratory has shown that citric acid improves phytate P utilization in chicks fed a P-deficient corn-soybean meal diet. The current study was conducted to determine if other organic acids also are effective, with an emphasis on gluconic acid. Four experiments were conducted in which 4 replicate groups of 5 crossbred chicks (New Hampshire x Columbian) were fed a P-deficient diet (0.16% nonphyate P) from 8 to 22 d of age. In Experiment 1, chick weight gain and tibia ash were significantly increased (P < 0.05) by 1.5 and 3% sodium gluconate (NaGlu), 1.5% calcium gluconate (CaGlu), 1.5 and 3% glucono-delta-lactone, and 1% 2-hydroxy-4-methylthio butanoic acid (Alimet). In experiment 2, tibia ash was significantly increased (P < 0.05) by 2% NaGlu, CaGlu, and citric acid in chicks fed the P-deficient diet but not in chicks fed a 0.45% nonphytate P diet, indicating that the organic acid responses were due to increased P utilization. In experiments 3 and 4, tibia ash was significantly increased by 3% NaGlu and 3% citric acid, but not by 3% fumaric acid or 0.025, 0.05 and 0.1% EDTA. The results of this study showed that NaGlu, CaGlu, glucono-delta-lactone, Alimet, and citric acid, but not fumaric acid or EDTA, improved phytate P utilization in chicks fed a corn-soybean meal diet.