Citric acid is a common organic acid used extensively in diets for young and growing pigs. It enhances appetite and has a strong antimicrobial effect. It also lowers digestive pH and, being absorbed at the stomach level, it can be a good source of readily available energy for young pigs.

There is often a query whether citric acid could also be used to any benefit in diets for breeding sows. To this effect, an experiment was conducted to determine the effects of citric acid on the performance, coefficient of total tract apparent digestibility (CTTAD) of crude protein (CP), calcium (Ca) and phosphorus (P), plasma biochemistry parameters, colostrum and milk composition, and immunoglobulin concentration of sows during late gestation and lactation.

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Forty-eight sows were randomly allotted to four dietary treatments supplemented with 0 (control), 5, 10 or 15 g/kg citric acid. The experiment started at day 90 of gestation and ran until day 24 of lactation. Results indicated that supplementation of 15 g/kg citric acid could significantly increase the CTTAD of CP and P (P < 0.05). Additionally, the CTTAD of Ca was significantly increased with 10 and 15 g/kg citric acid supplemented diets (P < 0.05). There were no significant differences in sow and litter performance among treatments (P > 0.05). The total protein (TP) of plasma on the days of farrowing and weaning and the TP of colostrum and milk were improved by adding 15 g/kg citric acid (P < 0.05). Supplementation of 10 and 15 g/kg citric acid enhanced the IgG and IgA levels in the plasma of sows. Immunoglobulin levels in colostrum and milk were significantly enhanced with 15 g/kg citric acid supplemented diets compared with the control (P < 0.05), with the exception of IgG of milk (P > 0.05).

In conclusion, dietary supplementation of citric acid during late gestation and lactation had no significant or immediate effects on sow and litter performance. Nevertheless, additions of 10 and 15 g/kg citric acid enhanced the absorption of dietary Ca, P, which may have long-term effects on bone structural integrity. It also improved humoral immune function in sows, something that could be beneficial to piglets via colostrum and milk.