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Nitrate supplementation, well-known for its vascular benefits in humans, is gaining interest in animal nutrition, particularly in swine. Recent studies have shown positive effects on farrowing and lactating sows when supplemented with calcium nitrate. This study aimed to determine whether increased dietary nitrate from calcium nitrate would affect serum and tissue nitrate and nitrite levels, hemoglobin, methemoglobin, and myoglobin in finishing pigs.
Methods: A total of forty-eight finishing pigs were fed diets supplemented with varying levels of calcium nitrate over a 28-day period. In the study, complete diets were formulated using corn, wheat middlings, and soybean meal as the primary ingredients, with increasing concentrations of calcium nitrate (Ca nitrate) of 0%, 0.08%, 0.16%, and 0.32%, providing supplemental nitrate concentrations of 0, 500, 1000, and 2000 mg/kg, respectively. These concentrations corresponded to dietary nitrate levels of 0, 4.2, 8.4, or 16.8 mg/kg body weight, based on the average initial weight of the swine. On day 28 of the study, the pigs were weighed and then fasted for 14 to 16 hours overnight. On day 29, prior to euthanasia, blood samples were collected through jugular venipuncture. The animals were then euthanized using a penetrating captive bolt followed by exsanguination. Liver and loin (longissimus dorsi) samples were taken and immediately snap-frozen in liquid nitrogen.
Results: No significant differences were observed in average daily gain, average daily feed intake, or feed efficiency, with supplemented pigs performing at 104% to 120% of the control group. No notable differences were found in blood hemoglobin or methemoglobin levels. While serum nitrate levels were detected in a few samples from pigs receiving the highest nitrate dose (2000 mg/kg), none exceeded the quantification limit. Additionally, all liver and loin samples showed undetectable levels of nitrate or nitrite. Interestingly, total myoglobin in loin samples increased linearly with higher dietary nitrate, but redox forms of myoglobin, including metmyoglobin, showed no differences across treatments.
Conclusion: These findings confirm the safety of dietary nitrate supplementation up to 2000 mg/kg in finishing pig diets, offering a new avenue for sustainable and beneficial feed practices.
Sheppard, A. M., van de Ligt, J. L. G., Pillai, P., Crincoli, C. M., Faris, R. J., McGhee, M. L., & Frederick, B. R. (2023). Safety of dietary nitrate supplementation by calcium nitrate for finishing pigs as measured by methemoglobin and serum and tissue nitrate levels. Translational animal science, 8, txad135. https://doi.org/10.1093/tas/txad135
