This study aimed to investigate the impact of dietary L-citrulline supplementation on the health of mares during late gestation. Thirty-two healthy mares in late pregnancy were randomly assigned to four groups: a control group (CON, 0 g/d) and three treatment groups receiving 15, 30, and 45 g/d/head of L-citrulline, respectively. The trial spanned 72 days, including a 12-day adaptation phase and a 60-day formal feeding period. A fixed daily feeding amount of 11.2 kg/head was provided, ensuring complete consumption and consistent dry matter intake across all groups. Results demonstrated that supplementation with 30 g/d/head of L-citrulline significantly improved the apparent digestibility of crude protein and nitrogen metabolism rate (p < 0.05), while notably increasing plasma superoxide dismutase (SOD) activity (p < 0.01) and reducing plasma malondialdehyde (MDA) concentration by 10.53% (p < 0.01). Furthermore, mares receiving 30 g/d of L-citrulline showed a 14.81% increase in plasma estradiol (E2) concentration (p < 0.01). Urinary concentrations of E2, estrone sulfate (ESS), and 17α-dihydroequilin sulfate (17α-DHEQS) were also significantly elevated (p < 0.05). This supplementation also enhanced plasma amino acid levels related to the urea cycle and improved the diversity of fecal microbiota, increasing the abundance of beneficial bacteria. A multi-indicator scoring system identified 30 g/d as the optimal supplemental dose of L-citrulline. These findings suggest that 30 g/d of L-citrulline may act as a nutritional regulator, offering valuable insights for enhancing the physiological and metabolic health of mares during late gestation.
Liu et al. (Thu,) studied this question.