Effects of Dietary Iodine and Selenium on Nutrient Digestibility, Serum Thyroid Hormones, and Antioxidant Status of Liaoning Cashmere Goats

Forty-eight 2-year-old Liaoning Cashmere goats (body weight = 38.0 +/- 2.94 kg) were used to investigate the effects of dietary iodine (I) and selenium (Se) supplementation on nutrient digestibility, serum thyroid hormones, and antioxidant status during the cashmere telogen period to learn more about the effects of dietary I and Se on nutrition or health status of Cashmere goats. The goats were equally divided into six groups of eight animals each that were treated with 0, 2, or 4 mg of supplemental I/kg dry matter (DM) and 0 or 1 mg of supplemental Se/kg DM in a 2 x 3 factorial arrangement of treatments. The six treatments were I0Se0, I2Se0, I4Se0, I0Se1, I2Se1, and I4Se1. The concentrations of I and Se in the basal diet were 0.67 and 0.09 mg/kg DM, respectively. The study started in March and proceeded for 45 days. Supplemental I or Se alone had no effect on nutrient digestibility and nitrogen metabolism. However, the interaction between I and Se was significant regarding the digestibility of acid detergent fiber (ADF; P < 0.05), and compared with group I4Se1, the digestibility of ADF was significantly increased in group I4Se0 (P < 0.05). Selenium supplementation did not affect serum triiodothyronine (T-3) or thyroxine (T-4) concentrations. However, the concentration of serum T-4 but not that of T-3 was significantly increased with I supplementation (P < 0.05). In addition, serum superoxide dismutase (SOD) activity was not affected (P > 0.05), but serum glutathione peroxidase (GSH-Px) activity was significantly decreased by I supplementation (P < 0.05). The antioxidant status was improved by Se supplementation, and the activities of SOD and GSH-Px were significantly increased (P < 0.05).