半胱胺对断奶前后仔猪血清皮质醇、T3、T4和IL-2水平的影响

选取新生仔猪18窝，随机分为对照组和处理组各9窝。从12日龄开始，对照组饲喂基础乳猪料；处理组在基础乳猪料中添加半胱胺，剂量为120mg／kg饲料。两组仔猪均在35日龄断奶。分别于断奶前7d(28日龄，D28)，断奶当天(D35)，断奶后36h(D36．5)、72h(D38)、7d(D42)、10d(D45)，随机选取对照组和处理组仔猪各6头，屠宰采集血样。采用放射免疫分析法测定仔猪血清皮质醇、三碘甲腺厚氨酸(T3)、甲状腺激素(T4)和白细胞介素-2(IL-2)水平。结果表明：(1)对照组血清皮质醇水平在断奶前保持稳定，在D36．5时升高，在D42时恢复至D35水平，随后保持稳定；处理组血清皮质醇水平在D36．5时较D35有升高趋势，在D38时恢复至D35水平，随后保持稳定。对照组血清T3水平在D36．5显著高于D28，其他日龄点间无显著差异，处理组基本保持稳定。对照组血清T4水平在D36．5时升高，在D38日时恢复至D35水平，随后保持稳定；处理组血清T4水平从D35至D45基本保持稳定。两组中血清IL-2水平在D28至D42保持稳定，D45升高。(2)在D36．5时，处理组血清皮质醇水平较对照组降低30％，处理组血清T3水平在D35和D45较对照组提高49．2％和38．6％，T4水平在D35和D45提高31％和45．8％，在其他日龄点，处理组T3、T4水平较对照组有升高趋势，但差异不显著。处理组IL-2水平在D36．5、D38、D45也分别较对照组提高22．1％、12．6％和17．8％，在其他日龄点有升高趋势。以上结果提示半胱胺能抵抗仔猪断奶应激，提高仔猪血清T3、T4水平，增强仔猪的免疫力。

Effects of Cysteamine on Serum Levels of Cortisol,T3,T4 and IL-2 in Pre- and Post-Weaning Piglets

Eighteen litters of newborn piglets were divided randomly to control and treatment groups. From 12 days of age,piglets in treatment group were fed starter diet supplemented with 120 mg/kg cysteamine (CS),while the control group were fed basal diet. Piglets were weaned at 35 days of age (D35) in both groups. 6 piglets from each group were slaughtered on D28 (7 d before weaning),D35 (weaning day),D36.5,D38,D42 and D45 (36 h,72 h,7 d and 10 d after weaning),respectively. Radioimmunoassay was applied to determine the serum levels of cortisol,T3,T4 and IL-2. The results indicated that: (1) Cortisol level was stable before weaning in control group,followed by an abrupt increase on D36.5,and was restored to the level of weaning on D42. In treatment group,cortisol level exhibited a tendency of increase from D35 to D36.5,and was restored and stabilized at the level of weaning from D38 onwards. T3 level in control group was higher on D36.5 than that on D28,but there were not significant differences among other age groups. In treatment group,T3 level kept stable throughout the period of investigation. For control,T4 level increased on D36.5 and returned to the weaning day level on D38. T4 level was stable from weaning day to 45 days in treatment group. IL-2 level was kept stable in both groups until D45 when a significant increase was observed. (2) Cortisol level in treatment group decreased markedly by 30% compared with control group on D36.5. CS treatment increased both T3 and T4 levels by 49.2% and 31% on D35, and 38.6% and 45.8% on day 45 (P<0.05),respectively. No significant differences were observed on other ages for T3 and T4,although a tendency of increase was shown in treatment group. IL-2 concentration in treatment group increased by 22.1% (P<0.05),12.6% (P<0.05) and 17.8% (P<0.05) on D36.5,D38 and D45,respectively. The results suggested that cysteamine might help to enhance the resistance of the piglets to weaning stress through increased serum levels of T3,T4 and IL-2,and decreased cortisol secretion during pre- and post-weaning period.