南京地区奶牛日粮中添加碘对产奶性能和甲状腺机能的影响

EFFECTS OF IODINE SUPPLEMENTATION ON MILK PERFORMANCE AND THYROID FUNCTION OF DAIRY COWS IN NANJING AREA

选用10头健康成年黑白花奶牛、按2×2交叉试验设计进行饲养试验。试验组日粮中添加KT20mg/头·日,对照组不添加。试验期70天(2×35),于各试验期最后一天进行促甲状腺素释放激素(TRH)兴奋试验。结果试验组奶牛日平均产奶量(kg)、乳脂率(％)分别为20.01±1.06和3.45±0.05,均显著高于对照组(P<0.05),折合成标准乳(4％FCM),试验组较对照组提高了7.7％(P<0.05)。注射TRH前,血清中甲状腺素(T_4)、三碘甲腺原氨酸(T_3)和促甲状腺素(TSH)含量试验组均显著高于对照组(P<0.05);注射TRH后60min,两组血清中T_4、T_3、TSH含量极显著上升(P<0.01),试验组T_4上升值显著高于对照组(P<0.05),而T_3、TSH上升值则无组间差异(P<0.05)。提示:南京地区冬春两季饲料条件下,日粮中添加适量碘(20mgKI/头·日)可显著促进T_4的合成与储备,改善垂体-甲状腺轴分泌机能,进而提高奶牛产奶性能。

10 Holstein cows from the Experimental Stock Farm at mid-late lactation were paired into two groups in a double-reversal trial from March 20 to May 30, 1989 and thc trcatment group was supplemented KI 20 mg/head per day while the control with no additives. On the last day of each trcatment period, thyrotropin releasing hormone (TRH) test was conducted. Both milk yield and milk fat percentage were elevated significantly by dictary iodine supplementation (P<0.05) and scrum basal concentrations of T_3, T_4 and TSH of trcatment group were higher than those of the control (P<0.05). 60 minutes after intravcnously injection of TRH, the concentrations of T_3, T_4 and TSH in serum were raised significantly (P<0.01), and the mean incrcase of T_4 of the treatment group was higher than that of the control (P<0.05), while no statistical dilTcrence was found in T_3 and TSH incrcase between two groups (P>0.05).