| The effects of orally administrating cysteamine (CS) on the production performance of meat-wool-type sheep were studied in this test and the mechanisms were also initially discussed.1. The effects of cysteamine on body weight (B.W.) and the levels of several hormones in sheep blood plasmaTwenty 90-day (?5d) weaning Dorset Horn x Chinese Xiaoweihan sheep were randomly divided into treatment group (T) and control group (C) according to their sexes and body weights, feeding with the same diet and fixed amount daily. After 7 days' preparatory test, the treatment diet was added with lOOmg-kgBW"1 cysteamine (CS), once every 5 days, for 20 days. On dO, d5, dlO, d!5, d20 after first CS administration, all the sheep, with empty stomach, were weighed respectively each time in the morning, and jugular blood samples were taken after each weighing and prepared into plasma for T3, T4, TSH, PRL, cortisol and plasma AA content determination. The results showed that, compared with the control, the body weight of the treated sheep increased by 4.78%( P=0.07 )and by 8.74%( P=0.017 )in the first 10 days and the first 20 days separately; body weight growth rate increased by 3.70% (P<0.01) and 3.58% ( P<0.01 ) respectively during 5 to 10 days and 15 to 20 days. In hormone incretion, the plasma T3 level of the treated sheep, lower by 6.00% ( P>0.05 )before CS administration than the control, were higher than the control by 8.40% ( P>0.05 ) , 34.50% ( P<0.05 ) , 23.90% ( P>0.05 ) and 6.00% ( P>0.05 ) ond5, d10,d15 and d20, respectively; the plasma T4 levels were slightly raised in all test stages, but without significant difference ( P>0.05 ) compared with the control; the plasma TSH levels of the treatment, though significantly lower than the control (P<0.01 ) on dO, was close to the control after d5; the plasma PRL levels of the treated sheep dropped remarkably on d5 and waved in the same way as the control after d5, while there was no evident difference between d0 and d5 in the control; there was no marked difference between the treatment and the control on plasma cortisol level, but the increasing rate of plasma cortisol levels in the treated sheep was significantly lower than that in the control (P<0.01 ) . The results further indicated that CS administration didn't significantly affect the total amino acid contents as well as the content of each individual amino acid in sheep plasma(P>0.05). The results hinted that orally administrating cysteamine significantly increased the sheep body weight and weight growth rate while raised the plasma T3 level and the plasma TSH level with no marked raising effect on the plasma T4 level, lowered the fluctuating scope of the plasma cortisol level and declined the PRL level on d5.2. The effects of cysteamine on wool production performance Forty 90-day ( ±5d) weaning Dorset Horn x Chinese Xiaoweihan sheep were randomly divided into treatment group (T) and control group (C) according to their sexes and body weights, feeding with the same diet and fixed amount daily. After 7 days' preparatory test, the treatment diet was added with 100 mg-kgBW"' cysteamine (CS), once every 5 days, for 20 days. Wool samples, used for the determination of stretched length of wool, fiber diameter, wool fiber type, clean wool yield and wool amino acid contents, were taken from the middle patchs of one side of sheep body before and after test respectively. The results showed that, compared with the control, the net increase of stretched length of wool and wool growth rate in the treatment raised by 3.84mm(P<0.01) and by 8.52%(P<0.01) respectively; the diameter of unmedullated fiber (fine wool fiber) enlarged remarkably (P<0.05), while the diameter of dead wool decreased evidently (P<0.05), with other wool type unaffected; the composition of wool types and clean wool yield were not evidently92affected (P>0.05). In wool amino acid content, the total wool amino acid contents of the control dropped significantly (PO.01) after test in addition to the mean amino acid contents of all wool types dropp...
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