Effects Of Different Supplementing Level Of Cysteamine On Digestion And Metabolism And Performance Of Sheep

The aim of the paper was to probe into the mechanism of promoting growth of cysteamine and to determined optimal supplemental level of cysteamine, by investigating the effects of supplementing cysteamine everyday on digestion and metabolism and productivity performance, which laid the theoretical foundation for application of cysteamine in animal feeding.Part one : Effects of different levels of cysteamine on activities of digestive enzymes in gastro-intestinal tract were studied. 16 healthy Xiaoweihan sheep with approximate weight were divided into group C, L, M and H fed with the basal diet containing 0, 7.5 , 15 and 22.5 mg of cysteamine/kg BW everyday for 20 days. These sheep were slaughtered at the end of experiment to collect the digesta in gastro-intestinal tract. Then activities of the digestive enzymes were determined. The results showed that 7.5 mg CS/kg BW in the diet significantly increased the activities of amylase, trypsin in duodenum and jejunum, cellulase in rumen and pepsin in abomasum (P < 0.05); 15 mg CS/kg BW in the diet significantly increased the activities chymytropsin in duodenum and jejunum (P < 0.05), while difference between group L and group M was not significant (P > 0.05). Therefore, the activities of the digestive enzymes were improved by supplementing optimal level of cysteamine in the diet every day.Part two: Effects of supplementating different levels of cysteamine on nutrient digestion and metabolism were investigated by total feces and urine collection method. Groups were divided in the same way of part one. Results showed that 7.5 mg CS/kg BW in the diet significantly increased apparent digestibility of crude protein and dry matter (P < 0.05); 15 mg CS/kg BW in the diet significantly promoted net protein utilization, digestibility of organic matter and acid detergent fiber, while the difference between group L and group M was not significant (P > 0.05). As a result, supplementing optimal level of cysteamine in the diet everyday can improve the nutrient digestibility and the nitrogen utilization.Part three: Effects of supplementing different levels of cysteamine on productive performance in sheep were studied. 28 healthy Xiaoweihan sheep with approximate weight were divided into 4 groups in the same way of part one. Sheep in treated groups were fed with cysteamine every day for 60 days. Results showed that body weight gain of group supplemented with 7.5 mg CS/kg BW in the diet was significantly greater than that of control group in the first forty days. With the increase of dosage and extension of time, the response of promoting growth decreased. Group supplemented with 7.5 mg CS/kg BW significantly increased daily feed intake and feed conversion rate (P < 0.05), but had no significant difference from group supplemented with 15 mg CS/kg BW (P > 0.05). 22.5 mg CS/kg BW significantly decreased daily feed intake (P < 0.05), but had no influence on feed conversion rate.In conclusion, the optimal supplemental level of cysteamine in the diet was 7.5 mg CS/kg BW. Cysteamine improves sheep growth as a result of increase of activities of digestive enzyme and nutrient digestibilities.