Study On Growth-Promoting Effect Of Cysteamine In Piglets And Its Mechanism

The purpose of this experiment was to study the effects of CS on growth performance,digestive enzyme activities in alvine contents,serum levels of hormones and expression of GH receptor in the heart and liver of piglets.9 litters of newborn "Duroc×Landrace×Yorkshire" crossbred piglets(90 piglets total)were randomly divided into 3 groups(Groupâ… ,Groupâ…¡,Groupâ…¢)with 3 litters(30 piglets total) each.At 14 days of age(D14),piglets were fed with basal diet(Groupâ… ,control group),basal diet + CS 120 mg.kg^-1(Groupâ…¡)and basal diet + 200 CS mg.kg^-1 (Groupâ…¢),respectively.The trial was conducted for 31d.Piglets and their feed from each group were weighed to calculate the average daily feed intake(ADFI),the average daily gain(ADG),and the ratio of feed to gain(F/G)at D14,D24 and D45. Serum samples of 10 piglets from each group were collected for testing the levels of GH,SS,T₃,T₄ and IGF-â… at D14,D24,D32 and D45,respectively.6 piglets from each group were slaughtered at 45 days of age.Tissues of heart and liver were taken to measure the changes of GHR mRNA by RT-PCR.Besides,contents of duodenum, proximal jejunum,distal jejunum and ileum were gathered for testing digestive enzyme activities.The results were as follows:(1)The diets supplemented with CS increased significantly the growth performance of pigletsCompared with Groupâ… and Groupâ…¢,the weight(AW)of piglets in Groupâ…¡increased by 11.92%(P＜0.05)and 17.30%(P＜0.01)at 45 days of age,respectively. But there were no distinctions between Groupâ… and Groupâ…¢.Compared with Groupâ… and Groupâ…¢,the average daily gain(ADG)of piglets in Groupâ…¡increased by 17.23%(P＜0.01)and 41.62%(P＜0.01)from D24 to D45, respectively.Compared with Groupâ… ,the average daily gain of piglets in Groupâ…¢decreased by 17.23%(P＜0.01)at the same time.Compared with Groupâ… and Groupâ…¡,the average daily feed intake(ADFI)of piglets in Groupâ…¢decreased by 16.67%(P＜0.05)and 21.33%(P＜0.05)from D24 to D45,respectively.Besides,compared with Groupâ… and Groupâ…¢,the ratio of feed to gain(F/G) of piglets in Groupâ…¡increased by 9.73%(P＜0.05)and 11.30%(P＜0.05)from D24 to D45,respectively. The results showed that basal diet with 120 mg.kg^-1CS(Groupâ…¡)increased the weight(AW)and average daily gain(ADG),decreased the ratio of feed to gain (F/G)in piglets,significantly(P＜0.05).(2)The diets supplemented with CS increased significantly ingestive enzyme activities in alvine contents of pigletsThere were no distinctions in the amylase activities of contents of duodenum, proximal jejunum and distal jejunum among three groups at 45 days of age. Compared with Groupâ… ,the amylase activities in contents of ileum in Groupâ…¡and Groupâ…¢increased by 4.76%(P＜0.05)and 4.10%(P＜0.05),respectively.Compared with Groupâ… ,the trypsin activities of piglets in Groupâ…¡and Groupâ…¢increased respectively by 39.24%(P＜0.05)and 39.56%(P＜0.05)in contents of duodenum,by 57.21%(P＜0.01)and 54.23%(P＜0.01)in contents of proximal jejunum,by 46.84%(P＜0.01)and 34.49%(P＜0.05)in contents of proximal jejunum, by 51.14%(P＜0.05)and 35.23%(P＜0.05)in contents of ileum at 45 days of age.Compared with Groupâ… ,the lipase activities of piglets in Groupâ…¡and Groupâ…¢increased respectively by 36.35%(P＜0.01)and 36.55%(P＜0.01)in contents of duodenum,by 34.02%(P＜0.01)and 36.39%(P＜0.01)in contents of proximal jejunum,by 26.29%(P＜0.01)and 28.29%(P＜0.01)in contents of proximal jejunum, by 36.48%(P＜0.01)and 31.67%(P＜0.01)in contents of ileum at 45 days of age.(3)The diets supplemented with CS had significant effect on the serum hormone levels of pigletsCompared with Groupâ… ,the serum SS levels of piglets in Groupâ…¡and Groupâ…¢decreased respectively by 20.37%(P＜0.05)and 23.05%(P＜0.05),but the GH levels increased respectively by 62.89%(P＜0.05)and 61.01%(P＜0.05)at D32.Compared with Groupâ… ,the serum SS levels of piglets in Groupâ…¡and Groupâ…¢decreased respectively by 24.64(P＜0.01)and 17.78%(P＜0.05)at D45.But the GH levels increased respectively by 49.30%(P＜0.01)and 46.86%(P＜0.01),the T3 levels increased respectively by 35.87%(P＜0.01)and 21.74%(P＜0.05),the T4 levels increased respectively by 27.99%(P＜0.05)and 12.04%(P＜0.05),the IGF-â… levels increased respectively by 53.10%(P＜0.05)and 57.10%(P＜0.05).(4)The diets supplemented with CS had significant effect on the expression of GH receptor in the liver of piglets.There were no distinctions on the expression of GHR mRNA in the heart(P＞0.05) among there groups of piglets at D45.Compared with Groupâ… ,the expression of GHR mRNA in the liver of piglets from Groupâ…¡and Groupâ…¢increased significantly by 35.98%(P＜0.05)and 41.70%(P＜0.05),respectively.There were no distinctions between Groupâ…¡and Groupâ…¢(P＞0.05).The experiments showed that feeding the diets supplemented with CS could deplete SS,increase the digestive enzyme activities in alvine contents,enhance the levels of serum GH,T₃,T₄ and IGF-â… ,increase the expression of GHR mRNA in the liver,improve the growth performance of piglets,prevent effectively weanling stress syndrome.