Effects Of Dietary Protein And Methinion Levels On Production Performance, Fur And Skin Development Of Minks

The paper studied on the protein and methionine (Met) level of minks'diet, and worked on the performance, hair follicle development of the mink and some important growth factors which had special functions in skin and hair follicle growth. From nutrition, microstructure morphological and molecular aspects, respectively, to study how the protein and Met affected the fur characters of mink.Main contents were as follows:1. 128 healthy male minks were selected and randomly divided into eight groups with different types of diet, average body weight was similar in all groups. The first five groups dietary protein level were 36%, 32%, 28%, 24% and 20%, the last three groups were supplemented with Met (0.3%, 0.6% and 0.9% DM) in 28% diet, the experiment lasted for 60 days. The results showed that: minks in 28% protein level diet with 0.6% Met group obtained the best body weight, average daily gain, F/G and the daily retention of nitrogen.Conclusion: the digestible protein level of growing minks'diet was 24.0%, the ME of diet was 20.73MJ/kg and the level of Met in diet was 1.39%, sulphur containing amino acids in diet was 2.70%, minks obtained the best performance.2. Based on the growing period experiment, each group left 14 healthy minks, total was 112, and average body weight was similar in all groups. The first five groups dietary protein level were 32%, 28%, 24%, 20% and 16%, the last three groups were supplemented with Met (0.4%, 0.8% and 1.2% DM) in 24% diet, the experiment lasted for 85 days. The results showed that: minks in 24%+0.8% Met group obtained the maximized body weight, daily retention of nitrogen and dry fur length.Conclusion: the digestible protein level of diet was 19.7%, the ME of diet was 21.66MJ/kg, the level of Met in diet was 1.54%, and sulphur containing amino acids in diet was 2.82%, minks obtained the best performance.3. We studied on the mink's skin from groups 32%, 24%, 16% and 24%+0.8 Met by paraffin slice. The result showed that: mink's hair follicles mostly have three primary hair follicles, and they arranged regularly in the same side of the secondary hair follicles. Secondary hair follicles and primary hair follicles average ratio (S/P) was 20~22:1 in the pelting period of minks. Being dyed with Sacpic method, the inner root sheath was dyed red if it was an activated hair follicle. High protein level and optimal Met level diets promoted the hair follicles to the downward period of activity cycle simultaneously.Conclusion: Sacpic dyeing method was suitable for mink's skin dyeing; the activity of primary hair follicles and secondary hair follicles were not synchronizated in hair follicles activity cycle; dietary protein and Met levels affected the hair follicles development.4. We studied on the growth factor gene expressions, which were relevant mink's skin and fur growth from groups 32%, 24%, 16% and 24%+0.8 Met. We used real-time PCR technology to study the gene expression quantity of IGF-â… , IGF-â… R and EGF mRNA in mink's skin. The result showed that each gene mRNA expression quantity decreased with the declining dietary protein levels, the expressions of each gene mRNA improved when the low-protein diet was supplemented with Met. The quantity of IGF-â… and IGF-â… R mRNA expressions significantly correlative with the length of the guard hair, under hair and S/P of the minks. EGF gene expression was correlative with the IGF-â… R mRNA expressions.Conclusion: High dietary protein level and optimal Met level diets improved the quantity of IGF-â… and IGF-â… R mRNA expressions. The quantity of IGF-â… and IGF-â… R mRNA expressions were significantly correlative with some skin and fur performance characters of the minks. 5. We studied on the position of IGF-â… , IGF-â… R and EGF in mink's skin by frozen section and immunohistochemical method. The result showed that: IGF-â… , IGF-â… R and EGF mainly distributed in the cell cytoplasm of skin epidermis cells and out root sheath cells.Conclusion: dietary protein and Met influenced the IGF-â… , IGF-â… R and EGF mRNA expressions, these genes played a role in skin epidermis cells and out root sheath cells in mink's skin and then affected the skin growth, hair follicles and fur characteristics of minks.