Effects Of Rumen-protected Cysteine And Methionine On Growth Performance,Nutrient Digestion,Blood Indices And Cashmere Production Performance Of Liaoning Cashmere Goats

In this paper,two experiments were conducted to systematically study the effects of rumen protected cysteine(RPCys)and rumen protected methionine(RPMet)supplementation on the growth performance,nutrients digestion,blood indexes and cashmere production performance in Liaoning Cashmere goats.Test 1:The saliva disappearance rate,rumen disappearance rate and small intestinal digestibility of RPCys and RPMet were measured by artificial saliva method,nylon bag method and in vitro method.The results showed that the degradation rates of RPCys and RPMet in artificial saliva were lower than 10% at 2 h and 12% at 4 h.The degradation rates at4 h and 12 h in rumen were lower than 22% and 32%,respectively.The degradation rate was higher than 80% in 2 h in the simulated small intestine in vitro.The data demonstrated that the RPCys and RPMet products had well stability and digestibility.Test 2:Using a 2×2 factor design was adopted,the RPCys supplemental level was 0g/d and 1.5g/d,and the RPMet level was 0g/d and 2.0g/d.Twenty-four female lambs with average body weight of 19.91±0.44 kg were randomly divided into 4 groups and fed 4 experimental diets,the four experimental groups were named NC,Cys,Met and Cys-Met groups.The experiment lasted for 12 weeks,during which the feeding and management conditions remained the same.The results showed:(1)Growth performance: RPCys and RPMet supplementation alone or simultaneously increased the daily gain and body height and decreased the ratio of feed to gain of Liaoning cashmere goats(P < 0.05),the Met group had the best effect,but had no significant effects on end body weight,daily dry matter intake and other body size indexes(P > 0.05).(2)Nutrient digestion: When RPMet was only supplemented in daily diet,the ratio of fecal nitrogen to dietary nitrogen was significantly decreased and the apparent digestibility of nitrogen was increased(P < 0.05).Dietary supplementation of RPCys and RPMet alone or simultaneously increased the digestibility of neutral detergent fiber and acid detergent fiber(P < 0.05).(3)Blood indexes: RPCys increased the content of free Cys in plasma(P < 0.05),RPMet increased the content of Cys and Met in plasma(P < 0.05).Dietary supplementation of RPCys and RPMet alone or simultaneously significantly increased the contents of essential amino acids such as leucine and lysine and non-essential amino acids such as glutamic acid and glycine(P < 0.05),and significantly increased the contents of total amino acids,sulfur amino acids and branch chain amino acids(P < 0.05).Dietary supplementation of RPCys and RPMet alone or simultaneously significantly increased the average concentrations of total protein,albumin and globulin in plasma during the whole trial period(P < 0.05),but significantly decreased the concentration of urea nitrogen(P < 0.05).RPCys significantly decreased the plasma thyroxine concentration on day 10 of the trial period and increased the mean plasma concentration of growth hormone during the whole trial period(P < 0.05).(4)Cashmere production performance: Dietary supplementation of RPCys and RPMet alone or simultaneously significantly increased the activity of secondary hair follicles(P < 0.01),and had a trend of increasing cashmere fibre length,but had no significant effects on cashmere fibre diameter,local cashmere yield and final cashmere yield(P > 0.05).Supplementation of RPCys alone in diet increased the width of secondary hair follicles(P = 0.047).(5)Skin gene expression level: Diets supplemented with RPCys and RPMet alone or simultaneously had significant effects on the m RNA expression of TCF4,c-Myc,Cyclin D1 and KAP 1 genes in Liaoning cashmere goat skin(P < 0.05).The m RNA expression levels of TCF4,c-Myc and Cyclin D1 genes were the highest in the Cys-Met group,and the m RNA expression levels of the KAP 1 gene in the Cys group were the highest.Based on the above results,RPMet supplementation promoted nitrogen utilization and improved the growth performance of cashmere goats.Dietary RPCys increased skin hair follicle activity and m RNA expression of KAP 1 gene,and improved cashmere production performance of cashmere goats.