Effects Of Dietary Tryptophan On Production Performance, Digestion Metabolism And Blood Indices Of Growing Rex Rabbits

The experiment was conducted to study the effects of dietary tryptophan on growthperformance, nitrogen metabolism, serum biochemical indices and fur quality of weaner to5-month-old growing Rex Rabbits. Two hundred weaned Rex Rabbits were randomlyassigned to5groups with40replicates in each group and each replicate contained1rabbit.Rabbits in5groups were fed with experimental diet with the following tryptophan levels:0.086%,0.135%,0.176%,0.218%and0.268%. The trial lasted for7days for adaptation and53days for test. The results showed that:Weaner to3-month-old growing Rex Rabbit: Dietary tryptophan levels did not affectedsignificantly on average daily intake (ADI), average daily gain (ADG) and feed/gain (F/G)(P>0.05). Dietary tryptophan levels had significant influence on fecal nitrogen (FN)(P=0.0006), DN/IN (P=0.0020), intake nitrogen (IN)(P=0.0320) and nitrogen biologicalutilization (RN/DN)(P=0.0148), but had no significantly influence on urine nitrogen (UN),digestible nitrogen (DN), retention nitrogen (RN) and RN/IN (P>0.05). Dietary tryptophanlevels had significant influence on the digestibility of lysine, methionine, arginine, threonineand tryptophan（P<0.01）. Dietary tryptophan levels had significant influence on serum ureanitrogen (SUN)(P=0.0005), cholesterol (CHO)(P=0.0406) and triglycerides (TG)(P=0.0457), but had no significantly influence on alanine aminotransferase (ALT)(P>0.05).Dietary tryptophan levels had no significant influence on GH, IGF-1, INS and NLT (P>0.05),but it has a increasing trend decreases after first. under the condition of no significantdifference in fur area, dietary tryptophan levels had significant influence on fur weight(P=0.0108). Dietary tryptophan levels did not affected significantly on the expression ofGHR-mRNA and FGF5-mRNA. In conclusion, the appropriate tryptophan concentration inthe diet of weaner to3-month-old growing Rex Rabbit was0.176%~0.218%.3to5-month-old growing Rex Rabbit: Dietary tryptophan levels did not affectedsignificantly on average daily intake (ADI), average daily gain (ADG) and feed/gain (F/G) (P>0.05). Dietary tryptophan levels had significant influence on intake nitrogen (IN)(P<0.01), and it had significant on digestible nitrogen (DN)（P=0.0271）, but had nosignificantly influence on nitrogen biological utilization (RN/DN), fecal nitrogen (FN),DN/IN, urine nitrogen (UN), retention nitrogen (RN) and RN/IN (P>0.05). Dietarytryptophan levels had significant influence on the digestibility of alanine （P=0.0035）,phenylalanine（P=0.0074）, valine, proline and tryptophan（P<0.01）, dietary tryptophan levelshad influence on the digestibility of methionine （P=0.0109）and arginine （P=0.0311）, buthad no significantly influence on the digestibility of other amino acids. Dietary tryptophanlevels had significant influence on serum urea nitrogen (SUN)(P=0.0299), but had nosignificantly influence on alanine aminotransferase (ALT), cholesterol (CHO) andtriglycerides (TG)(P>0.05). Dietary tryptophan levels had no significant influence on GH,IGF-1, INS and NLT (P>0.05), but it has a increasing trend decreases after first. under thecondition of no significant difference in fur weight, dietary tryptophan levels had significantinfluence on fur area (P<0.01), but had no significant influence on the thickness of fur and thelength of hair. Dietary tryptophan levels did not affected significantly on the expression ofFGF5-mRNA, but had significant influence on the expression of GHR-mRNA. In conclusion,the appropriate tryptophan concentration in the diet of3to5-month-old growing Rex Rabbitwas0.135%~0.176%.