This experiment was conducted to study the effects of dietary tryptophan level on growth performance, nitrogen metabolism, serum biochemical indices and fur quality of growing Rex rabbits. Two hundred weaner Rex rabbits were randomly assigned to 5 groups with 40 replicates in each group and each replicate contained 1 rabbit. Rabbits in the 5 groups were fed experimental diets with the measured levels of 0.086%, 0.135%, 0.176%, 0.218% and 0.268% tryptophan, respectively. The trial lasted for 7 days for adaptation and 53 days for test. The results showed as follows: under the condition of no significant difference in initial body weight (P>0.05), dietary tryptophan level did not significantly affect the average daily feed intake (ADFI), average daily gain (ADG) and feed/gain (F/G) (P>0.05), but the group with the diet containing 0.176% tryptophan had the lowest F/G. Dietary tryptophan level had significant effects on fecal nitrogen (P=0.000 6), nitrogen apparent digestibility (P=0.002 0), nitrogen intake (P=0.032 0) and biological value of nitrogen (P=0. 014 8), but had no significant effects on urine nitrogen, digestible nitrogen, retention nitrogen and nitrogen retention rate (P>0.05). The biological value of nitrogen in the group with the diet containing 0.218% tryptophan had the highest value, and was significantly higher than that in the groups with the diets containing 0.086% and 0.286% tryptophan (P<0.05). Dietary tryptophan level had significant effects on the contents of serum urea nitrogen (P=0.000 5), cholesterol (P=0.040 6) and triglycerides (P=0.045 7), but had no significant effect on serum alanine aminotransferase activity (P>0.05). Dietary tryptophan level had no significant effect on fur area, but had a significant effect on fur weight (P=0.010 8), and that in the groups with the diets containing 0.176% and 0.218% tryptophan was significantly higher than that in the groups with the diets containing 0.086% and 0.135% tryptophan (P<0.05). Dietary tryptophan level had no significant effect on fibroblast growth factor 5 (FGF5) mRNA expression level, but the group with the diet containing 0.218% tryptophan had the highest FGF5 mRNA expression level. Considering all indices of this experiment, the appropriate tryptophan levels in the diet of growing Rex rabbits are 0.176% to 0.218%.
YIN Qingqing
,
LI Fuchang
,
WANG Xuepeng
,
WANG Chunyang
,
LI Bing
. Effects of Dietary Tryptophan Level on Growth Performance, Nitrogen Metabolism, Serum Biochemical Indices and Fur Quality of Growing Rex Rabbits[J]. Chinese Journal of Animal Nutrition, 2013
, 25(5)
: 1010
-1016
.
DOI: 10.3969/j.issn.1006-267x.2013.05.016
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