Effects of Dietary Lysine on Growth Performance,Serum Concentrations of Insulin-Like Growth Factor-I （IGF-I） and IGF-I mRNA Expression in Growing Rabbits

The effects of dietary lysine on production performance,serum concentrations of metabolites,growth hormone （GH）,insulin-like growth factor-I （IGF-I） and IGF-I mRNA expression in growing rabbits were examined.One hundred weaned New Zealand rabbits were allocated to individual cages and randomly offered a diet containing 5.5 （L1）,6.5 （L2）,7.5 （L3）,8.5 （L4）,or 9.5 g （L5） lysine per kg diet.The results showed that the average daily gain （ADG） of the rabbits from L3,L4 or L5 was higher than those from L1 or L2 （P 〈 0.05）.The feed gain ratio （F/G） in the rabbits from L4 or L5 was lower than those from L1 or L2 （P 〈 0.05）.Dietary lysine did not affect serum concentrations of total protein （TP）,glucose,insulin （INS）,and growth hormone （GH） （P 〉 0.05）.The quadratic effects of lysine on the serum urea nitrogen （SUN） concentration was detected （P = 0.035）.Serum IGF-I concentrations had a trend to increase quadratically with the increasing dietary lysine （P = 0.07）.A significant correlation was found between serum IGF-I concentrations （x,ng mL-1） and ADG （y,g kg-1）： y = -0.017x2 ＋ 1.984x ＋ 20.87 （R2 = 0.8982,P = 0.003）.The relative abundance of hepatic and muscular IGF-I mRNA tended to increase with increasing dietary lysine levels （P = 0.053 and 0.082,respectively）.Providing the diets mainly consisted of corn,wheat bran and peanut vine,the most appropriate dietary lysine level for growing meat rabbits from weaning to 70 d old was found to be 8.5 g kg-1,and IGF-I may be an important factor controlling growth of weaned rabbits.

Effects of Dietary Lysine on Growth Performance, Serum Concentrations of Insulin-Like Growth Factor-I (IGF-I) and IGF-I mRNA Expression in Growing Rabbits

The effects of dietary lysine on production performance, serum concentrations of metabolites, growth hormone (GH),insulin-like growth factor-I (IGF-I) and IGF-I mRNA expression in growing rabbits were examined. One hundred weaned New Zealand rabbits were allocated to individual cages and randomly offered a diet containing 5.5 (L1), 6.5 (L2), 7.5 (L3),8.5 (L4), or 9.5 g (L5) lysine per kg diet. The results showed that the average daily gain (ADG) of the rabbits from L3, L4 or L5 was higher than those from L1 or L2 (P<0.05). The feed gain ratio (F/G) in the rabbits from L4 or L5 was lower than those from L1 or L2 (P< 0.05). Dietary lysine did not affect serum concentrations of total protein (TP), glucose, insulin (INS), and growth hormone (GH) (P>0.05). The quadratic effects of lysine on the serum urea nitrogen (SUN) concentration was detected (P=0.035). Serum IGF-I concentrations had a trend to increase quadratically with the increasing dietary lysine (P=0.07). A significant correlation was found between serum IGF-I concentrations (x, ng mL-1) and ADG (y, g kg-1:y=-O.Ol7x2+ 1.984x+20.87 (R2=0.8982, P=0.O03). The relative abundance of hepatic and muscular IGF-I mRNA tended to increase with increasing dietary lysine levels (P=0.053 and 0.082, respectively). Providing the diets mainly consisted of corn, wheat bran and peanut vine, the most appropriate dietary lysine level for growing meat rabbits from weaning to 70 d old was found to be 8.5 g kg-1, and IGF-I may be an important factor controlling growth of weaned rabbits.