Effect of dietary methionine on growth performance and insulin-like growth factor-I mRNA expression of growing meat rabbits

Abstract

An experiment was conducted to determine the effects of different amounts of dietary methionine on growth performance, serum protein, growth hormone (GH), insulin-like growth factor-I (IGF-I) concentrations and IGF-I mRNA expression of growing meat rabbits. One hundred weaned growing meat rabbits were allocated to individual cages and randomly divided into five groups. The methionine addition concentrations of the five groups were 0, 2, 4, 6 and 8 g/kg diet (as-fed basis) and sulphur amino acids (SAA) concentrations ranging from 3.8 to 11.6 g/kg diet, respectively. The results obtained were as follows: the average daily gain of 2, 4 and 6 g/kg diet groups was higher than that of 0 g/kg diet group (p < 0.01). The feed gain ratio of the 4 g/kg diet group was lower than those of 0 and 8 g/kg diet group (p < 0.01). Methionine concentrations did not affect serum urea nitrogen, total protein, insulin and IGF-I concentration (p > 0.05). The quadratic effects of methionine on the serum concentration of albumin (Alb) and GH were obtained (p = 0.013, p = 0.018). The quadratic effect of methionine amount on IGF-I mRNA expression was obtained (p = 0.045). The serum concentration of Alb of the 4 g/kg diet group was higher than those of 0 and 8 g/kg diet group (p < 0.01). The serum concentration of GH of 8 g/kg diet group was higher than that of the 0 g/kg diet group (p < 0.05). The liver IGF-I mRNA expression of 4 g/kg diet group was higher than those of the 0 and 8 g/kg diet group (p < 0.05). Providing a diet mainly consisted of corn, wheat bran and peanut vine, the optimum dietary methionine addition concentration and SAA concentration for a weaner to 2-month-old growing meat rabbits were shown to be 2 and 5.7 g/kg diet respectively.

dl-Methionine supplementation in a low-fishmeal diet affects the TOR/S6K pathway by stimulating ASCT2 amino acid transporter and insulin-like growth factor-I in the dorsal muscle of juvenile cobia (Rachycentron canadum)

“…Some studies have demonstrated that dietary AA influence serum or plasma INS, GH and IGF-I concentrations in fish (26,54) . In the present study, there was no significant influence between dietary Met and serum INS, which is consistent with other studies (53,55) . However, the concentration of serum GLU was significantly influenced by dietary Met level, and a lower serum GLU concentration was found in fish fed Met-deficient diets, which is similar to that previously reported in cobia (35) and orange-spotted grouper (49) .…”

“…In this experiment, a deficiency or excess of dietary Met decreased the concentration of serum IGF-I. This is similar to that previously reported by Zhang et al (55) , suggesting that lower serum IGF-I due to a sub-optimal Met level may suppress the transcription of IGF-I. Katsumata et al (60) reported that the potential mechanisms underlying reductions in plasma IGF-I due to an imbalance of limiting AA are (1) the suppression of post-transcriptional events in IGF-I expression and (2) differences in IGF-I clearance from plasma other than suppression of IGF-I mRNA expression.…”

“…Moreover, fish fed a Met-deficient diet showed the lowest GH concentration, which corresponds with their lower growth performance. These results are in agreement with studies on the growth of farmed rabbits (55) and goats (57) , but contrast with a study on rainbow trout (58) where the plasma GH levels were not affected by Met supplementation. The different results obtained by the present study may due to the diet formulations used, which were formulated under low fishmeal conditions and had seven-set Met levels.…”

“…Katsumata et al (60) reported that the potential mechanisms underlying reductions in plasma IGF-I due to an imbalance of limiting AA are (1) the suppression of post-transcriptional events in IGF-I expression and (2) differences in IGF-I clearance from plasma other than suppression of IGF-I mRNA expression. In addition, circulating concentrations of IGF-I have been demonstrated to be positively correlated with SGR (r 0•573, P<0•01), which is consistent with Zhang et al (55) . Thus, the decrease in serum IGF-I levels observed in the present study probably implies a reduction in fish growth.…”

Effect of methionine supplementation on the growth performance of rabbit

“…This result agrees with Al-Homidan (2001) who reported that daily live weight gain increased significantly with supplementation of methionine (0.2%) in the diet. Zhang and Li (2010) showed that 0.2%, 0.4% and 0.6% methionine in the diet resulted higher average daily gain than that of 0% methionine diet group (p < 0.01).…”