Effects of a synthetic growth hormone-releasing peptide on growth and carcass traits of pigs

The current study was to determine the effects of growth hormone-releasing peptide ([His 1 , Lys 6 ]-GHRP) on growth performance and carcass traits in pigs, and to determine whether the results were comparable to those of recombinant porcine growth hormone (r-PGH) treatment. Thirty Landrace and Yorkshire pigs (40-45 kg) were randomly divided into three groups, each group consisted of two boars, five gilts and three barrows. Peptides were administered daily by intramuscular injection with the following schemes and dosages: Group A ([His 1 , Lys 6 ]-GHRP, 200 μg/day in 0.5 ml saline), Group B (r-PGH, 3 mg/day in 0.6 ml saline), and Group C (sterilized physiological saline, 0.5 ml/day). [His', Lys 6 ]-GHRP caused significant improvements both in pig growth and carcass traits. The average daily gain (ADG) and feed efficiency of the [His 1 , Lys 6 ]-GHRP treated group were higher than those of the control, but less than with the r-PGH treatment. The net increase in the ADG by [His', Lys 6 ]-GHRP was c. 14%, and was 23 % by r-PGH (both P < 0.01). The feed efficiency was improved 17 % by [His 1 , Lys 6 ]-GHRP (P < 0.01) and 20 % by r-PGH (P < 0.01). On the other hand, the back-fat thickness in both [His 1 , Lys 6 ]-GHRP and r-PGH treated groups (1.76±0.041 cm and 1.72±0.040 cm, respectively) was considerably less (P < 0.05) than that of the control group (1.81±0.040 cm). In addition, the lean cuts percentage and the rib longissimus muscle area were comparable in the [His 1 , Lys 6 ]-GHRP and r-PGH treatments (lean cuts percentage: 57±2.0% and 57±1.5%, respectively; rib longissimus muscle area: 32.8±0.91 cm 2 and 32.9±1.10 cm 2 , respectively), and both were significantly (P < 0.05) greater than those of the control group (lean cuts percentage: 53±1.5%; rib longissimus muscle area: 28.3±1.61 cm 2 ). In conclusion, [His 1 , Lys 6 ]-GHRP appeared to be a promising tool for controlling carcass fat in pigs.