Influence Of GHRP-2 On Growth Performance And Protein Utilization In Difference Genoeotype Growing Pigs

GH-releasing peptide-2(GHRP-2) can release the endogenous GH in all species of animals ,but there are a few studies about the effect of GHRP-2 on animal growth. For the pigs,there are a few studies about the effect of GHRP-2 on the growth performance in finishing lean pigs and no studies on the different geneotypes pigs during growth period. This experiment was designed to investigate the effect of GHRP-2 on the growth performance and protein utilization efficiency in different geneotypes of growing pigs(Yanan and DLY) to understand the role of GHRP-2 and to supply the basic data for the application of GHRP-2 in practice.10 Yanan growing pigs at 22.06±2.70kg and 10 DLY at 26.55±1.36kg of mean body weight were respectively allocated into control and treatment group randomly. The corn-soybean-meal diet forYanan or DLY was formulated to contain CP15.5% or 16.5% and DE13.4MJ/kg or 14.1 MJ/kg. Pigs of control group and treatment group were injected with GHRP-2 intramuscularly at the dose of 0 and 30ug/kgBW/d respectively for 15 days, and received no injection for the following 15 days to study the growth performance of all the pigs in the period of injection and post injection. N banlace experiment was conducted from day 6 to day 10 in the injection period to study the protein utilization efficiency ,the whole-body protein turnover of DLY was estimated from the excretion of ¹⁵N in 48 hours' urine after a single oral dose of [¹⁵N]-glycine on day 7 in the injection period. At 10:00, 15:00, 20:00 on day 15, blood sample was collected to detect the level of GH ,total protein and urea nitrogen in the serum. Results indicate that:1. For the Yanan pigs,in treatment days, there was no significant difference of the growth performance between treatment and control pigs,but performance was numerically higher in treatment group than in control group, average daily gain was increased by 4.76%(p>0.05)> 12.5% (p>0.05) and 5.45% (p>0.05) respectively during the period from day 1 to day 5,day 1 to day 10 ,and day 1 to day 15 for the treatment group. After stopping injection,compared with the control pigs,the average daily feed intake of treatment pigs was increased by 27.7% (P<0.01), 12.6% (p>0.05) and 8.6% (/?>0.05) respectively during post-injection period from day 1 to day 5,day 1 to day 10 ,and day 1 to day 15,average daily gain of treatment pigs was increased by 25.4% (PO.05) , 15.2% (p>0.05) and 16.4%(/?>0.05) from day 1 to day 5,day 1 to day 10 ,and day 1 to day 15 in the period of the stopping treatment days , F/G in treatment pigs nearly had no difference with control pigs during the post-injection period. From the N palance experiment in the period of day 6 to day 10 and serum indexes in day 15,the digestible N of treatment group was increased by 4.17% (p>0.05 ), the protein efficiency ratio(PER)was increased by 14.78% (p>0.05 ), the serum total protein was increased by 4.81% (p>0.05) and the urea nitrogen was decreased by 6.4% (p>0.05 ) in treatment groups. There had no differences between the two groups of the other protein utilization efficiency indexes.Compared with the control pigs, the serum GH level at 10:00,15;00 , 20:00 and the average value on day 15 of treatment days of treatment group was increased by 9.59% (p>0.05) , 17.89% (p>0.05), 6.41%(/?>0.05) and 12.20% (/?0.05) respectively.2.For the DLY pigs, in treatment days, compared with the control pigs, the average daily feed intake, daily gain and the feed utilization efficiency in the treatment pigs were decreased numerically,but there was no significant difference between the two groups. After stopping treatment, compared with the control pigs,the average daily feed intake of treatment pigs did not change, the daily gain of treatment pigs was increased by 16.9%(/?>0.05) and 10.2% (p>0.05) respectively during post-injection period from day 1 to day 5 and day 1 to day 10, F/G of treatment pigs was decreased by 13.7% (p>0.05) and 8.8%(P<0.01) respectively during post-injection period from day 1 to day 5 and day 1 to day 10. F/G and daily gain of the treatment pigs were a little improvement in the whole post-injection period. From the N palance experiment in the period of day 6 to day 10 andthe protein turnover experiment in the period from day 7 to day 8,the protein protein utilization efficiency and the whole-body protein turnover metabolic efficiency of the treatment pigs were decreased numerically, on the day 15 of the experiment, the serum total protein of treatment groups was increased and the urea nitrogen of treatment groups was decreased numerically. Compared with the control pigs, the serum GH level at 10:00,15;00 and 20:00 and the average value on day 15 of treatment group was increased by 31.8% (P>0.05), 12.3% (P>0.05), 39.7% (P>0.05) and 26.4%(P<0.05) respectively.In conclusion, intramuscular injection of GHRP-2 at the dose of 30ug/kgBW/d has no significant effects on the growth performance and protein utilization efficiency in Yanan and DLY growing pigs, but there has the tendency that GHRP-2 can increase the growth performance and protein utilization efficiency in Yanan growing pigs. Pigs injected with GHRP-2 tend to grow faster during post-injection period for the two geneotypes of pigs and the tendency was more significant for Yanan pigs than DLY.