| Different type NMDA were used to study the effect of NMDA ordinary NMDA(O-NMDA), adsorbed NMDA(A-NMDA) and nano NMDA(N-NMDA)on growth performance, carcass characteristics, incretion and approach to mechanism of NMDA affect growth by determining dynamic secretion model of growth hormone(GH) and somatostatin(SS) , as well as its influence to GH mRNA abundance in pituitary gland and growth hormone releasing hormone(GHRH) mRNA abundance in hypothalamus. GH secretion and cell messages were also investigated in vitro by pituitary and hypothalamus cell cultivation. 300 finishing pigs (DurocxLandracexYorkshire) which weighed about 52.5kg were selected in feeding experiment. Pigs were allotted to ten groups by weight and sex, each of which included 3 replicates of ten pigs. The group received the same corn- soybean based diet, supplemented with 0 (control group) and 50, 100 and 150 mg/kg of each type NMDA. All pigs were given adequate diets (four times per day) and free access to water. Before finishing the feeding experiment, six pigs were chose from control and best growth group respectively and blood sample of each pig was collected to study dynamic secretion model of growth hormone (GH) and somatostatin (SS). On finishing the feeding trial, 12 pigs were picked out by similar body weight from control group and best growth group in each type NMDA treatment respectively to be slaughtered at the local abattoir to determine carcass characteristics. The skeletal muscle (Longissimus dorsi, Semi-membranosus, Semitendinosus, Quadriceps femoris and Biceps femoris ) were separated from the carcass of the pigs to investigate the response of different muscles to NMDA. The sample of liver, hypothalamus, pituitary gland and serum werecollected for laboratory analysis. In vitro trial. 10-8, 10-6 and 10-4 mol/L NMDA were set as concentration grads in cell culture and each concentration includes 6 replicates. The main results are as follows.1. The results of feeding trial showed that all types NMDA improved average daily gain(ADG) of pigs, but only ADG in 100 mg/kg N-NMDA group increased significantly compared with control group (p<0.05). 100 and 150 mg/kg NMDA improved feed gain ratio obviously (p<0.05). There were no difference in feed intake between all the treatments (p>0.05).2. Carcass composition was apparently changed by adding NMDA. lOOmg/kg N-NMDA group showed significant results, percentage of dissected lean of carcass (PDL) was increased by 5.81%(p<0.05); percentage of dissected fat (PDF) was decreased by 18.93% (p<0.05), and longissiums dorsi muscle area was increased by 8.78% (p<0.01). Backfat depth analysis showed O-NMDA and N-NMDA decreased scapular site backfat depth, A-NMDA and N-NMDA decreased which of the last rib site. The results also showed N-NMDA increased longissimus dorsi and Biceps femoris weight by 26.20% (P<0.05) 21.39% (P<0.05 ) respectively, and A-NMDA enhanced semitendinosus weight significantly by 17.50% (P<0.05) compared with the control.3. Study of dynamic secretion model of GH and SS indicated that NMDA increased whole level, basal line and peak intensity of GH secretion significantly by 41.01%(P<0.05), 44.70% (P<0.05) and 29.44%(P<0.05)respectively, and the similar effect were showed in gilts and barrows. There were no obvious effects on GH peak frequency and peak lasting time. NMDA also have no effect on SS secretion in present experiment.4. Assay of serum sample indicated that N-NMDA enhanced IGF-I concentration by 21.91%(P<0.05), A-NMDA and N-NMDA increased T3 by 51.79% (P<0.05) and 60.71% (P<0.05), and improved T4 by 200.75% (P<0.05) and236.48% (P<0.05) respectively. Adding NMDA has no obvious effect on insulin concentration.5. A-NMDA and N-NMDA decreased cAMP level in hypothalamus by 10.12% and 12.73% (P<0.01). N-NMDA also increased NOS activity significantly. A-NMDAand N-NMDA enhanced cAMP level in pituitary by 23.56% and 52.67% (P<0.05) . cAMP in liver was increased 7.75% (P<0.05) by N-NMDA added compared with control group. Furthermore,...
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