| Growth and development of animals were regulated by many factors including gene, environment,nutrition and endocrine.In endocrine system,growth hormone(GH) always taks up a centerlly regulative place.Previous studies have shown that patients with gigantism or dwarfism have abnormal high or low plasma GH levels,respectively,and animals treated with exogenous GH markedly improved its growth.Therefore,it is reasonable to enhance the levels of GH in plasma by some techniques will result in improvement of animal production performance.A series of studies indicated that the pituitary release of GH was regulated by two hypothalamically derived neurohormones GHRF ,which stimulated secretion of GH, and somatostatin(SS),which inhibated pituitary secretion of GH.So theoretically,!! is inferred that immunoneutralization of SS would increase secretion of GH ,and finally get the goal of improvement performance.The objective of this study is to evaluate the effects of active immunization against SS on nutrient digestion and metabolism,growth and carcass composition of the growing Hu-sheep;2,on the SS secretion in fundus, antrum and pancreas and the ablity of the antibodies to integrate free SS;3,on passage rates of digesta;4,on activities of digestive enzymes in pancreas and digesta;4,on gene expression of GH in pituitary.Twelve male Hu-sheep,aged six-month,were randomly assigned to one of two treatment groups,!.e.control group,and immunized group.The animals in the immunized or control groups were immunized with human a globin-conjugated SS or conjugated a globin alone,respectively. Whole immunization period went on 7 weeks,for that time primary and boosted immunization were carried out at 0, 2, 4, 7 week, respectively.The results shown that antibodies titer of immunized animals were 0.54 and 0.61(OD)at 4, 7 week, respectively,and control animals had no production of specific antibodies. High levels antibodies in plasma of immunized animals draw on large numbers of free SS, and its titer or integrated free SS concentration were 0.48-0.72 or 2.4-11.3nmol/l, respectively. Active immunization against SS did not alter pattern of GH secretion(over mean, basline mean, peak frequency, peak amplitude) and mRNA abundant of GH secration. Compared to control, retention times of digesta in whole alimentary tract of immunized animals increased by 20 hours(to use cumlative excretion of 5%marker as reference). Immunoneutralization of SS significantly augmented activities of digestive enzymes(proteolytic ,trypsin,chymotrypsin, amylase) in pancreas and the small intestine(control and immunized animals were 1693.67unit/g,CP, 2728.33 unit/g,CP, 3055.50 unit/g,CP, 12.9X106 unit/g,CP; 2.57X102unit/g,CP, 1.20X103unit/g,CP, 1.12X 103unit/g,CP, 2.98X 107unit/g,CP ft 2451.33 unit/g,CP, 2904.17 unit/g,CP, 4279.33 unit/g,CP, 20.61 X 106 unit/g,CP; 6.45 X 102unit/g, CP, 2.53 X 103unit/g,CP, 1-83 X 103unit/g,CP, 5.77 X 107unit/g,CP, respectively, P<0.05 or P<0.01).The enhancement of digestive enzyme activeies and retention times of digesta resulted in a significant improvement of apparent digestibilities of DM, OM, CP, CF, ADF, NDF, which were obviously enhanced from 61.28%, 64.11%, 69.11%, 62.55%, 63.87% ft 60.12%to 64.51%, 66.28%, 72.31%, 64.66%, 65.23%, 62.98%, respectively( P<0.05).Active immunization against SS significantly increased IGF-I level,but had no effect on GH,insulin,,glucagon,T4,T3,TSH, gastrin concentrations in plasma,at the same time, the content of plasma urea for immunized animals clearly decreased.As the time of immunization time went on, total protein level in plasma gradually increased,and albuman level gradually decreased. This indicated that a part of plasma protein were used for synthesis of IgG.Immunoneutralization of SS had also no influence on creatinine, NEFA, Tg, Glu, Ch, GPT and GOT activities, which indicated that in immunized animals compared to control animals, the fat metabolism and protein catalism had no change.As a result.immunized animals had high growth rate and feed conversion effic...
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