共查询到20条相似文献，搜索用时 265 毫秒
1.
半胱胺对香猪胃液分泌、血液胃泌素和生长抑素水平的影响 总被引：23，自引：2，他引：21
在制备长久性隔离小胃和颈静脉导管的５头雄性香猪实验表明,由大胃瘘管灌注半胱胺（８０ｍｇ／ｋｇ体重）后,一周内小胃胃液分泌量较对照期大幅度增加（Ｐ＜０．０５）,胃泌素水平明显升高（Ｐ＜０．０１）;血液生长抑素水平降低（Ｐ＜０．０１）。提示半胱胺耗竭生长抑素,使胃泌素水平升高,从而促进了胃液的分泌。 相似文献
2.
家牦牛,半血野牦牛年产毛量的比较 总被引：1，自引：1，他引：0
对１７６头各龄家牦牛和半血野牦牛的年产毛量进行了测定。测定结果：家牦牛１岁０．９８±０．２９ｋｇ／头，２岁１．１２±０．２２ｋｇ／头，３一５岁１．１８±０．３８ｋｇ／头，６岁以上０．８８±０．２７ｋｇ／头；半血野牦牛相应为０．９０±０．２０ｋｇ／头，１．０５±０．２７ｋｇ／头，０．６８±０．２８ｋｇ／头，０．９０±０．３８ｋｇ／头；３一５岁家牦牛组的年产毛量极显著高于６岁以上年龄组（Ｐ＜０．０１），同１岁、２岁年龄组的年产毛量差异不显著（Ｐ＞０．０５），２岁与６岁以上年龄组之间呈显著性差异（Ｐ＜０．０５）；半血野牦牛各年龄组的年产毛量差异不显著（Ｐ＞０．０５）；１岁家牦牛公母间，２岁半血野牦牛公母间，年产毛量差异极显著（Ｐ＜０．０１）。 相似文献
3.
二甲苯胺噻唑对绵羊血液及脑脊液中乙酰胆碱的影响 总被引：3，自引：1，他引：2
用荧光分光光度计的方法研究了二甲苯胺噻唑（静松灵）对乙酰胆碱（ＡＣＨ）的影响，肌注２．５ｍｇ／ｋｇ该药后，血液及脑脊液中ＡＣＨ浓度呈上升趋势，于２．５小时达峰值，血液ＡＣＨ由０时７．９６５±０．４１８ｎｇ／ｍｌ２．５小时的４３．９３９±１．３０７ｎｇ／ｍｌ（ｎ＝５，Ｐ＜０．０１），ＡＣＨ浓度增加了４．５倍，脑脊液ＡＣＨ则由０时的１２．７２２±１．３４７ｎｇ／ｍｌ增７１、９５４±２．２５７ｎｇ／ｍｌ 相似文献
4.
半胱胺引起绵羊外周血液β－内啡肽和几种主要代谢激素的变化 总被引：31，自引：3，他引：28
在４头装置长久性胃肠道瘘管和临时性颈静脉血管插管公绵羊研究表明，经十二指肠瘘管灌注半胱胺（８０ｍｇ／ｋｇ体重）后５ｄ内外周血液的血浆ＳＳ浓度降低３３．６８％（２３３．１±４．４ｐｇ／ｍｌ对１５４．６±＋５．２ｐｇ／ｍｌ，Ｐ＜０．０１）；胃泌素水平升高２３．９％（Ｐ＜０．０５），ＧＨ、胰岛素分别升高１２４．２％（Ｐ＜０．０１）和１４４．０８％（Ｐ＜０．０１）；Ｔ３、Ｔ４水平分别增加７１．８％（ｐ＜０．０１）和１７．５５％（Ｐ＜０．０５）；β－ＥＮＤ水平第３天升高５８．１１％（５７．２９±１．６９ｐｇ／ｍｌ对３２．４４±２．５０ｐｇ／ｍｌ，Ｐ＜０．０１），第５天回落（Ｐ＜０．ｍ）。本实验证明半胱胺可抑制反刍动物ＳＳ水平，使外周血液ＧＨ、胃泌素、胰岛素、Ｔ_３、Ｔ_４和β－ＥＮＤ水平均相应升高，提示促进了反刍动物的消化代谢水平。 相似文献
5.
选用３头雄性中国海仔水牛,观察了去势及去势后注射睾酮对血清胃泌素水平的影响。结果去势后血清胃泌素水平明显下降（５０１．００±３７．２０ｖｓ,４３３．６±１０３．４ｐｇ／ｍｌ,Ｐ＜０．０５）,去势后水牛注射睾酮（２００μｇ／ｋｇＢＷ·ｄ,持续１２ｄ）血清胃泌素水平明显上升（４０８．１±６４．５ｖｓ,５１９．８±３４．４ｐｇ／ｍｌ,ｐ＜０．０５）。表明睾酮影响反刍动物胃泌素分泌。 相似文献
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7.
按大、中、小三组剂量给公兔灌服“天王饮”提取物。用药３０ｄ后试验组血浆睾酮浓度极显著地高于对照组（７．３８±７．０２ｎｇ／ｍＬ，１．０１±０．３１ｎｇ／ｍＬ，Ｐ＜０．０１），高剂量组睾酮水平略高于中、低剂量组但差异不显著（Ｐ＞０．０５）。试验组外周血淋巴细胞转化率显著或极显著高于对照组（Ｐ＜０．０５ｏｒＰ＜０．０１）。腹腔巨噬细胞激活、增殖试验表明，试验组巨噬细胞剌激指数和增长指数均显著高于对照组（３．５９±０．２７，１．８７±０．２８；２．６５±０．４３，１．１４±０．１０，Ｐ＜０．０５），不同剂量组间差异不显著。试验组睾丸实质重量显著高于对照组（４．６５±１．３８ｇ，３．４１±０．９０ｇ，Ｐ＜０．０１），但剂量间差异不显著。以上结果表明，“天王饮”能提高兔子的免疫机能，并具有促性腺激素样作用，提高动物的性激素水平并促进性腺发育，从而表现其养生、保健作用。 相似文献
8.
甜菜碱对杜长大肥育猪生长性能、胴体组成和肉质的影响 总被引：8，自引：0，他引：8
１５０口“杜长大”肥育猪（始重６３±０．４２ｋｇ）,按饲养试验要求分成５组（每组设３个重复）,分别饲喂甜菜碱含量（ｍｇ／ｋｇ）为０、１０００、１２５０、１５００、１７５０的饲粮,体重达９３ｋｇ左右时结束饲养试验;然后从每组选择体重相近的试验猪１２口,公、母各半,共６０口,进行屠宰测定。结果表明,①饲粮中添加甜菜碱均提高了日增重,其中以１７５０ｍｇ／ｋｇ组效果最为显著,提高了１３．３２％（Ｐ＜０．０１）;②添加甜菜碱出现了采食量增加和料重比降低的趋势（Ｐ＞０．０５）：③添加不同剂量的甜菜碱均显著提高了胴体瘦肉率,降低了胴体脂肪率,其中１０００ｍｇ／ｋｇ组最明显。瘦肉率提高了５．７１％（Ｐ＜０．０１）,脂肪率降低了１８．２７％（Ｐ＜０．０１）;④添加甜菜碱使眼肌面积显著增大,其中１７５０ｍｇ／ｋｇ组和１０００ｍｇ／ｋｇ组较明显,分别增大了１２．９％（Ｐ＜０．０１）和９．２％（Ｐ＜０．０１）;⑤首次发现,不同骨骼肌对甜菜碱的反应存在明显差异。其中１７５０ｍｇ／ｋｇ组背最长肌、股二头肌及半膜肌的重量分别增大了１０．８４％（Ｐ＜０．０２）、１１．０２％（Ｐ＜０．０５）和２２．８７％（Ｐ＜０．０３）;⑥添加甜菜碱明显增 相似文献
9.
运输性应激对商品猪影响的研究 总被引：2，自引：0，他引：2
商品猪７２０头，每头体重７５～１００ｋｇ。按常规行车，经历２小时，行程５０ｋｍ的公路汽车运输试验观测．在运输过程中猪只表现兴奋、不安和互相干扰、咬斗等现象。运输结束后表现精神沉郁和食欲不振。对猪的生理状态影响显著，心博率显著加快；运输前平均为７５．５±４．６次／分钟，运输后平均为９９．２３±１４次／分钟（Ｐ＜０．０１）；呼吸率显著增加，运输前平均为１２．２５±３．４次／分钟．运输后平均为２４．３±３．２次／分钟．（Ｐ＜０．０１）；体温明显增高．运输前平均为３９．３±０．３℃，运输后平均为３９．９８±０．５℃（Ｐ＜０．０５）。体重耗损较大．运输前平均为８８．５±３．１ｋｇ，运输后平均为８４．７±２．５ｋｇ，耗重率平均为４．３％。病残猪为２５头（占３．４％），死亡８头（占１．１％）．共计为４．５％。 相似文献
10.
以５头断奶仔猪进行两期消化试验。第一期为对照期,饲喂基础日粮;第二期为试验期,饲喂基础日粮＋０．１５％溢酸宝。采用内源指示剂法测定日粮中营养物质消化率。试验结果,试验期日粮中粗蛋白质,总氨基酸,粗脂肪,粗纤维,钙和磷的表观消化率分别为：８６．６１％,８４．６６％,６８．０３％,２７．１８％,８４．７１％和６３．３２％;比对照期分别提高９．３７％（Ｐ＜０．０１）,９．７６％（Ｐ＜０．０１）,１１．０７％（Ｐ＜０．０５）,２６．５４％（Ｐ＜０．０１）,１．４７％（Ｐ＞０．０５）和６．４０％（Ｐ＞０．０５）。试验结果表明,仔猪日粮中添加０．１５％的溢酸宝能显著地提高日粮中有机营养物质的消化率。 相似文献
11.
S R Davis R J Collier J P McNamara H H Head W J Croom C J Wilcox 《Journal of animal science》1988,66(1):80-89
Four cows received thyroxine injections (T4; 20 mg/d) and three cows received growth hormone injections (GH, 44 mg/d) for 4 d during successive 16-d experimental periods. Milk fat, lactose output, mammary uptake of glucose, oxygen and milk fat precursors were determined with each treatment. Injection of T4 increased lactose yield by 25% and fat yield 42%. The injection of GH increased fat and lactose yields by 24%. Both GH and T4 increased mammary glucose uptake by 35% and 45%, respectively, while T4 administration was associated with an increase in plasma glucose concentration from 67 to 84%. Thyroxine, but not GH, increased the ratio of mammary glucose uptake to lactose output from 1.24 to 1.58. Blood plasma acetate concentration declined following GH and T4 treatment by 17%. Mammary acetate uptake increased in response to GH injection in two of three cows but did not change with T4 injection. The injection of GH had no effect on plasma propionate concentration or mammary uptake. Thyroxine reduced plasma propionate content and mammary uptake. Neither T4 nor GH changed plasma free fatty acid concentration or mammary uptake. Thyroxine had no effect on plasma triglyceride concentration or mammary uptake, whereas GH increased mammary triglyceride uptake to the end of the experimental period. Mammary oxygen uptake was increased by GH as milk production increased. Increased mammary oxygen uptake following T4 treatment was transient. Change in mammary metabolism with T4 treatment permitted increased milk output without change in mammary oxygen consumption. Such a change may involve increased mammary utilization of pre-formed long-chain fatty acid and increased metabolism of glucose via glycolysis. 相似文献
12.
Effects of thyroxine and growth hormone treatment of dairy cows on milk yield, cardiac output and mammary blood flow 总被引：5，自引：0，他引：5
Four cows received thyroxine injections (T4; 20 mg/d) and three cows received growth hormone injections (GH; 44 mg/d) for 4 d during successive 16-d experimental periods. Measurement was made of milk yield, protein yield, mammary tyrosine and phenylalanine uptake, blood plasma hormone concentrations, mammary blood flow and cardiac output. Milk yield increased by 25% with T4 and 21% with GH treatment. Milk protein content tended to decline during T4 treatment and increase following GH treatment. Cardiac output increased by 8.9 liter/min (20%) and 4.6 liter/min (10%) with T4 and GH injection. Mammary blood flow (half-udder) increased from 3.6 to 4.9 liter/min (35%) and from 3.3 to 4.4 liter/min (33%) with T4 and GH treatment, respectively. These increases calculated on a whole-udder basis, accounted for 28% (T4) and 48% (GH) of the increases in cardiac output. The proportion of cardiac output perfusing the (whole) udder increased to 19.1% (T4) and 18.7% (GH), increases of 17 and 30%, respectively. Heart rate increased with T4 (but not GH treatment) from 80 to 115/min. Ratio of blood flow to milk yield was not changed by either treatment. The proportion of cardiac output perfusing the udder likely plays a major role in facilitating the partitioning of nutrients for milk synthesis. 相似文献
13.
本试验旨在探讨轻音乐对奶牛产奶量及血液激素水平的影响。选取产奶量、年龄、胎次、泌乳期相近的荷斯坦泌乳牛32头,随机分成2组,每组16头。试验组于早、中、晚3次给料时间各播放轻音乐2 h,轻音乐选用理查德·克莱德曼的经典钢琴曲20首,对照组常规饲喂。预试期7 d,正试期60 d。正试期当天起(0 d),每隔10 d测定单产1次并采集血样1次。结果表明,试验组产奶量在第10、40天时显著高于对照组(P<0.05);试验组产奶量在第20、30、50、60天时高于对照组,差异均不显著(P>0.05);整个试验期,试验组平均产奶量较对照组高1.72 kg,差异极显著(P<0.01)。整个试验期,轻音乐能提高奶牛血液中γ-氨基丁酸(GABA)、生长激素(GH)含量,降低血液中皮质醇(COR)、五羟色胺(5-HT)含量,差异均不显著(P>0.05)。综上所述,轻音乐可通过提高奶牛血液中γ-氨基丁酸含量,促进生长激素的分泌,降低皮质醇、五羟色胺的含量,稳定奶牛情绪,从而降低奶牛应激反应,提高产奶量。 相似文献
14.
半胱胺对高邮鸭增重及相关激素分泌和基因表达的影响 总被引：21，自引：0，他引：21
随机选取 5日龄体况良好的雄性高邮鸭 2 4只 ,分成对照组和半胱胺 (CS)试验组。试验组每周按体重在日粮中添加 1次 CS(10 0 mg/ kg) ,以观察半胱胺对高邮鸭增重及相关激素分泌和基因表达的影响。结果表明 ,前 3周平均日增重试验组比对照组提高 12 .86 %,料肉比下降 12 .82 %;整个试验期平均日增重提高 4.5 3%,料肉比下降 4.0 3%。血清 IGF- 1水平 ,试验组为 (2 2 9.88± 8.6 9) μg/ L,显著高于对照组 (2 0 2 .31± 7.10 ) μg/ L(P<0 .0 5 ,n=10 ) ;血清 GH水平 ,试验组为 (0 .5 4± 0 .0 3) μg/ L,显著高于对照组 (0 .45± 0 .0 2 ) μg/ L(P<0 .0 5 ,n=10 ) ;垂体 GH m RNA的净灰度(net intensity) ,试验组为 (2 .2 3× 10 5± 0 .19× 10 5) ,显著高于对照组 (1.6 5× 10 5± 0 .12× 10 5) (P<0 .0 5 ,n=9) ,而下丘脑生长抑素 (SS) m RNA的净灰度 ,试验组为 (1.33× 10 5± 0 .10× 10 5) ,比对照组 (2 .14× 10 5± 0 .5 7× 10 5)降低37.85 %(P=0 .0 97,n=8) ,提示半胱胺对 SS基因转录水平可能没有影响。半胱胺促进生长和提高饲料转化率的机制 ,可能与 GH基因表达的上调和血清 IGF- 1水平的提高有关。 相似文献
15.
本试验旨在研究日粮中应用生物制剂对发酵床育肥后期猪生长性能、血清生化指标及内分泌激素的影响.选取健康无病的70 kg左右的苏钟猪120头,随机分为2组,每组4个重复,每个重复15头猪.对照组饲喂基础日粮,试验组在基础日粮中添加生物制剂(包括植酸酶、复合酶、枯草芽孢杆菌、酵母菌、乳酸菌),预试期7 d,正试期28 d.结果表明,与对照组相比,试验组平均日增重提高了4.62%,料重比降低了6.53%,但差异均不显著(P>0.05).与对照组相比,试验组血清中甘油三酯(TG)含量极显著降低(P<0.01),其他血清生化指标均无显著差异(P>0.05).与对照组相比,试验组血清中胰岛素(INS)和胰岛素样生长因子(IGF-Ⅰ)含量分别显著和极显著升高(P<0.05;P<0.01),血清中甲状腺素(T3、T4)、生长激素(GH)含量虽有升高的趋势,但差异均不显著(P>0.05).综上所述,在发酵床育肥后期猪日粮中添加生物制剂,可提高猪的生长性能,改善营养物质代谢水平,降低血清中TG的含量,并提高猪血清中IGF-Ⅰ及INS的含量,改善猪体内内分泌激素的水平,建议生产中在发酵床育肥后期猪日粮中应用由植酸酶、复合酶、枯草芽孢杆菌、酵母菌、乳酸菌组成的生物制剂. 相似文献
16.
Kaskous S Grün E Gottschalk J Hippel T 《Berliner und Münchener tier?rztliche Wochenschrift》2003,116(3-4):117-123
The concentrations of lactogenic hormones (prolactin--PRL, growth hormone--GH, insulin-like growth factor I--IGF-I) and steroid hormones (progesterone--PG, estradiol--E2) were determined by RIA in the blood plasma of 8 lactating ewes (3 with twins) and compared with that of 3 non-lactating cycling ewes of the same age. All animals live in a flock of 30 Awassi sheep under identical conditions in Syria. The lactation period (192 +/- 25 days) is divided to a suckling period (until day 63) and a hand milking period (2 fold daily) with different levels of milk production (near 2 litres/day in the former, decreasing from 0.8 to 0.1 litre/day in the latter). During the suckling period the concentrations of steroid hormones in the blood plasma are lower, these of lactogenic hormones are higher of lactating than of non-lactating ewes. During the milking period only the concentrations of E2, PRL and IGF-I in the blood plasma of lactating animals are lower than in non-lactating ewes. But, during this time more and more seasonal influences (increasing day length and temperature) overwhelm the influence of lactation on the hormone secretion. Suckling of twins is accompanied with higher levels of E2, PRL and IGF-I in the blood plasma of their mothers than suckling of single lambs. During the lactation period a strong correlation exists between milk yield and the level of GH (r = 0.85) and IGF-I (r = 0.71), a smaller correlations to the level of E2 (r = 0.49) in the blood plasma of the lactating ewes. During the suckling period the milk yield is influenced positively by PRL (r = 0.77) and GH (r = 0.68), but negatively by PG (r = -0.76). During the milking period the milk yield is determined extensively by the level of IGF-I (r = 0.89) in the blood plasma. The concentrations of the analyzed hormones in the blood plasma correlate always positively together. 相似文献
17.
High body weight gain and reduced bovine mammary growth: physiological basis and implications for milk yield potential 总被引：6，自引：0，他引：6
Available evidence concerning the relationship between growth rate, mammary growth and milk yield in heifers leads to these conclusions: 1) Increased growth rate due to high feeding level before puberty onset can lead to reduced pubertal mammary growth and reduced milk yield potential. 2) Increased growth rate due to high feeding level after puberty and during pregnancy have no effect on mammary growth and milk yield. 3) Higher body weight gain due to higher genetic potential for growth is positively related to milk yield. The negative effect of high feeding level before puberty occurs in all breeds, but the level of feeding causing reduced yield varies. Variation in responses between experiments suggests that feeding regimes that support high growth rates without negative effect on yield can be developed. A breakthrough most likely will originate from increased knowledge of the physiological relationship between nutrition and mammary development. Our investigations suggest that blood growth hormone (GH) is important for mammary development, and that the negative effect of high feeding level on mammary development may be due to reduced blood GH. GH, however, does not bind to mammary tissue. Experiments with exogenous GH suggest that GH acts on mammary tissue via IGF-I, but IGF-I is increased by high feeding level - not decreased as GH. This paradoxical relationship cannot be explained by changes in circulating IGF binding proteins. However, the sensitivity of mammary tissue to IGF-I is reduced by high feeding level, probably due to the action of locally produced binding proteins and/or growth factors. 相似文献
18.
将96头体质量约65 kg的杜长大三元杂交猪,按体质量相近、公母各半的原则随机分成4组,每组3个重复.试验猪1组设为对照,饲喂基础饲粮,其余3组为试验组,分别饲喂在基础饲粮基础上添加来源于氯化铬、吡啶羧酸铬,纳米铬的含200 μg/kg铬试验饲粮.试验猪充分饲喂,自由饮水,试验为期40 d.饲养试验结束前1 d,从每组中选择6头猪,间隔15 min颈静脉采血1次,连续3 h,制备血清用于生长激素动态分泌模式研究.饲养试验结束后,按体质量相近原则从每组中选择8头猪进行屠宰,测定背膘厚和背最长肌面积;并各采取3头猪的脑垂体,RT-PCR法测定生长激素mRNA水平.结果表明,饲粮中添加200μg/kg三价纳米铬使肥育猪日增重提高了6.31%(P<0.05),料重比降低了4.61%(P<0.05),背膘厚降低了24.32%(P<0.05),背最长肌面积提高了20.22%(P<0.05).生长激素动态模式分析结果显示,纳米铬组试验猪生长激素总体水平、最低值、峰值和峰持续时间分别提高了42.62%(P<0.05)、87.94%(P<0.05)、26.60%(P<0.05)和17.19%(P<0.05),吡啶羧酸铬组试验猪生长激素总体水平、峰值分别提高了36.58%(P<0.05)和27.18%(P<0.05).垂体生长激素基因RT-PCR分析结果显示,纳米铬组试验猪垂体生长激素mRNA水平提高了27.63%(P<0.05).研究结果提示,三价纳米铬可提高肥育猪垂体生长激素mRNA水平,促进机体生长激素分泌,从而促进生长和改善胴体特性. 相似文献
19.
饲粮粗蛋白质水平对中国荷斯坦奶牛产奶性能、氮利用及血液激素的影响 总被引：1，自引：0，他引：1
本试验旨在研究饲粮粗蛋白质（ＣＰ）水平对中国荷斯坦奶牛产奶性能、氮利用及血液激素的影响。采用重复 ４×４拉丁方设计,８头经产中国荷斯坦奶牛随机分为 ４个处理。４个处理的饲粮 ＣＰ水平分别为 １２．５６％、１３．９６％、１５．５３％和 １６．９３％。试验分为 ４个周期,每个周期１８ｄ。在 ４ｄ收集期内,全量收集粪、尿,每天测量产奶量、乳成分和干物质摄入量（ＤＭＩ）,并在收集期最后 １ｄ采集血样。结果表明：４个饲粮处理的 ＤＭＩ基本相同（Ｐ＞０．０５）;饲粮 ＣＰ水平１２．５６％的产奶量和能量校正奶（ＥＣＭ）明显低于饲粮 ＣＰ水平 １３．９６％至 １６．９３％（Ｐ＜０．０５）,饲粮 ＣＰ水平 １３．９６％至 １６．９３％的产奶量和 ＥＣＭ 基本相同,其中饲粮 ＣＰ水平 １３．９６％和１６．９３％的产奶量分别为２８．１８和２８．７２ｋｇ／ｄ,ＥＣＭ分别为３２．６４和３２．０４ｋｇ／ｄ;乳成分中仅乳蛋白率随着饲粮 ＣＰ水平增加而提高（Ｐ＜０．０５）;饲粮 ＣＰ水平 １２．５６％和 １３．９６％的乳氮效率明显高于饲粮 ＣＰ水平 １５．５３％和 １６．９３％（Ｐ＜０．０５或 Ｐ＜０．０１）;随着饲粮 ＣＰ水平的提高,尿氮排出量不断增加,乳氮排出量也缓慢上涨,体内氮沉积显著增加（Ｐ＜０．０５或 Ｐ＜０．０１）,只有饲粮 ＣＰ水平 １６．９３％的粪氮排出量明显增加（Ｐ＜０．０５）;饲粮 ＣＰ水平 １２．５６％的血液瘦素浓度最高（Ｐ＜０．０５）,催乳素（ＰＲＬ）、生长激素（ＧＨ）、胰岛素样生长因子 １（ＩＧＦ １）、血糖、非酯化脂肪酸（ＮＥＦＡ）和 β－羟丁酸（ＢＨＢＡ）浓度较高;而饲粮 ＣＰ水平 １６．９３％的血浆尿素氮（ＰＵＮ）浓度最高（Ｐ＜０．０１）,胰岛素和 ＧＨ浓度较高,ＩＧＦ １浓度较低。由此可见,饲粮 ＣＰ水平１３．９６％适合中国荷斯坦奶牛产奶量２８ｋｇ／ｄ或 ＥＣＭ３２ｋｇ／ｄ的泌乳性能、氮利用和内分泌调节。 相似文献
20.
Fifty Holstein cattle, either second to fourth generation daughters of cows randomly bred to non-commercial sires originating in the Virginia Tech dairy herd (estimated mean PDM84 = -455 kg, control animals), or daughters of cows bred to commercially available sires (mean PDM84 = +368 kg, selection animals), were randomly assigned to be milked twice or thrice daily starting at parturition. Serial blood samples were collected via jugular cannulae at 30, 90 and 200 d post-partum (DPP) during both the first and second lactations. Blood samples were collected for 3 h prior to and 4 h following thyrotropin releasing hormone (TRH) administration, and were analyzed for growth hormone (GH) and prolactin (PRL) concentrations. Dry matter intake, body weight and milk yield and fat content were used to calculate net energy balance (NEB) of animals at each DPP sampling period. Mean plasma GH concentrations were greater (P less than .01) in selection vs control animals both before and after TRH administration, and decreased (P less than .01) with advancing lactation (30 greater than 90 greater than 200 DPP). However, NEB was not influenced by genetic merit, implying that observed differences in GH concentrations were not due to that trait. Plasma PRL concentrations were not affected by genetic merit or DPP, but were greater (P less than .01) in the second vs first lactation. Neither PRL or GH concentrations were affected by frequency of milking. The results support the contention that increased plasma GH concentrations are associated with selection for increased milk yield. 相似文献