鸽乳的组成及其生成调控机制的研究进展

鸽乳是由鸽嗉囊组织生成并分泌的半固态营养物质,是乳鸽唯一的营养来源。乳鸽出生后不能自主觅食,需由亲鸽哺育,鸽乳对其生长发育极为重要。鸽乳的生成及分泌是一种特殊的生理过程,在禽类中极为少见,也不同于哺乳动物的泌乳过程。鸽乳主要由蛋白质、脂质、碳水化合物和矿物质等物质组成,其合成与分泌受催乳素、胰岛素和松弛素等多种激素共同调控,通过激活JAK/STAT、PI3K/Akt/TOR、AMPK和Wnt等信号通路,调控相关基因的表达,进而调节嗉囊上皮细胞增殖、变性和营养物质合成、富集等过程。本文综述了鸽乳的组成及其生成调控机制,并与哺乳动物进行了比较,进一步明确了嗉囊产生鸽乳的生理机制及与哺乳动物乳腺泌乳的异同。通过研究鸽乳的组成,可为种鸽营养需要标准制定及人工鸽乳研发提供参考;通过研究鸽乳生成的调控机制,进一步深入挖掘调控泌乳的基因,结合分子标记辅助育种技术,应用于提高种鸽的泌乳能力。     

西农萨能奶山羊泌乳期产奶量、乳成分及血液生理生化指标变化规律研究

旨在探索西农萨能奶山羊泌乳期生产性能、乳成分、血液生理生化指标和营养物质摄入量等变化规律及其相互关系.本研究选取15只体重、胎次、产奶量、分娩日期相近,体况健康的西农萨能奶山羊.单圈饲喂54周,试验期内准确测定个体生产性能、乳成分、血液生理生化指标和营养物质摄入量等,建立各项指标随泌乳期变化规律模型及泌乳期内指标间的相...     

不同时期鸽乳营养水平及生理活性物质动态变化分析

试验通过测定不同日龄乳鸽嗉囊中鸽乳外观品质、能量蛋白质浓度、消化酶活性、免疫球蛋白水平及生长因子浓度,分析这些指标在乳鸽不同日龄的动态变化,旨在为系统了解乳鸽营养与生理需求提供理论依据。随机选择0、7、14、21、28日龄健康白羽王鸽乳鸽各12只,待亲鸽哺喂后屠宰,取出其嗉囊全部内容物。一部分用生理盐水稀释后取上清,用于消化酶活、免疫球蛋白及生长因子的测定;另一部分制成风干样用于常规营养水平的检测。结果显示,0日龄鸽乳外观呈乳白色油性奶酪样,7日龄鸽乳为奶酪样鸽乳和饲料的混合物,14日龄之后逐渐过渡为软化的饲料。日龄对鸽乳的能值和蛋白质浓度均有显著影响（P<0.05）,0日龄鸽乳的能值和蛋白质浓度显著高于后期鸽乳（P<0.05）,7日龄后,鸽乳能值和蛋白质浓度趋于平缓。不同时期鸽乳的淀粉酶、胰蛋白酶和糜蛋白酶活性差异显著（P<0.05）,且均随日龄增加呈一次线性上升（P<0.05）。不同时期鸽乳的免疫球蛋白A （IgA）、免疫球蛋白M （IgM）和免疫球蛋白G （IgG）水平均有显著差异（P<0.05）,且均先下降后上升,与日龄呈二次曲线关系（P<0.05）。不同时期鸽乳中胰岛素生长因子-1（IGF-1）和表皮生长因子（EGF）浓度差异显著（P<0.05）,且均先下降后上升,与日龄呈二次曲线关系（P<0.05）。0~7日龄鸽乳以亲鸽嗉囊黏膜上皮细胞的脱落物与细胞碎片为主,能量、蛋白质、免疫因子和生长因子均处于最高水平;8~14日龄鸽乳能量和蛋白质浓度趋于平缓,免疫因子和生长因子降至最低;15~28日龄鸽乳营养水平与亲鸽饲粮相似,且乳鸽消化能力逐渐增强。     

高温对母猪泌乳和相关调控激素影响的研究进展

母乳的产量和质量对哺乳仔猪的成活率、生长速度及健康程度至关重要,而高温是影响家畜泌乳健康的一个重要环境因素。特别是夏季,动物因长期处于高温环境而容易引发热应激。此外,动物的泌乳过程受到机体内分泌系统的严格调控,涉及多种激素,包括催乳素（PRL）、生长激素（GH）、胰岛素样生长因子-1（IGF-1）等。很多生产数据和研究结果表明,高温会造成母猪采食量降低,泌乳性能下降以及内分泌状态的改变,进而对母猪、仔猪均产生不利影响。为了保证母猪的健康状态及仔猪良好的生长性能,了解高温对母猪泌乳及相关内分泌激素的影响十分必要。作者针对高温对母猪泌乳量、乳成分和泌乳相关激素的影响进行总结,得到高温会降低母猪泌乳量,改变乳糖、乳脂和乳蛋白的含量及泌乳调控激素水平的结论,为后续探索高温影响母猪泌乳的内分泌机制及寻找适宜的缓解高温对母猪泌乳危害的措施提供参考。     

Crop milk protein is synthesised following activation of the IRS1/Akt/TOR signalling pathway in the domestic pigeon (Columba livia)

1. The experiment was conducted to study whether insulin receptor substance 1 (IRS1) / Protein kinase B (Akt)/target of the rapamycin (TOR) signalling pathway activation stimulates crop milk protein synthesis in the domestic pigeon (Columba livia).

2. Crop milk was collected from ten 1-d-old squabs and analysed for nutrient content. During the non-breeding period and the first day of lactation, blood samples were collected from 5 pairs of breeding pigeons and the levels of prolactin and insulin were determined.

3. Crop samples were collected from 5 pairs of breeders at d 14 and 16 of the incubation period and d 1, 3 and 7 of the lactation period. Crop samples were evaluated for changes in crop weight and thickness and changes in the expression patterns of IRS1/Akt/TOR signalling pathway–related proteins.

4. The results demonstrated that prolactin induces a gradual increase in the relative weight and thickness of the crop, with crops reaching a maximum size at the third day of lactation.

5. Pigeon crop milk contains 64.1% crude protein and 29.7% crude fat based on dry weight.

6. Serum prolactin and insulin levels in the lactation period were significantly higher than those in the non-breeding period. Compared with non-breeding pigeons, the expression of the phosphorylated IRS1 phosphorylated Akt, phosphorylated TOR, phosphorylated ribosomal protein S6 kinase, phosphorylated S6, phosphorylated eukaryotic initiation factor 4E binding protein 1 and eukaryotic initiation factor 4E were significantly up-regulated in the crop of pigeons in the lactation period.

7. In conclusion, prolactin might induce changes in crop tissue and form the physiological structure for crop milk synthesis. Furthermore, the synthesis of crop milk protein is regulated by activation of the IRS1/Akt/TOR signalling pathway.

     

Lactation Biology Symposium: circadian clocks as mediators of the homeorhetic response to lactation

The transition from pregnancy to lactation is the most stressful period in the life of a cow. During this transition, homeorhetic adaptations are coordinated across almost every organ and are marked by changes in hormones and metabolism to accommodate the increased energetic demands of lactation. Recent data from our laboratory showed that changes in circadian clocks occur in multiple tissues during the transition period in rats and indicate that the circadian system coordinates changes in the physiology of the dam needed to support lactation. Circadian rhythms coordinate the timing of physiological processes and synchronize these processes with the environment of the animal. Circadian rhythms are generated by molecular circadian clocks located in the hypothalamus (the master clock) and peripherally in every organ of the body. The master clock receives environmental and physiological cues and, in turn, synchronizes internal physiology by coordinating endocrine rhythms and metabolism through peripheral clocks. The effect of the circadian clock on lactation may be inferred by the photoperiod effect on milk production, which is accompanied by coordinated changes in the endocrine system and metabolic capacity of the dam to respond to changes in day length. We have shown that bovine mammary epithelial cells possess a functional clock that can be synchronized by external stimuli, and the expression of the aryl hydrocarbon receptor nuclear translocator-like gene, a positive limb of the core clock, is responsive to prolactin in bovine mammary explants. Others showed that 7% of genes expressed in breasts of lactating women had circadian patterns of expression, and we report that the diurnal variation of composition of bovine milk is associated with changes in expression of mammary core clock genes. Together these studies indicate that the circadian system coordinates the metabolic and hormonal changes needed to initiate and sustain lactation, and we believe that the capacity of the dam to produce milk and cope with metabolic stresses in early lactation is related to her ability to set circadian rhythms during the transition period.     

不同日龄鸽乳粗蛋白质和矿物元素含量变化规律的研究

【目的】 试验旨在研究1~28日龄乳鸽嗉囊中鸽乳粗蛋白质和矿物元素含量的变化规律。【方法】 选取36对种鸽,每对种鸽哺育2只乳鸽,于乳鸽1、3、5、7、14、28日龄采集鸽乳,每个时间点6个重复,每个重复2只乳鸽,在种鸽哺喂后通过挤压嗉囊的方式采集乳鸽嗉囊内鸽乳。分别在乳鸽1、7、14、21、28日龄时称重,并记录种鸽每周的采食量。【结果】 乳鸽体重随日龄增加呈显著的线性和二次增加(P<0.05),在1~21日龄乳鸽体重随日龄增加而增加(P<0.05),之后维持稳定。种鸽颗粒料和原粮以及总采食量随日龄增加呈显著的线性和二次增加(P<0.05),原粮和颗粒料采食量以及总采食量均于7日龄后显著增加(P<0.05),并在15~28日龄维持稳定。不同日龄鸽乳的粗蛋白质和矿物元素含量均有显著差异(P<0.05)。粗蛋白质含量随日龄增加呈显著的线性和二次减少(P<0.05),1~5日龄粗蛋白质含量维持稳定,在7日龄显著降低(P<0.05),在14~28日龄维持稳定。钙含量随日龄增加呈显著的线性增加(P<0.05),磷含量呈显著的线性减少(P<0.05),钙磷比呈显著的线性升高(P<0.05)。铜、锰、锌含量均随日龄增加呈显著的线性和二次增加(P<0.05)。铁含量随日龄增加呈显著的二次增加(P<0.05),铜、铁、锰、锌含量均在1~3日龄维持稳定,铜含量在5日龄显著增加(P<0.05),之后维持稳定,于14日龄显著增加(P<0.05),随后于28日龄显著降低(P<0.05)。铁、锌和锰含量均于5日龄显著增加(P<0.05),在5~28日龄维持稳定;硒含量随日龄变化无显著差异(P>0.05)。【结论】 乳鸽在21日龄前生长速度快,21~28日龄乳鸽体重维持稳定,种鸽颗粒料和原粮采食量以及总采食量均随乳鸽日龄增加而增加。鸽乳中粗蛋白质和磷含量均随日龄增加而减少,而钙、铜、铁、锰、锌含量均随日龄增加而增加。     

鸽沙门氏菌病及其抗生素替代品防控措施研究进展

鸽沙门氏菌病是由沙门氏菌引起的养鸽业常见且多发的疾病,主要侵害雏鸽,给养鸽业造成严重经济损失。引起该病的沙门氏菌为一种兼性胞内寄生菌,可于宿主细胞内生存繁殖并逃避机体免疫防御机能,增加了该病净化的难度。目前,使用抗生素防治鸽沙门氏菌病是生产中最常用的有效措施,但抗生素的大量使用甚至滥用,导致沙门氏菌这一人兽共患病原菌耐药菌株的不断产生,以及药物残留等危害食品和公共卫生安全问题的出现。寻求抗生素替代品来减少或替代抗生素在畜禽养殖生产中的应用已成为动物疫病防控研究的主流。由于养鸽业起步较晚,有关鸽沙门氏菌病及其防控的研究相对较少,文章主要对鸽沙门氏菌病、沙门氏菌致病机制和近年来针对沙门氏菌病的抗生素替代品防控措施的研究进展进行综述,以期为鸽沙门氏菌病相关研究提供参考。     

中国肉鸽主要品种资源与育种现状

肉鸽因具有较高的食用价值,越来越受世人的关注。通过对中国主产区肉鸽的优良品种进行种资源特点调查,促使人们进一步了解肉鸽;并针对在生产中发现的不同品种间存在的一些有利经济性状提出了发展建议,以此指导中国肉鸽生产迈入更加科学的良性发展环节;同时简述了中国肉鸽育种的一些研究进展,并结合今后肉鸽育种科研发展方向提出了几点拙见。     

中国荷斯坦奶牛RPL23A、ACACB基因3个SNPs检测及其与产奶性状的关联分析

旨在开展奶牛群体高乳成分功能基因的验证与筛选,利用微流控芯片自主选育技术分析北京地区母牛群体高乳蛋白、高乳脂基因频率,同时分析基因多态性及其与产奶性状的相关性。本研究对北京地区8个大型奶牛场1 596头中国荷斯坦奶牛RPL23A、ACACB基因的多态性进行了检测,所有个体均为3胎以内的泌乳牛,收集每头牛所有测定日的产奶量、乳脂率、乳蛋白率等数据,同时对3个多态位点不同基因型与产奶性状进行了关联分析。RPL23A基因的SNP位点g.20146771G>A,在第一泌乳期,与产奶量、乳脂量、乳脂率和乳蛋白量均达到极显著关联（P<0.01）,第二泌乳期,g.20146771G>A与5个产奶性状均呈极显著关联（P<0.01）。ACACB基因的SNP位点g.63962768C>T,在第一泌乳期,与产奶量、乳脂量、乳脂率和乳蛋白量均呈极显著关联（P<0.01）,在第二泌乳期,与产奶量、乳脂量、乳脂率和乳蛋白率呈极显著关联（P<0.01）。结果表明,RPL23A、ACACB基因可以作为影响中国荷斯坦奶牛产奶性状的候选基因用于标记辅助选择,以上基因位点可能通过直接或间接的途径影响奶牛的乳脂或乳蛋白性状,对产奶性状起到重要调控作用。本研究为荷斯坦奶牛后续的标记辅助选择奠定了良好基础。     

母乳能量水平对仔猪生长的影响及其分子机理

母体是仔猪胚胎期和初生时唯一的营养来源,也是哺乳期主要的营养源。妊娠期和泌乳期母体的营养和体况不仅影响繁殖性能和泌乳性能而且直接决定仔猪的生长。妊娠期添加纤维日粮能升高母猪血液VFA浓度,特别是乙酸浓度,它可以直接合成乳脂,提高乳汁能量。在妊娠后期和哺乳期调整母猪饲料组成可以改善产奶量和乳成分,从而影响仔猪生长性能。本文从仔猪的生理特点、日粮养分尤其是纤维和脂肪对母猪泌乳、繁殖性能和仔猪生长的影响以及调控仔猪生长的分子机理等方面进行了综述。     

Computer simulation model of swine production systems: II. Modeling body composition and weight of female pigs, fetal development, milk production, and growth of suckling pigs

Theoretical concepts and relationships used to develop a deterministic computer simulation model of female pigs during their reproductive life are described. The model predicts, in a continuous form, body composition and weight of female pigs, fetal development, sow milk yield, and growth of suckling pigs according to genotype, diet, and management conditions. The model simulates growth of adult female pigs. Dietary nutrients are used first for maintenance and second for fetal growth or milk production. Any surplus is retained in the body. Energy and protein body reserves are mobilized when a nutrient deficit occurs during gestation or lactation. However, the rates of body protein and fat accretion as well as the fat/protein ratio are limited by boundaries, the values of which depend on the nutritional and physiological status of the pig. The model's ability to simulate sow body weight changes and composition, fetal growth, milk production, and suckling pig's growth is illustrated.     

基于鸽胸肌转录组挖掘其卓越飞行性能的分子标记

目的对赛鸽和观赏鸽胸肌组织的转录组进行比较分析,探讨鸽胸肌中与飞行性能相关的关键基因。方法通过差异分析获取赛鸽和观赏鸽胸肌中显著上调和下调的差异基因并进行富集分析。结果数据经质量控制共获得18.3 G的有效数据,筛选出477个差异表达基因,包含194个上调基因和130个下调基因。KEGG pathway显著性富集分析共筛选出3个与鸽飞行性能相关的候选基因,分别为MUSTN1、PDK4和MSTN。结论通过比较赛鸽和观赏鸽胸肌转录组数据,筛选与鸽飞行性能相关的关键基因,丰富了鸽的基因组信息,为进一步揭示鸽胸肌分子机理奠定了基础。     

不同日龄乳鸽肠道CaBP-D28k基因表达的变化规律研究

为了解乳鸽肠道钙吸收规律,以满足乳鸽生产中钙的营养需要,试验将48对健康种鸽随机分为8个重复,每个重复6对,产蛋后由种鸽自然孵化和哺育乳鸽,在乳鸽7、14、21、28日龄时称量体重,平均体重分别为(120.27±31.37)g、(264.35±88.77)g、(399.22±75.04)g和(454.16±38.39)g,分别从每个重复选取1只体重适中的乳鸽,取其嗉囊内容物(鸽乳),并对其十二指肠和空肠肠段进行采样,测定鸽乳钙含量和肠道CaBP-D28k的相对表达量。结果表明:7日龄鸽乳钙含量显著低于21、28日龄鸽乳钙含量(P<0.01);7日龄时十二指肠和空肠中CaBP-D28k的表达量显著高于14、21、28日龄的表达量(P<0.01);且CaBP-D28k在7～28日龄乳鸽十二指肠的表达量显著高于在空肠的表达量(P<0.05)。由此可见:鸽乳的钙含量随着乳鸽日龄的增大而增加,乳鸽肠道CaBP-D28k基因表达量随着日龄增大而减少,十二指肠是鸽进行钙载体吸收的主要部位。     

泌乳母猪乳腺对乳汁前体物的摄取及其乳汁成分的分泌

乳汁产量和营养成分在很大程度上决定哺乳期仔猪的生长性能,但由泌乳期第 ８天至断奶,乳腺不能合成足量乳汁以支持仔猪最大生长潜力的发挥。因此,有必要弄清泌乳母猪乳腺对乳汁前体物的摄取及乳汁成分分泌的这种“进—出”生化代谢规律,以便利用营养措施调控乳汁成分。本文阐述了乳腺对乳汁前体物质,如葡萄糖、脂肪酸、氨基酸、矿物质、维生素的摄取及其乳汁成分的分泌,并讨论了调控“摄取—分泌”这个过程中的潜在生化机制。     

鸽GnIH和GnRH基因克隆及其在不同繁殖阶段下丘脑中的表达

为研究促性腺激素抑制激素（gonadotropin-inhibitory hormone,GnIH）和促性腺激素释放激素（gonadotropin-releasing hormone,GnRH）基因在鸽繁殖不同阶段下丘脑组织中的表达变化,探讨GnIH和GnRH基因与鸽繁殖调控之间的关系,本研究以鸽cDNA为模板扩增GnIH和GnRH基因CDS区序列并进行克隆测序,采用实时荧光定量PCR技术检测了产蛋前、产蛋后及哺乳期鸽下丘脑组织中GnIH和GnRH基因mRNA表达水平。序列分析结果表明,鸽GnIH基因CDS区全长522 bp,已提交GenBank,登录号：MG589638,编码173个氨基酸,与已知其他鸟类GnIH同源性达85%以上;鸽GnRH基因CDS区全长276 bp,已提交GenBank,登录号：MG589639,编码91个氨基酸,与已知其他鸟类GnRH同源性达80%以上。鸽GnIH前体包含1个GnIH和2个GnIH相关肽（GnIH-RP-1、GnIH-RP-2）,具有典型的"LPXRF"基序;GnRH前体包含1个信号肽、1个GnRH和1个GnRH相关肽（GAP）。实时荧光定量PCR结果表明,产蛋前鸽下丘脑中GnIH基因表达量最高,且极显著高于产蛋后和哺育期（P<0.01）;产蛋后鸽下丘脑中GnRH基因表达量最高,且极显著高于产蛋前和哺育期（P<0.01）;产蛋前鸽下丘脑中GnIH基因表达量极显著高于GnRH基因（P<0.01）,而产蛋后和哺育期鸽下丘脑中GnRH基因表达量极显著或显著高于GnIH基因（P<0.01;P<0.05）。结果表明,GnIH和GnRH基因的表达与母鸽不同繁殖阶段的转变有关,为进一步研究鸽繁殖分子机制奠定基础。     

The control of milk ejection in the mammal

Extract

Occasionally the need arises for a review of a subject aimed at putting the available evidence into perspective. Over the past decade a considerable amount of work has been done on the milk-ejection mechanism of the mammal. Too frequently this reflex has been regarded as isolated from other aspects of mammalian reproduction. In this review, an attempt is made to outline our basic knowledge of the nature of the milk-ejection process and the mechanisms involved in it against the background of the mammalian reproductive system. For along time it has been known that the suckling stimulus has an effect on the ability of the mammal to secrete milk. At the same time it is known that there are no neural pathways to the anterior pituitary which releases the hormones controlling mammary gland activity. Thus the mechanism by which the stimuli of suckling could affect the release of anterior lobe hormones has not been at all clear. Evidence is rapidly accumulating for the idea that the posterior pituitary hormones, which must pass through the anterior pituitary gland on their way to the systemic circulation, may have an effect on the release of anterior lobe substances. This effect is made possible by the peculiar system of circulation which exists between the neurohypophyseal tract and the anterior pituitary. Evidence for this view is summarized in what follows, and its significance as a factor in the maintenance of milk secretion is considered. It has been thought worth while to present a generalized picture of the milk-ejection reflex and of certain other reproductive reflexes as recent developments within the mammals superimposed upon the “water balance” regulating mechanisms which are to be found throughout the entire vertebrate phylum. In doing this, a certain amount of over-simplification has been inevitable, but it is hoped that the review will place some of the problems of lactation in perspective and, in so doing, show the many gaps in our knowledge which must be filled before we have an adequate understanding of the process controlling the secretion and ejection of milk in the mammal.     

Lactation Biology Symposium: effects of photoperiod on mammary gland development and lactation

Photoperiod, or the daily sequence of light and dark, has dramatic effects on many physiological systems across animal species. Light patterns alter melatonin secretion profiles and, subsequently, the release profiles and circulating concentrations of several hormones that influence a variety of physiological responses. Although the impact of photoperiod on reproductive processes is perhaps the most common example, it is often the seasonal aspects of ovulation and anestrus that are considered. However, in cattle, the final phase of reproduction, that is, lactation, is significantly influenced by photoperiod. In contrast to short days (SDPP; 8 h light:16 h dark), exposure to long days (LDPP) of 16 to 18 h of light and 6 to 8 h of darkness increases milk yield 2 to 3 kg/d, regardless of the stage of lactation. There is evidence that this LDPP effect is due to increased circulating IGF-I, independent of any effect on GH concentrations. Cows that are housed under SDPP during the dry period have increased mammary growth and produce 3 to 4 kg/d more milk in the subsequent lactation compared with cows on LDPP when dry. While cows are on SDPP, circulating prolactin (PRL) diminishes but expression of PRL receptor increases in mammary, liver, and immune cells. Moreover, PRL signaling pathways within those tissues are affected by photoperiod. Further, replacement of PRL to cows on SDPP partially reverses the effects of SDPP on production in the next lactation. Thus, effects on dry cows are mediated through a PRL-dependent pathway. Before maturity, LDPP improve mammary parenchymal accumulation and lean body growth, which lead to greater yields in the first lactation. The accumulated evidence supports the concept that photoperiod manipulation can be harnessed to improve the efficiency of production across the life cycle of the dairy cow.