母乳蛋白质组研究进展

母乳是人类及所有哺乳动物生命最初阶段的唯一食物,乳蛋白质是乳中最重要的营养物质,近年来随着蛋白质组学技术的发展及其在乳蛋白质研究中的应用,人类对乳蛋白质的组成、分泌调控及其中的过敏蛋白原等的认识越来越深入.本文对蛋白质组学在乳蛋白质的全面鉴定、乳蛋白质分泌调控以及乳中过敏原分析鉴定方面的研究策略和进展进行综述,以提高人类对乳蛋白质组相关生物学过程的认识.     

乳蛋白合成的信号通路与营养调控

乳蛋白是衡量乳品质高低的重要指标之一。研究乳腺合成乳蛋白的机理,探索奶牛将摄入的营养物质转化成乳蛋白的代谢过程及对关键基因的调控作用,已为提高乳品质提供了新的思路。本文从日粮蛋白质、能量、氨基酸、维生素等营养素的角度,结合相关的信号通路关键基因,综述了营养素对乳蛋白合成的调节作用,为利用日粮营养素对乳蛋白合成的调节研究提供理论基础。     

牦牛乳蛋白质组成及特性

牦牛乳是营养价值极其丰富且珍稀的乳制品.相比普通牛乳,牦牛乳蛋白质含量更高.本文主要介绍了牦牛乳蛋白质的组成及其营养与功能特性,也介绍了牦牛乳中的微量活性蛋白及其功能,以期为牦牛乳的进一步研究和开发提供一定的参考.     

泌乳性状遗传标记研究进展

乳蛋白质决定着乳产品的品质和风味。研究表明乳蛋白类型及其基因多型性与泌乳性状如产乳量、乳脂率、乳蛋白量及乳蛋白率有很强的相关性。本文就乳蛋白作为泌乳性状遗传标记的研究做一简要评述。     

饲料蛋白质组分对泌乳奶牛乳脂率和乳蛋白的影响

本试验研究采用粗蛋白质相同而蛋白质组分水平不同的四种日粮(日粮粗蛋白质中瘤胃未降解蛋白质(RUP)比例由35.9%逐步提高到40.9%,其他营养成分基本保持一致),选择32头处于中产水平的荷斯坦奶牛,根据产奶量、胎次和泌乳日龄按配对法随机分为四组,研究了不同蛋白质组分水平的日粮对奶牛乳脂率、乳蛋白率和乳蛋白质产量的影响规律。结果表明,粗蛋白质相同而蛋白质组分水平不同的日粮对奶牛乳脂率、乳蛋白率和乳蛋白产量没有显著的影响(P>0.05),但乳脂率有下降的趋势,乳蛋白产量有增加的趋势。     

泌乳反刍动物乳腺中小肽的摄取、利用及影响因素

乳蛋白是人类饮食中重要的动物蛋白质来源.乳腺是合成乳蛋白的主要场所.然而,反刍动物乳腺由血液摄取的游离氨基酸并不能满足乳腺合成蛋白质的需要,动物对完整蛋白质本身或小肽有着特殊需要.近年来,由于小肽优于氨基酸的跨膜转运机制和特殊的生理功能,小肽营养受到越来越多的关注.本文主要从泌乳反刍动物乳腺对小肽的摄取、利用以及影响乳...     

驴乳蛋白质组成及其与人乳和牛乳的比较

本文阐述了驴乳蛋白质的主要组分,并和牛乳及人乳的蛋白质组成特征进行了对比.驴乳中乳清蛋白比例明显高于牛乳,富含溶菌酶、乳铁蛋白和α-乳白蛋白,主要成分与人乳非常相似.驴乳是一种较理想的动物蛋白质资源.     

乳蛋白基因在转基因动物乳腺细胞中特异性表达的研究进展

乳蛋白是乳的主要营养成分，乳蛋白的种类及其在乳中的浓度都影响乳的品质，而乳中各乳蛋白的含量都受到相应乳蛋白基因的控制。通过转基因技术，可以在转基因动物乳腺细胞中特异性地表达目的蛋白，从而改善乳的品质以及生产具有特殊药用价值的乳产品。本文主要概述乳蛋白多态性及其作用，乳蛋白基因及多态性，并着重介绍乳蛋白基因在转基因动物体内的表达调控；通过介绍大量转基因试验的研究成果，以探寻改变乳成分的分子遗传基础。     

营养素调控奶牛乳蛋白合成的研究进展

乳蛋白含有机体几乎所有的必需氨基酸,有较高的营养价值。随着蛋白质营养研究的深入,如何提高乳蛋白的产量,改善乳品质已成为当今研究的热点。本文从营养素角度,对碳水化合物、氨基酸及小肽三方面对奶牛乳蛋白合成调控的影响做综述。     

日粮组成对牛奶中乳成分合成与调控机制影响的研究

牛奶中乳蛋白和乳脂肪含量的高低直接关系到牛奶的品质和风味。牛奶中乳蛋白主要可以分为酪蛋白和乳清蛋白两种类型,其合成代谢过程均受到mTOR信号分子通路、JAK-STAT信号分子通路、GCN2-eIF2a信号分子通路的影响。牛奶中乳脂肪主要为三酰基甘油酯、磷脂等,对于牛奶的营养和风味均有重要影响,其受到脂肪酸相关酶ACACA、FAS、SCD1的调控。饲料营养是影响牛奶中乳蛋白和乳脂肪的关键因素之一,包括精粗饲料配比及饲料添加剂的应用等方面。本文对牛奶中乳蛋白和乳脂肪的合成调控机理,及日粮组成对其的影响机制进行阐述,为改善乳品质提供参考。     

乳过氧化物酶的特性及其在羊乳产业中的应用

羊乳富含维生素和蛋白质等营养物质,易被人体消化吸收,却也极利于微生物的生长,如何使用安全、便捷、成本低廉的保鲜方法促进羊乳产业的发展是必须要解决的现实难题。本文从乳过氧化物酶（lactoperoxidase,LP）的结构特性、组成成分、抑菌机理、热力学特性以及稳定性等方面进行论述,并综述了LP在羊乳产业中用于保鲜、检测对原料乳、干酪和发酵型乳制品的影响,为了解LP在羊乳产业的发展与应用提供参考。     

Supporting the extensive dairy sheep smallholders of the semi-arid region of Crete through technical intervention

The objective of this field study was to depict the extensive system of dairy sheep farming in the semi-arid environment of the island of Crete and to assess the potential margins of improvement through technical intervention. Forty-three family-run farms keeping a total of 13 870 sheep were surveyed in seven representative areas of the island. Several parameters were dealt with, concerning socio-economy, flock management and productivity. Study areas differed widely regarding feeds supplied per sheep, land cultivated for feeds, grazing land utilized and housing space. A range of parameters were recorded on flock size and their production characteristics such as births, fertility and number of lambs weaned. Milk yield and parameters associated with milk quality, such as somatic cell counts and total microbial flora, were also recorded. Technical intervention was directed towards removal of non-productive animals, programming of matings, balancing of diets, management of grazing lands and health care. Ewe fertility and numbers of lambs weaned per ewe, as well as harvested milk and milk quality (based on somatic cell counts and microbial load of milk) were also significantly improved. Information derived from this study stresses the important role of extension services to small farm sustainability and contributes to our knowledge of the dairy sheep farming systems in countries around the Mediterranean and elsewhere.     

The impact of genetic merit on ewe performance and efficiency parameters

The aim of this study was to investigate the impact of ewe genetic merit on ewe performance and efficiency parameters. The study consisted of three genetic merit groups (New Zealand [NZ], High Irish, and Low Irish) and ran from 2016 to 2019, inclusive. Each genetic merit group contained 30 purebred Suffolk and 30 purebred Texel ewes, which were selected based on their maternal genetic indexes in their country of origin, namely Ireland (€uro-star Replacement index) or New Zealand (New Zealand Maternal worth). Ewe body condition score (BCS), ewe body weight (BW), milk yield, milk composition, dry matter intake (DMI), and efficiency parameters were all analyzed using linear mixed models. Ewe BW was similar across all genetic merit groups at each time point (P > 0.05). In comparison to both High and Low Irish ewes, NZ ewes had a higher BCS at mating, mid-pregnancy, lambing, week 10 post-lambing (PL, P < 0.05). Ewe BW change was similar across genetic merit groups, except between mating and mid-pregnancy where ewe BW loss was greater for NZ ewes than Irish ewes (P < 0.05) and between weeks 6 PL and 10 PL, where NZ ewes gained BW and High and Low Irish ewes lost BW (P < 0.01). Ewe milk yield, milk fat, total solids, and gross energy content were superior for milk produced by NZ ewes at week 6 PL in comparison to milk produced by High Irish and Low Irish ewes (P < 0.01). NZ ewes produced a greater quantity of milk solids/kg of BW at week 6 PL compared with High Irish ewes (P < 0.01), whereas Low Irish ewes did not differ from either NZ or High Irish (P > 0.05). Low Irish ewes had a greater daily DMI than High Irish ewes in late lactation (week 10 PL, P < 0.05) and had a greater DMI/kg of ewe BW compared with the High Irish ewes at the same time point (P < 0.05). NZ ewes weaned a litter BW equivalent to 60.4% of their mating BW, which was more than the Low Irish ewes who weaned 57.1% of the ewe’s BW at mating (P < 0.01), whereas the High Irish ewes did not differ from either the NZ or Low Irish ewes at 59.3% of the ewe’s BW at mating (P > 0.05). This study presents a range of parameters across ewes of high and low genetic merit, demonstrating the ability to achieve gains through selection of animals of high genetic merit. Sheep producers should consider genetic indexes as a tool to assist in the decision-making process of selecting replacement ewes and/or breeding rams, once satisfied the animal is correct, and meeting the breeding objectives of the system.     

Proteomic identification of ruminal epithelial protein expression profiles in response to starter feed supplementation in pre-weaned lambs

The present study aimed to comparatively characterize the ruminal epithelial protein expression profiles in lambs fed ewe milk or milk plus starter diet using proteome analysis. Twenty new-born lambs were randomly divided into a group receiving ewe milk (M, n = 10) and a group receiving milk plus starter diet (M + S, n = 10). From 10 d old, M group lambs remained with the ewe and suckled ewe milk without receiving the starter diet. The lambs in the M + S group were separated from the ewe and received starter feed. All lambs were slaughtered at 56 d old. Eight rumen epithelia samples (4 per group) were collected to characterize their protein expression profiles using proteomic technology. Proteome analysis showed that 31 upregulated proteins and 40 downregulated proteins were identified in the rumen epithelium of lambs in response to starter diet supplementation. The results showed that starter feeding regulates a variety of biological processes in the epithelium, especially blood vessel development and extracellular matrix protein expression. Meanwhile, the expression of proteins associated with synthesis and degradation of ketone bodies, butanoate metabolism, and citrate cycle signaling transduction pathway were upregulated in the group with starter diet supplementation, including 3-hydroxy-3-methylglutaryl coenzyme A synthase (HMGCS2, fold change [FC] = 1.93), 3-hydroxybutyrate dehydrogenase 1 (BDH1, FC = 1.91), and isocitrate dehydrogenase 1 (IDH1, FC = 8.12). The metabolic processes associated with ammonia detoxification and antioxidant stress were also affected by starter diet supplementation, with proteins, microsomal glutathione S-transferase 3 (MGST3, FC = 2.37) and IDH1, linked to the biosynthesis of glutamate and glutathione metabolism pathway being upregulated in the group with starter diet supplementation. In addition, starter feeding decreased the expression of Ras-related protein rap-1A (RAP1A, FC = 0.48) enriched in Rap1 signaling pathway, Ras signaling pathway, cyclic adenosine monophosphate (cAMP) signaling pathway, and mitogen-activated protein kinase (MAPK) signaling pathway. In summary, starter feed supplementation changed the expression of proteins related to energy production, ammonia detoxification, antioxidant stress, and signaling pathways related to proliferation and apoptosis, which facilitates the rumen epithelia development in lambs. The results provide new insights into the molecular adaptation of rumen epithelia in response to starter diet supplementation at the protein level in lambs.     

羊乳酪蛋白稳定性分析

羊奶酪蛋白稳定性的高低直接决定着羊奶蛋白质的品质,为了获得高品质的羊奶有必要对羊奶中的酪蛋白稳定性进行分析研究.本文概述了我国羊奶制品行业的发展现状,对羊奶酪蛋白的特性进行了简要的分析,并总结了影响羊奶酪蛋白稳定性的因素.综述了温度、pH值、无机盐离子、食品添加剂及超高压处理分别对羊奶酪蛋白稳定性的影响.对羊奶酪蛋白稳定性的控制对羊奶产品的开发具有一定指导意义.     

Growth and reproductive performance of ewe lambs fed corn or soybean meal while grazing pasture

In a 2-yr study a total of 120 Suffolk and Suffolk-cross ewe lambs, approximately 3 mo of age, were assigned within weight strata to one of three treatments: 1) control, pasture only (C), 2) .09 kg soybean meal/(hd.d) (SBM) plus pasture or 3) .45 kg whole shelled corn/(hd.) plus pasture to compare growth and reproductive performance and to determine lamb selectivity of forage quality and type. Each year, supplements were offered from June through the 3rd wk in November. Ewe lambs were managed as one flock on Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) pastures except for a brief daily supplementation period when all lambs were brought into a corral and sorted into treatment groups for the feeding. Ewe lambs were exposed to fertile rams from October 1 through the 3rd wk of November each year. Growth rates of ewe lambs grazing pasture alone were slower than those of corn-supplemented ewe lambs and were comparable to those of SBM-supplemented ewe lambs, but reproductive performances were similar (P greater than .05). Date of first detected rise in serum concentrations of progesterone and date of first observed estrus and lambing performance were similar (P greater than .05) among treatments for each year. Compared to hand-clipped forage, forage samples collected by esophageally fistulated lambs were higher (P less than .05) in crude protein and lower (P less than .05) in acid detergent fiber each year, indicating that lambs selectively grazed higher-quality forage. These data indicate that neither protein nor energy limited growth or reproductive performance of these ewe lambs.     

Postweaning growth, feed efficiency and chemical composition of sheep as affected by prenatal and postnatal testosterone

Data were collected from intact males, castrated males and ewe lambs to investigate the effect of presence or absence of testosterone prenatally and during the postweaning period on postweaning growth, feed intake and carcass chemical composition. Half the lambs from each sex were the progeny of dams that had received five injections of testosterone cyprionate from d 32 through d 87 of gestation. Linear contrasts were used to detect differences. Postweaning daily gain of intact males was greater (P less than .01) than that of male castrates. Ewe lambs from treated dams had approximately 12% greater rate of growth (P less than .04) than ewe lambs from control dams. Ewe lambs from dams that had been treated were 28% more efficient (P less than .01) in the conversion of food to weight than those from untreated dams. Ewe lambs from treated dams had heavier livers (P less than .07). Carcass protein for intact males was greater (P less than .11) than for castrates, and extractable fat was less (P less than .05). Masculinization of growth characteristics of ewe lambs affected the quantity of carcass fat relative to control ewes (7.59 vs 8.92 kg). These ewe lambs also had more water in the carcass than did the control ewes (13.93 vs 12.29 kg). Administration of exogenous testosterone to pregnant ewes over an interval of time approximating time of sexual differentiation in the fetus enhances postweaning growth rate, feed conversion efficiency and chemical composition of genetic females.     

钙螯合盐对乳饮料加工与贮藏稳定性的影响

乳饮料体系中,乳蛋白在加工和贮藏过程中容易出现稳定性问题,从而导致品质的劣化。钙螯合盐有助于解离酪蛋白胶束,增加水相酪蛋白,从而达到增加稳定性的目的。为研究不同构型的钙螯合盐对乳饮料加工和贮藏过程中蛋白稳定性的影响,选用4种不同类型的螯合盐以及4个浓度,分析其对体系加热后浊度、溶解度、粒径分布、乳蛋白的影响,以及贮藏过程中溶解度、各蛋白含量的变化。结果表明：钙螯合盐能显著提高体系的稳定性,尤其是贮藏稳定性,随着螯合作用越高,稳定性越好。但同时也发现螯合能力大的盐可能会带来成胶、促进聚集等不良作用。     

市售婴幼儿乳粉中乳清蛋白的胃肠消化稳定性及其抗原性评估

牛乳含有丰富的蛋白质、脂肪等营养素，是婴幼儿重要的营养来源，牛乳蛋白也是诱发婴幼儿食物过敏的 主要因素之一。对5 种市售婴幼儿乳粉进行体外模拟静态消化，通过电泳、水解度测定分析蛋白消化稳定性，并利 用间接竞争酶联免疫吸附实验评价乳清蛋白的抗原性。结果表明：5 种配方乳粉中，α-乳白蛋白和β-乳球蛋白在样 品1、2、4中具有较好的消化稳定性，胃肠消化后，样品1中α-乳白蛋白和β-乳球蛋白的抗原性降低，样品2中2 种过 敏原蛋白的抗原性增加，样品4中α-乳白蛋白的抗原性增加，β-乳球蛋白的抗原性降低；α-乳白蛋白和β-乳球蛋白在 样品3和5中消化稳定性较低，经胃肠消化后，样品5中2 种过敏原蛋白的抗原性增加，样品3中α-乳白蛋白的抗原性 增加，β-乳球蛋白的抗原性降低。     

Carry-over effects of body condition in the early pregnant ewe on peri-partum adipose tissue metabolism

This study evaluated the carry‐over effects of ewe body reserves during early pregnancy on peri‐partum adipose tissue metabolism. Forty‐nine multiparous ewes were divided in three categories according to their body condition score (BCS) at day 30 of pregnancy (BCS < 3, 2.5–2.75; BCS = 3; BCS > 3, 3.25–3.5). Live‐weight (LW) and BCS gains from 1st to 4th month of pregnancy were greater in ewes with BCS < 3 and 3 than in >3 animals. In contrast, in the last month of pregnancy, there was BCS decrease in all groups, although LW continued increasing. There were no differences in LW or BCS across ewe categories during this period. Peripheral leptin levels throughout the three last weeks of pregnancy were greater in ewes with BCS > 3 than in the rest, but this difference did not persist after lambing. Plasma metabolites related to energy metabolism, milk yield and lamb growth were not affected by ewe BCS in early pregnancy. Long‐chain saturated milk fatty acids (FA) (C16–C24) were greater in ewes with lowest BCS (<3 and 3). Ewes with greater BCS showed greater monounsaturated and lowest polyunsaturated milk FA content. Ewe post‐mating body reserves affect both pre‐partum leptinaemia and post‐partum milk polyunsaturated fatty acids content, but it had little effect on lamb performance.