Anomalous Pregnancies during Late Embryonic/Early Foetal Period in High Producing Dairy Cows

This study analyses anomalous cases of gestation ending in pregnancy loss during the early foetal period and their effect on progesterone and plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations. Data derived from a large-scale ultrasound pregnancy diagnosis programme in high producing dairy cows. Over a 3-year period (2004–2007), a very low incidence (0.5%: 15 of 3094) of anomalous pregnancies was recorded. The results revealed that the following anomalies were detected on days 35–41 of gestation in cows carrying singletons with one single corpus luteum: embryo death in eight cows (0.3%); and embryo in the uterine horn contralateral to the corpus luteum in seven cows (0.2%). All these animals suffered pregnancy loss during the early foetal period. In cows carrying dead embryos, no signs of conceptus degeneration were observed on pregnancy diagnosis. Amnion size (approximately 25 mm diameter) and uterine horn fluid contents were estimated to be similar to those of the normal pregnant cows in this period. In the contralateral gestations, live embryos were observed in all ultrasound checks before pregnancy loss. Uterine fluid contents increased in the two cows in which gestation continued for more than a week. In the cases of embryo death but not in those of contralateral gestation, a drop in PAG-1 levels was noted prior to pregnancy loss. Two cows carrying dead embryos increased with time allantoic fluid contents. The PAG-1 values increased with time in one cow bearing a dead embryo (from 2.31 to 6.79 ng/ml) and in two of the contralateral gestations (from 1.66 to 2.33 ng/ml and from 0.39 to 6.79 ng/ml, respectively). Results of this study indicate that the foetal membranes continue to undergo some activity following embryo death, and that contralateral pregnancy may determine failure of the gestation process.     

Early Detection of Pregnancy and Embryonic Loss in Dairy Cattle by ELISA Tests

Over a 25-month period 8118 blood samples were assayed for the presence of the serum pregnancy specific-protein B (PSPB) and progesterone (P4) concentrations on three Hungarian large-scale dairy farms. Pregnancy (n = 4085) was checked by BioPRYN assay at 30-36 days post-insemination (PI). Samples from all cows that tested not pregnant and from cows with an optical density (OD) reading in the BioPRYN test that was between 0% and 30% above the cutoff OD value were tested for serum P4 concentration. According to serum P4 concentration, cows were assigned to three categories: high (>4 ng/ml), medium (2-4 ng/ml) and low (<2 ng/ml) serum progesterone. The authors predicted a presumed (low) or possible (medium) late embryonic loss (LEL) or maintenance of the pregnancy (high). A total of 710 LELs were detected (17.4%) and 31.8% of them were predicted because of a low OD value at 30-36 days after insemination. Lower PSPB serum level significantly refers for LEL (p < 0.0001). The prediction rate for the true embryonic loss was 31.8% when OD cutoff from 0% to + 30% of cutoff was examined while it was 62.5% when the threshold was OD cutoff of 0% to 10% of cutoff. The authors conclude that BioPRYN was useful for prediction of a part of LEL in dairy cows and serum P4 concentration in these cows related to the rate of LEL.     

Therapeutic Approaches to Pregnancy Loss of Non‐infectious Cause During the Late Embryonic/Early Foetal Period in Dairy Cattle. A Review

The problem of pregnancy loss during the late embryonic/early foetal period due to non‐infectious causes in dairy cattle is on the rise, especially in high milk producing cows. This review discusses recent therapeutic approaches designed to reduce the incidence of early foetal loss. These strategies are based on the fact that low plasma concentrations of progesterone are commonly related to foetal loss. Progesterone supplementation during the late embryonic/early foetal period has proven useful in curtailing losses, mainly in single pregnancies, whereas a more positive effect of treatment with GnRH than progesterone has been found in twin pregnancies. Therapeutics is not necessary in cows with an additional corpus luteum. In practical terms, suggestions include recording the number of embryos and corpora lutea on first pregnancy diagnosis and checking for normal pregnancy progression on day 60 post‐insemination.     

Early Foetal Loss Correlates Positively with Seroconversion against Mycobacterium avium paratuberculosis in High‐Producing Dairy Cows

This study was designed to examine (i) the seroprevalence of Mycobacterium avium subs paratuberculosis (MAP) in a high‐producing dairy herd with clinical symptoms of bovine paratuberculosis, (ii) MAP seroconversion and seronegativation dynamics in the herd and (iii) possible relationships between MAP infection status and herd reproductive performance. One single blood test per cow was performed early post‐partum on a monthly basis from day 10–40 post‐partum during the first year of the study in 519 cows belonging to a commercial dairy herd. A subset of 111 cows that became pregnant during the study was tested again 60–200 days later during the early foetal period, immediately after the first confirmation of gestation at 58–64 days post‐AI. Logistic regression analysis indicated no effect of any independent variable on MAP seropositivity and conception rate 28–34 days post‐AI. MAP seropositivity was not a factor affecting the anoestrous, subfertility and early foetal loss rates. In the subset of 111 cows, animals that seroconverted had a 3.9 times greater risk of suffering from early foetal loss (30.3%, 10/33) than the remaining pregnant animals (10.3%, 8/78), (95% confidence interval: 1.11–13.4; p = 0.003). In conclusion, early foetal loss was positively correlated with seroconversion to MAP. Reproductive performance was not impaired by MAP infection.     

妊娠相关糖蛋白(PAG)在奶牛早期妊娠诊断上的应用现状

妊娠相关糖蛋白(pregnancy associated glycoproteins,PAG)是反刍动物妊娠后外周血液出现的特异性蛋白,在妊娠过程中发挥着重要的作用。目前,在生产上通过检测PAG在血清中浓度能够进行奶牛的妊娠诊断。作者综述了PAG的发现、分离纯化及其在奶牛体内的代谢水平和近年奶牛早期妊娠诊断上的应用情况。     

奶牛早期流产及不孕与黏附分子

黏附分子与奶牛卵巢功能、受精、早期胚胎发育、胚胎附植具有密切关系。黏附分子在卵巢颗粒细胞和大黄体细胞呈周期性表达 ,对卵巢的周期性变化起到调节作用 ;成熟的精、卵细胞其表面分别表达黏附分子及相应的受体 ,对受精具有重要作用 ;早期胚胎发育的不同阶段表达的的黏附分子不同 ,一些黏附分子影响胚胎血管的形成 ,该期不同阶段的滋养层细胞所表达的黏附分子种类和数量也不同 ,这与滋养层的浸润密切相关 ;黏附分子在子宫内膜的表达也呈周期性和细胞特异性。而一些细胞因子、甾体激素对黏附分子表达又具调节作用。研究黏附分子在早期胚胎的作用机理及临床意义 ,分析黏附分子与奶牛早期流产、不孕的关系及该研究领域目前存在的问题 ,展望其研究方向 ,对提高奶牛自然妊娠、胚胎移植及克隆的成功率具有重要意义     

影响奶牛早期胚胎丢失的因素

早期胚胎丢失,即胚胎着床之前的胚胎死亡,是影响奶牛妊娠率的主要因素。奶牛妊娠早期的胚胎死亡率较高,给牧场造成了严重的经济损失。目前,对于早期胚胎丢失的研究主要集中在染色体异常、生殖激素紊乱、热应激、免疫因素、双胎妊娠、疾病、B族维生素缺乏等方面。本文综述了早期胚胎丢失发生的原因,为预防早期胚胎丢失提供依据。     

奶牛钙的营养需要

功能 细胞外钙是骨骼形成、神经冲动传递、骨骼肌兴奋及心肌收缩、血液凝固所必需的,是牛乳的成分。细胞内钙的浓度为细胞外钙浓度的万分之一,细胞内钙与许多酶的活性有关,是细胞表面向细胞内部传递信息的重要的第二信使。 机体内的钙约有98％存在于骨骼中,钙与磷酸根离子一起维持骨骼的强度和硬度。其余2％的钙主要分布于细胞外液中。成年奶牛血浆钙的正常浓度为2.2-2.5mM(9-10mg/dl,或4.4-5mEq/     

酶免疫分析测定法诊断奶牛早期妊娠诊断的研究与应用进展

介绍了酶免疫分析测定法的概念、种类、作用机理,及其在奶牛早期妊娠诊断的研究应用和孕酮酶免疫试剂盒的研究与应用。     

Twinning in Dairy Cattle

Twinning in dairy cattle is an unavoidable outcome of reproduction and is undesirable because it reduces the overall profitability of a dairy operation through negative effects on cows calving twins as well as on calves born as twins. Cows calving twins are at greater risk for many periparturient reproductive and metabolic disorders than nontwinning herdmates, and incidences of abortion, stillbirth, neonatal calf mortality, and reduced birth weight are greater among twin compared with singleton calves. Twinning is a complex trait with multiple causative factors, and empirical evidence supports a role for both genetic and environmental risk factors in cattle. Risk factors for twinning include genetics, season, parity, ovulation rate, and milk production. The observation that twinning has increased in the dairy cattle population over time suggests a concurrent change in one or more of these causative factors during this same period. At present, dairy farmers and their consultants are ill prepared to make sound-management decisions to mitigate the negative effects of twinning on their operations because of a lack of applied scientific data on management strategies for periparturient dairy cows carrying twin fetuses. A clear understanding of the factors responsible for twinning is essential for future development of strategies to manage twinning in dairy operations.     

OC8Effect of Progesterone Supplementation During Early Foetal Period in Neospora caninum Seropositive Dairy Cows

The aim of this study was to analyse the effect of filtration through Sephadex on the subpopulation characteristics of the boar semen. For this purpose 3 ml of 16 commercial doses of fresh diluted boar semen were filtered through a Sephadex G-15/Polypropylene column. Motility parameters were analysed by a CASA system and statistical study was performed by SAS package using the VARCLUS and the FASTLUST procedures. Statistical study revealed four subpopulations in fresh boar semen, as previously had described (Theriogenology 61: 673–690).Total motility was higher in control than in filtered semen, but there were not statistical differences (65.63 ± 9.65 vs 41.40 ± 9.02). Moreover, the analysis did not show many changes neither in the characteristics nor in the distribution of the four subpopulations. As example although ALHmed of filtered samples were slightly higher, there were only significant differences (p < 0.001) in two subpopulations (subpopulation 2 : 2.2 ± 0.05 in control vs 2.7 ± 0.08 in filtered. Subpopulation 3 : 4.5 ± 0.11 in control vs 5.8 ± 0.23 in filtered semen). HME was also statistically different (p < 0.005) in one subpopulation, showing great values in filtered semen (1.7 ± 0.15 vs 3.0 ± 0.30). In conclusion, the filtration by Sephadex/Polypropylene column does not cause strong changes in subpopulation sperm distribution.     

奶牛前期泌乳性能与305天产奶量的相关分析

本文对西安草滩农场第四奶牛场 66头奶牛的第一泌乳期完整的原始资料进行分析 ,利用最高月产奶量、90 d奶量、高峰日、乳脂率等泌乳前期产奶指标对 30 5 d奶量进行相关分析 ,结果表明高峰日、最高月产奶量、90 d奶量与 30 5 d奶量分别呈强正相关 ,相关系数显著性检验均达到显著或极显著的程度 ,分别为 0 .367( P<0 .0 1 )、0 .41 1 ( P<0 .0 1 )和 0 .2 62 ( P<0 .0 5 ) ;乳汁率与 30 5 d奶量呈弱负相关 ,相关系数为 - 0 .2 5 5 ,达到显著程度 ( P<0 .0 5 )。本文分析的奶牛几项泌乳前期产奶指标与 30 5 d产奶量的关系密切 ,为奶牛的早期选育工作提供了实际依据。     

奶牛近亲交配及控制

1．科学认识近亲交配 近亲交配是全球荷斯坦牛群所普遍面临的问题，现在，全球荷斯坦牛的主要系谱都可以追溯到北美的几个共同祖先。2004年5月美国农业部动物遗传改良计划实验室(AIPL)公布了美国荷斯坦牛近交情况，如下图所示。     

应用DHI对某奶牛群生产性能的综合分析

应用DHI对某奶牛群生产性能进行综合分析,探索在奶牛牧场管理过程中,牛奶体细胞数SCC与奶牛产奶量、健康、胎次的关系,以期应用DHI提高奶牛生产性能。应用奶牛生产性能测定(DHI)体系对900头产奶牛进行测定和分析,发现在奶牛泌乳的各个阶段,随着牛奶体细胞数增高,各胎次奶牛产奶量呈逐渐下降趋势;体细胞数随着胎次的增加而上升,奶牛产奶量随奶牛胎次的变化而变化。奶牛存在产犊间隔长,繁殖障碍和营养问题,需采取相应的改进措施。     

奶牛与热应激

盛夏,气候炎热,空气潮湿,极易引起奶牛热应激。由于炎热对奶牛带来的负面影响远远高于寒冷对其产生的影响,所以在夏季避免奶牛热应激,是保证奶牛有较高生产性能的根本措施。因此,广大奶农要切实加强对奶牛的饲养管理工作,确保奶牛顺利度过夏暑季节,以保持牛场良好的经济效益。     

利用性控精液体外生产奶牛早期胚胎

实验进行了精子处理方法、洗精液中添加抗生素种类及浓度、常规培养小滴(50μL)中入胚数的筛选,按照不同荷斯坦公牛个体分选的性控精液对体外生产的牛早期胚胎发育潜力的影响。结果表明:离心法处理性控精液效果最优。利用经过分选的性控精液进行体外受精(IVF)后都较易导致污染,且受精后的体外胚胎发育效果都较差。在洗精液中添加10μL/mL头孢哌酮钠的IVF胚胎体外发育较好,囊胚率达到16.9%;且在常规培养小滴中适当减少入胚数,能有效抑制利用性控精液制备的奶牛IVF胚胎自身对培养微滴的污染。利用直接离心法处理精液,在洗精液中添加头孢哌酮钠10μL/mL,可以成功进行牛性控精子的体外受精,但目前的受精效果低于用普通精子的体外受精效果。