Pregnancy diagnosis in cattle by measuring vaginal electrical resistance

The results of early pregnancy diagnosis using a milk progesterone assay and a measurement of electrical resistance of the vaginal mucosa made on 135 dairy cows in two herds are compared. The tests were carried out on the day of insemination and 21 days later. Ninety-eight cows were diagnosed as pregnant by both tests. Of these, 92 calved and there were 6 cases of suspected embryonic mortality. Thirty animals were diagnosed as non-pregnant by both tests and none calved. One cow, diagnosed as non-pregnant by the vaginal electrical resistance method, calved later. Of the remaining 6 cows, 4 had extended postparturition anoestrus, one had cystic ovarian disease and another had a long oestrus cycle.The results of this study suggest that measurements of the electrical resistance of the vaginal mucosa in dairy cows may have a part to play in on-farm pregnancy diagnosis.     

Effects of a Progesterone‐Based Oestrous Synchronization Protocol in 51‐ to 57‐Day Postpartum High‐Producing Dairy Cows

The aim of this study was to investigate the effect of applying a progesterone‐based oestrous synchronization protocol at 51–57 days postpartum in high‐producing dairy cows. The data analysed were derived from 1345 lactating cows. Cows between 51 and 57 days postpartum were assigned to the groups: control, PRID (receiving a progesterone‐releasing intravaginal device for 9 days, and prostaglandin F_2α 24 h before PRID removal) or GnRH–PRID (the same as the PRID group plus GnRH at PRID insertion). Oestrus was detected by using pedometers and confirmed by examination of the genital tract at AI. Oestrous and conception rates before days 71–77 postpartum, pregnancy loss in early pregnant cows or the cumulative conception rate registered on day 120 postpartum were considered as the dependent variables in four consecutive logistic regression analyses. Based on the odds ratios, the oestrous rate increased by a factor of 1.73 in cows showing oestrus before treatment for each unit increase in the number of previous oestruses; decreased by a factor of 0.44 in the control group with respect to the treatment groups; and by a factor of 0.61 in cows without luteal structures at treatment with respect to cows with corpora lutea. The conception rates of cows inseminated before days 71–77 postpartum remained similar across the groups, whereas the likelihood of pregnancy loss for cows becoming pregnant during this period was 0.11 times lower in the PRID group than in the control. Based on the odds ratio, the likelihood of a higher cumulative conception rate on day 120 postpartum: increased in cows showing oestrus before treatment by a factor of 1.41 for each unit increase in the number of previous oestruses, was reduced 0.56‐fold in control cows compared with treated cows, and was also reduced by a factor of 0.98 for each kilogram of milk production increase recorded at treatment. In conclusion, although oestrous synchronization programmes performed in this study did not improve fertility, cows treated with progesterone could be inseminated earlier than untreated cows, such that the treatments increased the cumulative pregnancy rates determined on day 120 postpartum. In addition, fewer pregnancy losses were observed in early pregnant cows in the PRID group than the GnRH–PRID group.     

Oestrous cycles, oestrus and ovulation of the zebu in the Mexican tropics

The length of the oestrous cycle, oestrus and the time of ovulation were assessed in 20 adult, non-lactating zebu cows over 53 consecutive days of observation. Oestrus was detected at 30-minute observation periods daily. Peripheral blood samples were collected twice weekly for progesterone determination. To measure the length of the synchronised oestrous period, 10 cows with a palpable corpus luteum were injected with prostaglandin F2 alpha and continuously observed for 96 hours. Two cows at a time were exposed to a bull with a deviated penis for five minutes every three hours during this period. To measure the length of the natural oestrus, eight of the 10 cows from the previous experiment were continuously observed from day 21 after prostaglandin injection. They were kept during the daytime in a field with two teaser bulls and at night in a cattle pen where they were exposed to a teaser bull every three hours. Oestrus was considered to occur when the cow stood to be mounted. Ovulation was detected by rectal palpation every three hours in five cows starting six hours after receptivity commenced until ovulation took place. The length of the oestrous cycle was 20.1 +/- 1.9 days; 20 per cent of the animals did not show oestrus although their progesterone levels demonstrated that they were cycling. Two cows showed oestrus following prostaglandin F2 alpha injection although they were cycling as revealed by serum progesterone. Five animals showed behavioural oestrus around 118 hours after injection and following their release. Oestrus duration was 15.3 +/- 6.0 hours and ovulation occurred 28.2 +/- 5.0 hours after the start of the period of sexual receptivity.     

Evaluation of real time B-mode ultrasound scanning for detecting early pregnancy in cows

A real time B-mode ultrasound scanner with a 7.5 MHz rectal linear transducer was used in two trials to detect whether dairy cows, less than 25 days after insemination at standing oestrus, were pregnant. In the first trial 17 cows were inseminated on the same day, and their reproductive tracts were examined 14, 15, 16 or 17 days after insemination. All the cows were diagnosed accurately as either pregnant or not pregnant. In the second trial 22 cows were inseminated on the day of observed oestrus while 14 were observed at oestrus but not inseminated. The animals were kept as a mixed group and an experienced operator scanned the uterus of each cow on one occasion, without knowing either the dates of observed oestrus or which cows had been inseminated. The rate of correct diagnosis was only 33 per cent in cows up to 16 days after oestrus, but increased markedly after 17 days and was 100 per cent by day 20.     

Improved Detection of Reproductive Status in Dairy Cows Using Milk Progesterone Measurements

This study tested a model for predicting reproductive status from in-line milk progesterone `measurements. The model is that of Friggens and Chagunda [Theriogenology 64 (2005) 155]. Milk progesterone measurements (n = 55 036) representing 578 lactations from 380 cows were used to test the model. Two types of known oestrus were identified: (1) confirmed oestrus (at which insemination resulted in a confirmed pregnancy, n = 121) and (2) ratified oestrus (where the shape of the progesterone profile matched that of the average progesterone profile of a confirmed oestrus, n = 679). The model detected 99.2% of the confirmed oestruses. This included a number of cases (n = 16) where the smoothed progesterone did not decrease below 4 ng/ml. These cows had significantly greater concentrations of progesterone, both minimum and average, suggesting that between cow variation exists in the absolute level of the progesterone profile. Using ratified oestruses, model sensitivity was 93.3% and specificity was 93.7% for detection of oestrus. Examination of false positives showed that they were largely associated with low concentrations of progesterone, fluctuating around the 4 ng/ml threshold. The distribution of time from insemination until the model detected pregnancy failure had a median of 22 days post-insemination. In this test, the model was run using limited inputs, the potential benefits of including additional non-progesterone information were not evaluated. Despite this, the model performed at least as well as other oestrus detection systems.     

Farmer record of pregnancy status pre-slaughter compared with actual pregnancy status post-slaughter and prevalence of gross genital tract abnormalities in New Zealand dairy cows

AIMS: To record the prevalence of gross abnormalities of the reproductive tract in culled New Zealand dairy cows, to determine how accurately farmers classify the pregnancy status of their animals and to establish if this was influenced by method of pregnancy diagnosis. METHODS: The reproductive tracts from 1134 cull dairy cows were examined after slaughter and evisceration for the presence of gross abnormalities, ovarian activity and pregnancy at a commercial abattoir. The farmers that had submitted these animals for slaughter were surveyed for information about the farm and herd from which each cow was derived and to establish whether the farmer believed each cow to be pregnant or not. The method that had been used to determine pregnancy status was recorded for each animal. RESULTS: Gross abnormalities were evident in 5.7% of reproductive tracts. Ovarian activity (presence of follicles 5 mm diameter and/or a corpus luteum) was apparent in 88% of non-pregnant cows. Pregnancy was detected in 39% of cows, of which 2.3% carried twins. The pregnancy status evident at slaughter varied from that reported by farmers in 7.0% of the 954 cows for which farmers were able to provide information. Of the cows that had been examined by palpation or ultrasound per rectum prior to slaughter, 10.3% that were recorded as non-pregnant by farmers were pregnant, and 3.2% of those recorded as pregnant were not. Of the cows that had not been examined, 3.8% of those recorded as nonpregnant by farmers were pregnant while 10.4% of those recorded as pregnant were not. There was no apparent association between gross genital tract abnormalities or ovarian activity and the misclassification of pregnancy status. Amongst cows that were pregnant at slaughter the foetus was significantly smaller in cows that had been recorded as 'not pregnant' after palpation or ultrasound examination than in cows that had been recorded as 'not pregnant' on the basis of farmer observation only. CONCLUSIONS: The prevalence of gross abnormalities of the reproductive tract was comparable to that reported in similar studies overseas. Farmer observation as a method of pregnancy detection overestimates pregnancy rate. Pregnancy status may be misclassified or misrecorded following palpation or ultrasound examination of cattle per rectum. Accurate classification of pregnancy status is dependent on the method and timing of pregnancy diagnosis and on minimising errors of diagnosis, cow identification and recording.     

Behavioural signs of oestrus during pregnancy in lactating dairy cows

Abstract

Two herds of approximately 50 dairy cows were observed for oestrous behaviour for 6 weeks, 12 times a day for 30 minutes. It appeared that 3.08% of the pregnant cows showed oestrous behaviour during pregnancy (EBP) in such an intensity that they would have been considered in oestrus. With a less rigid oestrus detection threshold, 10.8% of the pregnant cows would have been considered to be in oestrus. Animals showed EBP during all months of pregnancy, but most of the behavior was observed in the middle of the gestation period.     

Progesterone concentration in defatted milk of dairy cows in early pregnancy.

Progesterone concentrations have been measured in defatted milk of British Friesian cows of four herds during the oestrus cycles (other than short cycles) immediately before artificial insemination (AI) at oestrus and immediately after AI (in non-pregnant cows), and during early pregnancy. Differences in mean progesterone concentrations between herds were significant (P less than 0.05) on all days within the day 10-18 period after AI, both in pregnant and in non-pregnant, inseminated cows but were not significant between pregnant and non-pregnant cows within herds until day 17 or 18. It is concluded that up to this time (that of luteolysis in non-pregnant cows) undefined factors, variable among herds, can have a much greater influence on the rate of progesterone secretion by corpora lutea and consequent progesterone concentration in plasma and milk than does the presence of conceptuses. Maximum mean progesterone concentration reached during early pregnancy in two herds did not differ significantly; it was reached in the 11-15-day period in one herd but not until 46-50 days in the second. Mean progesterone concentration declined after day 90.     

同步发情对奶牛冷冻胚胎移植受体牛妊娠率的影响

[目的]探讨提高奶牛冷冻胚胎移植妊娠率方法。[方法]对比1次、2次同步发情奶牛冷冻胚胎移植受体母牛的试验妊娠率。[结果]1次、2次同步发情胚胎移植妊娠率分别为44.45%和70.73%。[结论]同步发情对胚胎移植妊娠率有很大影响,2次同步发情可显著提高奶牛冷冻胚胎移植妊娠率。     

Accuracy of bovine pregnancy detection using transrectal ultrasonography at 28 to 35 days after insemination

OBJECTIVE: To estimate the accuracy of real-time ultrasonography to detect pregnancy in dairy cows at 28 to 35 days after insemination. METHODS: Cows that did not return to oestrus between 18 and 24 days after a first insemination (n = 526) were examined by transrectal ultrasonography from 28 to 35 days after insemination. Pregnancy was confirmed by the observation of a foetus, but fluid in the uterine horn and the presence of embryonic membranes were also noted. When pregnancy was not confirmed by the observation of a foetus, a second examination 7 days later, confirmed these remaining cows as pregnant or not pregnant to the first insemination. Detection of pregnancy at this early examination was compared with manual transrectal pregnancy examination performed 10 to 13 weeks after insemination (13-week examination). RESULTS: There were 44% of cows that were pregnant to the first service, 34% that had returned for a second service 18 to 24 days after the first insemination, and 20% of cows that were not pregnant, and had not returned normally for a second service (non-pregnant, non-return) within 24 days of their initial insemination. The presence of a foetus at 28 to 35 days after insemination was accurately predicted by a simplified method where uterine fluid accumulation and embryonic membranes were observed. Foetal loss between the early detection and the 13-week examination (9% of pregnancies) indicated that 28 to 35 days post insemination was too early to reliably detect pregnancy. CONCLUSION: Early examination of pregnancy with transrectal ultrasonography is an accurate method to identify non-pregnant, non-return cows. The examination can be simplified by the observation of uterine fluid accumulation and embryonic membranes, as opposed to the more involved process of observing the foetus.     

使用性激素提高奶牛性控冻精受胎率的探讨

我国东北地区地域辽阔,饲草资源丰富,是发展奶牛、肉牛的主要产业带,但是东北地区冬天较冷,对奶牛养殖有一定影响,在繁殖方面会影响奶牛的发情率和受胎率,雌性激素对奶牛的发情和配种妊娠有一定效果。为了提高奶牛的发情率和怀孕率,本试验于10～12月份在阜新地区,随机选择了一些青年牛分为对照组、促排卵素组和促黄体素组,探讨提高受胎率的方法,结果显示受胎率并没有显著提高(P>0.05),下一步应该从其他方法再做努力。     

不孕奶牛宫颈黏液相关ASA免疫印迹分析

为探讨和分析免疫性不孕奶牛和可孕奶牛宫颈黏液ASA能够识别的精子膜抗原及其差异,本试验通过提取精子膜总蛋白,对24头免疫性不孕奶牛和14头可孕奶牛宫颈黏液ASA能够识别的精子抗原进行了比较分析。免疫印迹试验结果显示,不孕奶牛宫颈黏液ASA对分子质量为88-90ku、66ku、55~57ku、25-27ku的精子膜抗原有特殊免疫性反应,识别抗原率为100％（24／24）、100％（24／24）、87．5％（21／24）、70．8％（17／24）;而可孕奶牛宫颈黏液AsA对分子质量为88-90ku、55-57ku、25-27ku的识别率仅为21．4％（3／14）、14．2％（2／14）、14．2％（2／14）,可孕奶牛宫颈黏液不能识别分子质量为66ku#~精子膜抗原。结果表明,不孕奶牛宫颈黏液ASA~g够识别更多的精子膜抗原,这些精子膜抗原可能与免疫性不孕有密切相关,对其深入的研究将有助于免疫性不孕相关精子膜抗原的筛选和鉴定。     

Oestrus synchronisation with a prostaglandin analogue: I. Systems in lactating dairy cattle

Three trials were completed to compare different regimes for the use of an analogue of prostaglandin F₂ alpha(“Estrumate”: ICI) in the breeding management of herds of lactating dairy cows with seasonally concentrated calving patterns. The first regime involved two injections of ‘Estrumate’ 11 days apart, followed by insemination, either at 72h and 96h after the second injection, or at the first observed oestrus. Every cow had calved at least 40 days before the first injection. The second regime involved a single ‘Estrumate’ injection given to every cow not inseminated during the first seven days of the breeding programme. Treated cows were inseminated when observed in oestrus within 48h of injection, or at 72h and again at 96h. The third regime utilised the technique of tail-painting during the pre-mating period to identify groups of cycling cows which were subsequently givena single injection of “Estrumate” and inseminated 72h lateror at a subsequent behavioural oestrus.

All regimes significantly altered the conception pattern from that obtained in untreated herd-mates. The variable incidence of post-partum anoestrus, genuine short oestrous cycles and the degree of precision in oestrus synchronisation in lactating dairy cows resulted in many animals being unnecessarily injected and/or inseminated. The third regime overcame most of these problems and could have application in many largeherds. The identification of cycling animals and insemination at detected oestrus are important components of programmes using prostaglandins for the purpose of oestrus synchronisation in lactating cows in seasonal dairy herds.     

基于UHPLC-QTOF-MS代谢组学方法筛选奶牛不同妊娠状态时的候选生物标志物

旨在筛选人工授精后第17天奶牛在不同妊娠状态时的候选生物标志物。本研究以宁夏某奶牛场体重为（550±50） kg,体况评分相近的经产（2~3胎次）健康荷斯坦奶牛为试验对象。同期发情后,在人工授精后第17天晨饲前对奶牛进行尾静脉采血,后期采用计步器和B超仪诊断出奶牛的妊娠状态。根据诊断结果将奶牛分为妊娠组（A组,n=12）和未妊娠返情组（B组,n=24）,将这两组血样进行代谢轮廓及代谢物变化分析。主成分分析（PCA）和正交偏最小二乘法-判别分析（OPLS-DA）结果显示,A、B两组血浆代谢轮廓均发生了明显变化,A、B两组之间共检测出8种ROC （Receiver operating characteristic curve）曲线下面积（area under the ROC curve,AUC）＞0.8的差异代谢物。丙氨酸-亮氨酸、甘氨酸、脯氨酸、L-正亮氨酸、DL-苯丙氨酸、肌氨酸、吡咯-2-羧酸和缬氨酸-蛋氨酸有望成为识别妊娠组（A组）和未妊娠返情组（B组）的差异代谢物。综上表明,血浆中的这8种代谢物有望成为奶牛妊娠识别阶段潜在的生物标志物,为配种早期妊娠识别提供新思路。     

The reproductive performance of New Zealand dairy cows after induction of calving

Induction of premature calving contributes to subsequent failure of some dairy cows to become pregnant and calve. Of a sample of 276 cows 16.7% failed to calve the following year despite the occurrence of oestrus relatively early after calving, and several matings. The cows which did conceive had a normal first-mating calving rate of 53.9%, requiring 1.7 matings per pregnancy. Two of the 18 survey herds under consideration suffered lengthy calving-to-first-mating oestrus intervals, presumably because the induced cows were in poor condition at the time of calving.     

Behavioural and Physical Signs Associated with Oestrus and Some Aspects of Reproductive Performance in Fogera Cows and Heifers

An investigation was carried out into the behavioural and physical signs of oestrus in 70 Fogera cows and heifers between December 1993 and May 1994 at Metekel Cattle Breeding and Improvement Ranch, Ethiopia. Retrospective information generated from records made between 1991 and 1994 was evaluated for some aspects of the reproductive indices. The mean±SD duration of oestrus (n = 136) was 10.6±4.5 h (range 2.2–21). Most oestruses (63.2%) started during the day (06:00–18:00). The incidence of oestrus was significantly affected by months (² = 21.86; p<0.001). Among the physical signs, standing to be mounted was the most consistent indication (97.8%) of oestrus. About 12.5% of the cows in oestrus did not mount other cows. The retrospective study indicated that the mean inter-oestrus interval for 46 oestruses was 29.2±19.7 days. The average gestation length for 141 cows was 276 days. Continuous and careful observation of oestrus would reduce the reproductive wastage that arises from less pronounced heat periods and those occurring at night, especially for ranches that use artificial insemination and have a limited number of bulls.     

Effect of Acute Bull Exposure Around the Time of Artificial Insemination on Serum Oxytocin and Progesterone Concentrations and Pregnancy Rates in Dairy Cows

This study examined the effect of acute bull exposure around the time of artificial insemination (AI) on oxytocin and progesterone concentrations, and pregnancy rates in dairy cows. Ninety six dairy cows, stratified according to parity into primiparous and pluriparous, were divided into three groups; short bull exposure (SBE; 10 min, n = 32), long bull exposure (LBE; 4 h, n = 32) or no bull exposure (NBE; n = 32). On day 45 post‐partum, all cows were treated with PGF2α on three occasions 11–14 days apart to synchronize oestrus. They were submitted to fixed time AI 80 h after the third PGF2α injection. Cows in the SBE and LBE groups were artificially inseminated 5 min after the introduction of the bull. From a subset of cows (n = 6 per group; three primiparous and three pluriparous), blood samples were collected once every 5 min starting 15 min before AI until 15 min after AI and analysed for oxytocin concentrations. Additional blood samples were collected for measurements of progesterone (P4) concentrations once daily for 4 days starting on the day of AI and once every 3 days thereafter until day 22. The effects of bull exposure, time, parity, difficulty of AI, and pregnancy on oxytocin and P4 concentrations were analysed using the mixed linear model procedure. Mean oxytocin concentrations or change in oxytocin concentrations after bull exposure or AI were not different among groups. Pregnancy rates for the NBE, SBE and LBE groups were 55.5%, 33.3% and 44.4%, respectively, and were not different among groups. In conclusion, acute bull exposure around the time of AI did not affect oxytocin and progesterone concentrations and did not improve pregnancy rates in dairy cattle under these farms conditions.     

用血清酸滴定法对牛进行早期妊娠诊断的研究

采用血清酸滴定法对配种后16 d～45 d的1 008头不同品种的母牛进行了早期妊娠诊断研究,检出妊娠牛764头,未妊娠牛244头;与直肠检查结果对比,妊娠符合率为90.31%(690/764),未孕符合率为93.03%(227/244),总符合率为90.97%(917/1008).对3种不同品种牛试验结果经3组间及两组间卡方检验统计分析,无显著差异(P＞0.05).表明血清酸滴定法用于牛的早孕诊断具有诊断时间早、方法简便、结果准确等优点,宜于在基层推广.     

Chemical contamination of the cervical mucus in cows in relation to pregnancy and age factors]

Applying the method of absorption atom spectrometry (AAS), the contamination of cervical mucus by chemical elements (Cd, Pb, Hg, Cr, Cu, Zn) was demonstrated in the oestrus period of cows in different ecological agricultural regions of the North Moravian region. The results of observation revealed only a statistically significant difference (P less than 0.05) in Cd contents in the test groups; test group mean = 0.015 micrograms.g-1 Cd, control group mean = 0.006 micrograms.g-1. Cr findings in cervical mucus are of priority importance, the same applies to Cu findings. Zinc was found to be an element influencing negatively the conception of cows. The Zn values in cervical mucus of nonpregnant cows were demonstrated to be significantly higher (P less than 0.01) (conception--group = 0.841 micrograms.g-1, conception + group = 0.219 micrograms.g-1 Zn. So called sum of chemical elements: Cd + Pb + Hg + Cr + Cu + Zn was proposed and evaluated as a picture of the total contamination of cervical mucus. This characteristic was also influenced by the Zn findings in the group of pregnant and nonpregnant cows. Zn: Cd antagonism in cervical secretions of barren and pregnant cows was statistically highly significant (P less than 0.01). Chemical elements in cervical mucus were determined for the first time in a digested sample of cervical secretion. The correlation coefficients used for the cows (n = 99) from a contaminated region showed that the content of chemical elements in cervical secretion was not influenced by the age of cows. The content of chemical elements in cervical secretion was not increasing with the age.     

New trends in the control of reproduction in the bovine

The new trends in the control of animal reproduction have been theoretically well-known for 25 years, and some of these methods have now been found to have a practical value.A short-term treatment (10 days) of a progestagen implant (SC 21009) begun by oestradiol valerate administration and followed by PMSG injection, induces oestrus and ovulation in nursing cows. The synchronisation of oestrus is adequate for artificial insemination at a predetermined time, with 68% of cows ultimately calving.If there is a large number of cyclic cows in a herd, this treatment does not give such a precise synchronisation of oestrus.Limited superovulation using PMSG is not restricted to the production of twins, but includes triplets and quadruplets. However, the viability of embryos and calves in multifoetal pregnancy can be improved by choosing a proven bull, a particular breed of cow, and by super-alimentation towards the end of pregnancy. All can be won or lost at the time of parturition.Such methods for the control of certain phases of the reproductive cycle are useful in improved cattle production.