In utero transmission of bovine leukemia virus

In an initial study, 18 calves born to cows persistently infected with bovine leukemia virus (BLV) were tested for infective virus and antibodies at birth, and no infected or seropositive animals were found. Four of these calves were maintained in quarters where infected animals were housed, and 3 of the 4 subsequently became infected. These were probably contact infections acquired during, or at some time after, birth. The remaining 14 calves were kept in isolation pens in a building housing no infected cattle. None of this group was found to be BLV infected during 1 year of observation. In further studies, 15 pregnant cows inoculated with BLV became infected. One abortion, considered to be unrelated to the BLV inoculation, occurred 38 days later. The remaining 14 cows gave birth to 1 dead and 14 live calves. The dead calf and its live twin were seropositive for BLV at birth, indicating that they had been infected in utero. The remaining 13 calves were negative for BLV antibodies at birth and remained so during 1 year of observation.     

Reproductive performance of apparently healthy cattle persistently infected with bovine viral diarrhea virus.

A Holstein-Friesian bull and three Holstein-Friesian cows were seronegative for bovine viral diarrhea (BVD) virus but were persistently infected with the virus. Virus was isolated from buffy coat cells and nasal and lacrimal secretions during their lifetime, and they remained free of clinical signs of BVD. The three cows were pregnant when purchased, and they gave birth to full-term calves. One calf lived only a few hours, one calf became ill and died within a few days, and one calf became ill and was euthanatized within a few weeks. One cow was then bred and became pregnant but aborted a 7-month fetus. A second cow was bred approximately 5 months after parturition but did not conceive. The third cow was necropsied 6 weeks after calving, because of loss of weight. Although the bull's semen contained BVD virus when seropositive cows were bred, normal calves were born. When seronegative heifers were bred, they became seropositive to BVD virus within two weeks, with higher titers in six weeks. On heifer conceived after one service but aborted a 6-month fetus. Three others continued to have estrous cycles until their titers rose to 1:128, then they conceived and gave birth to normal calves. Another heifer conceived on the first service, had a titer of 1:128 two weeks after breeding, and gave birth to a normal calf.     

Evaluation of the diagnosis of subclinical endometritis in dairy cattle using ultrasound

The aim of this study was to determine signs of subclinical endometritis found by ultrasound that are associated with reduced fertility in dairy cows.The maximum diameter of the uterine lumen was determined by ultrasound in 324 cows without clinical signs of endometritis after evaluation of the genital tract 21 to 27 days postpartum. Cows were classified into healthy or with subclinical endometritis by three threshold values for the maximum uterine lumen diameter of 0.2 cm, 0.5 cm or 0.8 cm. Examinations by rectal palpation and ultrasound as well as classifications were repeated 14 days later. In addition, ovaries were scanned by ultrasound to determine the stage of the estrous cycle. In a subgroup of 103 cows the echotexture of the uterus and its contents was evaluated. In these cows the diagnosis of subclinical endometritis was performed by a scoring system. The diameter of the uterine lumen was significantly affected by stage of the estrous cycle at the time of examination. However, no effects were found for the stage of the cycle at the time of examination on subsequent reproductive performance. A uterine lumen with a maximum diameter of more than 0.2 cm showed a significant negative association with conception rate and proportion of cows pregnant. Classification based on higher threshold values did not reveal an association with reproductive performance. Echogenic content in the uterus also decreased reproductive performance. A classification based on the echotexture of the uterus and its contents revealed significant differences between healthy cows and cows with subclinical endometritis regarding the proportion of cows inseminated and pregnant.The results of this study showed that the diagnostic of bovine endometritis should be broadend by ultrasonography. The definition of subclinical endometritis diagnosed by means of ultrasonography has to be evaluated in further studies.     

The thermoresistance test of spermatozoa and fertility in bulls

The spermiograms of 17 bulls were studied and 160 ejaculates were subjected to the thermoresistance test (38 degrees C) to evaluate sperm survival after thawing. After the first insemination of 10 682 cows, statistically significant differences were found in the fertilizing capacity of the ejaculates with various values of the thermo-resistance test. The best sperm fertilizing capacity was obtained in the ejaculates which retained progressive movement in 40% of the spermatozoa after two hours of exposure to the thermoresistance test. Out of the 1496 cows inseminated, 971 (i.e. 64.9%) got in calf, whereas after the insemination of 4216 cows with semen where only 30% of spermatozoa moved progressively at the end of the test, the number of pregnant dams was 2403, i.e. 56.98%; this difference is statistically significant (p0.05). At a lower sperm activity in the test the fertility after the first insemination was even lower. Although there was some difference in the individual fertility of bulls (54 to 67%), a positive relationship between the results of the thermoresistance test and fertility was recorded in all bulls.     

Effects of periparturient events on subsequent culling and fertility in eight UK dairy herds

The occurrence of five periparturient events and their effects on subsequent culling and fertility was recorded in eight herds in the UK. Combining data from all 2105 calvings, the proportion affected by assisted calving, dead calf, retained fetal membranes (RFM), milk fever or twins was 5.9, 8.2, 5.3, 5.0 or 3.3 per cent, respectively. Compared with unaffected herdmates, cows with an assisted calving or a dead calf had higher early (but not late) culling rates, (assisted calving: 8.8 per cent being culled before 100 days after calving compared with 5.7 per cent; P=0.05; dead calf: 12.2 per cent culled compared with 5.3 per cent; P=0.001). Compared with unaffected animals, cows with milk fever were four times more likely to be culled before 100 days after calving (16.2 per cent compared with 5.3 per cent; P=0.001), whereas those with RFM were twice as likely to be culled between 100 and 200 days (14.3 per cent compared with 7.6 per cent; P=0.003), and both groups were twice as likely to not be pregnant by 200 days. Cows with RFM or milk fever also had markedly reduced subsequent fertility: both conditions extended calving to pregnancy intervals (by 20 days; P=0.001, or by 13 days; P=0.03, respectively), lowered 100-day in-calf rates (by 24.5 per cent; P=0.001, or by 17.8 per cent; P=0.008, respectively) and lowered 200-day in-calf rates (by 20 per cent; P=0.001, or by 15 per cent; P=0.002, respectively). The birth of twins had no effect on subsequent culling or fertility.     

Relationship of fertility to ovarian follicular waves before breeding in dairy cows

Cows with two waves of follicular growth during the estrous cycle yield follicles that are older and larger at ovulation compared with cows having three waves. The objectives of the current research were 1) to compare fertility in cows with two or three follicular waves and 2) to examine associations between luteal function, follicular development, and fertility after breeding. Follicular waves were monitored by ultrasonography during the estrous cycle before insemination in 106 dairy cows. Fewer cows had three follicular waves before next estrus and ovulation than two waves (P < 0.01; 30% vs 68%, respectively), but pregnancy rate was higher (P = 0.058; 81 vs 63%, respectively). Cows with two waves had shorter estrous cycles (P < 0.01), with the ovulatory follicle being both larger (P < 0.05) and older (P < 0.01). In cows with three waves, luteal function was extended (P < 0.05) and the peak in plasma progesterone occurred later (P < 0.05) in the estrous cycle compared to two wave cows. Considering cows that became pregnant, luteal phase length was shorter (P < 0.05) during the estrous cycle preceding insemination than for nonpregnant cows. In conclusion, fertility was greater in lactating cows inseminated after ovulation of the third-wave follicle that had developed for fewer days of the estrous cycle as compared with two-wave cows.     

Effect of twinning on the feed intake, performance and health of dairy cows

The aim of this study was to assess the effect of bearing twins on the health and performance of dairy cows. Data from twin-bearing Holstein Friesian cows at the Langhill Dairy Research Centre between January 1990 and July 2002 were compared to single-bearing cows to determine if there was any significant difference in milk production, feed intakes, health and fertility. There were 122 twin births (from 104 different cows) in the Langhill herd, a rate of 4.7% during the study period.

The incidence of twinning was higher in high genetic merit cows (select genetic line cows) and increased with parity (r = 0.870, P < 0.01). Compared to a single-bearing cow, a twin pregnancy was associated with a shorter gestation period, an increased chance of a retained placenta after calving and a poorer body condition score post-calving. The post-calving condition score of twin-bearing cows was negatively correlated with the total weight of calves born (r = − 0.235, P < 0.05). Twin-calving cows also had significantly more dystocia, a higher chance of having a dead calf, an increased number of days from calving to their first observed heat and number of days from calving to their first service. Dystocia was positively correlated with the number of dead calves at birth (r = 0.309, P < 0.01) and with the total weight of calves born (r = 0.211, P < 0.05). Twin-bearing cows on a low-concentrate diet had an increased chance of having metritis and/or endometritis compared to single-bearing cows on the same diet. There was no significant difference in the reason for culling or the time at which cows were culled post-calving, however, twin-bearing cows on a low-concentrate diet were 3.2 times more likely to be culled than a single-bearing cow, with cows on a high-concentrate diet having equally high levels of culling. There were no significant differences between twin- and single-producing cows' mean daily feed intakes, daily milk yields, total milk yields and milk fat and protein compositions during early, mid and late lactation pre and postpartum on a low- or high-concentrate diet. The body condition and drying off period of twin pregnant cows should be managed to avoid post-calving health and performance problems.     

Use of postpartum vaginoscopic (visual vaginal) examination of dairy cows for the diagnosis of endometritis and the association of endrometritis with reduced reproductive performance

OBJECTIVE: To assess the association between the findings from vaginoscopic examination of postpartum dairy cows with peripartum reproductive disease and their subsequent reproductive performance, and to determine the factors that might be associated with a positive vaginoscopic examination (VV). METHODS: Cows (n=1325) from 17 seasonal calving dairy herds were enrolled if they had been calved at least 7 days and had at least one of the following conditions that placed them at risk of endometritis: retained fetal membranes (RFM), dystocia, a dead calf, hypocalcaemia, twin birth, calving induction or an observed vulval discharge (VD). Examination was undertaken 28-37 days before mating start date (MSD) within each herd. All cows were body condition scored (BCS) and were VV scored on a scale of 0 (clear) to 3 (purulent). The uterus and ovaries were assessed by rectal palpation. RESULTS: Cows with a positive VV score (1-3) were less likely to conceive to first service and had a lower pregnancy proportion than cows that had a negative VV score (score 0). Mean MSD to conception interval was longer in VV-positive cows. A positive VV score was associated with a low BCS, primiparity, intrapelvic uterus, poor uterine tone, large uterus, RFM, VD, dystocia, dead calf and twins. CONCLUSION: In the present study a positive VV score was associated with reduced reproductive performance and was more common in primiparous and low BCS cows. Of the at-risk cows, those with RFM, VD, dystocia, dead calf or twins were more likely to have a positive VV score.     

Effect of various degrees of dystocia in dairy cattle on calf viability, milk production, fertility and culling

The objective of this study was to analyse the effect of dystocia on calf viability, milk production, fertility and culling under field (farm) conditions in a retrospective case-control study. A total of 253 calvings that were attended by a veterinarian were classified into three categories: mild dystocia (MD), severe dystocia (SD) and caesarean section (CS). For every case of dystocia, a control was chosen from the same farm and matched for calving month, breed and parity. Cases and controls were compared concerning calf viability, milk production, fertility and culling. The proportion of stillbirths was significantly higher in cows with dystocia compared with their controls. However, the difference was lower in CS cows than in the other two groups. MD had no significant effects on milk production, fertility and culling. There were no obvious effects of SD on monthly test day milk production, while CS cows produced significantly less milk than their controls. Compared with controls, less SD (50.0% versus 61.6%) and CS cows (48.6% versus 70.3%) conceived until 200 days in milk and more CS cows (31.1% versus 16.2%) were culled in the same time interval. These data demonstrate the scope of economic and animal welfare opportunities associated with the reduction of dystocia by management and breeding.     

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.     

Evaluation of Subclinical Endometritis and Consequences on Fertility in Piedmontese Beef Cows

Subclinical endometritis (SEM) is poorly investigated in beef cows, as stated in the literature. This project aims to evaluate the rate and the consequences of SEM in Piedmontese cows, with a focus on bacteriological findings and fertility parameters. Uterine cytology was performed for 97 subjects; a total of 31% of the cows were diagnosed as being positive for SEM and as having an 8% neutrophil (PMN) presence on the slide, which is considered as the best cut‐off to diagnose the pathology. Only 13% of the cows positive for SEM were pregnant within 130 dpp and generally showed increases of 40 days in the partum to conception interval compared with the negative cows (142 vs 182, p = 0.01). Cows positive for both bacteriology and cytology showed a lower fertility than cows with only inflammation or only a bacterial presence (p = 0.0004). Bacterial isolation detected different species, but no difference in regard to the impact of these bacteria on SEM was shown. Parity, presence of calves, hygiene condition, age and number of service did not affect whether a cow was positive for subclinical endometritis (p < 0.05). The housing system (free stalls vs tie stalls) used seems to affect the SEM rate in Piedmontese cows; cows bred in tie stalls were more likely to be positive for SEM (OR = 2.2; p = 0.04). In conclusion, cytology seems to be a good technique for the diagnosis of subclinical endometritis in beef cows, and as in dairy cows, subclinical endometritis has a detrimental effect on fertility, causing an increase in partum to conception and a decrease in the rate of cows who become pregnant within 130 dpp, particularly for those cows housed in a tie stall.     

SYNCHRONISATION OF OESTRUS IN BEEF CATTLE ARTIFICIAL BREEDING PROGRAMS USING PROSTAGLANDIN F2α

PGF2α either as a subcutaneous injection (8 or 10 mg) or intrauterine infusion (dose 5 mg) successfully synchronised oestrus in beef cattle AI programs. The beef cattle programs were managed by 1 of the following 2 systems.

• 1 Two 10-day insemination periods, 1 for the first and the second for the repeat inseminations. Oestrus was detected and oestrus cows inseminated for the first 4 days of the first period. On the fifth day all cows not inseminated were treated with PGF2α. The treated cattle came into oestrus and were inseminated over the following 2 to 5 days.
• 2 Two PGF2α treatments 10 days apart followed by two 4-day insemination periods. During the first 4-day period, cows exhibiting synchronised oestrus were inseminated. Cows returning to oestrus were inseminated during the second 4-day period, about 18 days after the first period.

Synchronisation of oestrus was not sharp, oestrus being distributed over 7 days, with the majority of cows being in oestrus on the third (42.3%) and fourth (22.4%) days. The route of administration of PGF2α (injection or infusion) did not effect oestrus synchronisation. PGF2α by either route of administration did not effect the fertility of cows inseminated at either the synchronised or subsequent oestrus. Pregnancy rates at the synchronised oestrus were higher when cows were inseminated after detection of oestrus than when they were inseminated without reference to oestrus at a fixed time 3 days after PGF2α treatment (mass injection). Oestrus synchronisation greatly reduced the input of time, labour and feed required during the total program. However, oestrus synchronisation did not alter the overall efficiency of artificial breeding programs measured in terms of the proportion of cattle entering a program that were inseminated and became pregnant. The main problem encountered was drug wastage through unknowingly treating cows and heifers that were not cycling.     

Transmission of bovine virus diarrhoea virus (BVDV) by artificial insemination (AI) with semen from a persistently-infected bull

Twelve heifers that did not have antibodies to bovine virus diarrhoea virus (BVDV) were inseminated with semen from a bull that was persistently infected with the virus and contained 10(4.0)-10(6.5) TCID50 0.1 ml-1. All 12 became infected, as indicated by seroconversion within 2 weeks of insemination. Four control heifers were inseminated with virus-free semen. The virus was not transmitted to these animals in spite of close contact with the heifers inseminated with the infected semen. All the heifers became pregnant and gave birth to clinically normal calves at term. However, one calf was born persistently infected with BVDV. After the birth of this persistently-infected calf the control heifers and their calves seroconverted. The study demonstrates that BVDV may be transmitted in cattle by artificial insemination (AI). Therefore entry of persistently-infected animals into AI centres should be prevented.     

Plasma concentration of estrone sulfate during pregnancy in different breeds of Japanese beef cattle

Plasma concentrations of estrone sulfate in different breeds of Japanese beef cattle and the relationship between those concentrations and feto-placental growth were examined in order to assess the possibility of monitoring abnormal growth of the fetus. Blood samples were obtained from cows from day 90 of gestation to parturition. The plasma concentration of estrone sulfate was measured by direct enzyme immunoassay. From day 180 of gestation, the mean concentration of estrone sulfate increased gradually and it was drastically elevated after day 240 of gestation with the maximum at day 285. Plasma concentrations of estrone sulfate on day 240 of gestation was significantly increased in F(1) cows (Holstein Friesian and Japanese Black) compared with those in other breeds of cow. From day 270 to 278 of gestation, estrone sulfate concentrations of Holstein Friesian cows inseminated by Holstein Friesian differed from those inseminated by Japanese Black. In the cow with retained placenta, the plasma concentration of estrone sulfate reached plateau at day 240 of gestation and did not increase thereafter. There was no significant relationship between estrone sulfate concentration and duration of gestation, calf birth weight, weight of placenta or viability of newborn calves. These results indicate that changes of plasma estrone sulfate concentration in Japanese beef cattle are very similar to those in Holstein dairy cattle. They also suggest that the plasma concentration of estrone sulfate is associated with the breed of pregnant cow and that its concentration is also affected by calf birth weight depending on the breed of bull. It seems possible to predict the incidence of retained placenta but not the calf birth weight and viability of newborn calves in Japanese beef cattle.     

母牛同期发情试验及受胎产犊效果观察

[目的]为了解决牛群分散,交通不变问题.[方法]本文利用同期发情处理方法,并为了观察牛同期发情及受胎产犊效果.在红塔、新平和元江分三批对102头母牛进行同期发情处理(放置阴道栓+注射氯前列烯醇),撤栓后根据发情情况用冷冻精液对97头母牛进行人工授精,[结果]表明同期发情率95.1%.150～160 d后对输精母牛进行妊...     

Influence of the semen deposition site on the calves' sex ratio in Simmental dairy cattle

It has been suggested that the time of insemination has effect on the calves' sex ratio because of the differences in timing of capacitation, motility and survival time of the X and Y spermatozoa in the female reproductive tract. We have conducted a field trial to study the effects of different semen deposition sites on the sex ratio and fertility in cattle. Two groups of 450 cows were inseminated via artificial insemination: group A was inseminated into the uterine body and group B was inseminated deep into the uterine horn ipsilateral to the ovary with dominant follicle. After applying several exclusion criteria, a total of 607 pregnant cows were considered for data analysis (group A = 318 and group B = 289 cows). The conception rate was 7% higher (p < 0.05) in the group A, with 23% more of the male calf pregnancies (p < 0.001). At the same time, 18% more of the female calves were calved in the group B (p < 0.005). The difference in male calves between the two groups was 21% and in female calves was 20% (p < 0.001). We conclude that semen deposition site plays a significant role in differences in gender ratio observed after calving. Intracornual semen deposition resulted in a higher ratio of female calves, whereas uterine body deposition site resulted in higher male calves ratio, probably contributing physiologically to the differences in motility, capacitation time, the lifespan of X vs Y spermatozoa and to the pronounced shift of X spermatozoa in the female genital tract.     

Suitability of sonographic evaluation of ovarian dynamics and uterine involution for prediction of postpartum fertility in the cow

To investigate the suitability of sonography for prediction of puerperal fertility, we used 34 cows with normal puerperium. For this purpose, the animals were examined gynecologically and by transrectal sonography at 10-day intervals between day 15 and day 45 p.p. as well as at oestrus, when they were inseminated. We judged uterine involution by diameter and sonographic structure of the uterine cross-section and ovarian activity by the presence of follicles and corpora lutea. Cows, which became pregnant after first insemination p.p., were assigned to group G1 (n = 16) and animals, which failed to conceive, to group G2 (n = 18). The cows of G1 obtained significantly better results concerning both uterine involution and ovarian activity than cows of G2. Thus, diameter of the uterine horn decreased faster and sonographic structure of the uterine cross section returned markedly earlier to the nonpregnant appearance in G1 than in G2. Group G1 also showed a significantly higher percentage of dominant follicles at all examinations. The results of the study show a distinct relationship between uterine involution and ovarian activity and puerperal fertility. But it has also to be resumed that the prediction of fertility for individuals will always be restricted by other reasons causing failure of conception.     

A clinical trial using a regimen which includes a norgestomet implant and norgestomet plus oestradiol valerate injection as a treatment for anoestrus in dairy cows

In seasonally calving dairy herds in the Macalister Irrigation Area of Gippsland, Victoria, cows that had not been observed in oestrus by the start of the mating season and which had inactive ovaries based on rectal palpation and progesterone assay were treated with a hormonal treatment (n = 49). Mature cows had calved at least 40 days previously and 2-year-olds had been calved at least 60 days. The treatment consisted of a norgestomet implant and a norgestomet and oestradiol injection on day 1; prostaglandin analogue Prosolvin) on day 8; withdrawal of implant on day 10 and an injection of PMSG; and fixed time artificial insemination 54 to 56 h after implant withdrawal. This treatment was called the Syncro-mate regimen. Control cows (n = 46) were injected with water on days 1, 8 and 10 and artificially inseminated or served by a bull when seen on heat. Forty seven percent of the treated cows became pregnant within 14 days from the start of treatment compared with 20% of control cows (P less than 0.01). There was an effect of age group on the response to treatment. A greater proportion of 2-year-old cows than mature cows became pregnant within 14 days of treatment (79% of 19 v. 27% of 20; Chi square interaction, treatment by age, 6.4, P less than 0.05). In the younger cows there was also a gain of 22 days in the treatment to conception interval over the control cows (P less than 0.001). It was concluded that the Syncro-mate regimen can be an effective treatment for post partum anoestrus in dairy cows under certain conditions.     

Reproductive efficiency of cows with endometritis after treatment with intrauterine infusions or prostaglandin injections, or no treatment

Data from 3276 cows with 6598 lactations in 85 herds participating in a herd health monitoring programme were selected for an observational study. Cases of endometritis were diagnosed based on a clinical examination after 21 days postpartum. The cases were grouped by the severity of endometritis (mild, severe) and by the treatment performed (intrauterine infusion, prostaglandin injection, no treatment). The conception rates and the calving-to-conception intervals of these groups were compared statistically. Conception rate was lower in cows with severe endometritis compared to cows with mild endometritis while it did not differ between treatment groups. In cows with mild endometritis a significantly longer calving-to-conception interval was observed if intrauterine infusions were performed compared to the other two treatment options. The occurrence of other fertility problems during the same service period had a significant effect on conception rate and calving-to-conception intervals. In cows with severe endometritis intrauterine or prostaglandin treatments appeared to be beneficial, whereas intrauterine infusions in cows with slight endometritis had a negative effect on reproductive efficiency.     

Effect of clenbuterol administered during the expulsive stage of bovine parturition on uterine activity and the fetus.

The effect of an intravenous injection of 0.3 mg clenbuterol on myometrial activity, fetal heart rate and fetal outcome was studied in three groups of animals: six heifers in active labour at term, in which fetal oversize was diagnosed just before the drug was injected and whose calves were delivered by caesarean section within 50 minutes; four cows at the start of the expulsive stage of parturition which had been induced with flumethasone on day 270 of gestation; and in four parturient cows which had had electrodes implanted on the myometrium at least one week before calving was induced with flumethasone on day 270. Electrocardiograph electrodes were placed on the calf and an intrauterine pressure catheter was inserted between the calf and the uterine wall upon rupture of the amniotic membrane. Clenbuterol induced a significant decrease of myometrial activity for at least 20 minutes. Recovery was most rapid in the heifers in which an obstetrical examination had taken place during active labour. There was no significant effect on basal fetal heart rate but decreases in heart rate were absent as long as uterine contractions were inhibited. The fetal outcome, judged either before or at birth by blood pH, base-excess and PCO2 and by a clinical examination, was not adversely affected.