Bovine pregnancy and nonreturn rates following artificial insemination using a covered sheath

Contamination transferred into the uterus from external genitalia during artificial insemination (AI) has been hypothesized to cause lowered bovine pregnancy rates (PR). Using aseptic techniques, there is still a possibility of uterine contamination during routine AI. Two experiments were conducted to evaluate the effect of two types of sheath covers (CS) placed over the conventional French Medium Syringe assembly (FMS) used for AI. Their use entailed passing the assembly to the external os of the cervix, pushing the FMS through the CS and manipulating the FMS to the cervical uterine junction in the normal manner. Fifty-six day non-return rate (NRR) in dairy and actual PR in beef cattle were evaluated. In Experiment 1, 30 professional technicians were employed to inseminate 7, 387 dairy cows, while in Experiment 2, six technicians with varying levels of experience inseminated 416 beef cows. Least-squares means for NRR in dairy cattle were 78% using a CS and 79% without. Means for PR in beef cattle were 57% using a CS and 62% without. In Experiment 2, the overall PR was lower in Trial l than in other trials (P<0.05). Since some technicians improved with time, the difference due to trial was attributed to technician variation in gaining experience with a CS. Results indicate that general use of a CS in routine AI of apparently healthy cows will not increase PR.     

Pregnancy outcome in dairy and beef cattle after artificial insemination and treatment with seminal plasma or transforming growth factor beta-1

Reduced capability of the uterus to support pregnancy in the absence of its interaction with secretions from male accessory glands has been demonstrated in rodents and to some extent in pigs. However, in cattle, the role of postmating inflammatory response on pregnancy success has not been studied. The current study examined the influence of uterine presensitization with seminal antigens at breeding on pregnancy outcome in cows. Lactating beef (n = 1090) and dairy (n = 800) cows received 0.5 mL seminal plasma (SP), 40 ng recombinant human transforming growth factor-β1 (rhTGF-β1), or 0.5 mL bovine serum albumin (BSA), or were left untreated before or at insemination. Semen was deposited into the anterior cervix using a second insemination gun. Pregnancy was diagnosed at 35 to 40 d postinsemination by transrectal ultrasonography or from records of calves born the subsequent calving season. Pregnancy rates in beef cows did not differ among treatments but differed among trials (69.8%, 52.5% vs. 40.3%; P < 0.05). In trials where average pregnancy rates were below 50%, treatments with TGF-β1 but not SP tended (P < 0.07) to increase pregnancy rates in beef cows. In dairy cows, SP and TGF-β1 improved pregnancy outcome by 10 percentage points, but these increments did not achieve statistical significance. In conclusion, this study did not find any conclusive evidence for the effect of TGF-β1 or seminal plasma on pregnancy outcome in lactating dairy or beef cows but realized marginal improvements when pregnancy rates were below 50% (compromised fertility).     

奶牛阴道菌群分析与乳酸菌的分离及鉴定

目的研究奶牛阴道菌群,并从健康奶牛阴道分离出产酸能力很强的乳酸菌。方法采用常规的方法对奶牛阴道进行细菌的分离及鉴定,并进行菌群分析。结果健康奶牛阴道优势菌群主要为乳酸菌(P<0.01),屡配不孕奶牛阴道优势菌群主要为金黄色葡萄球菌(P<0.01);从健康奶牛阴道分离出的乳酸菌为55株,其中产酸能力很强的6株乳酸菌鉴定结果分别为Lactobacillus plantarum、Lactobacillus brevis、Enterococcus faecalis、Lactococcus garvieae、Lactobacillus kitasatonis和Lactobacillus amylovorus。结论奶牛阴道菌群中分离的6株乳酸菌可作为潜在的奶牛阴道微生态制剂进行深入研究。     

Effect of cow replacement strategy on cow and calf performance in the beef herd

Two contrasting replacement strategies are used by Irish beef farmers to select replacement females – animals sourced from within the suckler beef herd and sourced from the dairy herd. The objective of this study was to investigate the effect of replacement strategy (i.e. beef v. beef×dairy (BDX)) on cow and calf performance using data from the national beef database across a range of beef and dairy breeds. The association between replacement strategy and calving difficulty score, calving interval, weaning weight, weaning price and all carcass traits was investigated using a mixed model. The effect of replacement strategy on cow survival, calving dystocia and calf perinatal mortality was quantified using logistic regression. Beef cows were older (10.92 days; P<0.001) at their first calving, but were 1.15 times (P<0.01) more likely to survive to a subsequent lactation compared with BDX cows. Calving interval was 1.53 days shorter (P<0.001) for BDX compared with beef cows. Greater calving difficulty and calving dystocia was associated with beef cows (P<0.001) relative to BDX. However, BDX were 1.36 times (P<0.001) more likely to have a dead calf at birth relative to beef cows. Calves weaned from BDX were heavier (18.49 kg; P<0.001) at weaning, reached slaughter 12.8 days earlier (P<0.001), had 7.99 kg heavier carcass (P<0.001) and a greater fat score (P<0.001) compared with the progeny of beef cows. Beef cow progeny had a superior conformation score (0.5; P<0.001) and achieved a greater price per kilogram (P<0.001) compared with progeny from BDX. Beef cull cows had a heavier carcass (5.58 kg), superior carcass conformation, greater carcass price per kilogram and greater overall carcass value (P<0.001) than BDX. Results from this study show that replacement strategy is of fundamental importance depending on the type of system implemented by farmers and consideration must be given to the traits of importance within the context of the individual production system.     

Evaluation of production efficiencies at pasture of lactating suckler cows of diverse genetic merit and replacement strategy

Feed costs account for the largest proportion of direct cost within suckler beef production systems. By identifying the cow type with enhanced capability of converting grazed herbage to beef output across lactations, suckler cow systems would become more efficient and sustainable. The objective of this study was to estimate grass DM intake (GDMI) and production efficiency among lactating suckler cows of diverse genetic merit for the national Irish maternal index (Replacement Index) which includes cow efficiency components such as milk yield and feed intake. Data from 131 cows of diverse genetic merit within the Replacement Index, across two different replacement strategies (suckler or dairy sourced), were available over two grazing seasons. Milk yield, GDMI, cow live weight (BW) and body condition score (BCS) were recorded during early, mid and late-lactation, with subsequent measures of production efficiency extrapolated. Genetic merit had no significant effect on any variables investigated, with the exception of low genetic merit (LOW) cows being 22 kg heavier in BW than high genetic merit (HIGH) cows (P < 0.05). Beef cows were 55 kg heavier in BW (P < 0.001), had a 0.31 greater BCS (P < 0.05) and 0.30 Unité Fourragère Lait (UFL) greater energy requirement for maintenance compared to dairy sourced beef × dairy crossbred (BDX) cows (P < 0.001). The BDX had 0.8 kg greater GDMI, produced 1.8 kg more milk (P < 0.001), had a 0.8 UFL greater energy requirement for lactation and produced weanlings that were 17 kg heavier in BW than beef cows (P < 0.05). Subsequent efficiency variables of milk per 100 kg BW (P < 0.001), milk per kg GDMI (P < 0.001) and GDMI per 100 kg BW (P < 0.001) were more favourable for BDX. The correlations examined showed GDMI had moderate positive correlations (P < 0.001) with intake per 100 kg BW, net energy intake per kg milk yield, RFI and intake per 100 kg calf weaning weight but was weakly negatively correlated to milk yield per kg GDMI (P < 0.001). No difference was observed across genetic merit for beef cows for any of the traits investigated. Results from the current study showed that, while contrasting replacement strategies had an effect on GDMI and production efficiency, no main effect was observed on cows diverse in genetic merit for Replacement Index. Nonetheless, utilising genetic indexes in the suckler herd is an important resource for selecting breeding females for the national herd and phenotypic performance generated from this study can be included in future genetic evaluations to improve reliability of genetic values.     

Effect of a single growth hormone (rbST) treatment at breeding on conception rates and pregnancy retention in dairy and beef cattle

Initiation of long-term treatment with rbST (Posilac, Monsanto, St. Louis, MO) coincident with first insemination increased pregnancy rates in dairy cattle, but neither the efficacy of using only the initial injection, nor its effects on retention of pregnancy are known. Lactating dairy cows, dairy heifers, and lactating beef cows were assigned at random to treatment (rbST) or control. Dairy cows, dairy heifers, and beef cows received 500 mg rbST (n = 48, 35, 137 inseminations, respectively) at artificial insemination or were left untreated (n = 62, 33, 130 inseminations, respectively). Pregnancy was diagnosed by ultrasonography at 28-36 days. Treatment with rbST at insemination improved conception rates in dairy cows (60.4% versus 40.3%; P < 0.05), but not in dairy heifers or beef cows. Conception rates did not differ in dairy cows at < or =100 days in milk (DIM), but were improved in cows treated with rbST after 100 DIM (64.3% versus 25.8%; P < 0.05). Retention of pregnancy to approximately 60 days and sizes of CL, diameter of follicles > or =5 mm, and crown-rump lengths of embryos were not affected by treatment. The second objective was to examine the effects of rbST at insemination on birth weight and post-natal calf growth in beef cows. However, birth and weaning weights of beef calves were not affected by treatment. In conclusion, a single treatment with rbST at insemination increased conception rates in dairy cows, specifically in those >100 DIM.     

Relationships between days post partum, observed estrus and uterine microflora in commercial dairy cows

This study was conducted to determine relationships between the uterine microflora and reproductive characteristics of dairy cows. Uterine lumina were swabbed during estrus immediately prior to artificial insemination (A I). Swabbings were cultured for bacteria and accessed for cytologic evidence of inflammation. The time of sampling averaged 104 d post partum. Bacteria in the uterus were cultured from 65% of the cows (n = 85). The number of cows with any given microbial genus ranged from 1 to 35 and the number of different genera per cow ranged from 0 to 8. There were on significant correlations between amount and type of uterine microflora, days post partum, numbers of observed estrus, conception rate and uterine inflammation. The number of observed estrus periods was not correlated with the presence of aerobic bacteria. No significant relationships were found between microbes and uterine inflammation or conception to the A.I. service at the time of sampling. A negative correlation between uterine inflammation and conception approached significance (r=-0.24, P > 0.10). Acquisition of uterine lumen samples by the technique utilized had no effect on conception to A I service.     

Risk factors associated with detailed reproductive phenotypes in dairy and beef cows

The objective of this study was to identify detailed fertility traits in dairy and beef cattle from transrectal ultrasonography records and quantify the associated risk factors. Data were available on 148 947 ultrasound observations of the reproductive tract from 75 949 cows in 843 Irish dairy and beef herds between March 2008 and October 2012. Traits generated included (1) cycling at time of examination, (2) cystic structures, (3) early ovulation, (4) embryo death and (5) uterine score; the latter was measured on a scale of 1 (good) to 4 (poor) characterising the tone of the uterine wall and fluid present in the uterus. After editing, 72 773 records from 44 415 dairy and beef cows in 643 herds remained. Factors associated with the logit of the probability of a positive outcome for each of the binary fertility traits were determined using generalised estimating equations; linear mixed model analysis was used for the analysis of uterine score. The prevalence of cycling, cystic structures, early ovulation and embryo death was 84.75%, 3.87%, 7.47% and 3.84%, respectively. The occurrence of the uterine heath score of 1, 2, 3 and 4 was 70.63%, 19.75%, 8.36% and 1.26%, respectively. Cows in beef herds had a 0.51 odds (95% CI=0.41 to 0.63, P<0.001) of cycling at the time of examination compared with cows in dairy herds; stage of lactation at the time of examination was the same in both herd types. Furthermore, cows in dairy herds had an inferior uterine score (indicating poorer tone and a greater quantity of uterine fluid present) compared with cows in beef herds. The likelihood of cycling at the time of examination increased with parity and stage of lactation, but was reduced in cows that had experienced dystocia in the previous calving. The presence of cystic structures on the ovaries increased with parity and stage of lactation. The likelihood of embryo/foetal death increased with parity and stage of lactation. Dystocia was not associated with the presence of cystic structures or embryo death. Uterine score improved with parity and stage of lactation, while cows that experienced dystocia in the previous calving had an inferior uterine score. Heterosis was the only factor associated with increased likelihood of early ovulation. The fertility traits identified, and the associated risk factors, provide useful information on the reproductive status of dairy and beef cows.     

Uterine infections in the postpartum cow: I. Effect of dietary crude protein restriction

The relationship between adequate (0.96 kg per head daily) and deficient (0.32 kg per head daily) intake of crude protein between 150 days prepartum and 110 days postpartum and the incidence of postpartum infections in the bovine uterus was studied. The incidence of infection at 25 days postpartum was 52.2% and 48.1% (P > .10) for cows in the protein adequate and protein deficient groups, respectively. However, at 40 days postpartum, 21.7% of cows in the protein adequate group had infections $\text{vs}$ 51.9% (P < .05) of cows in the protein deficient group. In addition, the incidence of infection within the protein adequate group between sampling times was different (P < .10); whereas, the incidence within the protein deficient group between sampling times was not different (P > .10). Eighty-three bacterial isolates representing 27 species were recovered from the total of 100 samples. $\text{Corynebacterium}$$\text{pyogenes}$ and $\text{Fusobacterium}$$\text{necrophorum}$ were the most frequently isolated aerobe and anaerobe, respectively. Although there was no difference between diets (P > .10), these two organisms occurred most frequently in cows on the protein deficient diet and were associated with clinically severe uterine infections. These data suggest that the amount of crude protein in the diet affects both the incidence and duration of postpartum infections in the bovine uterus.     

Bacterial contamination of the uterus after parturition and its effect on the reproductive performance of cows on large-scale dairy farms

The bacteriological status of the uteri of 150 cows was examined on 14 large-scale dairy farms 10 to 20 d after parturition and then twice again in 2-wk intervals during uterine involution. The degree of bacterial contamination and the proportion of the infected uterus as well as the composition of the isolated flora were determined. The antibiotic sensitivity of the important bacterium strains was also studied. The relationship between the reproductive data and bacterial contamination of the uteri was analyzed, and the influence of certain environmental and genetic factors on the rate of infection was examined. The proportion of cows having moderate or more serious uterine infection remained above 30 % at the end of involution on more than 35 % of the farms. Infections were caused mainly by streptococci, E. coli and corynebacteria. The bacterium strains showed broad resistance against commericially available antibiotics. There were significant differences in the length of time from the parturition to the first insemination and conception among cows at the various farms. There was a significant correlation between these differences and the bacteriological status of the uteri. Reproductive data were the lowest in the group of cows infected with Corynebacterium pyogenes. The rate of the infected uteri was considerably higher after the third parturition and in cows producing less than 20 l of milk per day. No connection was found between the bacteriological status of the uteri and the breed, type of housing, and season of the parturitions.     

Mycoflora of cervicovaginal fluids in dairy cows with or without reproductive disorders

Fungal infection of reproduction system of dairy cattle have not been received much more attention. The aim of this study was to determine the fungal infection of Holstein dairy cows with reproductive disorders or healthy. Fungal isolates of cervicovaginal fluids of 176 Holstein dairy cows were collected by using the double rod swabs for cervix and the sterilized cotton swabs for discharges of vagina. They were evaluated for fungal infections. The treatment group included 70 dairy cows with reproductive diseases, such as abortion, repeat breeder, endometritis, metritis, retention of fetal membrane, dystocia, cervicitis, and vaginitis. The control groups were included 42 healthy non-pregnant cows and 64 pregnant cows. Isolates of fungi were obtained from cervix and vagina of 27.1% and 28.6% of treatment group, 26.7% and 31.2% of pregnant cows, and 33.3% and 21.4% of healthy non-pregnant cows, respectively, indicating no significant differences. It is showed that the cervix and vagina of the treatment group have been infected by six different mycotic isolates. However, the cervix and vagina of pregnant and non-pregnant healthy cows in control group were infected with 5, 6 and 5, 4 different fungal agents, respectively. Penicillium and yeast were the most common isolated agents. Regarding to the result of this study, it is concluded that fungal infections can occur in cervicovaginal cavity of Holstein dairy cows with or without reproductive diseases.     

Endometrial expression of selected transcripts involved in prostaglandin synthesis in cows with endometritis

Several cytokines and prostaglandins play an important role in preparing the endometrium for implantation and mediating pro-inflammatory events. The aim of the present study was to examine mRNA expression of interleukin 1α (IL-1α), interleukin receptor antagonist (IL-1-RN), cytosolic prostaglandin E synthase (cPGES), microsomal PGES (mPGES-1 and mPGES-2) and lipocalin-type PGDS (L-PGDS) in the bovine endometrium. Endometrial epithelium samples were collected ex vivo from cows with different status of health at day 21-27 postpartum on a dairy farm. Three groups (n = 9 animals each) were defined: (1) healthy cows with no signs of endometritis (control group), (2) cows with subclinical endometritis, and (3) cows with signs of clinical endometritis. Oestrous cycle-dependent mRNA expression pattern was investigated using bovine endometrial epithelial cells from healthy uteri collected at the abattoir. These uteri were classified into post-ovulatory, early-to-mid luteal, late luteal or pre-ovulatory phase (n = 8 animals for each cycle phase). After collecting endometrial epithelium using the cytobrush-method, mRNA analysis was performed by real-time RT-PCR. L-PGDS, IL-1α and IL-1-RN mRNA were expressed significantly higher (P < 0.05) in the endometrium of cows with subclinical or clinical endometritis compared with healthy cows. A twofold lower cPGES mRNA expression (P < 0.05) was detected in cows with subclinical endometritis compared to healthy cows. L-PGDS and IL-1-RN mRNA expression was increased (P < 0.05) after ovulation compared with the pre-ovulatory or luteal phase, respectively. These results support the hypothesis that a dys-regulated cytokine and/or prostaglandin profile in the uterus could be induced by subclinical endometritis or clinical endometritis.     

Studies of bovine genital tracts: Mycoplasma isolations from dairy cows

Mycoplasma was isolated from the genital tracts of 8 of 96 culled dairy cows. Procedures were used to reduce the possibility of uterine contamination by vaginal fluids. The mycoplasma isolates were identified by the fluorescent antibody technique as: $\text{Mycoplasma bovigenitalium}$ (4), $\text{M. canadense}$ (1), an untyped bovine pathogen from the mammary gland designed as ST-6 (2), and an isolate that could not be identified with the labeled antibodies used in this study. All isolations were made from vaginal swabs, except in one case of pyometra where $\text{M. bovigenitalium}$ was isolated concurrently from the uterus and vagina, along with $\text{Pasteurella hemolyticum}$. These results suggest that mycoplasma may be found in the cervico-vaginal flora of some cattle but are rarely isolated from the uterine environment.     

Use of plasma concentrations of 13,14-dihydro,15-keto-PGF2 alpha (PGFM) in the diagnosis of sub-clinical endometritis and its relationship to fertility in the postpartum dairy cow

The objective of this study was to determine the value of using plasma concentrations of PGFM to diagnose subclinical endometritis in the dairy cow, and its relationship to subsequent fertility. A total of 274 cows between 24 to 29 d post partum was divided into 4 groups on the basis of clinical features of the uterus and ovary. Cows in Group 1 (n = 74) had a normal, involuting uterus and a CL on the ovary; cows in Group 2 (n = 51) had a normal, involuting uterus but no CL on the ovary; cows in Group 3 (n = 83) did not have a normal, involuting uterus but had a CL on the ovary; and cows in Group 4 (n = 66) did not have a normal, involuting uterus or a CL on the ovary. A blood sample was obtained from each cow on the day they were placed on the study, and plasma concentrations of PGFM and P4 were determined using RIA. Cows were artificially inseminated (AI) at the first observed estrus after Day 60 post partum, and pregnancy was determined by palpation of the uterus per rectum between 45 and 50 d postAI. Reproductive responses evaluated were conception rate to first service, days open, and percentage of cows pregnant by 90, 120, 150 and 180 d post partum. Data were analyzed using GLM procedures of SAS and a 2 x 2 factorial with contrast procedures. Polynomial regression analysis was used to determine the shape of the PGFM, P4 and fertility curves. There was no difference among mean PGFM concentrations of cows in each group. The rate of decline of plasma PGFM concentrations was lower in cows with an abnormal uterus and a CL on the ovary compared with those without a CL. A lower percentage of cows with abnormal uteri was pregnant by 90 d post partum compared with cows with normal uteri. From the results of this study, it was concluded that plasma PGFM concentrations between Days 24 to 29 post partum were not effective in identifying cows with subclinical endometritis.     

Effect of infusion of uterine purulent exudate into the bovine uterus

Purulent exudate from the uteri of two nonlactating Holstein cows with chronic pyometra was aspirated into a 50 cc syringe via an artificial insemination pipette. The two fractions were mixed, cultured, divided into 14 equal parts and infused into the uteri of 14 other nonlactating cows. All recipient cows had had at least one estrous cycle of normal length and were in the early luteal phase (day 4-8). On days 3, 7, 14 and 21 following infusion, the reproductive tract was examined per rectum, content of the uterus was cultured for bacteria, and endometrial condition was assessed by biopsy and histopathology. The lengths of the estrous cycles of the recipient cows were shortened P < 0.01) from 21 +/- .5 days to 13.3 +/- 1.4 days. Estrus was determined by palpation per rectum and/or observation. Over the experimental period, Pasteurella sp., Corynebacterium pyogenes and other diphtheroids were isolated from 64, 57 and 86% of the cows, respectively. An inflamed endometrium was associated (P<0.10) with the presence of Pasteurella sp. on day 7 following infusion. No other associations were found when the presence of bacteria, vaginal discharge, or short estrous cycles were compared. The infusion of purulent exudate apparently irritated the endometrium causing an early return to estrus rather than causing pyometra. It is probable that postpartum and lactational stress are involved in the development of pyometra.     

Prevalence of Carriage of Shiga Toxin-Producing Escherichia coli Serotypes O157:H7, O26:H11, O103:H2, O111:H8, and O145:H28 among Slaughtered Adult Cattle in France

The main pathogenic enterohemorrhagic Escherichia coli (EHEC) strains are defined as Shiga toxin (Stx)-producing E. coli (STEC) belonging to one of the following serotypes: O157:H7, O26:H11, O103:H2, O111:H8, and O145:H28. Each of these five serotypes is known to be associated with a specific subtype of the intimin-encoding gene (eae). The objective of this study was to evaluate the prevalence of bovine carriers of these “top five” STEC in the four adult cattle categories slaughtered in France. Fecal samples were collected from 1,318 cattle, including 291 young dairy bulls, 296 young beef bulls, 337 dairy cows, and 394 beef cows. A total of 96 E. coli isolates, including 33 top five STEC and 63 atypical enteropathogenic E. coli (aEPEC) isolates, with the same genetic characteristics as the top five STEC strains except that they lacked an stx gene, were recovered from these samples. O157:H7 was the most frequently isolated STEC serotype. The prevalence of top five STEC (all serotypes included) was 4.5% in young dairy bulls, 2.4% in young beef bulls, 1.8% in dairy cows, and 1.0% in beef cows. It was significantly higher in young dairy bulls (P < 0.05) than in the other 3 categories. The basis for these differences between categories remains to be elucidated. Moreover, simultaneous carriage of STEC O26:H11 and STEC O103:H2 was detected in one young dairy bull. Lastly, the prevalence of bovine carriers of the top five STEC, evaluated through a weighted arithmetic mean of the prevalence by categories, was estimated to 1.8% in slaughtered adult cattle in France.     

Prevalence of urovagina and its effects on reproductive performance in Holstein cows

Two hundred fifty-eight Holstein cows (n = 344 lactations) from seven dairy herds were examined every month by vaginoscopy and transrectal palpation to determine the prevalence of urovagina, to investigate its effects on fertility, and to determine some risk factors for urovagina. Accumulation of urine in the vagina of a cow was diagnosed as urovagina and was classified into mild (urine only on the floor of vagina), moderate (urine covering less than or equal to half portion of the external cervical os), or severe (urine covering more than half or whole portion of the external cervical os). In total, 26.7% of lactations had urovagina (mild 11.3%, moderate 11.0%, and severe 4.4%). Survival analysis was used to derive the case definition of clinically relevant urovagina based on the factors associated with increased time to conception. Only moderate (hazard ratio [HR] = 0.39) and severe (HR = 0.20) degrees of urovagina were associated with reduction in pregnancy rate and thus defined as clinically relevant urovagina. Cows with clinically relevant urovagina had decreased AI submission rate (HR = 0.52) and pregnancy rate (HR = 0.35), required more inseminations per conception (5 vs. 2; P < 0.001), had more days open (370 vs. 136; P < 0.001), and were more likely not to get pregnant by 210 d postpartum (odds ratio [OR] = 6.62) and to be culled for any reasons (OR = 5.32) or for reproductive reasons (OR = 9.54) compared with those in cows with no urovagina. Cows with clinically relevant urovagina had a higher risk of endometritis (36.4% vs. 9.2%; P < 0.001) compared with that in cows without urovagina. Cow, low BCS at first postpartum examination (OR = 2.85), endometritis within 60 d (OR = 2.50), and horizontal vulva (OR = 9.30) were risk factors for urovagina. In conclusion, 15.4% of lactations had clinically relevant urovagina that increased the risk of endometritis and had detrimental effects on fertility. Individual susceptibility, low BCS, and horizontal vulva increased the risk of diagnosing urovagina in Holstein cows.     

Prostaglandins and oxytocin: Their effects on uterine smooth muscle

A subcellular fraction was isolated from uteri of non-pregnant and pregnant cows. ATP-dependent calcium binding was shown to take place in this fraction. This calcium binding was inhibited in a dose related fashion when increasing amounts of prostaglandin (PG) E₂ or F_2α were added to the in vitro experimental medium. The physiologically inactive PGF_1β had no inhibitory effect. Oxytocin caused inhibition of calcium binding in preparations from both pregnant and non-pregnant cows. The response to PGE₂ and PGF_2α was somewhat greater in preparations from pregnant uteri than from non-pregnant uteri. The response to oxytocin was very much greater in pregnant uteri. Because of the high PG sensitivity of calcium binding in preparations from the non-pregnant uterus, it is concluded that the PGs may be the more suitable agent in the control of reproduction.     

Low peripheral progesterone and late embryonic/early fetal loss in suckled beef and lactating dairy cows

Pregnancy failure during placentation in lactating dairy cows was associated with low concentrations of serum progesterone. Beef cows have greater serum progesterone and less pregnancy failure. Experiment 1 determined that reduction of serum progesterone affected late embryonic/early fetal loss in suckled beef cows. Cows (n = 40) received progesterone from two new or used controlled internal drug releasing devices, replaced every 5 d, beginning on Day 28 of gestation (mating = Day 0); CL were enucleated on Day 29. Retention of pregnancy was 77% in treated cows and 97% in 78 control cows (P < 0.05). Experiment 2 determined how pregnant, lactating dairy cows with high or low progesterone concentrations during Days 28-34 differed in luteal function or in serum progesterone during replacement therapy. Luteal tissue from such cows was assayed for progesterone and expression of mRNA for genes of endothelin and prostaglandin (PG) systems. Secretion of progesterone and prostaglandins by dispersed luteal cells was determined during incubation with LH, endothelin-1, or arachidonic acid. Neither luteal progesterone nor mRNAs for endothelin or prostaglandin systems differed. Endothelin-1 inhibited secretion of progesterone more (P < 0.05) in luteal cells from cows with low versus high serum progesterone, when incubated with arachidonic acid. Secretion of prostaglandin F₂α was increased and that of 6-keto-PGF₁α decreased by endothelin-1 in vitro. Serum progesterone during replacement was lower (P < 0.05) for cows with low than high serum progesterone at lutectomy. Thus, clearance, more than luteal production, determined peripheral progesterone in pregnant, lactating dairy cows.     

奶牛产后感染性子宫疾病对子宫和卵巢的影响研究进展

微生物入侵是引起奶牛产后子宫疾病的主要因素,产后子宫能检出丰富的微生物种群,主要包括公认的致病菌如大肠杆菌、隐秘脓杆菌、坏死梭杆菌等,机会病原菌如产气荚膜梭菌、肺炎克雷伯菌、微球菌等和潜在致病菌如消化链球菌、金黄色葡萄球菌等。近年来,运用分子微生态技术发现子宫中的微生物属于变形菌门、梭杆菌门、厚壁菌门、拟杆菌门和软壁菌门5个已知的门和一类未被培养的种群,其中拟杆菌属、梭菌属等种群与子宫疾病密切相关。细菌侵入子宫后,以大肠杆菌为代表的革兰氏阴性菌和以化脓隐秘杆菌为代表的革兰氏阳性菌可被子宫内膜细胞上的Toll样受体识别引起炎症反应,改变子宫前列腺素分泌类型,影响卵泡发育、黄体大小,降低血清中雌激素和孕激素浓度,造成奶牛不发情、不排卵,导致产犊间隔延长、产奶量和产犊数量下降,严重影响奶业经济效益。本文从产后奶牛子宫内主要病原菌的种类及其与子宫健康状态的关系、子宫内膜对病原菌的识别与先天免疫、子宫疾病对子宫和卵巢功能的影响等方面对国内外研究进展进行了综述。