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.     

An attempt to isolate Brucellaabortus from uterine flushings of brucellosis-reactor donor cattle

Two experiments were conducted to test for the recovery of brucella organisms from uterine flushings and harvested embryos of sero-positive embryo donor females. In Experiment I, 16 sero-positive cows were superovulated with FSH treatments and artificially inseminated at 12, 24 and 36 hours following the onset of estrus with brucella-free semen. At 48 hours after the onset of estrus, one half the potential donor females were administered an intrauterine inoculation of 3.3 to 4.6 × 10⁴$\text{Brucella}$$\text{abortus}$ (strain 2308) organisms while the remainder received a control inoculation. In Experiment II, the same 16 cows were similarly administered superovulatory treatments and inseminated following estrus. The uterine inoculation was increased to 1.5 to 2.5 × 10⁸ organisms administered 48 hours following estrus. Samples of recovered flushing medium and homogenized embryo residues were placed into a validated $\text{in}$$\text{vitro}$ culture system to detect the presence of brucella bacteria. Uterine flushings and embryos recovered from 31 females exhibiting estrus following FSH treatments were free from either field strain or the inoculated $\text{B.}$$\text{abortus}$ (strain 2308) contamination. The flushings obtained from a single female, which did not respond with estrus following FSH treatment but was inoculated at appointment, did contain $\text{B.}$$\text{abortus}$ which was identified as the inoculated strain 2308 and not field strain organisms. These results indicate that brucella contamination of flushing media and harvested embryos will not likely be incurred when collecting embryos from sero-positive donor females. These findings offer further encouragement for the use of embryo transplantation as a method to produce brucella-free offspring from infected cows.     

Non-specific uterine infection and bovine fertility. I. Infection patterns and endometritis during the first seven weeks post-partum

From a total of 93 dairy cows which were sampled repetitively throughout the non-gravid period, 14 cows developed persistent purulent endometritis, failed to complete uterine involution and were chronically infertile. The remaining 79 cows had completed uterine involution prior to 50 days post-partum. Forty-seven of these cows subsequently proved to be fertile and 32 cows were infertile. Fertility was not influenced by the variable uterine flora or by the endometritis which was found in all the cows within the first two weeks post-partum. Cows which had uterine infection with $\text{Corynebacterium pyogenes}$ subsequent to Day 21 developed severe endometritis and were almost invariably infertile to the first service. Fertility to subsequent services was not necessarily impaired in those cows which eliminated $\text{C. pyogenes}$ sufficiently early to allow complete uterine involution prior to Day 50. Cows with abnormal oestrous cycles were not particularly susceptible to uterine infection.In all the cows the composition of the uterine flora fluctuated constantly throughout the first 7 weeks pp. as a result of spontaneous contamination, clearance and recontamination. Contamination of the uterus by other non-specific bacteria during the 3 to 4 week period which is required for resolution of severe endometritis induced by $\text{C. pyogenes}$ could lead to a false correlation between the endometritis and the bacterial flora as determined by a single sample. It is concluded that the information which is derived from $\text{in vivo}$ sampling of the uterus in clinically normal cows during the first 7 weeks pp. is of little value in predicting subsequent fertility.     

Some observations on Corynebacterium pyogenes infection of the bovine uterus

Throughout the non-gravid period, bacteriological samples and endometrial biopsy specimens were taken repetitively from the uteri of 93 cows in 9 dairy herds. The genital organs of 7 of the 14 cows which developed chronic purulent endometritis or pyometra were examined at slaughter 8 to 9 months after parturition. $\text{C.}$$\text{pyogenes}$ was recovered at least once from 61 (65.6 $\text{per}$$\text{cent.}$) of the cows. The highest rate of infection was found during the second week post-partum. Intrauterine infection with $\text{C.}$$\text{pyogenes}$ invariably induced endometritis. The severity of the endometrial reaction was determined by the duration of the infection but the lesions never progressed to the “gland site mass” lesions and extensive stromal sclerosis which have been described as the “significant lesions” in endometritis.The duration of the infection also determined the effect of $\text{C.}$$\text{pyogenes}$ on fertility. Transient infection during the puerperium did not affect fertility; transient infection at a later period reduced fertility to one service, rarely to a second or third service; persistent infection induced chronic purulent endometritis or pyometra accompanied initially by functional anoestrum and, after some months, by organic anoestrum. The factors which determined the duration of the intrauterine infection with $\text{C.}$$\text{pyogenes}$ were not identified.     

Effect of monensin and suckling on the GnRH induced luteinizing hormone surge and the effect of monensin on the postpartum interval in Brangus cows

Twenty-seven fall calving Brangus cows were randomly allotted to one of four treatment groups: nonsuckled monensin (NSM), suckled monensin (SM), nonsuckled control (NSC), and suckled control (SC). Cows were group fed 1.82 kg/hd/day concentrate and Coastal bermuda grass hay $\text{ad}$$\text{libitum}$. Monensin cows received 200 mg monensin/hd/day in the concentrate. At 0800 hr on day 21 postcalving, the calves were separated from the cows. Suckled monensin and SC cows were allowed to suckle their calves for 30 min at 6-hr intervals. Nonsuckled monensin and NSC cows were not suckled. Calves were given free access to the cows after 1400 hr on day 22 postpartum. At 0800 hr on day 22 postpartum, a blood sample was collected. A 100 μg GnRH challenge was administered IM at 0801 hr. Blood samples were collected at 15-min intervals for 6 hr postinjection. Changes in body weight and body condition from day 21 postpartum to the day of first estrus were not different (P>0.10) by dietary treatment. Monensin cows consumed 10.7% less hay than did the control cows. Serum luteinizing hormone (LH) following GnRH was greater (P<0.005) in suckled than nonsuckled cows. Control cows released more (P<0.005) LH in response to GnRH than did the monensin cows. The postpartum interval (to first estrus) for the monensin cows (92.4±14.7 days) was shorter (P<0.025) than the controls (138.5±9.5 days). A greater proportion (P<0.005) of the monensin cows (8 of 14) exhibited estrus by 90 days postpartum compared to the control cows (0 of 13). Monensin and suckling appear to exert independent and agonistic influences on pituitary function in the postpartum beef cow.     

Investigations into the potential for embryo transfer from Brucellaabortus infected cows without transmission of infection

Thirty-six attempts were made to isolate $\text{Brucella}$$\text{abortus}$ from the uterine flushings of culture positive and serologic reactor cows. Sixteen of these attempts were made after cows had been programmed for superovulation and a simultaneous attempt was made to recover eggs. Udder secretion samples for culture and blood for serology were collected at the time of the flushing procedure. In addition, a field isolate of $\text{Brucella}$$\text{abortus}$ suspended in three different solutions (one commonly used for nonsurgical embryo retrieval) was quantitated at various intervals up to 24 hours.Brucellae were not cultured from any of the uterine flushings although it was demonstrated that the organisms would remain viable in the media used for up to 24 hours. Udder secretions contained brucella at the time of flushing in 17 of the 36 attempts. Results indicated that transfer from infected donors might be achieved without transfer of infection. It is cautioned that final evidence of success would have to come after recipients had undergone serologic and cultural surveillance through their gestation period.     

Effects of intrauterine infection on the function of the corpora lutea formed after first postpartum ovulations in dairy cows

This study was carried out to determine the relationship between postpartum intrauterine infections, endocrine patterns and the function of corpora lutea formed following the first postpartum ovulations in dairy cows. Blood samples were collected daily starting from the day of parturition until 30 d after parturition or until the second postpartum estrus, whichever occurred first. Sera were assayed for progesterone (P(4)), prostaglandin F(2alpha) metabolite (PGFM), and luteinizing hormone (LH) concentrations. Palpations per rectum and real-time ultrasound scanning of the reproductive tracts were carried out in all cows once every 4 d for 1 mo, starting from Day 4 after parturition. In addition, endometrial swabs were collected aseptically from each cow once every 4 d during the first month postpartum. The swabs were cultured for aerobic and anaerobic bacteria. Twelve cows (60%) exhibited short estrous cycles (SC; 6 to 14 d long) following first postpartum ovulations. The mean preovulatory LH surges and LH patterns during the first postpartum cycles were similar in both groups, leading us to believe that lack of luteotrophic stimulation was not a factor in the occurrence of SC. Bacterial isolations were frequent in SC cows. The occurrence of moderate to heavy bacterial growth patterns and the repeated isolations of the similar organisms during postpartum suggests the persistence of uterine infections in SC cows. Increases in PGFM concentrations prior to luteolysis in SC cows were associated with moderate to heavy infection. Thus, postpartum uterine infections do not appear to affect ovulations, but prostaglandin (PGF(2alpha)) released in response to uterine infection may contribute to early demise of the corpus luteum formed after the first postpartum ovulation.     

Spontaneous uterine infections are associated with elevated prostaglandin F(2)alpha metabolite concentrations in postpartum dairy cows

Postpartum Holstein (n=21) and Jersey (n=4) cows were used to determine if uterine infections are associated with elevated plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F(2)alpha (PGFM). Based upon clinical examinations and bacterial content of intrauterine fluid samples, cows detected with uterine infections between 21 and 28 d post partum were used (infected; n=14). These cows were matched with herdmates that were free of infection (control; n=11). Beginning on the day the cows were assigned to the experiment (Day 1), blood samples were collected on alternate days for the next 14 to 15 d. Plasma samples were stored at -20 degrees C until assayed. From Day 1 until the end of the experiment, uterine fluid samples were collected transcervically twice weekly for aerobic bacterial culture. Endometrial biopsies were collected between Days 6 and 8 and Days 13 and 15. Control cows did not show signs of uterine infection throughout the trial, and bacterial cultures indicated that there were no significant bacterial populations in the uteri of the control cows. The uteri of infected cows harbored numerous microbes. Actinomyces pyogenes was most prominent. Various species of Streptococcus and Pasteurella were also prevalent in the infected cows. Escherichia coli was present in the uterus of both infected and control cows. Biopsies showed that infected cows had more (P<0.05) neutrophils, plasma cells and lymphocytes in the endometrium than did the control cows. As determined by plasma progesterone concentrations, 83% of the control and 50% of the infected cows had functional luteal tissue during the 2-wk sampling period. Plasma PGFM profiles were linear (P<0.03) and did not differ between treatment groups (P>0.01). However, average plasma PGFM concentrations were greater (P<0.0001) in infected than in control cows. These data indicate that plasma PGFM concentrations are greater in postpartum cows with spontaneous uterine infections then in herdmates free of infection.     

Synchronized breeding in cattle using PGF2α and LHRH/FSHRH stimulatory analogs

Two studies were conducted to synchronize breeding in cattle using PGF₂α and LHRH/FSHRH analogs. In the first study, 60 mature lactating Angus cows were assigned at random to 4 treatment groups: saline and saline (SS); 30 mg PGF₂α tham salt + saline (PS); saline + 2 mg D-ala⁶-des-GlyNH₂¹⁰ LHRH/FSHRH ethylamide (D-ala⁶) (SA); 30 mg PGF₂α tham salt + 2 mg D-ala⁶ (PA). The first letter of the two-letter code for each group always indicates a dual injection at an 11-day interval. PGF₂α or saline was administered intramuscular (im) twice at an 11 day interval. D-ala⁶ or saline was administered 48 hr after PGF₂α treatment. In the SA group, the D-ala⁶ was administered at first signs of estrus, and cows were then artificially inseminated (AI) 24 hr later. All cows in the PS group were inseminated 72 hr after the second PGF₂α injection. In the SS group, cows were inseminated 24 hr after first signs of estrus. An additional 6 mature lactating Angus cows were added equally to the PS and PA groups to evaluate changes in serum LH. The percent calf crops was: SS = 40% (frsol|6/15); PS = 47% ($\text{7}\text{15}$); SA = 47% ($\text{7}\text{15}$); PA = 53% ($\text{8}\text{15}$). In the second study, 51 mature lactating Angus cows and 39 Holstein heifers were assigned at random to 3 treatment groups: saline + saline (SS); 33.4 mg PGF₂α tham salt + saline (PS); 33.4 mg PGF₂α tham salt + 1 mg D-leu⁶-des GlyNH₂¹⁰ LHRH/FSHRH ethylamide (D-leu⁶) (PL). PGF₂α tham salt or saline was administered im twice at an 11 day interval. D-leu⁶ or saline was administered 68 hr following the second PGF₂α treatment. Cows pretreated with PGF₂α were inseminated 80 hr after the second PGF₂α injection. In the SS group, cows were administered saline at the time of natural estrus and were artificially inseminated 12 hr later. Calving percent to the first AI was SS = 70% ($\text{21}\text{30}$); PS = 53% ($\text{16}\text{30}$) and PL = 40% ($\text{12}\text{30}$). An additional 10 mature lactating Angus cows were used to evaluate changes in serum LH. Five of the cows were assigned to the PS treatment and five to the PL treatment. Sequential blood samples were collected to monitor serum LH levels. Using the Chi-square test, there were no significant differences between calving percentages of the control and PGF₂α treated cows in either study. These results indicate that the PGF₂α treatments were successful in timed artificial insemination of cows without detection of estrus. The LHRH/FSHRH analogs did not improve the conception even though they appear to induce a pituitary release of LH simultaneously in all cows within 1 hr of treatment.     

Comparison of invivo and invitro uterine contractility in the ewe

Uterine contractions were observed $\text{in}$$\text{vivo}$ by laparotomy and exposure of the uterus. Ten hours after the beginning of estrus, an average of 39 contractions per 10 min originated in the posterior ends of the uterine horns and moved toward the oviducts, while an average of, 13 contractions originated in the anterior ends of the horns and moved toward the cervix. Two days later (58 hr after the beginning of estrus), the contractions had changed in origin and direction; only 6 contractions originated in the posterior ends of the horns and moved anteriorly, while 39 originated in the anterior ends and moved posteriorly.Experiments were done to determine whether the change in origin of contractions $\text{in}$$\text{vivo}$ was reflected in the contractility of strips of myometrium in a tissue bath. The number and amplitude of contractions were recorded from strips of circular and of longitudinal myometrium taken from the posterior and anterior ends of the uterine horns at 10 and 58 hr after the beginning of estrus. The myometrial strips contracted approximately 3 to 4 times per minute regardless of the time after the beginning of estrus, the end of the uterine horn from which the tissue was taken, or whether the contracting muscle was circular or longitudinal. Thus, the physiological mechanisms that controlled the number and origin of uterine contractions $\text{in}$$\text{vivo}$ did not maintain that control over myometrial tissue $\text{in}$$\text{vitro}$.     

Effect of monensin on postpartum interval to first estrus and serum LH response to 0, 1, 2 or 4 mg estradiol-17β at 21 days postpartum

A 2×4 factorial design was used to evaluate the effects of monensin (0 vs 200 mg) and estradiol-17β (E2) dose (0, 1, 2 vs 4 mg) on postpartum interval (PPI) to first estrus and on serum LH release at 21 days postpartum. Forty-eight spring calving Brangus cows were randomly stratified by calving date and sex of calf into two feeding groups within 24 hr of calving. Each group received 2.7 kg/head/day of a milo:cottonseed meal (4:1) mixture containing either 0 or 200 mg monensin. Coastal bermuda grass hay and water were available $\text{ad}$$\text{libitum}$. During the period of E2 treatment and bi-hourly blood sampling, suckling was controlled at 6-hr intervals.Mean cow weight and body condition score within cell changed less than 23 kg and 0.5 points, respectively, from day 1 to day 21 postpartum and were unaffected by treatment (P>0.10). PPI was reduced (P<0.01) and proportion of cows exhibiting estrual behavior by 85 days postpartum was increased (P<0.05) by treatment with 200 mg monensin and unaffected by E2 dose. Monensin fed cows had a longer (P<0.05) interval to LH response (ILH) and to peak LH (ILHP) at the 4 mg E2 dose. Monensin had no effect (P>0.10) on LH variables at 0, 1 or 2 mg E2.     

The effect of PGF-2 alpha on reproductive performance of naturally bred dairy cows with or without pyometra

Five hundred thirty-four naturally bred Holstein dairy cows from two Colorado dairies were examined $\text{per}$$\text{rectum}$ between 21 and 36 days after calving. Alternate cows in each herd received either 25 mg PGF-2 alpha or no treatment at the time of initial examination. No differences were found in days open or pregnancy rates between groups (P>0.25).Days open in 23 cows with pyometra were 98.7 ± 9.4, and 77.0 ± 2.2 in 493 herdmates without pyometra. The large inequalities in numbers precluded valid statistical comparisons between these groups. No overall difference (P>0.25) in reproductive performance was found in cows with pyometra treated at the initial examination compared to those not treated until two to four weeks after the initial examination. Contributing to the lack of significance were a number of cows with pyometra that had spontaneous cures before treatment was considered. Untreated cows that recovered spontaneously had better (P<0.05) reproductive performance than herdmates that required later treatments to initiate uterine evacuation. No overall advantage in reproductive performance was obtained by the routine treatment of postpartum dairy cows with PGF-2 alpha but treatment of cows with pyometra should not be delayed.     

Steroidal regulation of uterine resistance to bacterial infection in livestock

Postpartum uterine infections reduce reproductive efficiency and have significant animal welfare and economic consequences. Postpartum uterine infections are classified as nonspecific, but Arcanobacterium pyogenes and Escherichia coli are usually associated with them in cattle and sheep. Pyometra is the most common type of uterine infection in dairy cattle, and it is detected almost exclusively in cows with active corpora lutea. Luteal progesterone typically down-regulates uterine immune functions and prevents the uterus from resisting infections. Progesterone also can down-regulate uterine eicosanoid synthesis. This seems to be a critical event in the onset of uterine infections, because eicosanoids can up-regulate immune cell functions in vitro. In addition, exogenous prostaglandin F2 alpha stimulates uterine secretion of prostaglandin F2 alpha and enhances immune functions in vivo. Thus, one may hypothesize that eicosanoids can override the negative effects of progesterone and that the up-regulatory effects of exogenous prostaglandin F2 alpha allow the uterus to resolve an infection, regardless of progesterone concentrations. Based on the results of studies to test that hypothesis, cows, sheep, and pigs in various physiological statuses are resistant to intrauterine infusions of Arcanobacterium pyogenes and Escherichia coli, unless progesterone concentrations are increased. In sheep and pigs, exogenous prostaglandin F2 alpha stimulates uterine production of prostaglandin F2 alpha and allows the uterus to resolve Arcanobacterium pyogenes-Escherichia coli-induced infections, even when progesterone is maintained at luteal phase concentrations before and after treatment. Prostaglandin F2 alpha is a proinflammatory molecule that stimulates the production of various proinflammatory cytokines, and it may enhance uterine production of leukotriene B₄. Proinflammatory cytokines and leukotriene B₄ enhance phagocytosis and lymphocyte functions. Even though there are clear associations among prostaglandin F2 alpha, leukotriene B4, proinflammatory cytokines, phagocytosis, and lymphocyte functions, the mechanism of action of exogenous prostaglandin F2 alpha in overriding the down-regulatory effects of progesterone and resolving uterine infections has not been elucidated. Defining this mechanism should yield new prevention and treatment strategies for uterine infections that do not rely on antibiotic and antimicrobial compounds.     

Effects of Alfaprostol and uterine palpation on postpartum interval and pregnancy rate to embryo transfer in Brahman influenced beef cows

Two trials were conducted to determine the effects of Alfaprostol, a prostaglandin F2 alpha analogue, and uterine palpation on reproductive performance in postpartum beef cows. In Trial J, 143 multiparous and 132 primiparous Brahman crossbred embryo recipient cows were assigned to receive one 5 mg injection of Alfaprostol between 29 and 65 d postpartum or to serve as controls. Alfaprostol treatment between 29 and 42 d postpartum decreased (P < 0.05) postpartum interval in multiparous but not primiparous cows. Alfaprostol treatment increased pregnancy rate to embryo transfer. Trial II utilized 369 multiparous Brangus cows, 17 to 49 d postpartum, that were assigned to one of three groups: 1) Alfaprostol plus uterine palpation (APP), 2) Uterine palpation only (UP) or 3) Control. Completion of uterine involution was determined at treatment. Alfaprostol plus uterine palpation decreased postpartum interval regardless of uterine involution, while UP had a greater effect if uterine involution was not complete. Both APP and UP increased the number of cows which were detected in estrus by 80 d postpartum. Alfaprostol and uterine palpation, alone or in combination, can increase postpartum reproductive performance in Brahman crossbred and Brangus beef cows.     

Detection of antibodies against Fusobacterium necrophorum and Porphyromonas levii‐like species in dairy cattle with papillomatous digital dermatitis

Bovine digital epidermitis involves different pathologies, including PDD, interdigital dermatitis, and foot rot. Bacteriological and molecular biological studies suggest that these are multimicrobial infections. During our study on the isolation of treponemes from biopsies of PDD, colonies producing black pigment were isolated frequently from the primary cultures, suggesting that Porphyromonas species were present. Moreover, 16S rRNA genes of Fusobacterium necrophorum and Porphyromonas levii‐like species were detected in the lesions. We therefore determined whether an immunological response could be elicited by a P. levii‐like organism isolated from a PDD lesion, as well as two subspecies of F. necrophorum in the sera from cows with and without PDD. A total of 151 serum samples were collected from 85 cows with PDD lesions and 33 cows without lesions on 12 PDD‐positive farms and from 33 cows on two PDD‐free farms. ELISA data showed that IgG antibody levels against antigens of P. levii‐like species and F. necrophorum subsp. necrophorum were significantly higher in cows on PDD‐positive farms than in cows on PDD‐free farms, regardless of the presence of PDD lesions in the cows on the PDD‐positive farms. However, F. necrophorum subsp. funduliforme was present at low levels in both groups. The ELISA results were confirmed by western blot analysis. Furthermore, antigens of these bacteria were detected in PDD‐biopsy sections examined by immunohistochemical staining. F. necrophorum subsp. necrophorum and P. levii‐like species may be involved in the pathogenesis of PDD.     

Commercial splitting of bovine embryos

Independent studies were undertaken at Alberta Livestock Transplants (ALT) and at Select Embryos, Inc. (SEI) to develop procedures for splitting bovine embryos. At both locations embryos were recovered seven days after the onset of estrus and superovulation. Initially, survival after splitting was evaluated by culture $\text{in}$$\text{vitro}$ for 18 to 24 hours. Culturing half or demi-embryos without a zona pellucida at ALT resulted in 15% survival compared to 35% survival when both halves were in separate zonae. Culturing demi-embryos on a monolayer of luteal cells at SEI did not improve survival $\text{in}$$\text{vitro}$. In fertility trials, best results were obtained at ALT when both demi-embryos within separate zonae were nonsurgically transferred into separate uterine horns of the same recipient (55% pregnancy rate) and at SEI when one demi-embryo was surgically transferred into the uterine horn ipsilateral to the corpus luteum (65% pregnancy rate). Culturing demi-embryos more than 4 hours reduced fertility at both locations. Splitting embryos was a worthwhile addition to the commercial ET programs and further trials are in progress to improve survival $\text{in}$$\text{vitro}$ and pregnancy rates.     

Localization of prostaglandin F in the ovine uterus during early pregnancy

As part of a study on the anti-luteolytic action of the sheep conceptus, the distribution of prostaglandin F (PGF) within the uteri of 19 pregnant and 14 non-pregnant ewes was studied using three antisera to PGF_2α and fluorescent antibody tracing. In the uteri of seven non-pregnant ewes up to Day 11 after estrus (Day 0) and in uteri of $\text{18}\text{19}$ pregnant ewes up to Day 50, PGF was localized mainly in the lamina propria, with very little on epithelial cells lining the uterine lumen. After Day 11, in the uteri of seven non-pregnant ewes, PGF was localized on the surface of luminal epithelial cells and throughout their cytoplasm, and to a lesser extent in the lamina propria. The distribution of PGF on Days 14 and 17 in the gravid and non-gravid horns of the uteri of 13 ewes made unilaterally pregnant (conceptus confined to one uterine horn) was similar to that described above for normal pregnant and non-pregnant ewes after Day 11 respectively.These results are interpreted to indicate a change in the distribution of PGF in sheep uteri due to the presence of a conceptus.     

Reproductive studies of Brahman cattle I. Behavioral effect of various dose levels of Estradiol-17β upon ovariectomized Brahman,Brahman × Hereford and Hereford cows

Six ovariectomized mature cows each of Brahman (B), Brahman × Hereford (BH) or Hereford (H) breeding were injected intramuscularly with Estradiol-17β (E). Dose levels of 1, 2, 4 and 8 mg E were given in 2 ml corn oil. Cows were allowed a 2 week recovery period between treatments. After injection the cows were placed with 18 epididymectomized bulls and observed constantly for 36 hours. B failed to accept the bulls at any E dose level. Proportions of BH accepting the bull were $\text{2}\text{6}$, $\text{6}\text{6}$, $\text{6}\text{6}$ and $\text{6}\text{6}$ and proportions of H accepting the bull were $\text{5}\text{6}$, $\text{6}\text{6}$, $\text{5}\text{6}$ and $\text{6}\text{6}$ at 1, 2, 4 and 8 mg E, respectively. BH were less responsive at 1 mg E than H (P<.10) and B were less responsive at any level (P<.005). The number of stances increased significantly with dose level (P<.005) and a breed × dose level interaction (P<.10) was found. The duration of standing estrus behavior was longer in H cows at 1 and 2 mg E than in BH (P<.05) but was identical at 4 and 8 mg E. Duration of estrus was shorter in B except at the 2 mg dose level. Breed (P<.005) and breed × dose level interactions (P<.05) were found. Response time (injection of E to stance event) did not differ between dosages of E within breed groups. However, response time was significantly longer in B (19.3 hrs, P<.05) versus the response time of either H (10.1 hrs) or BH (12.8 hrs). If homosexual stance behavior is accepted as estrus, B were less responsive at 1, 2, 4 and 8 mg E than were BH or H (P<.10).