Calving rate following fixed time insemination after a 12-day progesterone treatment in dairy cows, beef cows and heifers.

Farm trials were carried out to determine if cows and heifers could be inseminated on a fixed time basis following a 12-day treatment with progesterone coils and an injection of 5 mg oestradiol benzoate and 200 mg progesterone at the start of treatment. The retention rate of the coils was significantly higher (P less than 0.05) when a 5.5 cm diameter was used compared with a diameter of 7.0 cm. Calving rate was similar in treated cows bred at a detected oestrus, at 56 + 74 hours after treatment or at 56 hours after treatment and injection of 100 microgram gonadotrophin releasing hormone 20 hours previously and in control cows bred at oestrus. Fertility to the first repeat oestrus was also similar in treated and control cows. Significantly (P less than 0.05) more synchronised cows calved following fixed time AI compared with the calving rate in control cows inseminated for a 24-day experimental period. In beef suckler cows, calved at least 50 days, and dairy heifers weighing over 280 kg, calving rate was similar in treated animals bred at 56 and 74 hours after treatment compared to calving rate in control animals bred at oestrus.     

Effects of xylazine hydrochloride on urine in cattle.

Urine volume, urine pH, and urine glucose concentration were monitored for up to 24 hours after physiological saline or one of two dosage levels (0.22 mg/kg or 0.44 mg/kg) of xylazine was administered to cows. During the first 2 hours after xylazine was given, urine output was greatly increased (relative to the control animals), with the high dosage group having more output than the low dosage group. The influence of the drug on urine volume had ended by 5 hours after injection when urine output in both dosage groups had returned to that of the control group. Glucose was detected in the urine of xylazine treated animals, beginning at 15 to 30 minutes after injection, reached a maximum at 2 hours, and was undetectable at 5 to 6 hours. Urine pH decreased in control and treated animals, but in treated animals the pH began to increase 2 hr after treatment.     

Intramammary administration of gentamicin as treatment for experimentally induced Escherichia coli mastitis in cows.

In 8 Holstein cows, 50 colony-forming units (CFU) of Escherichia coli was administered into 1 mammary gland. Infections were established in all inoculated glands. In 4 of the 8 cows, 500 mg of gentamicin sulfate was administered by intramammary infusion 14 hours after inoculation; the other 4 cows were untreated controls. Infusions of gentamicin also were given after each of the 3 successive milkings after the initial infusion, so that a total dose of 2 g of gentamicin was given to each of the treated cows. During the 33-hour treatment period and for the first milking after the last infusion of gentamicin, the treated cows had a mean gentamicin concentration of greater than or equal to 31.0 micrograms/ml in milk samples that were collected from inoculated quarters immediately before each milking. Concentrations of 0.34 and 0.69 micrograms of gentamicin/ml were detected in milk from 2 cows at 8 days after inoculation with E coli. Mean serum concentrations of gentamicin were greater than or equal to 0.37 micrograms/ml throughout the treatment period and the first 12 hours after the last infusion, with a mean peak concentration of 0.96 micrograms/ml at 24.4 hours. The range of peak concentration of gentamicin detected in urine from all treated cows was 42 to 74.4 micrograms/ml. Peak concentration of E coli in milk in the treated cows (6.08 +/- 1.02 log10 CFU/ml) did not significantly (P greater than 0.05) differ from that of the control cows (5.26 +/- 1.00 log10 CFU/ml). Similarly, mean duration of infection in the treated cows (54 hours) did not differ significantly from that of the control cows (48 hours).(ABSTRACT TRUNCATED AT 250 WORDS)     

Lack of LH response to oestradiol treatment in cows with cystic ovarian disease and effect of progesterone treatment or manual rupture.

The luteinising hormone (LH) surge in response to 1 mg oestradiol benzoate intramuscular injection was studied on 67 occasions in 45 cows with cystic ovarian disease 20 to 150 days post partum. Cows diagnosed as having luteal cysts were given 500 micrograms cloprostenol intramuscularly 24 hours before oestradiol, to induce luteolysis. Oestradiol benzoate was also given to eight post partum acyclic and eight cyclic cows and in all these cases a control LH response was characterised for comparison. Eight of 17 cows with luteal cysts (47 per cent), and 10 of 21 cows with follicular cysts (48 per cent), released LH in response to oestradiol. Some cows with cysts were given one of two treatments. Seven cows with follicular cysts were treated with a progesterone-releasing device (PRID) for seven days: all responded to a second oestradiol treatment given 24 hours after removal of the PRID. Luteal cysts in three cows and follicular cysts in nine cows were ruptured manually: only one cow (a luteal case) responded to the second oestradiol treatment given 24 hours after manual rupture. In eight cows initially diagnosed with luteal cysts, cloprostenol was not given and plasma progesterone concentration at the time of oestradiol treatment was high (over 0.9 ng ml-1): none released LH in response to oestradiol. As manual rupture did not improve the LH response to oestradiol, it is concluded that the defective LH response to oestradiol in cows with cystic ovarian disease was not influenced in the short-term by cyst fluid contents.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of Parturition in the Cow using Cloprostenol and Dexamethasone in Combination

Two experiments were designed to test the hypothesis that induction of parturition in the cow would be more predictable with the simultaneous use of a combination of cloprostenol and dexamethasone than with either hormone used alone.

In experiment I all 19 beef cows treated with 500 μg cloprostenol and 25 mg dexamethasone in combination calved within 72 hours whereas dexamethasone (n = 19) or cloprostenol (n = 16) treatments alone each resulted in two induction failures. In those cows successfully induced, the mean interval from treatment to birth was 34.6 ± 1.4 hours for the cloprostenol plus dexamethasone group, 43.3 ± 2.4 hours for the dexamethasone group and 44.9 ± 2.1 hours for the cloprostenol group. Control cows (n = 15) did not calve during the first 72 hours after treatment with saline. The incidence of retained placenta ranged from 19 to 53% in induced groups whereas placentae were not retained by cows in the control group.

In experiment II all 30 beef cows in the cloprostenol plus dexamethasone group calved within the 72 hour limit, with a mean interval of 39.1 ± 1.0 hours. Twenty-six of 31 cows calved within 72 hours with a mean interval of 51.9 ± 3.4 hours after a single injection of cloprostenol and 29 of 33 cows calved within 72 hours with a mean interval of 52.6 ± 3.3 hours after two injections of cloprostenol, 12 hours apart. Five of 34 control cows calved within 72 hours of time of treatment. The incidence of retained placenta was again high in induced cows. Results indicate that the simultaneous administration of cloprostenol and dexamethasone does constitute a safe, reliable and effective method of inducing parturition in the cow.

     

Synchronised calvings after withdrawal of norgestomet implants from cows treated near term with prostaglandin

To investigate whether calving could be controlled by the withdrawal of progestogen implants from cows treated near term with prostaglandin three cows (group 1) received an intramuscular injection of 5 mg flumethasone on day 270 of pregnancy, and four cows (group 2) and three cows (group 3) received implants containing 3 mg norgestomet in both ears on day 262 of gestation and were treated with a prostaglandin F2 alpha analogue on day 264. On day 270 the implants were removed and at the same time the cows of group 3 were treated with 5 mg flumethasone. Jugular blood samples were taken daily to estimate progesterone concentrations in the plasma. Luteolysis was achieved by the injection of prostaglandin, as judged by the decrease in plasma progesterone concentration in the cows of groups 2 and 3 on day 264. Pregnancy was maintained in these cows until after the removal of the norgestomet implants. The interval from the removal of the implants and, or, the injection of flumethasone on day 270 until the onset of second stage labour ranged from 36 to 47 hours and the mean intervals for the three groups were not significantly different. In all the cows except one from group 3 the dilatation of the cervix and vagina and the softening of the pelvic ligaments appeared normal at calving. It is concluded that calving near term can be synchronised by a progestogen in the absence of a corpus luteum.     

Steroid concentrations in cows with corticotropin-induced cystic ovarian follicles and the effect of prostaglandin F2alpha and indomethacin given by intrauterine injection.

In 7 instances, cystic ovarian follicles resulted when adrenocorticotropin (ACTH) was administered daily during the follicular phase of the estrous cycle in cows. Two cows given daily injections of hydrocortisone (cortisol) during the follicular phase of the estrous cycle did not develop cystic ovaries. Plasma concentrations of estradiol in cows with induced cystic ovarian follicles were similar to the peak values observed at estrus and were between 6 and 12 pg/ml. Progesterone concentrations in plasma of cows with cystic ovaries were low, between 1 and 2 ng/ml. Ovulation occurred when 2 cows were given human chorionic gonadotropin (HCG) during the period of ovarian cyst development with ACTH administration. Several days of administration of ACTH was required to cause cyst development. Ovulation occurred at the expected time in 1 cow when injections began on day 19, that is, late in the follicular period. In another cow, when treatment was stopped on day 3, after the expected time of estrus a delayed ovulation occurred. In 2 cows with induced cystic ovarian follicles, cyst atresia occurred spontaneously about day 13 to 17 of the cycle. In these cows, new follicular growth and ovulation followed (although delayed in 1 cow). The time of atresia of cystic follicles was not influenced by the intrauterine injection of 10 ml of sterile saline solution on days 8, 9, and 10 in 1 cow. When 5 mg of prostaglandin F2alpha in 10 ml of sterile saline solution was given (uterine injection) in 2 cows on days 8, 9, and 10, cyst atresia occurred earlier than the time of spontaneous atresia. Intrauterine administration of 100 mg of indomethacin in 10 ml of sterile saline solution daily for 13 or 14 days to 2 cows, starting on day 12 or 13 of the cycle, resulted in persistence of the induced cystic ovarian follicles. After cessation of indomethacin treatment, atresia of cysts followed and new follicular growth and ovulation occurred.     

Efficacy of oral and parenteral ketoprofen in lactating cows with endotoxin-induced acute mastitis

One hind quarter of 27 healthy lactating cows was infused with 100 microg Escherichia coli endotoxin. Two hours later, nine of the cows were given physiological saline by intramuscular injection, nine were given 4 mg/kg ketoprofen orally, and nine were given 3 mg/kg ketoprofen by intramuscular injection. Ketoprofen administered either orally or parenterally significantly reduced the effect of the endotoxin on rectal temperature, ruminal contractions and respiratory rate. The size of the udder, the signs of pain and the concentrations of thromboxane B2, especially in plasma, were also reduced, and the appearance of their milk was almost normal. The response of cows to the oral treatment was as rapid as it was to intramuscular treatment.     

Sodium retention and cortisol (hydrocortisone) suppression caused by dexamethasone and triamcinolone in equids

Three ponies and 1 horse were bilaterally adrenalectomized (BADX). The initial hypoadrenal episode after BADX was reversed with 20 mg of dexamethasone (DXM) IM (n = 2) or 20 mg of triamcinolone (TMC) IM (n = 2). Nine hypoadrenal crises were reversed with 20 mg of DXM given IM (n = 4) or 20 mg of TMC given IM (n = 5). Sodium and chloride retention and potassium excretion were documented based on changes in serum electrolytes and urinary excretion. Eight intact adult horses were randomly assigned to 2 groups to study the effects of a single IM injection of DXM (0.044 mg/kg of body weight) or TMC (0.044 mg/kg). Cortisol (hydrocortisone) suppression was found to be maximal (nondetectable amounts of cortisol) by 12 hours in both groups. Cortisol was again detectable in the DXM group at 24 hours after injection and was at pretreatment values at 168 hours. Cortisol was not detectable in the TMC group for 192 hours and did not reach pretreatment values until 336 hours. The duration of the gluconeogenic effect was compared with the duration of cortisol suppression exerted by DXM and TMC in these intact animals. Assuming that the decrease in plasma glucose coincides with the decrease in glucocorticoid activity of the respective steroid, a relative hypoadrenocortical state was found in the animals treated with DXM between the 2nd and 7th day after treatment, whereas this state occurred between the 6th and 14th day after treatment with TMC.     

Flunixin meglumine and flurbiprofen in cows with experimental Escherichia coli mastitis

The effect of flunixin meglumine and flurbiprofen on the course of experimental Escherichia coli mastitis was examined. Nine cows (within one month post partum) were inoculated intramammarily with 20 x 10(5) viable E coli in both rear quarters. Three cows remained untreated (controls); three cows received three injections of flunixin meglumine and three cows received flurbiprofen as two intravenous infusions. Flunixin meglumine and flurbiprofen were initially given before clinical signs were observed. Treatment was repeated if the cows' temperature increased by more than 1 degree C. In the untreated cows, rectal temperature and heart rate increased from three hours after infection, and rumen motility (both frequency and amplitude) decreased from four hours after infection. Treatment with flunixin meglumine or flurbiprofen almost completely abolished the febrile response during the first nine hours after infection, and the decrease in rumen motility was less pronounced in the treated animals. These results suggest that the decrease in rumen motility during E coli mastitis is at least partly due to a mechanism involving prostaglandin.     

Prophylaxis of hormonal sterility in the cow: II. Observations during and after the use of gestagen postpartum

183 Holstein cows were studied during and after administration of ch lormadinone acetate (CAP) postpartum. CAP was either fed orally (10mg/d ay for 15 or 20 days) or applied parenterally twice (50 mg) or once (100 mg). By oral administration, estrus was completely (=100%) and ovulation mostly (greater than 95%) suppressed, but follicle growth and estrogen production in growing follicles was not inhibited. Out of 39 closely observed animals, 89.7% ovulated after CAP withdrawal, 79.5% of them within 96 hours. With all animals inseminated, 37.5% conceived at this 1st ovulation. In 144 cows, of which 101 were orally treated with CAP and 39 by injection, shortening of the calving interval and a reduction in fertility problems was achieved. A partly significant improvement of the overall conception rate, the curtailing of the interval between parturition and conception as well as a marked reduction of the standard deviations from the mean values of those intervals were observed. Parenterally treated cows responded in a similar way. But since their 1st ovulations were spread over several weeks and since at these 1st ovulations silent heat was a considerable problem, no prediction of the timing of the 1st ovulation could be made. On the basis of the data presented on uterine contractility, ovarian functions, vestibular hyperaemia, and mucus secretion during and after CAP administration are discussed.     

Betamethasone alcohol suspensions for the induction of parturition in dairy cows: a comparison with dexamethasone trimethyl acetate

A field trial was conducted to compare the efficacy suspensions of betamethasone alcohol with dexamethasone trimethyl acetate on the induction of parturition before term in dairy cows. Initial treatment consisted of a subcutaneous injection of either 20 mg of betamethasone as a 10 mg/ml suspension (Group A), 30 mg of a 15 mg/ml suspension (Group B), or 20 mg of dexamethasone TMA (Group C). Those cows not calving within 10 days received a further 25 mg of betamethasone alcohol as a 2 mg/ml suspension. Data were collected from 619 cows on 41 farms. A marked difference between groups was noted in the proportion of animals calving to the initial injection (55.0, 61.4 and 26.4% calved to first injection in Groups A, B and C respectively); the differences between the groups receiving the betamethasone suspensions and the group receiving dexamethasone trimethyl acetate were highly significant (P<0.001). Of the animals treated 6.9, 3.6 and 10.2% failed to calve within 17 days of the initial treatment in Groups A, B and C respectively (Group B significantly different from Group C (0.02 > P> 0.01). Nevertheless, the response-time (mean of 7.5 days for all those calving to the first injection, and of 12.4 days for all those calving to the second injection) was not significantly different between the three treatment groups. Calf mortality over all treatments was 15.2% at birth and 26.6% by 4 days old. The incidence of metabolic disease was 5.9%, and 203% of cows had retained foetal membranes 24 hours after calving. No differences were observed between groups in the incidence of dystocia and cow mortality. Four cases of mastitis were recorded in Group A and 12 cases in Group C. No cases were recorded in Group B.     

The effects of subcutaneous injections of sodium selenate on blood composition and milk yield in dairy cows.

Three groups of four lactating cows received a subcutaneous injection of 0 . 05, 0 . 10 and 0 . 15 mg Se/kg body weighty respectively administered as sodium selenate. A fourth group was injected with saline. In all the cows injected with sodium selenate, the concentration of Se in blood increased rapidly and was significantly higher than in control cows for two days in the group receiving the lowest dose and for 182 days (the duration of the experiment) in the two other groups. The activity of glutathione peroxidase in blood increased slowly in all cows injected with sodium selenate and was significantly greater than in control cows after 15, 22 and 29 days respectively, and remained significantly greater for 63, 91 and 182 days respectively. In a second experiment a single subcutaneous injection of 0 . 15 mg Se/kg body weight had no effect on the mean milk yield of 37 animals (19 . 1 kg/day) compared with the milk yield of a similar group of control animals (19 . 1 kg/day) during 70 days. The concentration of Se in milk was significantly higher on the first (168 microgram/litre) and second (69 microgram/litre) day after injection than in control animals (mean 26 microgram/litre).     

Efficacy of 1 alpha hydroxyvitamin D3 in the prevention of bovine parturient paresis

One hundred and seventeen Israeli-Friesian cows from herds with a milk fever incidence of more than 15 per cent were injected intramuscularly with either 350 micrograms 1 alpha hydroxyvitamin D3 (1 alpha OHD3) in propylene glycol or with the vehicle alone, close to calving. If parturition had not occurred within 72 hours a second injection was administered; parturition was induced two days after the second injection if necessary. There were 10 cases of milk fever among 57 control cows as opposed to two cases among the 60 animals treated with 1 alpha OHD3. In an attempt to prolong the effect of the drug, Israeli-Friesian cows were injected intramuscularly with 350 micrograms 1 alpha OHD3 in either 10 ml propylene glycol or arachis oil. 1 alpha OHD3 in arachis oil did not prolong the effect of the drug. 1 alpha OHD3 in propylene glycol increased plasma calcium concentrations more rapidly than when the drug was administered in oil. Additional cows of the same breed and age were injected intramuscularly with 350 micrograms 1 alpha OHD3 in propylene glycol. Five of the animals received a second dose four days, and five received a second dose five days after the first injection. Five animals served as uninjected controls. The plasma calcium levels of the injected cows were significantly higher (P less than 0.01) than those of the controls from the second until the 14th day after the first injection. Based on these results 451 Israeli-Friesian cows from herds with a milk fever incidence of more than 15 per cent were injected intramuscularly with 1 alpha OHD3 close to calving.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of endotoxin-induced mastitis on the pharmacokinetic properties of aditoprim in dairy cows.

Plasma disposition of aditoprim, a new dihydrofolate reductase inhibitor, was studied in healthy cows and cows with endotoxin-induced mastitis. A single dose of 5 mg of aditoprim/kg of body weight was administered IV to 5 healthy cows and to the same cows 3 weeks later at 2 hours after intramammary infusion of 0.1 mg of endotoxin into the rear quarters. Mastitis developed in all endotoxin-infused quarters and cows had systemic signs of disease (fever, tachycardia, depression) from 2 to 10 hours after infusion of endotoxin. Pharmacokinetic characteristics of aditoprim in healthy cows were a large volume of distribution (6.28 L/kg), a systemic clearance of 0.82 L/h/kg, and an elimination half-life of 7.26 hours. In cows with mastitis, plasma concentrations of aditoprim were lower between 5 and 26 hours after injection. The systemic clearance (1.00 L/h/kg) and the volume of distribution (12.25 L/kg) were significantly higher in cows with mastitis, but elimination half-life was not significantly different. The lower plasma concentrations of aditoprim between 5 and 26 hours after injection in cows with mastitis are explained by fluid compartment shifts and/or blood flow changes induced by mastitis, although increased elimination of aditoprim in cows with mastitis cannot completely be ruled out. The antibacterial activity of aditoprim is nearly the same as that of trimethoprim. The longer elimination half-life time of aditoprim, however, indicates that it may have a practical pharmacotherapeutic advantage over trimethoprim.     

Development of a gonadotrophin-releasing hormone and prostaglandin regimen for the planned breeding of dairy cows

Four studies were carried out to determine the ovarian responses of dairy cows undergoing natural oestrous cycles to sequential injections of gonadotrophin-releasing hormone (GnRH), followed seven days later by prostaglandin and, 48 to 72 hours later, by a second injection of GnRH. In study 1, of 60 cows so treated, 47 were in the intended periovulatory phase when a fixed-time insemination was given 72 hours after the prostaglandin. In study 2, detailed observations were made in 32 cows treated as in study 1, using ultrasound to determine the optimum time to administer the second dose of GnRH. Ovulation was most effectively synchronised by giving GnRH 56 to 60 hours after the prostaglandin. Study 3 investigated the timing of ovulation when no initial dose of GnRH was given. Six cows were injected with prostaglandin on day 12 of the oestrous cycle, followed by GnRH 60 hours later. Five of the six cows ovulated 24 to 36 hours after GnRH, an equivalent timing and synchrony to that in study 2, in which a dose of GnRH had been given seven days before prostaglandin. In study 4, an initial dose of GnRH was given to six cows late (day 17) in the oestrous cycle, and prostaglandin seven days later. The GnRH treatment delayed luteolysis in five of the cows so that they were responsive to the prostaglandin and ovulated 24 to 36 hours after the second dose of GnRH. The use of GnRH (day 0) - prostaglandin (day 7) - GnRH (day 9.5) appears to be an effective means of synchronising ovulation in most cows.     

Increased conception rate in dairy cows after early post partum administration of prostaglandin F2 alpha THAM

Commercial dairy cows were given a routine injection of dinoprost tromethamine (prostaglandin F2 alpha THAM) in the early post partum period. The first service conception rate of 64 cows given a single 25 mg injection of dinoprost during the period 14 to 28 days after calving was 68 per cent, that of 64 untreated controls was 43 per cent. The difference was highly significant at the level P = 0.007. In cows with no blood progesterone and with basal progesterone concentrations at the time of treatment, indicating absence of an active corpus luteum, the mean conception rates for 30 treated and 38 control cows were 70 and 44 per cent, respectively, demonstrating that this is not a luteolytic effect. Although that implies a positive myometrial effect, the interval from calving to first service was not shortened in treated cows.     

Synchronisation of oestrus and fertility in buffaloes using a prostaglandin analogue

Cloprostenol, a prostaglandin analogue, was administered intramuscularly to a total of 35 cycling buffalo cows and heifers in two doses, each of 0.5 mg, given 11 days apart. Out of five cows and 12 heifers subjected to observations after the second injection of cloprostenol (day 0), all except one heifer responded. Signs of oestrus were most marked on days 3 or 4. Eighteen treated heifers were kept with buffalo bulls for four days after the second injection while a control group of nine heifers was kept with bulls for 21 days. The first-service conception rate, diagnosed by rectal palpation at 60 days, was 33 1/3 per cent in both groups. Twelve treated heifers were artificially inseminated at 72 and 96 hours after the second injection of cloprostenol, using fresh semen diluted in egg yolk--citrate extender. The first service conception rate at 60 days was 30 per cent.     

Treatment of suckling beef cattle with a progestagen sponge and oestradiol benzoate or equine chorionic gonadotrophin

The ovarian responses of anoestrus beef cows to a combined treatment with medroxy-progesterone acetate (MAP) sponges and oestradiol benzoate or equine chorionic gonadotrophin (eCG) were evaluated. Forty-five suckling Hereford cows were allocated to three equal groups. Group 1 received a MAP sponge for seven days plus an injection of 2 mg oestradiol benzoate when the sponge was inserted (day 0) and 1 mg when the sponge was withdrawn; group 2 received identical treatment until day 7, when a dose of 400 iu of eCG was administered, and group 3 were left untreated as control animals. From day 0 to day 11 the cows' ovaries were examined daily by transrectal ultrasonography, and their oestrous behaviour was observed from 24 hours to 96 hours after the sponge was removed. Data from cows that had a corpus luteum present before the sponge was withdrawn were not used in subsequent analyses; there were four in group 1, five in group 2 and four in group 3. In 19 of the 21 cows in groups 1 and 2 a new follicular wave was observed to emerge at a mean (sd) interval of 3.9 (0.3) days after the insertion of the sponge, whereas in group 3 it occurred in all 11 cows after 3.4 (0.6) days. Only the six cows that had a follicle of 9 mm or larger in diameter ovulated (P < or = 0.001). Nine of the 11 cows in group 1 came into oestrus, compared with two of the 10 in group 2 and none of the control cows (P < or = 0.001). Ovulation was observed in four, two and none of the cows in groups 1, 2 and 3, respectively.     

Effects of standing estrus and supplemental estradiol on changes in uterine pH during a fixed-time artificial insemination protocol

Cows that exhibit estrus within 24 h of fixed-time AI have elevated concentrations of estradiol and greater pregnancy rates compared with cows not in estrus. Our objective was to determine whether estradiol, estrus, or both had an effect on uterine pH during a fixed-time AI protocol. Beef cows were treated with the CO-Synch protocol (100 mircog of GnRH on d -9; 25 mg of PGF(2alpha) on d -2; and 100 mircog of GnRH on d 0). One-half of the cows received an injection of estradiol cypionate (ECP; 1 mg) 12 h after PGF(2alpha). Cows detected in standing estrus within 24 h of the second GnRH injection were considered to be in standing estrus. Uterine pH was determined in all animals 12, 24, and 48 h after the PGF(2alpha) injection. For Exp. 1, pH was also determined 72 and 96 h after the PGF(2alpha) injection; in Exp. 2, pH was also determined at 54, 60, 66, 72, 78, 84, 90, and 96 h after the PGF(2alpha) injection or until ovulation. A treatment x time interaction (P < 0.01) influenced concentrations of estradiol. All cows had similar (P > 0.15) concentrations of estradiol at the time of ECP administration, but after ECP treatment all cows treated with ECP and control cows that exhibited estrus had greater (P < 0.01) concentrations of estradiol compared with nontreated cows that did not exhibit estrus. In all animals, estradiol diminished 48 h after the PGF(2alpha) (time of the second GnRH injection), but ECP-treated cows, regardless of estrus, had elevated (P < 0.02) concentrations of estradiol compared with control cows. There was a treatment x time interaction (P < 0.001) on uterine pH. All cows had similar uterine pH (P > 0.19) 24 h after the PGF(2alpha) injection. Control cows that did not exhibit estrus had a greater uterine pH compared with control cows that exhibited estrus (P < 0.01) and ECP cows that exhibited estrus (P = 0.05) 48 h after the PGF(2alpha) injection (7.0 +/- 0.1 vs. 6.7 +/- 0.1 and 6.8 +/- 0.1, respectively). Estradiol cypionate-treated cows not exhibiting estrus were intermediate (6.8 +/- 0.1; P > 0.05). All cows had similar uterine pH 72 h after the PGF(2alpha) injection through ovulation (P > 0.06). In summary, uterine pH was similar among all animals that exhibited estrus, regardless of treatment with ECP.