The Concentration of Faecal Progestins during the Oestrous Cycle in Nkone Cows and the Effect of Duration of Storage of Faecal Samples at Room Temperature on Faecal Progestin Levels

The objectives of this study were to determine whether ovarian function in Nkone cows could be monitored by measuring progestin concentrations in faeces and to assess the effect of duration of storage at room temperature on faecal progestin concentrations. Faecal and blood samples were obtained once a day for 26 days from 21 Nkone cows whose oestrous cycles had been synchronized. Faecal samples from each cow were divided into five portions that were kept at room temperature for 0, 6, 12, 24 and 48 h, respectively, and then frozen. After centrifuging the blood to recover plasma and extracting steroids from the faeces, analysis of progesterone (P₄) was carried out using solid-phase radioimmunoassay. The faecal progestin and plasma progesterone profiles corresponded well and were positively correlated (r = 0.70, p>0.01). Faecal progestin concentrations decreased with increasing duration of storage at room temperature during both the follicular and luteal phases (p>0.01). In both cases, the decline in faecal progestin concentrations followed an exponential pattern. The progestin concentrations in faeces after 48 h of storage at room temperature were higher (p>0.05) during the peak luteal phase than in the follicular phase.     

Estrone and Progesterone Plasma Levels of Normal Cows and Cows with Parturient Paresis

Blood plasma concentrations of estrone and progesterone, calcium and inorganic phosphorus were measured in 22 cows (Swedish Red and White Breed) from 4 weeks prepartum up to 6 days post partum. Ten cows with parturient paresis had Ca levels below 6 mg/100 ml. Data from plasma analyses in individual cows were grouped in the following periods: 28–22, 21–15, 14–8, 7–6, 5–4, 3, 2, 1 day(s) before parturition and 1, 2, 3–6 days after parturition. Statistical comparisons of the levels of the hormones and the ratio progesterone/estrone did not reveal any significant differences between the paretic and normal cows at any time period. The results do not support the theories that high systemic levels of estrogens or an imbalance between estrogen and progesterone predispose towards parturient paresis.     

Effects of storage times and temperatures on T3, T4, LH, prolactin, insulin, cortisol and progesterone concentrations in blood samples from cows

Little is known about stability of hormones in blood samples stored under various conditions. This study was conducted to examine stability of triiodothyronine (T3), thyroxine (T4), luteinizing hormone (LH), prolactin, insulin, cortisol and progesterone in blood and serum samples. Experiment 1 was designed to determine if concentrations of these hormones were affected by exposure to cellular elements of anticoagulated and coagulated blood when stored at 4 C and room temperature (22 to 26 C). Jugular venous blood was collected from six diestrous Holstein cows into evacuated bottles containing sodium ethylenediaminetetraacetic acid (EDTA), heparin or no anticoagulant. Subsamples of EDTA-treated and heparinized blood were stored .25, .5, 1, 2, 4, 8, 24 and 72 h at 4 C or room temperature. Subsamples of blood without anticoagulant were stored in polypropylene tubes (clot tubes) or serum separator tubes for 1, 2, 4, 8, 24 ad 72 h. Mean concentrations of T3, T4, LH, prolactin and cortisol did not change in plasma or serum from either of the four types of samples stored at 4 C or room temperature for 72 h. The mean insulin concentration decreased 18% by 72 h in serum from serum separator tubes stored at room temperature. At 4 C, mean progesterone concentrations decreased 55% by 24 h and 73% by 72 h in plasma from EDTA-treated blood; 41% by 72 h in serum from clot tubes, and 26% by 24 h and 36% by 72 h in serum from serum separator tubes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in Plasma Progesterone Levels in the Caudal Vena Cava and the Jugular Vein and Luteinizing Hormone Secretion Pattern After Feeding in Lactating and Non-lactating Dairy Cows

The present study was designed to assess progesterone profiles at the secreted (caudal vena cava) and circulating levels (jugular vein) and luteinizing hormone (LH) secretion pattern in lactating and non-lactating cows with reference to feeding. Four lactating and four non-lactating cycling Holstein cows were examined. Blood samples were collected simultaneously from the caudal vena cava (via a catheter inserted from the coccygeal vein) and the jugular vein every 15 min for 12 h (0500–1700 h) during the functional luteal phase. Cows were fed 50% of the daily diet 6 h after the start of blood sampling. During the 12-h sampling period, mean progesterone concentrations in the caudal vena cava did not differ between lactating and non-lactating cows (49.0 ± 2.9 and 53.3 ± 3.7 ng/ml; mean ± SE), whereas mean progesterone concentrations in the jugular vein in lactating cows were higher than those in non-lactating cows (6.4 ± 0.1 and 5.6 ± 0.1 ng/ml, P < 0.001). Lactating cows had a higher frequency of LH pulses than non-lactating cows (7.0 ± 0.7 and 4.3 ± 0.9 pulses/12 h, P<0.05). The influence of feeding was not observed on LH profiles but was observed on progesterone profiles in both veins. Progesterone concentrations in the caudal vena cava increased after feeding in both groups. Progesterone concentrations in the jugular vein decreased after feeding in lactating cows but not in non-lactating cows. These results indicate the difference in feeding-related changes in progesterone dynamics between lactating and non-lactating cows.     

Plasma Progesterone Profile in Ovariectomized Beef Cows after Intra-vaginal Insertion of New, Once-used or Twice-used CIDR

Objective of this study was to show plasma progesterone concentrations in ovariectomized beef cows after treatment with new, once-used and twice-used controlled internal drug-releasing devices (CIDRs). Four ovariectomized beef cows were used for the experiment. Plasma concentrations of progesterone were quantified using a validated ELISA. The CIDR was inserted into vagina of cows by using a standard CIDR applicator and then removed 7 days after insertion. One week later, once-used CIDR was inserted and removed on day 7. Twice-used CIDR was, then inserted at an interval of 7 days. Mean plasma concentrations of progesterone 24 h after new CIDR insertion was 4.0 ± 0.1 ng/ml, which thereafter decreased gradually to 1.4 ± 0.1 ng/ml at day 7. In cows treated with once-used CIDR or twice-used CIDR, mean plasma progesterone concentrations at day 1 were 2.4 ± 0.2 or 1.8 ± 0.2 ng/ml and 1.0 ± 0 or 0.9 ± 0.1 ng/ml at day 7 respectively. The results suggest that once-used CIDR may be still effective to produce luteal phase progesterone concentrations in plasma in non-suckling beef cows.     

The effect of handling methods on subsequent plasma progesterone levels in sheep

The mean progesterone concentration in the plasma of 10 adult Ethiopian Highland sheep obtained immediately after slaughter was 10.56±3.98 ng/ml. Samples were subsequently incubated at 4°C, room temperature (19–22°C) or 26°C as either plasma or intact but citrated blood. Failure to separate plasma affected the progesterone content at 2–72 h at room temperature or 26°C (p<0.01-p<0.0001). Incubation temperature affected the plasma concentration at 18 h (p<0.05) and 24 h (p<0.001). Although progesterone values were generally higher in separated plasma, disparity with the values from plasma separated from incubated citrated blood was small (r=0.76–0.98). Progesterone concentration declined haphazardly after collection but sometimes exceeded the initial readings. This kept the average concentration of progesterone in plasma separated immediately after collection fairly constant and within 15% of zero time samples during the first 48 h.     

The effects of gonadotrophin releasing hormone administration four days after insemination on first-service conception rates and corpus luteum function in dairy cows.

One hundred and eighty-five Holstein-Friesian dairy cows received either sterile water or 250 micrograms of gonadotrophin releasing hormone intramuscularly on the fourth day after the first service postpartum. Heparinized blood samples were taken immediately prior to treatment (day 4) and on day 8 postinsemination for analysis of plasma progesterone concentration. Pregnancy diagnosis was carried out by rectal palpation at 42 days postinsemination and reconfirmed after 60 days postbreeding. The pregnancy rates after first, second or third service were not significantly different between gonadotrophin releasing hormone-treated and control cows. Plasma progesterone concentrations on day 4 and day 8 postinsemination, as well as the change in plasma progesterone concentration from day 4 to day 8, were similar for gonadotrophin releasing hormone-treated and control cows. The plasma progesterone concentrations on day 8 postbreeding were significantly higher (p less than 0.005) and the change in progesterone concentrations between days 4 and 8 were significantly greater (p less than 0.002) in pregnant cows compared to nonpregnant cows.     

Changes of platelet function and blood coagulation during short-term storage of CPDA-1-stabilised ovine blood

The objective of this study was to detect the influence of short-term storage on the haemostatic function in whole citrated ovine blood at different storage temperatures. Ovine blood was collected in a commercial transfer bag system containing CPDA-1 and stored on a wobbler at room (20-25 °C; n = 5) or refrigerator temperature (4 °C; n = 5). The following analyses were performed initially and after 1, 2, 3, 4, 5, 6, 8, 12, 24, 48 and 72 h of storage: platelet count and (spontaneous) aggregates, agonist-induced platelet aggregation with two methods (impedance aggregometry, turbidimetric method), prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen concentration and resonance thrombography.Platelet count remained stable at room temperature, whereas a significant decrease was detected after 48 h storage at 4 °C. The latter was associated with the formation of a high percentage of platelet aggregates (50-60%) after 5 h storage. Decrease in platelet aggregation was significantly more pronounced when blood was stored at 4 °C. The plasmatic coagulation tests were stable within the observation period.Results indicate that platelet count and aggregability of CPDA-1-stabilised ovine blood is better preserved at room temperature and provides adequate haemostatic function for ex vivo experiments for one working day. Functional loss and high percentage of platelets within aggregates which were observed in ovine blood stored at refrigerator temperature have to be considered in blood transfusion in sheep.     

Progesterone Profiles in the Caudal Vena Cava and Jugular Vein in Response to Pulsatile Luteinizing Hormone Stimulation Induced by GnRH Treatment During the Mid-luteal Phase in Lactating Dairy Cows

The aim of this study was to examine whether increased frequency of luteinizing hormone (LH) pulses influences luteal progesterone (P₄) secretion by measuring progesterone concentrations at the secreted (caudal vena cava) and circulating levels (jugular vein) in lactating dairy cows. Cows received six intravenous administrations of 2.5 μg of GnRH (gonadorelin acetate, n=4) or 2 ml saline (n=3) at 1-h intervals on 12.4 ± 0.4 (mean ± SE) days after ovulation. Blood samples were collected from the caudal vena cava and jugular vein every 12 min for 12 h (6 h before and after treatment). During the 6 h after treatment, frequency of LH pulses (5.3 ± 0.3 and 3.0 ± 0.0 pulses/6 h) and mean LH concentration (0.50 ± 0.06 and 0.38 ± 0.05 ng/ml) were greater (P<0.05) in GnRH-treated cows than in saline-treated cows. Mean P₄ concentration and amplitude of P₄ pulses in the caudal vena cava during the 6 h after treatment were greater (P<0.05) in GnRH-treated cows than in saline-treated cows, but the frequency of P₄ pulses was not different between the groups. Mean P₄ concentration in the jugular vein during the 6 h after treatment was also higher (P<0.05) in GnRH-treated cows than in saline-treated cows (7.0 ± 1.3 and 5.4 ± 0.9 ng/ml). These results indicate that the increased frequency of LH pulses stimulates progesterone secretion from the functional corpus luteum and brings about higher P₄ concentrations in the circulating blood in lactating dairy cows.     

Quantification of normetanephrine in canine urine using ELISA: evaluation of factors affecting results

Catecholamine release increases in dogs with pheochromocytomas and in situations of stress. Although plasma catecholamines degrade rapidly, their metabolites, normetanephrine (NME) and metanephrine (ME), are stable in acidified urine. Our aim was to verify a human urine ELISA kit for the quantification of NME and ME in canine urine and to determine the effects on metabolite stability of sampling time (morning or midday) and day (ordinary or day spent in a clinic). We analyzed 179 urine samples from 17 healthy dogs. For NME, the mean intra-assay CV was 6.0% for all samples and 4.3% for the canine control; inter-assay CVs were 3.3, 3.8, and 12% for high and low concentration human urine positive controls supplied in the ELISA kit and a positive canine control, respectively; spike-recovery was 90–101%. For ME, mean intra-assay CV was 6.5% for samples and 9.0% for the canine control; inter-assay CVs were 12.7, 7.2, and 22.5% for high and low concentration human urine positive controls supplied in the ELISA kit and a positive canine control, respectively; spike-recovery was 85–89%. Dilution recovery was unsatisfactory for both metabolites. Based on our verification results, NME was selected for remaining analyses. We found no effect on NME concentrations of acidification or room temperature storage for up to 24 h. The NME:creatinine ratio was higher after the first of 3 clinic days compared to the same morning (111.2 ± 5.5 vs. 82.9 ± 5.3; p < 0.0001), but not on the other days. NME verification results were generally superior to ME. Dilution studies were unsatisfactory for both metabolites. Given that NME was stable without acidification at room temperature, urine samples can be collected at home. The clinic environment can cause higher NME:creatinine ratios, especially in unaccustomed dogs.     

Changes in fecal progestagen profile after excretion in miniature pigs

The aim of this study was to evaluate whether the fecal progestagen (progesterone and its metabolites) levels of miniature pigs would change after excretion at room temperature. Our initial investigation focused on the correlations between the fecal progestagen concentrations with and without ether extraction and between the plasma progesterone and fecal progestagen concentrations in order to develop an enzyme-linked immunosorbent assay (ELISA) for fecal progestagen without ether extraction. There were significant correlations between fecal progestagen concentrations with and without ether extraction (r=0.880) and between fecal progestagen concentrations without ether extraction and plasma progesterone (r=0.763). The fecal progestagen concentration obtained by ELISA without ether extraction was almost identical to that obtained with ether extraction. These results validate the ELISA method without ether extraction, which was therefore used for the latter experiment. Fecal samples collected from the pigs were preserved for 0-24 h at room temperature, and then their fecal progestagen concentrations were measured. The fecal samples preserved for 0 to 24 h were analyzed by high performance liquid chromatography (HPLC) and ELISA. The concentrations of all samples significantly increased with time after preservation. The progestagen concentration of fresh feces (0 h) with high progestagen concentration (>1000 ng/g) increased significantly after 3 h. The concentration increased significantly after 12 h for fresh feces containing about 500 ng/g progestagen. HPLC analysis is showed that the fecal progesterone concentration, but not its other metabolites, doubled 24 h after excretion compared with the concentration at 0 h. These results suggest that dynamic changes in the profile of progesterone metabolites occur in feces after excretion.     

Effects of storage on concentration of hydrocortisone (cortisol) in canine serum and plasma

A specific radioimmunoassay was used to measure concentrations of hydrocortisone (cortisol) in the serum and plasma of 4 dogs. Differences (P greater than 0.05) in concentrations of cortisol were not found between serum and plasma (from EDTA-treated and heparinized blood samples). Differences (P greater than 0.05) in serum or plasma concentrations of cortisol were not found between samples stored at 4 C for various times (10 minutes, 10 hours, 40 hours) after collection, but before removal of RBC. In a study designed to determine the stability of cortisol in serum samples stored at room temperature, degradation was dependent on the initial serum concentrations of cortisol. Decreases (P greater than 0.05) did not occur in concentrations of cortisol in serum samples stored up to 15 days when initial concentrations of cortisol were less than 15 ng/ml. However, when initial concentrations of cortisol were approximately 55 ng/ml and 80 ng/ml, significant (P greater than 0.05) degradation occurred after 9 and 5 days of storage, respectively. Results of this investigation indicate that either serum or plasma of dogs is suitable for radioimmunoassay of cortisol and that samples (with and without added coagulants) incubated at 4 C may be left uncentrifuged for up to 40 hours without cortisol degradation. However, prolonged storage of serum at room temperature is detrimental, particularly for samples having large concentrations of cortisol.     

Measurement of glucocorticoid metabolite concentrations in faeces of domestic livestock

After 14C-labelled cortisol infusion in ponies and pigs, faecal samples were collected. Extraction of 0.5 g faeces with 5 ml 80-90% methanol yielded the highest radioactivity in the supernatant. Most of the metabolites were ether soluble. After high performance liquid chromatography (HPLC), the presence of immunoreactive metabolites was demonstrated by measuring each HPLC fraction using enzyme immunoassays for cortisol, corticosterone and 11-oxoaetiocholanolone. Only the assay for 11-oxoaetiocholanolone revealed peaks with co-eluting radioactivity. For biological validation of the test system, adrenocorticotrophic hormone (ACTH) and dexamethasone were injected intravenously successively in both species (n = 6). Cortisol concentration in blood and the 11-oxoaetiocholanolone immunoreactive substances in faeces were determined. In horse faeces, basal values of 2.3-35.2 nmol/kg were measured. After ACTH administration, an increase (more than 200% above basal values) of these metabolites was seen about 1 day after ACTH administration. After dexamethasone injection the levels decreased, reaching minimum concentrations 2 days after administration. In pigs, an increase in these metabolites was measured in only three animals after ACTH; dexamethasone did not cause a decrease. The stability of the samples after defecation was tested by storing samples from cows, horses and pigs at room temperature. It was shown that there was a significant increase in the concentration of measured cortisol metabolites in bovine, equine and porcine faeces after storage for 1 h, 4 h and 24 h, respectively. In frozen samples this effect was diminished after thawing samples at 40 degrees C; thawing the samples at 95 degrees C prevented an increase in immunoreactive substances.     

Relationship between the somatic cell count in milk and reproductive function in peripartum dairy cows

The aim of the present study was to examine the effect of the somatic cell count (SCC) in milk on reproductive performance, such as pregnancy status in the prepartum period and ovarian function in the postpartum period, in dairy cows. Blood samples were collected every week from one month prepartum to parturition in order to measure the concentrations of 13,14-dihydro-15-keto-PGF_2α (PGFM), estrone sulfate (E1S) and progesterone. Milk samples were collected three times per week in both the prepartum (for one month before the dry period) and postpartum periods (for 3 months immediately after parturition) to measure the SCC. Progesterone was also determined in the whole milk of postpartum cows to define the day of the first ovulation. In the prepartum period, the maximum SCC negatively correlated with the pregnancy period (r = –0.77), but not the calf birth weight. Positive and negative correlations were observed between the average SCC and PGFM or progesterone concentrations in plasma, respectively (r = 0.84 or –0.92, respectively), at 39 weeks of pregnancy. In the postpartum period, a correlation was observed between the day of the first ovulation and both the average and maximum SCC (r = –0.74 and –0.75, respectively), whereas days open was not related to the SCC. These results suggest that a high SCC in the prepartum period may advance parturition by increasing PGF_2α and decreasing progesterone and that the first ovulation in the postpartum period was affected by a high SCC.     

Serum constituents analyses in dairy cows: effects of duration and temperature of the storage of clotted blood

We studied the effects of storage time and temperature of clotted whole blood on the amounts of 17 analytes in bovine blood serum. Serum separated after blood was allowed to stand for 2, 4, 6, 12 and 24h at room temperature or on ice. Results obtained for phosphorous, magnesium, urea, cholesterol, beta-hydroxybutyrate (BHBA), triglyceride, albumin, total protein and gamma-glutamyletransferase (GGT) were not influenced by storage at room temperature or on ice for as long as 24h. Duration of the clotted whole blood storage had a significant effect on calcium, glucose concentrations, creatine kinase (CK) and aspartate aminotransferase (AST) activities and temperature had a significant effect on glucose, non-esterified fatty acids, CK and bilirubin concentrations.     

Changes in canine ionised calcium under three storage conditions

OBJECTIVES: To determine the ionised calcium concentration following aerobic collection of blood and to compare ionised calcium concentration and pH of heparinised whole blood and plasma at 48 hours following collection under three different storage conditions to assess if ionised calcium concentration can be measured retrospectively. METHODS: Blood was collected from 17 dogs for analysis of ionised calcium concentration and pH using a Rapidpoint 400 (Bayer) blood gas analyser. Blood was collected into a commercial preheparinised syringe and into a plain syringe, with subsequent transfer to a commercially available heparinised sample tube. Samples were analysed within 10 minutes, and the remainder was divided for storage. One aliquot was set-aside at room temperature for 48 hours, and the other was immediately centrifuged and the plasma divided for storage at room temperature and at 4 degrees C for 48 hours each. In all samples, ionised calcium concentration and pH were measured again at 48 hours after storage. RESULTS: There was no significant difference in ionised calcium concentration or pH between anaerobically and aerobically collected heparinised whole blood analysed within 10 minutes of collection. At 48 hours, ionised calcium concentrations had decreased under all storage conditions irrespective of the direction of pH change. CLINICAL SIGNIFICANCE: Ionised calcium concentration can be measured in aerobically collected samples within 10 minutes and at 48 hours after collection under the conditions described.     

Pregnancy and peripheral plasma progesterone levels in cows inseminated after synchronization of estrus with prostaglandin F2 alpha

Fifteen Holstein cows were treated with two doses of 25 mg of a prostaglandin F₂α (PGF₂α as dinoprost tromethamine) administered intramuscularly 11 days apart. The cows were then divided into three groups and inseminated either at 72, 80 or 72 and 96 hours after the second dose of PGF₂α. Thirteen cows ovulated after the second prostaglandin treatment. Eight cows were diagnosed pregnant by rectal palpation 42 days after insemination but only five calved. PGF₂α induced luteolysis in cows with active corpora lutea as evidenced by the dramatic decreases in the plasma progesterone concentrations after treatment. In contrast, following PGF₂α administration to cows in follicular or late luteal phase the concentrations of plasma progesterone either increased gradually or remained low for several days before increasing to maximal levels. The ovulatory rate after the two doses of PGF₂α11 days apart was high. However, the pregnancy rate after this treatment was influenced by other factors including abnormal ovarian function.     

Prolactin, estradiol, and progesterone changes in paretic and nonparetic cows during the periparturient period

We studied the relationship of serum prolactin, estradiol-17 beta, and progesterone concentrations to plasma calcium, phosphorus, and free hydroxyproline concentrations, as well as to dry matter intake, in 14 aged dairy cows (mean of 4.5 parities), 7 of which became paretic, from 28 days before to 4 days after calving. Plasma calcium and phosphorus concentrations and dry matter intake decreased more at parturition in paretic cows than in nonparetic cows. Prolactin concentrations were not different between paretic and nonparetic cows, but were variable. Concentrations of estradiol were higher in paretic cows from 15 to 5 days before parturition, whereas hydroxyproline concentration was lower in paretic cows on days 10 through 3 before parturition. Progesterone concentration was lower in paretic cows and decreased earlier at parturition, compared with that in nonparetic cows. The findings suggested that high estradiol concentrations in late pregnancy inhibit bone resorption and predispose aged cows to parturient paresis. The earlier decrease in progesterone concentration at parturition and lower concentrations throughout late pregnancy might have contributed to the greater inappetence in paretic cows at parturition. The importance of prolactin in the pathogenesis of parturient paresis is not clear.     

Sequential Hormonal Changes in the Postpartum Dairy Cow

Peripheral plasma levels of 15-keto-13,14-dihydro-PGF_2α, progesterone, Cortisol, LH and prolactin were studied in 6 primiparous postpartum dairy cows. The cows were followed by hormone measurements and clinical examinations from parturition until pregnancy was established. Blood was collected 3 times per day. The cervix, uterus and ovaries were examined by rectal palpation at 6–10 days intervals. The cows were observed for signs of oestrus twice daily and were additionally teased with a bull to provoke standing heat.Four cows had a normal parturition and dropped their fetal membranes shortly afterwards. (NR group). The remaining 2 retained their fetal membranes for more than 24 h following parturition (RFM group). One out of 6 cows showed standing oestrus at the first ovulation, 4 animals were in oestrus at the second ovulation and all cows showed signs of oestrus at the third ovulation. Although the length of the first luteal phase varied from 9 to 22 days a corpus luteum was in all cases palpated. The secretion of progesterone during the first luteal phase was terminated by a PGF_2α release.A significant difference in 15-keto-13,14-dihydro-PGF_2α levels between the 2 groups was found on days 0–4 (2.39 vs 6.87 nmol/1 at Ρ < 0.06). Postpartum prostaglandin F_2α release as reflected by the level of 15-keto-13,14-dihydro-PGF_2α lasted shorter in the NR group than in the RFM group (15–17 vs 21 days). Significant positive correlations between 15-keto-13,14-dihydro-PGF_2α and Cortisol as well as between prolactin and Cortisol during the first 24 days postpartum were noted only in cows having normal parturition. The most pronounced daily prolactin variations occurred during the second luteal phase (NR group), when a significant difference between the times 8.00, 12.00 and 15.00 was recorded (14.7, 31.5 and 19.7 μg/l, respectively). Moreover, a partial negative correlation between log value of prolactin and arithmetical value of LH was found in these cows only during the first luteal phase after parturition.     

Cervix–rectum temperature differential at the time of insemination is correlated with the potential for pregnancy in dairy cows

This study sought to establish whether temperature gradients between the cervix, vagina, and rectum at and 7 days post-artificial insemination (AI) were associated with the incidence of pregnancy in lactating dairy cows (Experiment I; n = 90 ovulating cows) and to evaluate temperature gradient dynamics from the time of insemination to 7 days post-AI under heat stress conditions (Experiment II; n = 16 ovulating and 4 non-ovulating cows). In Experiment I, 39 cows (43.3%) became pregnant. The odds ratio for pregnancy was 2.5 for each one-tenth of a degree drop in cervical temperature with reference to the control rectal temperature at the time of AI (P = 0.01), whereas the same decrease in the cervix–rectum temperature differential 7 days post-AI resulted in an odds ratio of 0.44 (P = 0.02). In Experiment II, 5 of the ovulating cows (31.3%) became pregnant. The mean values of the vagina–rectum, vagina–cervix, and cervix–rectum temperature differentials at AI (day 0), 8 h, 24 h, and 7 days post-AI changed significantly from day 0 to day 7 (within-subject effect; P < 0.02) in ovulating cows but not in non-ovulating cows. Temperature differentials on days 0 and 7 were similar between ovulating cows and cows of Experiment I. Overall, our findings support the notion that a temperature differential between the caudal cervical canal and rectum at AI may be an indicator of the likelihood of pregnancy. Possible prospects of confirming estrus at the herd-level are also suggested.