Milk fat progesterone concentrations in goats and early pregnancy diagnosis

Blood and milk samples from foremilk during afternoon milking, were simultaneously collected from 285 dairy goats. In experiment 1, fiva cyclic goats were sampled daily for 21 days. In experiment 2, 280 females from 9 flocks were submitted to sampling 21 days after insemination. In addition, some milk samples were divided in two parts, after which one was frozen and the other kept at +4 degrees C until assay. Progesterone concentrations were measured in blood, whole milk and milk fat by radioimmunoassay. No difference in whole milk or fat progesterone levels was found between frozen and refrigerated milk samples. Milk butterfat progesterone concentrations paralleled those in plasma or whole milk throughout the estrous cycle and ranged from about 20 ng/ml at estrus to about 400 ng/ml in mid-luteal phase. The ratio of mid-luteal phase progesterone levels to those seen in the estrous period was over 20 in fat and in blood. This ratio was very much lower in whole milk. Consequently the determination of pregnant and non-pregnant goats from the samples collected 21 days after service was very much easier and accuracy was better when the progesterone content was assayed from milk fat than from whole milk. It was concluded that early pregnancy diagnosis in goats can be done routinely by determination of progesterone levels in milk fat.     

A simple enzymeimmunoassay of milk progesterone for monitoring fertility in dairy buffaloes

A simple, sensitive, direct (without extraction) enzymeimmunoassay (EIA) was usec to determine progesterone levels in whole milk samples of 400 Nili-Ravi dairy buffaloes. The mean progesterone values 22 d after A.I. were significantly higher in pregnant (16.6 +/- 9.2 ng/ml) than nonpregnant (below 5 ng/ml) animals. The mean progesterone values were below 0.34 +/- 0.12 (the detection limit) both at estrus and in cases of clinically diagnosed inactive ovaries, 3.18 +/- 1.9 at proestrus, 2.25 +/- 1.2 postestrus and 13.22 +/- 6.74 at Day 10 of the estrous cycle. Twenty buffaloes confirmed pregnant for 2 to 3 mo, had a mean value of 20.3 +/- 4.5 ng/ml. The EIA test is very reliable in the selection of nonpregnant buffaloes (100 %) and the confirmation of inactive ovaries and of estrus. Differential diagnosis of inactive or active ovaries can be made by analyzing two milk samples at a 7-d interval.     

Concentrations of LH, oestradiol-17 beta and progesterone in the peripheral plasma of swamp buffalo cows (Bubalus bubalis) around the time of oestrus

Peripheral plasma concentrations of LH, oestradiol-17 beta and progesterone were measured in 13 mature swamp buffalo cows at 4-h intervals from 36-40 h before until 36-40 h after the onset of oestrus. Mean LH concentrations increased sharply to a peak of 35 ng/ml and returned to basal levels of 5 ng/ml within a 12-h period beginning soon after the onset of oestrus. Mean oestradiol-17 beta concentrations were within the range 9-13 pg/ml from 36-40 h before until 12-16 h after the onset of oestrus, and within the range 7-9 pg/ml thereafter. Progesterone concentrations remained around 0.1 ng/ml throughout the sampling period. There were no significant differences in hormone concentrations or changes between cows that conceived and those that did not conceive to artificial insemination 12-24 h after onset of oestrus.     

Progesterone determinations and clinical examinations of reproductive organs in purebred and crossbred female Zebu cattle

Five experiments were undertaken to investigate variation in progesterone concentrations as related to the collection and handling of samples of milk and blood, to determine reference values for progesterone and to evaluate clinical findings in relation to progesterone data from pure- and crossbred Zebu cattle reared in the Peruvian tropics. Whole-milk progesterone concentrations obtained from 12 Holstein x Nellore pregnant cows at hourly intervals over a 24-h period were highest immediately after milking; this peak was followed by a sharp drop over the next 3 h. Milk-fat content from 28 Brown Swiss x Nellore pregnant cows increased from 2.4% before milking to 6.7% afterwards (P < 0.05), whereas progesterone concentrations in whole milk increased from 18.4 to 59.5 nmol/1 (P < 0.05). Progesterone concentrations in fat-free milk were stable, with the exception of the fore-milk sample, which was lower than subsequent samples collected during milking (P < 0.05). Blood samples collected from 23 purebred, pregnant Nellore cows, were divided into four aliquots, and plasma and serum were harvested periodically over the next 120 h of storage at +4 degrees C, or in the shade at ambient air temperatures. The results indicate that blood samples can be stored unseparated at both temperatures studied for up to 3 h without severe loss of progesterone. Milk samples collected at different intervals during the luteal phase of the estrous cycle and during early and mid-pregnancy from crossbred cows showed no significant differences in progesterone concentrations between Days 9 to 13 of the cycle and Days 9 to 13 of gestation. Progesterone levels during advanced gestation were higher (P < 0.05). Out of 2,607 clinical examinations, the level of agreement between palpatory findings and progesterone determinations was 95.6 and 81.9% in diagnosing non-luteal and luteal structures, respectively. Significant differences in the level of agreement between palpators were found (P < 0.01). It is concluded that milk samples, preferably composite milk or strippings, must be consistently collected at the same stage of milking, and that centrifugation of blood samples should be done as soon as possible and not later than 3 h after collection.     

Responses of different doses of prostaglandin F(2) alpha on estrus induction, fertility and progesterone levels in subestrous buffaloes

Responses of different doses of PGF(2) alpha (Lutalyse) on estrus induction, fertility, and progesterone levels were studied in buffaloes. Of the total 70 subestrous buffaloes, 71.0 percent (50) exhibited estrus and 44.0 percent (22) conceived to induced estrus with different doses of PGF(2) alpha. Serum progesterone levels were variable before treatment of PGF(2) alpha in subestrous buffaloes and ranged from 0.60 to 4.90 ng/ml. An abrupt decrease in progesterone levels was observed within 24 hours of treatment with 30 mg or 5.0 mg PGF(2) alpha given intramuscularly or by intrauterine fusion, respectively. Serum progesterone levels further decreased and were minimum or similar to those seen in spontaneous estrus (/ 0.5ng/ml) on day 2 to 5 or 6 after PGF(2) alpha treatment. Progesterone patterns further revealed that, in most of the buffaloes, corpora lutea were formed and were functional after the treatment. With 2.5 mg of PGF(2) alpha administered into the uterus, morphological regression of corpus luteum and progesterone were not adequate to induce estrus and ovulation.     

Milk progesterone levels to monitor reproductive status of Murrah buffalo

Concentration of progesterone in whole milk was used to diagnose pregnancy in 44 lactating buffaloes. Milk samples were taken from days 19 to 27 post breeding and analysed for progesterone by radio-immunoassay. A level exceeding 10 ng/ml of milk was taken as an indication of pregnancy. Using this criterion, the accuracy of the pregnancy test from a single milk sample on 19, 21, 23, 25 and 27 days after insemination ranged from 71.42 to 86.95% and 86 to 87.50% for pregnant and non-pregnant animals, respectively. Milk progesterone concentrations were significantly higher (P / 0.001) in pregnant compared with those in non-pregnant buffaloes on day 19, 21, 23, 25 and 27 post-insemination.     

Peripheral plasma progesterone concentration in zebu (Bos indicus) cows during pregnancy

Plasma progesterone concentrations were determined weekly during gestation averaging 283 +/- 2 d in Ethiopian zebu (Bos indicus) cows. Mean progesterone levels increased from 0.2 +/- 0.1 ng/ml at oestrus (service) to 3.1 +/- 1.6 ng/ml on d 7 and 8.1 +/- 2.1 ng/ml on d 21. Progesterone levels remained elevated throughout pregnancy. Hormone concentration differed significantly between cows (P less than 0.001) and with the wk of pregnancy (P less than 0.05); it tended to be higher during the last trimester of pregnancy. Mean levels dropped sharply to below 1 ng/ml during the last wk of pregnancy with considerable variation (C.V. = 39 to 63%) among cows. These data indicate that pregnancy in Ethiopian zebu cows can be reliably diagnosed by determining circulatory plasma progesterone levels.     

Use of milk progesterone enzyme immunoassay for early pregnancy diagnosis in cows

An enzyme immunoassay using beta-galactosidase as the tracer was applied to determine milk progesterone level in cows. The novel method was reliable and practicable and required only a spectrophotometer and a centrifuge as major equipment. The milk progesterone enzyme immunoassay successfully diagnosed early pregnancy in cows. Milk samples were collected from 268 Holstein-Friesian cows in commercial dairy herds on 20, 21 or 22 days(usually 21 days) after insemination. Progesterone level in skim milk higher than 1.0 ng/ml indi-cated pregnancy. Pregnancy was confirmed by rectal palpation on 60 to 120 days after insemination. The accuracy of the milk progesterone test was 60.0 % (132 220 ) for a positive diagnosis and 100 % (48 48 ) for a negative result. A high incidence of embryonic death, 27.9 % (51 183 ), may have reduced accuracy for a positive test result. The enzyme immunoassay may be an alternative to radioimmunoassay in milk progesterone analysis for pregnancy diagnosis.     

Progesterone profile in buffaloes during various stages of oestrous cycle using radioimmunoassy technique

Investigation were carried out to study the norms of progesterone concentration in the blood serum of buffaloes during various phases of oestrous cycle. Twenty four animals (12 heifers and 12 cows) were used. The blood serum samples were stored at -20 degrees C until processed for progesterone assay. The progesterone concentrations were measured by the radioimmunoassay technique. The progesterone levels were 0.360 +/- 0.062 and 0.334 +/- 0.066 ng/ml on the day of oestrus in buffalo-heifers and buffalo-cows, respectively. The values were around 1 ng/ml till day 6, followed by a gradual increase to a peak average value of 4.888 +/- 0.399 and 5.119 +/- 0.415 ng/ml on day 15 of the cycle in heifers and cows, respectively. Thereafter, the progesterone concentration fell abruptly to a level similar to that at oestrus. The mean progesterone value a day before oestrus was 0.488 +/- 0.067 and 0.577 +/- 0.053 ng/ml in buffalo-heifers and buffalo-cows, respectively. The mean progesterone concentration of different days of the cycle (except day 16) did not differ significantly (P / -0.01) between heifers and cows.     

Concentrations of progesterone in milk as a monitor of early pregnancy diagnosis in dairy cows

The objectives of the experiment were to evaluate the efficacy of using progesterone concentrations in milk and palpation per rectum on days 21 or 22 postbreeding to estimate pregnancy and evaluate management practices; and to investigate physiological occurrences leading to incorrect diagnosis of pregnancy when serial samples of milk were collected. Of particular interest were indications of early embyronic death and insemination of cows not in estrus. Milk samples were collected at the afternoon milking of days 0 or 1 (day 0 = day of estrus), 9 or 10, 21 or 22 and 27 or 28 following breeding in 200 lactating dairy cows. Tentative diagnosis of pregnancy was made based on concentrations of progesterone in milk on days 21 and 22 alone and on days 21 or 22 and 27 or 28. In addition all cows were palpated per rectum on days 21 or 22 postbreeding and a tentative pregnancy diagnosis was made. Pregnancy was confirmed by examination of the genital tract per rectum between 35 and 50 days after breeding. Values of 4 ng/ml or greater and/or the presence of a mature corpus luteum were considered positive signs of pregnancy. Progesterone in milk ranged from 0.1 to 18 ng/ml. On days 0 or 1, 9 or 10, 21 or 22 and 27 or 28 concentrations of progesterone in milk averaged 1.5 +/- 0.3, 11.1 +/- 0.5, 12.0 +/- 0.4 12.5 +/- 0.5 ng/ml for pregnant cows. Corresponding samples from nonpregnant cows averaged 1.2 +/- 0.2, 10.3 +/- 0.4, 3.0 +/- 0.4, 6.8 +/- 0.6 ng/ml, respectively. Ninety-six and 104 cows were classified as pregnant and nonpregnant on days 21 or 22 as compared to 78 and 118 cows diagnosed as pregnant and nonpregnant on days 21 or 22 and 27 or 28 combined. Pregnancy detection by progesterone in milk on days 21 or 22 with pregnancy determined via rectal palpation 35 to 50 days postbreeding was 77 and 100% accurate for positive and negative diagnosis, respectively. The percent agreement using progesterone in milk on days 21 or 22 and 27 or 28 combined was 95 and 100%, respectively, for positive and negative diagnosis. Diagnosis based on rectal palpation 21 or 22 days postbreeding was 63 92 (69%) and 76 88 (87%) for pregnant and nonpregnant cows, respectively. Ten of the 200 cows had progesterone concentratins in milk of > 4 ng/ml at the time of breeding. Six of these cows were pregnant from a previous insemination. The other four cows were nonpregnant and were inseminated during the luteal phase of the cycle. In conclusion, measurement of progesterone in milk is a useful tool in early detection of pregnant and nonpregnant cows and may be useful in detecting reproductive problems in a dairy herd. It will probably be most useful when used in combination with later pregnancy diagnosis per rectum .     

Serum progesterone concentration in pyometritic and normal postpartum dairy cows

Two studies were conducted to evaluate the concentration of serum progesterone in pyometritic cows and relate it to palpation of ovarian structures per rectum . In Trial 1, serum samples from 34 pyometritic cows were assayed for progesterone. Mean serum progesterone concentrations were 6.8 +/- 0.7 ng/ml. In Trial 2, each of 54 pyometritic cows was paired with a control cow on the basis of days post partum (18-50 days). Mean concentration of progesterone was 9.7 +/- 1.0 ng/ml for the pyometritic cows and 5.7 +/- 0.8 ng/ml in control cows (P<0.005). Progesterone concentration was greater (P<0.005) in both groups of cows with palpable corpora lutea (CLs). Ninety-six percent of the pyometritic cows had palpable CLs compared to 57% of the control group. Comparing serum progesterone only in cows with a palpable CL, the mean concentration was still greater (P<0.005) in the pyometritic group (10.6 +/- 1.0 ng/ml) than the control group (6.6 +/- 1.0 ng/ml). Compatability of rectal palpation findings and concentrations of serum progesterone were 92.6% for the pyometritic group and 72.2% for the control group. Progesterone concentration increased (P<0.05) by increased days post partum in Trial 2 (n=54) but not in Trial 1 (n=23). In both Trials 1 and 2, uterine size due to pyometra increased (P<0.05) with increased days post partum. No other associations were found.     

Progesterone concentrations in milk fat at first insemination--effects on non-return and repeat-breeding

The relationship between milk fat progesterone concentration at first artificial insemination (AI) and reproductive performance of Norwegian Red Cattle dairy cows was investigated in a field study. Fifteen AI technicians collected milk samples from 2250 cows from 458 herds and progesterone was analysed in the milk fat portion of the samples. Logistic regression revealed decreased probability of non-return, and increased likelihood of repeat-breeding, with increasing progesterone concentrations at insemination. The odds ratio for non-return and for repeat-breeding between the minimum and maximum value for milk fat concentrations between 4 and 32.2ng/ml was 4.5 (P < 0.01) and 3.2 (P = 0.01), respectively. The variable 'Technician' did not significantly influence non-return rate or repeat-breeding. Progesterone concentration at AI was positively related to calving to last insemination interval, and to number of inseminations per cow (P < 0.05). The association between the progesterone concentration at insemination and calving interval was only marginally significant. Technician was significantly (P < 0.01) associated with interval from calving to first AI, interval from calving to last AI (P = 0.05), and number of AI per cow (P = 0.01). Technician was not significantly related to the calving interval.We conclude that increased suprabasal progesterone concentrations at the time of first insemination, and higher return rate at AI may, at least partly, be due to endocrinological asynchrony at AI, a condition which may lead to decreased fertility.     

Effects of sample handling temperatures on bovine skim milk progesterone concentrations

The effects of incubation of whole milk at various temperatures and times on the concentration of progesterone in the skim milk fraction was determined. For the study, milk samples were collected from 10 pregnant Holstein cows. The milk from each cow was transferred to culture tubes to provide 32 replicates of 3 ml volume. To begin the incubation study, all samples were placed in a 37 degrees C water bath for 4 h. The end of this incubation was designated as time 0 and a sample from each cow was centrifuged to harvest skim milk. At time 0, samples from each cow were divided among incubation temperatures of 0 degrees, 4 degrees, 20 degrees and 37 degrees C. Samples were removed from each incubation group at 30, 60, 90 and 120 min. After 120 min, all remaining samples were returned to the 37 degrees C incubation and skim milk was collected at 30, 60 and 90 min. Progesterone was measured in skim milk by radioimmunoassay. The mean +/- SE concentration of progesterone in skim milk at time 0 was 10.9 +/- 1.1 nmol/L. The mean concentration of progesterone in skim milk was higher (P < 0.05) in all samples incubated at 0 degrees and 4 degrees C, with incremental increases ranging from 34% to 67% above time 0. Progesterone in skim milk returned to time 0 concentrations in milk samples transferred from 0 degrees or 4 degrees C to 37 degrees C. There was no change in skim milk progesterone in whole milk samples incubated at 20 degrees or 37 degrees C. From this study, it can be concluded that the concentration of progesterone in skim milk is temperature dependent. Inconsistency in handling whole milk samples can have a profound effect in the concentration of progesterone on skim milk. The temperature-dependent effect was reversible and may be related to solubility of progesterone in milk fat.     

Milk progesterone profiles in various reproductive states in dairy buffaloes under field conditions

Fifty-one dairy buffaloes in the last two months of gestation were selected at seven private peri-urban farms in the Peshawar district. Observations were recorded in buffaloes during normal (NBS, August to January) and low breeding seasons (LBS, February to July). After parturition, rectal examination of reproductive organs was carried out. Estrus detection was made through visual observation and the use of intact bull. Postpartum ovulation was confirmed by ovarian palpation per rectum and milk progesterone levels (MPL), determined through radio-immunoassay. MPL was higher (p < 0.01) at various intervals in NBS calves (1.97 +/- 0.30 ng/ml) as compared to LBS calves (0.68 +/- 0.08 ng/ml). During LBS, MPL remained < 0.30 ng/ml up to the third fortnight and started rising later, reaching a peak of 1.27 ng/ml during the sixth fortnight. During NBS, there was a sharp rise in MPL during the second fortnight, reaching 3.64 ng/ml during the sixth fortnight. MPL was significantly different on different experimental farms (p < 0.01). MPL reached the lowest levels on the day of estrus (0.10 ng/ml), reached it's peak on day 7 and started declining on day 17 of estrus. MPL showed two postpartum elevations. In true anestrus buffaloes, MPL remained consistently low. However, in the anestrus period, silent ovulations were also noted, as reflected by increasing MPL without estrus signs. In pregnant buffaloes, MPL remained > 1 ng/ml. Results of the study showed that the low postpartum reproductive performance in dairy buffaloes during LBS was primarily due to inadequate functioning of the corpus luteum in secreting optimum concentrations of progesterone. The higher incidence of silent estrus during LBS indicated improved management for the detection of estrus.     

Studies on serum progesterone levels in relation to occurrence of uterine torsion in buffaloes (Bubalus bubalis )

Serum samples from 32 buffaloes suffering from uterine torsion at approximately the completion of the gestation period were analyzed for progesterone concentrations by radioimmunoassay. Fifteen buffaloes had progesterone concentrations of more than 1.0 ng/ml (1.65 +/- 0.13 ng/ml; 1.1 to 2.8 ng/ml), while the serum progesterone concentrations of the remaining 17 buffaloes were below 1.0 ng/ml (599 +/- 59 pg/ml; 200 to 900 pg/ml). The occurrence of uterine torsion was associated with labour and/or abdominal pain around the expected time of parturition at the completion of the gestation period. High progesterone concentrations at labour in cases of torsion in almost half of the buffaloes may suggest that there were instances of premature labour resulting from an impaired hormonal milieu. Disturbances in the onset of labour owing to hormonal imbalance as evidenced by high progesterone levels may also contribute to the causation of uterine torsion. Cases of uterine torsion having low progesterone values are also discussed in this study.     

Effects of bull exposure on the cyclic activity of beef cows

In Experiment I, 38 crossbred suckled beef cows grazing fescue pastures and 34 crossbred beef cows grazing bluestem pastures were randomly allocated at the time of calving into a group with 4 teaser bulls or no bulls. Two blood samples were collected 7 d apart from the cows to determine cyclic activity 67 and 76 d after calving in the fescue and bluestem pastures, respectively. Progesterone greater than 1.0 ng/ml in one or both samples indicated cyclic activity. There was no difference in the percentage of cows cyclic among the different groups. The number of cyclic cows in the fescue pasture with bulls was 16/19 (84%); in the fescue pasture with no bulls, 14/19 (74%); in the bluestem pasture with bulls, 17/17 (100%); and in the bluestem pasture with no bulls, 16/17 (94%). Overall cyclic activity among all cows for teaser bull-exposed and no bull was similar, 33/36 (91%) and 30/36 (83%). Overall cyclic activity was greater (P < 0.05) in cows grazing bluestem (33/34), 97% than fescue pastures (30/38), 80%. Measurements of cyclic activity were initiated too late in the postcalving period to quantify differences in estrous activity between the bull and no bull treatment groups. Another trial was planned for the following year with a modified protocol. In Experiment II, blood samples were collected for progesterone concentrations soon after calving and were repeated at intervals to characterize both the occurrence and duration of estrous cycles. In this experiment, 29 crossbred suckled beef cows grazing fescue pastures were randomly allocated 12 d after calving (Day 0) into 1 of 2 groups with teaser bulls or without bulls. Nineteen crossbred beef cows grazing bluestem pastures were allocated similarly 10 d after calving (Day 0). Bulls were added to the groups with bulls in fescue and bluestem pastures on day 6 after the initial allocations. Blood samples were collected from all cows on Day 0 and every 3 d until Day 46. Means (+/- SEM) of the cumulative progesterone concentrations (ng/ml) per cow for the 16 samples from cows grazing fescue were 12.5 +/- 3.5 for cows exposed to bulls, 2.5 +/- 0.16 for cows not exposed to bulls, 27.6 +/- 4.42 for cows grazing bluestem pastures and exposed to bulls, and 16.0 +/- 2.75 for cows without exposure to bulls. Progesterone concentrations were higher in cows exposed to bulls (P < 0.01). The percentages of both short and normal cycles increased (P < 0.01) in groups exposed to bulls (88%, 21/24 and 63%, 15/24) when compared with the no bull groups (29%, 7/24 and 21%, 5/24), respectively. Cows exposed to bulls also showed increased cyclic activity.     

Monitoring ovarian cyclicity in postpartum Murrah buffalo through milk progesterone enzyme immunoassay

Milk samples were collected from Murrah buffalo between Day 30 and Day 120 post partum and analysed for progesterone concentration to monitor ovarian cyclicity. Progesterone levels were low (1 to 5 ng/ml) during the anestrous period. Levels were also low around estrus, but they began to increase at Day 6 postestrus; high levels (15 to 32 ng/ml) were maintained for different periods. There was a marked drop in progesterone level after Day 16 to 18 of the estrous cycle in those animals which returned to estrus. Progesterone levels remained high in buffalo which did not return to estrus, indicating that these animals were pregnant. Some of the progesterone cycles were not associated with the expression of estrus. This study indicated that a milk progesterone enzymoimmunoassay can be used to detect early pregnancy as well as conditions such as silent estrus and anovulatory estrus; it can thus help reduce the long intercalving period in buffalo.     

Mathematical approaches to detect low concentrations in progesterone profiles

There is a general need for higher objectivity and accuracy in describing the physiological fertility performance of dairy cows. To develop the alternative meaningful starting points for the selection of genetically superior dairy cows, this study focused on the detection of low progesterone concentrations, which are indicative of estrus events. Three mathematical approaches were used: one based on the exponentially weighted moving average control chart, and two threshold methods, which were developed in-house. Data were collected from one data set that included 97 insemination data of first-lactating Holstein dairy cows, and a second set that included 160 inseminations of primiparous and multiparous Holstein dairy cows. On the basis of these 2 data sets, and using a threshold of 1.2 ng progesterone/ml skimmed milk, the sensitivity of the 3 models was high and ranged between 100% and 93.13%, with an error rate between 4% and 22.17%. The specificity varied between 97.92% and 99.93%. The average concentration levels of true-positive–detected progesterone measures were low and ranged between 0.18 and 0.28 ng progesterone/ml skimmed milk (first data set) and 0.21 to 0.26 ng progesterone/ml skimmed milk (second data set). False-positive–detected low progesterone concentrations during estrus events were closely related to progesterone values around the 1.2 ng progesterone/ml skimmed milk threshold and the detecting rules of the control chart. Thus, we suggest that a threshold of 0.8 ng progesterone/ml skimmed milk is indicative for luteal activity in defatted foremilk. By means of the three methods used, the detection of low progesterone concentrations was possible and it can be assumed that this is a good starting point for further studies (such as interval calculation) in this area.     

Use of cow-side progesterone tests to improve reproductive performance of high-producing dairy cows

This study evaluated the effectiveness of the cow-side ELISA milk progesterone test in improving postpartum reproductive performance in the Dordt College dairy herd. Cows that produced more than 18,500 lb of milk per lactation were assigned to the high production group (40 cows), while cows that produced less than 18,500 lb of milk (42 cows) were assigned to the low production group. Twenty-one cows in the high production group and 19 cows in the low production group received no ELISA testing (untreated controls), while the remaining cows in each group were evaluated by ELISA test every 7 d beginning on Day 27 post partum (treated cows). A sequence of 2 high progesterone tests and 1 low test indicated the cows were cycling normally. Cows that had low milk progesterone levels (<5 ng/ml) for 3 consecutive tests were assumed to have follicular cysts and were treated with 2 ml GnRH (Cystorelin, 50 mug/ml). Cows that had 3 consecutive high tests (>5 ng/ml) were assumed to have persistent corpora lutea (CL) and were treated with 5 ml PGF(2)alpha (Lutalyse, 5 mg/ml). In both the high and low production groups, treated cows had higher (P < 0.08) pregnancy rates by Day 210 than the untreated controls (63.2 vs 38.1% and 56.5 vs 42.1%, respectively). The days open were reduced (P < 0.05) for the treated animals by 41.6 d compared with the controls. The treated cows produced a net savings of $70.42 (US) per cow assuming a $3.00 savings/day open.     

Comparisons of eight commercial on-farm milk progesterone tests

To evaluate eight commercial on-farm milk progesterone kits, milk samples (50 ml each of foremilk and postmilk strippings) were collected during the estrous cycle from 10 cycling Holstein cows for 24 consecutive days. Relative concentrations of progesterone were classified as low or high by comparison with standard progesterone samples supplied with each kit. The concentration of progesterone in each milk sample was determined by radioimmunoassay (RIA). Accuracy of classification into low or high levels by commercial tests was determined by the percentage of similarity with RIA values using discriminant analysis. Accuracy of the eight tests ranged from 89.0 to 98.9% for low progesterone, 74.8 to 85.6% for high progesterone, and 80.3 to 87.3% for all samples (n = 238). The percentage of fat in milk or an interaction of the percentage of milkfat by day of estrous cycle influenced commercial test results for all tests except Accufirm and Calfcheck. Progesterone levels, estimated by the test-kits, were low from 1.5 +/- 0.5 to 2.8 +/- 0.9 days before estrus (X +/- SEM) and until 4.0 +/- 0.6 to 5.9 +/- 1.3 days after estrus. These data support the principle that a single low progesterone sample cannot be used to determine proper timing of insemination. All eight commercial kits can be used to determine accurately the relative concentrations of progesterone in milk samples.