Mammary extraction of plasma triglycerides in the cow during lactogenesis

• 1.1. In control cows, extraction of triglycerides from the circulation by the mammary gland increased abruptly and markedly, and the concentration of triglycerides in arterial plasma fell, on the day of parturition.
• 2.2. In cows that had fluid regularly removed from the mammary glands before parturition, these changes occurred at varying times from more than 4 days before parturition in an animal that secreted triglyceride copiously to 24 hr before parturition in an animal that secreted little triglyceride pre-partum
• 3.3. In all animals, the time when triglyceride extraction increased was close to the time when K⁺ concentration in the mammary secretion became maximal.

     

Progesterone and the initiation of parturition in the goat

The corpora lutea were surgically removed from 6 goats between 134 and 136 days of pregnancy and progesterone was administered daily. Pregnancy was prolonged past normal term in 4 goats receiving 25 mgs. of progesterone daily as a split dose. However, eventual delivery following progesterone withdrawal was abnormal and foetal mortality high.The progesterone therapy regime maintained maternal jugular plasma concentrations of progesterone in excess of 3 ng/ml. In normal untreated goats, maternal plasma concentrations of progesterone declined over the last 6 days of gestation. In treated goats, plasma concentrations of progesterone fell only after the cessation of therapy. Maternal plasma concentrations of estrogen rose within 24 hours of parturition in normal untreated goats. In the 4 goats in which pregnancy was prolonged, by progesterone administration, maternal plasma concentrations of estrogen were elevated for several days in the period before eventual foetal delivery.     

The effect of pre-partum milking on the transfer of immunoglobulin into mammary secretion of cows.

The significance of local effects associated with mammary involution on transfer of immunoglobulin and especially on the selective transfer of IgG1 into mammary secretion of cows approaching parturition has been determined. This was carried out by measuring the changes in the concentration of IgG1, IgG2, IgM and IgA in serum and mammary secretion of 5 cows in which two mammary glands were milked continuously (twice daily) during the period preceding parturition, while the other two glands were allowed to undergo normal involution. In the secretion of unmilked glands of all cows there was a substantial increase in the concentration of IgG1 as cows approached parturition. In contrast, the increases in the concentration of IgG1 and in the selective index for IgG1 of milked glands were either virtually non-existent (1 cow) or generally reduced in magnitude and delayed in time of onset (4 cows). It is clear from the results that continued milking of a mammary gland throughout pregnancy tends to maintain milk production in the milked gland and at the same time reduces the massive selective transfer of IgG1 into secretion of that gland.     

Peripartal changes in plasma progesterone and 15-keto-13,14-dihydro-prostaglandin F2α concentrations in Holstein cows with or without retained foetal membranes

Peripheral blood plasma concentrations of progesterone and the main metabolite of prostaglandin F_2α, (15-keto-13,14-dihydro-PGF_2α) PGFM, were determined in 10 Holstein cows with retained foetal membranes (RFM) and 12 Holstein cows without RFM (NRFM) during the peripartal period. The rate of uterine involution in the postpartum cows was monitored.There was no difference in the rate of uterine involution between cows with or without RFM. Cyclical ovarian activity was resumed within a month after parturition in both group. Increases in the mean peripheral plasma PGFM concentrations were evident in the RFM cows 6 days before parturition, compared to 48 h before parturition in the NRFM cows. A gradual decline in PGFM to prepartum concentrations occurred in both groups by Day 12 after parturition, although in the RFM cows, PGFM concentrations remained high until the placenta was shed.In both groups, the mean peripheral plasma concentrations of progesterone showed a marked decline beginning 48 h before partusition. The mean plasma progesterone concentrations were less than 1 ng/ml during the immediate postpartum period.     

Peripheral plasma progesterone and utero-ovarian prostaglandin F concentrations in the cow around parturition

The concentration of prostaglandin F in utero-ovarian venous plasma and progesterone in jugular venous plasma were determined by radioimmunoassay in 3 cows over the last 2–3 weeks of gestation. Utero-ovarian prostaglandin F concentrations did not show any consistent pattern in two of three cows until 48–72 h before term when the levels rose sharply from 1 ng/ml to a maximum 4–9 ng/ml during labour. The concentration of progesterone in jugular venous plasma tended to fall gradually over the last 20 days of gestation with a further fall occurring 48-36 h before delivery.In two other cows at around 240 days of gestation the concentration of plasma progesterone in ovarian venous plasma was 50 to 150 times the concentration of progesterone in uterine or jugular venous plasma. It is concluded from these results that the ovaries are the major source of progesterone in cows during late pregnancy. The findings also suggest that prostaglandin F may be the luteolytic factor responsible for the sharp decline in plasma progesterone concentrations over the last 48-36 h preceding parturition.     

Relationship between LH and cortisol in acutely stressed beef cows

The influence of handling stress on tonic LH secretion was evaluated in eight ovariectomized Hereford cows. Four cows (acclimated group) were previously acclimated to stanchions and procedures for blood collection, whereas the other four cows (unacclimated group) were stanchioned and handled for the first time 2 hr before the evaluation period. Blood samples (10 ml) for cortisol, luteinizing hormone (LH) and progesterone quantitation were collected at 10-min intervals for 4 hr via an indwelling cannula inserted into the jugular vein 1 hr before the evaluation period. Mean plasma concentration of cortisol was lower (5.7 vs 66.1 ng/ml; P<0.01) but LH was higher (8.1 vs 4.1 ng/ml; P<0.05) in acclimated cows than in unacclimated cows. Plasma cortisol and LH concentrations were correlated negatively among cows (r = -0.83; P<0.01). Two- to four-fold increases (10 to 20 ng/ml) in systemic cortisol concentrations did not appear to affect LH secretion, whereas 10-to 20-fold increases associated with intensive stress suppressed tonic LH secretion, especially pulsatile LH releases. Plasma progesterone concentrations did not differ between the two treatment groups. Results suggest that the influence of stress on gonadotropin secretion, and subsequent reproductive responses, is dependent on the magnitude of the adrenal steroidogenic response and the animal's adaptation to stress. These results indicate the necessity to minimize and monitor animal stress when studying LH secretion.     

Evaluation of an on-farm blood progesterone test for predicting the day of parturition in cattle

An on-farm blood progesterone enzymeimmunoassay (EIA) was evaluated as a diagnostic test to predict the time of calving within a 24-hour period in near-term dairy cows. Blood samples were taken daily from 45 cows beginning 5 days prior to their expected due dates until calving, and plasma was stored at -20 degrees C until all cows had calved. The EIA test was performed on frozen-thawed plasma samples, and progesterone concentrations were determined to be low (positive test for calving within 24 hours) or high (negative test for calving within 24 hours). Sensitivity, specificity and predictive value of the EIA to accurately determine parturition within 24 hours were 86.7, 90.8 and 75.0%, respectively. The EIA correctly predicted the day of parturition in 168 of 187 (89.8%) plasma samples. Ten additional cows were similarly monitored except the EIA was performed on whole blood immediately after collection, and the sensitivity, specificity and predictive value of the test were 80.0, 97.6 and 88.9%, respectively. The day of parturition was correctly predicted in 49 of 52 (94.2%) whole blood samples. More than 95% of the cows calved within 24 hours when their plasma progesterone reached < 1.3 ng/ml. When results of the EIA were compared with those of a radioimmunoassay (RIA), the EIA findings were used to correctly classify 190 of 232 (81.9%) plasma samples as having low (< 2.0 ng/ml) or high (>/= 2.0 ng/ml) concentrations of progesterone. The EIA test was found to be a quick, practical means of estimating progesterone concentrations in bovine plasma or whole blood and was a useful test for predicting the day of parturition in cows.     

Ovarian activity and peripheral plasma levels of oestrogens and progesterone in the lactating sow

Ten gilts were examined for peripheral plasma levels of progesterone and oestrogens 3 weeks before and up to 8 weeks after parturition. The sows were slaughtered at different intervals after parturition and the ovaries were examined. Peripheral plasma levels of progesterone decreased dramatically from about 8ng/ml two days before parturition to about 2 ng/ml on the day before parturition. After parturition the mean progesterone level was about 1.5 ng/ml. Maximum oestrone levels of about 7 ng/ml were obtained two days before parturition. After parturition the level dropped to below 0.1 ng/ml. Three sows showed high levels of oestradiol (75–440 pg/ml) without signs of heat during the lactation. In no case were ovulated follicles or periodic corpora lutea registered.     

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.     

Plasma prolactin,progesterone and oestradiol-17β concentrations around parturition in the pig

Plasma concentrations of prolactin, progesterone and oestradiol-17β were measured by radioimmunoassay in samples taken from 2–15 days before until 1–4 days after spontaneous parturition in four sows and in one sow around prostaglandin F2α-induced parturition.Between Days ?15 and ?2 (Day 0 = parturition), prolactin concentrations in daily samples fluctuated somewhat, but exceeded 10 ng/ml only exceptionally. Plasma progesterone levels gradually declined or remained high until about 2 days before parturition. A final decrease of the progesterone concentrations coincided with distinct increases of the prolactin levels during the last 40 h of pregnancy.Maximal prolactin concentrations were measured before the onset of delivery of the piglets. Oestradiol-17β reached peak values around delivery. Prostaglandin F2α injection caused an immediate sharp increase of the prolactin concentration which lasted for about 6 h. During this period progesterone and oestradiol-17β concentrations did not change. A second elevation of prolactin levels was measured when progesterone finally decreased.Changes of prolactin concentrations found in this study were compared with those found in other domestic animals at the same reproductive stage.     

Mammary secretion of triglycerides in the cow pre-partum

1. Regular removal of fluid from the mammary gland, before parturition, stimulated its secretion of triglycerides, and particularly C18 fatty acids in the triglycerides, in some individual cows. 2. Cows that did not respond to pre-partum emptying were stimulated to secrete triglycerides by parturition. 3. The onset of secretion of milk triglycerides correlated with the onset of secretion of mammary fluid. 4. No increase in the ratio of C18:1 to C18:0 in the triglycerides, reflecting an onset of mammary desaturase activity, was observed.     

Manipulation of estrous cycle in dwarf goat (Capra hircus) using estrumate under different management conditions

A study was conducted to elucidate the effectiveness of exogenous estrumate (prostaglandin F(2alpha)) treatment as a synchronizing agent for Dwarf goats and to establish the progesterone levels at different reproductive stages under two different environmental and nutritional conditions. Female Dwarf goats of various ages were raised, 10 each at two sites, viz. the Bio-Saline Research Substation (BSRS), Lahore and at the Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad. The animals at the NIAB farm were reared on non-saline soil under normal grazing conditions, while the other animal lot was raised on salt-affected lands at the BSRS, Lahore and was fed on non-conventional fodders produced by salt-affected lands. The animals received two intramuscular doses (0.5 ml each) of estrumate (125 microg/ml) at 10 days interval. Nineteen of the 20 animals exhibited estrus after 56-72 h of the second injection of estrumate. The mean progesterone concentration in the NIAB and BSRS lots was 2.8 and 2.4 ng/ml, respectively, at the time of second injection and declined to the basal level (estrus) within 48 h. A gradual increase in the progesterone level occurred during the metestrus, reaching maximum during the luteal phase when it was 6.3 and 6.7 ng/ml in NIAB-lot and BSRS-lot, respectively. During the proestrous phase, the progesterone level decreased to the basal level (0.1 ng/ml) at the onset of the next estrus after 22 days. The length of the induced or natural estrous cycle (20+/-1 days) was not affected by the estrumate treatment, nor by the environmental and nutritional conditions. Breeding was allowed after the natural estrous cycle at the onset of third estrus and a high fertility rate (95%) was achieved. The progesterone concentrations remained at higher level (4.5-9.4 ng/ml) throughout the gestation period, declined gradually in the prepartum period, and dropped to the basal level at the completion of parturition. The results suggested that estrumate is an efficient synchronizing agent for the Dwarf goats kept under different environmental-nutritive conditions and that the progesterone profile is a useful indicator to assess the reproductive status of the goats.     

Seasonal variations in post-partum plasma progesterone levels and conception in primiparous and multiparous dairy cows

Progesterone concentrations in peripheral plasma of 18 primiparous and 34 multiparous dairy cows were determined by radioimmunoassay every 4 days, from 10 days post partum until the next conception. The interval from parturition to the first progesterone peak (greater than 4 ng/ml plasma) was significantly longer (P less than 4 ng/ml plasma) was significantly longer (P less than 0.01) in primiparous than in multiparous cows. The progesterone concentrations on Days 4-15 of the oestrous cycle were significantly lower (P less than 0.025) during the summer than in cycles occurring in winter. The conception rate during the summer was lower than in winter. In cows inseminated in summer, conception was related to the shape of the progesterone curve in the cycle preceding insemination.     

Endocrine changes during pregnancy, parturition and the early post-partum period in the llama (Lama glama)

Mean (+/- s.d.) pregnancy length for the 14 llamas in this study was 350 +/- 4.5 days. Plasma progesterone concentrations increased by 5 days after mating and remained elevated (greater than 2.0 ng/ml) throughout most of pregnancy. At about 2 weeks before parturition, plasma progesterone concentrations began to decline, dropped markedly during the final 24 h before parturition, and returned to basal concentrations (less than 0.5 ng/ml) by the day of parturition. The combined oestrone + oestradiol-17 beta and oestradiol-17 beta concentrations varied between 6 and 274 pg/ml and 4 and 114 pg/ml, respectively, during the first 9 months of pregnancy. Concentrations increased between 9 months after mating and the end of pregnancy with peak mean concentrations of 827 +/- 58 (s.e.m.) pg oestrone + oestradiol-17 beta/ml (range: 64-1658) and 196 +/- 10 pg oestradiol-17 beta/ml (31-294) during the last week of pregnancy. Concentrations then declined to 87 +/- 14 pg oestrone + oestradiol-17 beta/ml (7-488) and 25 +/- 5 pg oestradiol-17 beta/ml (2.5-142) during the first week post partum. Plasma cortisol concentrations varied between 2.6 and 51.9 ng/ml (14.0 +/- 0.5) from mating until 2 weeks before parturition when the concentrations began to decline. Only a slight increase in plasma cortisol concentrations was observed in association with parturition. Plasma triiodothyronine concentrations varied between 0.5 and 4.5 ng/ml (1.9 +/- 0.1) throughout pregnancy and the periparturient period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endocrine changes, with special emphasis on oestradiol-17 beta, prolactin and oxytocin, before and during labour and delivery in goats

Jugular plasma concentrations of oestradiol-17 beta, prolactin, progesterone and 13,14-dihydro-15-keto-prostaglandin F-2 alpha (PGFM) were measured at 2-h intervals during the last 4 days of pregnancy in 6 goats. During advanced labour and delivery, samples were obtained more frequently and assayed for oxytocin. The animals were housed in a barn with continuous dim lighting. A distinct pattern of oscillation in prolactin concentrations, with peaks during the late afternoon, was apparent during the last 3 days. Geometric means of peak concentrations doubled each day and became of longer duration; night-time nadir values remained low except during the last night before parturition. A progressive increase in oestradiol-17 beta, with mean levels doubling every 36 h, was apparent during the last 3 days. There was no sharp pre-partum increase in oestradiol-17 beta. Correlated (r = 0.83) with the increase in oestradiol-17 beta was a gradual increase in PGFM and when the latter reached approximately 1000 pg/ml, the non-reversible decline in progesterone reflecting pre-partum luteolysis occurred. Subsequent changes in PGFM related closely to an approximately 20-fold increase in the ratio of oestradiol-17 beta to progesterone until maximal PGFM levels of 26.5 +/- 4.2 ng/ml were reached at delivery. Basal concentrations of oxytocin (8-15 microU/ml) were measured before the last 60 min and markedly higher, though erratic, concentrations were detected at various times before appearance of the allantochorion. Maximal oxytocin values (range 180-1570 microU/ml) occurred within minutes before or after delivery of the first fetus. The results suggest that increased pre-partum production of oestradiol-17 beta, in addition to provoking sufficient release of prostaglandins to cause luteolysis, may modulate either the sensitivity or set-points for an endogenous rhythm in prolactin secretion at the end of pregnancy. The nature of the oxytocin changes suggest that, after labour has evolved sufficiently, delivery is precipitated by an abrupt increase in oxytocin secretion.     

Correlation between serum and fecal concentrations of reproductive steroids throughout gestation in goats

Non-invasive techniques such as the measurement of fecal steroids are now widely used to monitor reproductive hormones in captive and free-ranging wild-life. These methods offer great advantages and deserve to be used in domestic animals. The aim of the present study was to determine the endocrine profile of dairy goats throughout pregnancy by the quantification of fecal progestins and estrogens and assess its correlation with serum concentrations. Blood and fecal samples were collected weekly from 11 adult, multiparous goats, from mating through pregnancy and 2 weeks post-partum. The extraction of estradiol and progesterone fecal metabolites was performed by dilution in ethanol. The radioimmunoassay (RIA) in solid phase was used to quantify serum 17beta-estradiol (estradiol) and progesterone, as well as their fecal metabolites. The mean concentrations of both fecal and serum estradiol started to increase between weeks 7 and 11, reached peak values near parturition and then decreased sharply (range: 19.8+/-5.8 ng/g of feces to 608.6+/-472.4 ng/g of feces and 0.007+/-0.005 ng/ml to 0.066+/-0.024 ng/ml). An increase in both fecal and blood progestagens occurred in the second week, mean concentrations remained greater until week 20, and then decreased in the last week of gestation and 2 weeks post-partum (range: 108.8+/-43.6 ng/g of feces to 3119.5+/-2076.9 ng/g of feces and 0.12+/-0.04 ng/ml to 13.10+/-4.29 ng/ml). The changes in blood and fecal hormone concentrations were analyzed and compared throughout gestation for each single goat, for each breed and for the whole group. Results indicated that matched values of serum and fecal hormone concentrations were correlated (r=0.79; p<0.001 for progesterone and r=0.84; p<0.001 for estradiol mean concentrations in the whole group). Regression analysis showed that logarithmic model allows significant prediction of serum from fecal concentrations with an R(2)=0.729 (y=0.013ln x-0.021) for estradiol and R(2)=0.788 (y=3.835ln x-18.543) for progesterone. Neither fecal nor serum concentrations were affected by the breed but a significant effect of the number of fetuses on progestin concentrations was found. Therefore, the profiles of progesterone and estradiol fecal metabolites reflect the serum concentrations of the same hormones in pregnant goats.     

Peripartal changes of estrone, progesterone and prostaglandin in the water buffalo

The peripheral blood plasma concentration of estrone, progesterone and 15-keto-13, 14-dihydroprostaglandin F2alpha (PGF2alpha metabolite) were determined by radioimmunoassay techniques during the peripartal period in 5 buffalo cows belonging to a river type breed. Estrone levels started to increase from below 200 pg/ml about 15 days prior to parturition, and reached high concentrations (400-750 pg/ml) during the last 5 days of pregnancy. The estrone concentration decreased to baseline levels after delivery. The concentration of progesterone fluctuated between 800 and 2000 pg/ml until 15 days before calving and showed a gradual increase during the last 15 days of pregnancy. The progesterone levels declined abruptly on the day of calving and remained below 100 pg/ml for up to 60 days post-partum. Increased levels of the prostaglandin metabolite were recorded from 15 days prior to parturition with further increases occurring during the last 3 days of pregnancy. PGF2alpha metabolite levels declined gradually after parturition, reaching base line levels 15-20 days after calving.     

Changes in mammary development and composition of secretion during late pregnancy in the mare.

Small samples of mammary secretion were taken for analysis from Thoroughbred mares during the last 3 weeks of pregnancy up to the time of foaling. The concentrations of sodium and chloride decreased while those of lactose, potassium, citrate, phosphate, calcium, magnesium and protein increased. The time-course of these changes showed marked variation between animals. The concentration of whey proteins began to increase about 10 days before parturition. The appearance of the secretion and the size of the mammary glands increased in the last few days of pregnancy. It is suggested that the concentration of calcium in mammary secretion could provide the basis of a test for impending parturition in this species.     

Comparison of ovarian palpation, milk progesterone and plasma progesterone in the cow

Holstein cows were examined twice weekly, beginning at 13 to 18 days after parturition, using palpation per rectum and milk progesterone (P4) assay to determine the functional status of the corpus luteum (CL). These results were then compared with P4 concentrations in the plasma to determine which test was the more accurate in detecting functional luteal tissue, or if both tests were needed for optimal accuracy. The tests were found to be comparable except when the plasma P4 concentration was <1. 0 ng/ml. At this level, errors due to palpation occurred more frequently than those due to milk P4 concentrations since the still palpable CL of pregnancy could be mistaken for a functional CL at 14 to 21 days after parturition. However, at all the other concentrations including when plasma P4 was <1.0 ng/ml and the cows were more than 21 days post partum, neither the milk P4 assay nor palpation per rectum could be considered the better indicator of luteal status. Therefore, we conclude that the combined use of both tests does not afford better assessment of luteal function than either test alone.     

Progesterone and testosterone concentrations during oestrous cycle and pregnancy in the common vole (Microtus arvalis Pallas)

Serum progesterone and testosterone concentrations were measured during different stages of oestrous and pregnancy in paired and unpaired female common voles (Microtus arvalis). Hormone concentrations were measured by ELISA, and cycle stages were determined by vaginal smears. Paired females usually had serum progesterone concentrations of more than 10 ng/ml in the oestrous cycle. A significant maximum was detected in prooestrous (51.70 +/- 7.84 ng/ml, mean +/- S.D.). Serum progesterone concentrations increased from about 40 ng/ml at the beginning of pregnancy to about 70 ng/ml on days 15 and 16. The last 2 days before parturition (days 19 and 20) were characterised by a decrease of progesterone concentrations to ca. 30 ng/ml. The maximum concentration of testosterone was found in prooestrous (1.58 +/- 0.31 ng/ml). Concentrations during pregnancy varied between 1.5 and 2.1 ng/ml. In two of three cases unpaired females exhibited progesterone values below 10 ng/ml, but with varying vaginal smear patterns. The combination of progesterone concentrations and vaginal smear patterns was found to be regular in only 23.8% of the cases. The most frequent cycle stage found was the oestrous (44.2%). Mean concentrations of progesterone (10.43 +/- 13.81 ng/ml) and testosterone (0.85 +/- 1.11 ng/ml) in unpaired females were significantly lower than in paired females, thereby denoting reproductive inactivity in the former. The study presents basic data for several parameters of the reproductive biology in the common vole and confirms the importance of combining hormone assays and vaginal smear monitoring in reproductive research.