Fertility in the Afrikaner cow. 2. Ovarian recovery and conception in suckled and non-suckled cows post partum

The post-partum reproductive performance of suckled and non-suckled Afrikaner cows was compared in order to assess the importance of suckling in the resumption of post-partum ovarian function in this breed. Non-suckled cows were weaned at 3 days post partum whilst calves in the control group had continuous access to their dams. Commencement of ovarian activity was significantly (P < 0.01) earlier in non-suckled cows at 18.1 ± 5.2 (mean ± SD) days post partum than in suckled cows 53.2 ± 19.7 days. Conception rates were significantly higher (P = 0.01) in non-suckled cows (80%) than in suckled cows (50%). Mean intervals from parturition to conception were 45.8 ± 15.8 (mean ± SD) days in non-suckled cows as compared with 70.9 ± 17.9 days in suckled cows. The conception rate associated with each ovulation appears to be highest between 50 and 70 days post partum regardless of the degree of suckling stimulus. Four classes of ovarian activity were recorded from the progesterone profiles compiled. The incidence of short cycles was unaffected by the degree of suckling stimulus. Weaning may (P = 0.05) reduce the proportion of cows which exhibit regular cyclic ovarian activity without conceiving. Coitus during oestrus may (0.01 < P > 0.05) be more easily observed in non-suckled cows than in their suckled contemporaries. Suckling altered the diurnal distribution of coitus, with non-suckled cows showing the highest frequency for this component of oestrus before 09.00 h and after 15.00 h, whilst in suckled cows coitus appeared to be more evenly distributed throughout the day.     

Ultrasonic evaluation of uterine involution in Bulgarian Murrah buffalo after administration of oxytocin

The aim of this study was to determine the time taken for complete uterine involution in Bulgarian Murrah buffaloes following normal parturition and oxytocin stimulated milking; and to establish the time course of the change in size of the uterine horns, the cervix and caruncles between parturition and involution by means of ultrasonography. There were 17 animals in the study aged 3-6 years and average parity of 2.17 ± 0.18. They were administered 20 IU oxytocin 15 min before each milking. Rectal palpation and transrectal ultrasonography were performed at 3 d intervals from Days 1 to 34 post partum. The involution of the non-gravid and gravid uterine horns, and the cervix was complete by Days 22 and 25 post partum when their diameters were 2.7 ± 0.4 cm, 2.8 ± 0.3 cm and 3.12 ± 0.4 cm, respectively. Caruncles underwent rapid regression until Day 10 post partum. It was not possible to determine the dimensions of the caruncles after that time. The cumulative percentage of animals whose uterus was located in the pelvic cavity increased from 24% at Day 10 post partum to 100% at Day 34 post partum. The combination of rectal palpation and transrectal ultrasonography provided a reliable method of evaluating changes in the uterus over time and determining the time of uterine involution. The present study showed that complete uterine involution, with the uterus located in the pelvic cavity, was achieved by Day 34 after parturition in all 17 Bulgarian Murrah buffaloes treated with oxytocin before milking.     

Response of cyclic and post-partum suckled cows to injections of synthetic LH-RH.

Doses of 125, 250 or 500 micrograms LH-RH were injected i.m. into suckled beef cows on approximately Day 11 of an oestrous cycle synchronized by prostaglandin treatment. There was a positive linear relationship between dose of LH-RH and the area under the measured LH peak. Administration of 500 micrograms LH-RH as a single injection to suckled cows 13-32 days post partum resulted in LH release but failed to induce normal ovarian activity. A small transient rise in plasma progesterone for 6--9 days occurred at the expected time after injection in 50% of animals. Administration of 500 micrograms LH-RH to suckled beef cows approximately 20--30 days post partum and a second injection approximately 10 days later at the time when the resulting transient rise in plasma progesterone had returned to basal values induced normal cyclic activity (as shown by progesterone concentrations and observed oestrus) at 35 days compared with 70 days for untreated controls. Pituitary responsiveness to LH-RH, as assessed by LH levels, was found to increase up to 20 days post partum.     

Uterine involution and postpartum ovarian activity in Nili-Ravi buffaloes

Uterine involution and postpartum ovarian activity were studied in 53 Nili-Ravi buffaloes. Mean intervals to uterine involution (26 days), regression of the corpus albicans of pregnancy (22 days), resumption of follicular activity (21 days) and first postpartum estrus (56 days) were not affected by the month of calving or age. Mean interval to formation of first corpus luteum (CL) after calving as indicated by progesterone in plasma (>/= 1.5 ng/ml) was 23.8 +/- 1.7 days, but only 52% of these CL were palpable. The number of CL formed before first postpartum estrus ranged from zero to five per buffalo; mean values based upon progesterone and palpation were 1.6 +/- 1.3 and 0.8 +/- 0.2, respectively. Based upon either progesterone or palpation, length of first postpartum luteal phase (7.9 or 6.6 days) was shorter than the luteal phase immediately preceeding the first estrus (12.1 or 8.9 days). Intervals from regular cyclic ovarian activity was not established until first estrus and intervals from the end of one luteal phase to the onset of the next were as long as three weeks. High concentrations of progesterone (>/= 1.5 ng/ml) on the day of behavioral estrus were seen in 23% of the buffaloes studied.     

The accuracy of rectal diagnosis of corpora lutea in water buffalo (Bubalus bubalis)

The accuracy of rectal diagnosis of corpora lutea (CL) was determined by direct inspection of the ovaries by laparoscopy in 68 suckled water buffalo (Bubalus bubalis). Thirty-eight (81%) of the 47 CL diagnosed by rectal palpation were confirmed at laparoscopy. Errors in rectal diagnosis of CL were due to failure to palpate early CL (8.5%) and to follicles (> 10 mm in diameter) raised above the ovarian surface (10.6%) being diagnosed as CL. Twenty-six (89.7%) of the 29 diagnoses of luteal tissue by the progesterone assay were confirmed. Errors were due to the presence of CL with low progesterone (10.3%). The overall accuracy of diagnosing a follicle or a CL by rectal palpation and plasma progesterone assay was 81 and 86% respectively. The study indicated that rectal palpation is as reliable as the progesterone assay for the diagnosis of CL in the buffalo.     

Periparturient events in ovariectomized embryo transfer recipient mares

Ovariectomized mares treated with progesterone have established and maintained pregnancy after embryo transfer. This study evaluated the ability of ovariectomized embryo transfer recipients to successfully undergo parturition, raise a foal, and return to a useful reproductive status. Periparturient events in three ovariectomized embryo transfer recipient mares and three intact mares were compared. All mares foaled normally. Mammary scores were similar for both groups and all mares produced sufficient colostrum and milk to allow normal growth of healthy foals. Plasma progesterone levels decreased to < 5 ng/ml by Day 4 post partum in both groups. Progesterone concentrations continued to decrease and remained at <1 ng/ml in ovariectomized mares, but increased after the first postpartum ovulation (Day 9 to 15) in intact mares. Endometrial involution as determined by histological evaluation was complete in ovariectomized mares by Day 10 post partum and in intact mares by Day 11 post partum. As assessed by palpation per rectum and clearance of bacteria from the uterus, uterine involution was similar in all mares. The three ovariectomized mares subsequently received embryos by transcervical transfer and two of them established pregnancy. These results indicate that normal parturition, lactation, maternal behavior and uterine involution are independent of ovarian function.     

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.     

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.     

Interaction of calf suckling, use of oxytocin and milk yield with reproductive performance of dairy buffaloes

Calf suckling and oxytocin injections are commonly used for pre-milking stimulus in dairy buffaloes under field conditions. A study was conducted to investigate effect of these treatments on reproductive performance. Fifty one Nili-Ravi buffaloes were monitored from parturition up to 150 days postpartum through rectal examination. Data on milk yield, body condition score (BCS) and reproductive parameters were recorded weekly. Postpartum ovulation interval (POI) was determined by presence of an ovulation depression or a very soft corpus luteum haemorrhagicum and was confirmed through milk progesterone levels (MPL). Suckling was used to stimulate milk let down, and where the calf had died, injection of oxytocin was resorted to. Milk samples were analyzed for MPL using radioimmunoassay (RIA) and fat; and milk yield was converted to 4% fat corrected milk (FCM). The mean postpartum uterine involution length (PUI) was 34.30 ± 1.33 days. Mean POI was 59.37 ± 4.76 days and mean postpartum estrus interval (PEI) was 69.03 ± 6.03 days. Suckling period averaged 26.40 ± 5.57 days and correlated with POI (r = 0.19, P < 0.01) and PEI (r = 0.23, P < 0.01). POI was shortest in buffaloes suckled for one month (P < 0.05). Oxytocin was used with a mean dosage of 7.50 IU, delaying placental expulsion time (PET) and POI but shortening PEI. BCS shortened PET, POI and PEI (P < 0.01). Mean FCM was 14.50 ± 0.20, ranging from 2 to 35 kg/d; and was higher in estrus group; correlating positively with POI (r = 0.31, P < 0.01). MPL were 1.37 ± 0.17 ng/ml and increased after ovulation, remaining greater than 1.5 ng/ml from Day 4 to 14 of the estrus cycle, followed by a rapid decline up to next estrus. BCS in buffaloes resuming oestrus was constantly higher than those failing to resume ovarian cyclicity. Live weight, prepartum was 510.0 ± 5.9 kg with a loss of 3.7 ± 2.12 kg, 30 days postpartum. The present study suggests a lower reproductive efficiency of dairy buffaloes under the peri-urban farming system reflected by ovarian cyclicity in 68.63% buffaloes within 150 days postpartum and silent estrus in 51.5% of the cases. Increasing suckling duration and use of oxytocin delayed POI, however, POI was shortest in buffaloes suckled for one month. The high yielding buffaloes also manifested better reproductive cyclicity; while moderate yielder showed shorter ovulation intervals and higher conception rate.     

Plasma progesterone and gonadotrophin concentrations and ovarian activity in post-partum dairy cows

Plasma progesterone concentrations in jugular vein blood samples collected every other day after calving from 13 Friesian dairy cows indicated that ovarian cyclic activity was initiated by 16.6 +/- 1.1 (s.e.m.) days post partum, except for 1 cow which did not resume cyclic activity until Day 98 post partum. Rectal palpation of the ovaries indicated that a developing follicle was recognizable at a mean time of 15.7 +/- 2.0 days after calving. During the first oestrous cycle after parturition there was a significantly shorter period when plasma progesterone levels were elevated than during the next 2 cycles. Concentrations of progesterone, LH, FSH and prolactin were determined for 4 cows, in blood samples taken every 6 h from 2 to 36 days post partum. Tonic LH release was lower during the first 10 days than subsequently, but the lack of change in pattern for FSH suggests dissimilar control mechanisms for these hormones during this time. Three cows showed evidence of a resumption of ovarian cyclicity during the sampling period: in 2 there was an initial LH surge of a magnitude which would normally give rise to ovulation, followed 4 days later by an increase in plasma progesterone lasting only 5 and 9 days. This progesterone was considered to be of follicular origin. A second LH surge was followed by the presence of a corpus luteum.     

Effect of suckling on basal and GnRH-induced LH release in post-partum dairy buffaloes

Suckling, a common practice in smallholder dairy-farming systems in the developing world, delays the onset of post-partum ovarian activity in dairy buffalo. The present study was designed to assess the effect of suckling on pituitary function in lactating buffaloes 25-35 days post-partum. Six suckled and nine non-suckled buffaloes were challenged intravenously with a bolus injection of GnRH (20microg buserelin acetate; Receptal). Heparinized venous blood samples were collected at 15min intervals for 2h before and up to 4h after GnRH for luteinizing hormone (LH) estimation. Pretreatment basal LH concentrations were similar in the suckled (0.6+/-0.2ng/ml) and the non-suckled (0.5+/-0.1ng/ml) buffaloes. All but one suckled buffaloes released a LH surge, starting 15-60min post-GnRH treatment, which lasted for 180-225min. While one suckled buffalo did not respond to GnRH, the LH response in the remaining suckled buffaloes was significantly less than in the non-suckled buffaloes in terms of peak LH concentrations (14.3+/-2.7ng/ml versus 26.2+/-4.3ng/ml) and area under the LH curve (1575.6+/-197.4mm(2) versus 2108.9+/-323.9mm(2)). The LH response was least in suckled buffaloes challenged with GnRH while in the luteal phase of an oestrus cycle and with plasma progesterone concentration >1ng/ml. In conclusion, suckling suppressed pituitary responsiveness to exogenous GnRH challenge in post-partum buffaloes.     

Hormonal Interrelationships in Postpartum Suckled Dairy Cows

Three cross-bred cows calved in March and April and were followed until day 62 after parturition. Each animal was suckled by 2 calves ad libitum. All calves were removed from the cows on day 55 after parturition. Blood was collected 3 times per day from the jugular vein by venipuncture. On 4 occasions after parturition - i.e. days 7–8, 21–22, 35–36 and 49–50, the cows were bled through a jugular venous catheter every 30 min during the 24 h. The plasma samples were analyzed for the content of 15-keto-13,14-dihydro-PGF2α (main PGF2α metabolite), LH, prolactin, Cortisol and progesterone by radioimmunoassay methods. The concentration of PGF2α increased from 280 to 730 pmol/1 within the last 4 days before parturition. The highest geometric mean was 3106 pmol/1 on the day of parturition. Thereafter a steady decrease of PGF2α metabolite concentration was seen until day 21 when it reached plateau at 148 pmo/1. In all cows plasma LH concentrations increased significantly (P<0.05) from about 1.6 µg/l on days 7–8 to 2.4 µg/1 on days 21–22 post partum. The frequency of LH pulses showed no tendency to increase as the postpartum period progressed and averaged 6.5 pulses/24 h. Mean plasma LH concentrations increased from 2.1 µg/l 2 days before weaning to 3.2 µg/l 2 days after weaning (P<0.05). LH peaks occurred less frequently in association with prolactin and Cortisol peaks than in their absence. A partial positive correlation between PGF2α metabolite and Cortisol (r = 0.30) was found on days 7–8 post partum. Correlation between prolactin and Cortisol on days 7–8 and 21–22 post partum was also positive (r = 0.20 and r = 0.27, respectively). There was a negative correlation between LH and Cortisol on days 7–8 (r = −0.27) and days 49–50 (r = −0.21) post partum. The first and short progesterone increase observed after weaning was terminated in conjuction with PGF2α metabolite peaks.     

Improving the reproductive performance of Egyptian buffalo cows by changing the management system

The objective of the present study was to determine the possibility to improve the reproductive performance of buffalo cows through the continuous exposure to bull with grazing and free-stall housing management. Sixty-four Egyptian multiparous buffalo cows raised under two different management systems in two farms were used in this study. The cows in the first farm (management system 1, MS1) were loose--housed in a free-stall yard, grazed for 4 h per day, suckled their calves for 2-3 months and were continuously exposed to a fertile bull. The cows in the second farm (management system 2, MS2 ) were confined in an open-fronted tie-stall shed, not grazed, suckled their calves for only 7 days and were exposed to a fertile bull twice per day (30 min per session). All the cows were fed a diet of green berseem (Trifolium alexandrinum), rice straw and concentrates to meet their maintenance and production requirements. The cows during both the treatments were milked twice per day after weaning. The cows in both groups were between the second and the sixth parity, weighed 450-480 kg and had average daily milk yields of 5.0-6.0 kg. In each farm, cows were visually checked twice daily at 07:00 and 17:00 h for the signs of oestrus and animals proved standing heat were naturally mated. Rectal palpation was used to monitor uterine involution and for pregnancy diagnosis. Blood was sampled twice per week from 7 to 150 days post-partum for serum progesterone assay. The results revealed that post-partum intervals to each of first ovulation, first oestrus, conception and next parturition were significantly (P < 0.05) shorter in MS1 group than in MS2 group. In the meantime, MS1 increased (P < 0.01) the conception and calving rates by 21 and 25%, respectively compared to MS2. Percentages of post-partum cyclic animals and animals exhibiting ovulatory oestrus were greater (P < 0.01) in MS1 group than in MS2 group. However, the percentage of animals cycling before day 60 post-partum was significantly (P < 0.01) lower in MS1 group than in MS2 group (13% versus 28%). By day 120 post-partum, only 63% of the buffaloes were cycling in MS2 group versus 94% in MS1 group. Percentage of silent ovulation was insignificantly higher in MS2 group (34%) than in MS1 group (25%). However, the percentage of false oestrus was higher (P < 0.01) in MS1 group than in MS2 group (16% versus 3%). In addition, percentage of short ovulatory cycles (15-17 days) was greater (P < 0.01) in MS1 group than in MS2 group, whereas percentage of long ovulatory cycle (25-28 days) was higher (P < 0.01) in MS2 group than in MS1 group. It was concluded that continuous exposure of buffalo cows to a fertile bull with grazing management under free-stall housing system enhances resumption of post-partum ovarian activity and improves conception and calving rates.     

The postpartum buffalo. II. Acyclicity and anestrus

Prolonged postpartum acyclicity (absence of ovarian cyclic activity) and anestrum (absence of overt estrous signs) are major sources of economic loss to buffalo breeders. Studies on the epidemiology of these two problems are highly recommended to achieve successful control. Review of the available literature on controlled studies in dairy buffaloes revealed that first ovulation as detected by rectal palpation and progesterone analysis occurred between 28-71 and 24-55 days, respectively, after calving. Postpartum estrus in the same studies occurred between 44 and 87 days. Reports concerned with data compiled from breeding records of research stations, breeding farms and small holders where estrus is a subjective measure, gave much longer periods. Also data from Egypt, India and Pakistan indicate that only 34-49% of buffaloes showed estrus during the first 90 days after calving and 31-42% remained anestrus for more than 150 days. In swamp buffaloes both postpartum ovulation and estrus are more delayed than in dairy buffaloes. The role of suckling, nutrition, body condition score at calving, milk yield, parity, season of calving and other minor factors were discussed. First postpartum ovulation is frequently followed by one or more short estrous cycles (<18 days). Long anovulatory and anestrous periods due to prolonged inter-luteal phase were reported to occur after short cycles. Also long anestrous periods due to cessation of cyclic activity (true anestrus) for 3 or more weeks and prolonged luteal activity for 28 days or more were described to occur in about 25 and 8-11% of the buffaloes, respectively, after the first or second ovulation. These cycle irregularities certainly impose difficulties on estrus detection programs in postpartum buffaloes. Four main forms of anestrus i.e. true anestrus (inactive ovaries and small and medium sized anovulatory follicles), subestrus, prolonged luteal activity and ovarian cysts in addition to pregnancy are reviewed in this article. Differentiation between true anestrus and subestrus is particularly important in buffaloes because of their weak estrous signs. However, the accuracy of a single rectal palpation of the ovaries is limited with an overestimation of the frequency of true anestrus due to misdiagnosis of the corpus luteum. The possible causes are discussed.     

Effect of Bromocryptine on hormones and milk secretion in Murrah buffaloes ( Bubalus bubalis)

An experiment was carried out on 10 advance pregnant Murrah buffaloes to determine the role of hormones in milk secretion around parturition. Experimental animals were administered with a single injection of bromocryptine, @ 100 μg/kg BW, for 5 days before expected calving, whereas control group buffaloes were injected with placebo injections. Blood samples collected before parturition (-5,-4,-3,-2,-1 days), on day of parturition (day-0) and on day 1, 2, 3, 4, 5, 10 and 15 post partum were analyzed for growth hormone (GH), insulin like growth factor-I (IGF-I) and prolactin (PRL) by radioimmunassay methods. Milk samples were collected daily for 5 days and on day 10 and 15 after parturition. Milk fat, protein, lactose, citric acid, non-esterified fatty acids (NEFAs) and somatic cell counts (SCCs) were determined in milk samples. Bromocryptine treatment significantly (P < 0.01) decreased pre partum PRL and increased GH levels (P < 0.01) on day of parturition in experimental buffaloes without influencing plasma IGF-I level. Milk yield was significantly lower (P < 0.01) in experimental than in control group. Further, effect of bromocryptine on milk yield was only for a week. Milk yield increased (P < 0.01) gradually and was similar to control group on day 15 post partum. Bromocryptine treatment significantly increased milk SCC (P < 0.01) and protein content (P < 0.01) but there was no effect of treatment on fat, lactose, citric acid, glucose, milk and plasma NEFA concentration. It was concluded that prepartum suppression of PRL by bromocryptine impairs milk secretion temporarily in ensuing lactation. The significant rise in GH level before parturition and on day of parturition suggests a role of it in milk secretion of buffaloes.     

Oestrus synchronization in buffaloes (Bubalus bubalis)

A study was conducted on 34 Surti buffalo cows to determine the feasibility of synchronizing oestrus using prostaglandin F_2α and a 12-day progesterone intravaginal device. Eighteen cycling buffalo cows having palpable corpora lutea were treated with a single intramuscular injection of 30 mg of prostaglandin F_2α. Three cows exhibited oestrus approximately 54 h after treatment and two of these were diagnosed pregnant 90 days after natural breeding. Sixteen randomly selected post partum cows were treated for 12 days with a progesterone intravaginal device. Ten mg of oestradiol 17β in 5 ml of ether was also injected at the time of insertion of the device. Thirteen cows retained the device for 12 days and 10 of them returned to oestrus 4–5 days after its removal. Eight animals were diagnosed pregnant 90 days after natural breeding. The results indicate that short term progesterone intravaginal device treatment is more reliable than prostaglandin for synchronizing oestrus in buffaloes.     

Post partum patterns of circulating FSH, LH, prolactin, estradiol, and progesterone in nonsuckling cynomolgus monkeys.

Circulating levels of FSH, LH, prolactin (Prl), estradiol (E), and progesterone (P) were determined by RIA in four intact and four monkeys luteectomized (CLX) at parturition in order to a) characterize the patterns of these hormones during the puerperium, and b) examine a possible inhibitory role of the "rejuvenated" corpus luteum (CL) on the resumption of follicle growth post partum. In both groups during the first four weeks, FSH and LH were at tonic levels typical of ovulatory cycles. Recurrent puerperal "surges" of FSH, but not LH, unaccompanied by increments in serum E, were observed in both intact and CLX monkeys. No consistent pattern of serum Prl was apparent. CLX was followed by a prompt fall in serum P levels, which were elevated above typical follicular phase levels into the second week post partum in intact monkeys. Menstrual cycles resumed 2-4 months after delivery. Hormonal patterns during the first menstrual cycle post partum were indistinguishable from those observed in pregravidic ovulatory cycles. The findings indicate that in nonsuckling cynomolgus monkeys a) although it secretes progesterone, the puerperal CL does not inhibit the resumption of the ovarian cycle post partum, b) the puerperal ovary is not absolutely refractory to gonadotropins, since initial trials with Pergonal + hCG stimulated ovarian function, and c) ovarian activity during the puerperium may be limited by factors other than the tonic supply of gonadotropins.     

Postpartum ovarian activity,uterine involution and fertility in indigenous buffaloes at a selected village location in Sri Lanka

Reproductive events were monitored over a period of 30 months in a sample of 55 indigenous (Lanka) buffalo cows belonging to five farmers selected at random in a specific village in the dry zone low-country region of Sri Lanka. The animals were maintained under the existing traditional methods of extensive grazing management and low-intensity utilization for milk and draught power in a crop-livestock system. Annual calving rate was 87.2%, with 82.4% of all calvings occurring between December and March (peak calving season). Involution of the uterus, based on rectal palpation, was completed at an interval of (mean ± SD) 32.9 ± 8.2 days post-partum. The majority (70.8%) of first services postpartum were recorded between February and April. The interval from calving to first service was 57.3±49.2 days for 80 animals which calved during the peak calving season and 156.2 ± 95.6 days for eight animals calving outside the peak season (overall 66.4 ± 61.4 days, n = 88). The intervals to uterine involution and first service were correlated (r=0.53, P < 0.01) and both were significantly influenced by month of calving, but not by age or parity of the cow. The interval from calving to palpation of the first corpus luteum was 52.3 ± 16.8 days, and to the first elevation of progesterone above 0.5 ng/ml of fat-free milk was 54.9 ± 17.9 days.Of the 36 cases where complete progesterone profiles and clinical data were available, first services were recorded in 27 (75%) before palpation of a corpus luteum or elevation of progesterone after calving, and conception to this service was confirmed in 24 (88.9%). Elevation of progesterone preceded first service in seven (19%); the resultant luteal phases were short in four and normal in three. Overall conception rate to first service was 77.7% and the number of services per conception was 1.29. The calving to conception intervals ranged from 23 to 502 days (mean 71.5 ± 66.2, mode 41–60, n = 82) and the calving intervals from 329 to 816 days (mean 384.9 ± 62.9, mode 351–370, n=79).These findings confirm that Lanka buffaloes are capable of maintaining high fertility under certain traditional systems of management. The major cause of long calving intervals was prolonged postpartum acyclicity, which occurred mainly in animals calving outside the peak calving season.     

Plasma estradiol and progesterone levels during post partum ovulation and early pregnancy in the common marmosetCallithrix jacchus

The incidence of ovulation and subsequent pregnancy in post partum marmosets were studied. By two weeks following delivery, all the animals (N=10) had ovulated as determined by a gradual rise in plasma estradiol followed by a rise in plasma progesterone (p>31.8 nmol/l) levels. The mean day of ovulation was 11.3±1.5 (9–14 days). Eighty percent of these females became pregnant as indicated by a continued rise in plasma progesterone levels (p>127 nmol/l) and as confirmed by transabdominal uterine palpation. These results suggest that the day of delivery could serve as a useful parameter to monitor ovulation and pregnancy in this non-menstruating primate species.     

Initiation of fatty acid synthesis in rat mammary glands.

The rate of fatty acid synthesis from [6-14C]glucose in mammary tissue remained low until parturition at 22 days of gestation and increased 10-fold at 1 day post partum. Administration of progesterone on days 20 and 21 or removal of pups at parturition abolished this increase. In the latter case, administration of prolactin, corticosterone or oxytocin had no stimulatory effect; tissue from suckled glands in which the ducts had been ligated at parturition also showed no increased rate in 24 h. Foetoplacentectomy on day 18 did not stimulate fatty acid synthesis but subsequent suckling by foster pups did. Whereas lactose synthesis is initiated by withdrawal of progesterone from the circulation, a further stimulus related to removal of milk by suckling is required to initiate fatty acid synthesis.