Progesterone profiles in postpartum Holstein dairy cows as an aid in the study of retained fetal membranes, pyometra and anestrus

This study was carried out to investigate the utility of enzymeimmunoassay (EIA) - derived progesterone profiles in the investigation of postpartum reproductive abnormalities and the effect of their use on reproductive performance in Holstein cows. Whole milk samples, collected twice weekly from parturition until confirmation of pregnancy or removal from the herd, were assayed for progesterone (P4) concentration using a commercially available microtitre plate EIA. The sensitivity, specificity, precision and accuracy were satisfactory to distinguish cyclic changes of P4 reflecting ovarian activity. The P4 profiles indicated that retained fetal membranes and anestrus were associated with increased mean intervals to first ovulation and first estrus (P < 0.05). The first luteal phase of cows with pyometra was prolonged compared with that of normal herdmates (P < 0.05). Anestrus cows had an increased number of ovulations before first service and before pregnancy (3.9 and 5.9) in comparison with normal herdmates (2.1 and 3.5; P < 0.05). Calving to pregnancy interval was increased above normal (74.8) for pyometra (125.0) and anestrus (152.7) (P < 0.05). Pregnancy rate for anestrus cows (82%) was lower than for normal cows (100%) and more anestrous cows were culled (27%) than normal cows (5%) (P < 0.5). The P4 profiles indicated that the major problem in the herd studied, anestrus (32% incidence rate), was most likely due to the failure to observe estrus rather than acyclicity.     

Postpartum ovarian activity in dairy cows: Correlation between behavioral estrus, pedometer measurements and ovulations

The efficacy of pedometers as estrus detection aids was tested in a group of 47 Holstein cows during the postpartum period. Pedometers were strapped on the left front leg of each cow on the day of parturition and pedometer measurements were recorded twice daily for 60 days. The cows were also observed twice a day for behavioral signs of estrus. Daily blood samples were collected during Days 1-30, and thereafter once every two days from Days 30-60 after parturition for progesterone assay. Rectal palpations of the ovaries were carried out once every four days during the first month after parturition. Based on the progesterone profiles and rectal palpation findings, 91 ovulations were recorded in 42 cows and 5 cows remained acyclic during the observation period. Seventy-six percent (69 91 ) of the ovulations were associated with pedometer indications of estrus, while only 35% (32 91 ) of the ovulations were associated with observed estrus. Fifty-seven percent (24 42 ) of the first postpartum ovulations were associated with pedometer measurements, but only 19% (8 42 ) of the first postpartum ovulations were associated with behavioral signs of estrus. Similarly, pedometers were superior to observations as a method of detection of estrus associated with the second and third postpartum ovulations (91% vs 37%, 92% vs 78% respectively). It is concluded that pedometers are useful aids for estrus detection, particularly in the immediate postpartum.     

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.     

Induction of synchronized estrus and fertility in anestrous ZebuxTaurus crossbred cows

A major cause for reproductive failures in Zebu x Taurine crossbred cows is postpartum anestrus. Crossbred cows were diagnosed to be in postpartum anestrus by palpation per rectum of nonfunctional ovaries. To induce synchronized estrus, the cows were treated by placement of a progesterone releasing intravaginal device (PRID) for various number of days, together with a single administration of prostaglandin F(2) alpha (PGF, 5 mg intravulvosubmucos), estradiol-17beta (E2, 1 mg i.m.) or pregnant mare serum gonadotrophin (PMSG, 500 IU i.m.). Administration of PRID for 7 d, and of E2 and PMSG on Day 6, significantly improved the degree of behavioral estrus manifestation compared to single PRID for 12 d or PRID for 7 d, and of PGF on Day 6. However, the treatment combination of PRID and PMSG alone was associated with higher (P < 0.01) conception rate to 2 fixed time A.I. at induced estrus. The mean interval from treatment to conception was also shortest (P < 0.01) for this group. These results suggest that administration of PRID for 7 d, and of PMSG on Day 6 is highly effective in achieving synchronized behavioural estrus, a near normal CR to fixed time A.I. and a shorter interval from treatment to conception in anestrus Zebu x Taurine crossbred cows under Indian field conditions.     

Luteal competency during the resumption of ovarian cyclicity in postpartum Brahman cows

Twenty pluriparous, spring-calving Brahman cows were used to determine luteal competency, as measured by serum progesterone concentrations, during the first and the second postpartum estrous cycles. Prior to and after calving, all cows were maintained in good body condition on Coastal bermudagrass pasture (IFN 1-00-703). The calves were allowed to suckle ad libitum, and sterile marker bulls were maintained with the cow herd as an aid in estrus detection throughout the trial. Cow weight and body condition score were recorded within 24 hours after calving and again at the first behavioral estrus observed. From day 1 through day 14 (day 0 = estrus) of both the first and the second postpartum estrous cycles, blood samples were collected from each cow, processed to yield serum and analyzed by radioimmunoassay for progesterone concentrations. There was a higher incidence of abnormal estrous cycles following the first postpartum estrus (35%) than following the second (5%) postpartum estrus (P<0.05). The abnormal first estrous cycles were characterized by either a short luteal phase (four cows) or by standing estrus behavior without luteal tissue formation (three cows). When serum progesterone concentrations were compared for all cows during the first estrous cycle with those during the second estrous cycle, there was less progesterone released during the cycle (P<0.05) and lower peak progesterone concentrations (P<0.10) during the first estrous cycle. However, if the abnormal cows were excluded from the analyses, there was no difference (P>0.10) in either progesterone concentrations through the 14 days measured or in peak progesterone concentrations between the first and the second postpartum estrous cycles. It can be concluded from this study that the higher incidence of abnormal luteal function following the first postpartum estrus may contribute to the decreased conception rates observed when cows are bred at their first postpartum estrus.     

Milk progesterone profiles in crossbred Brown Swiss x Nellore cattle following natural service

Ovarian activity and estrous behaviour were monitored through milk progesterone determinations and twice daily visual observations in 70 crossbred Brown Swiss x Nellore cows following natural service. Whole milk samples were collected on the day of estrus (Day 1), Day 11, and every 5 d thereafter until the next estrus or pregnancy confirmation. Seventy percent of the cows behaved as expected, i.e. they showed a 19-to 25-d interval between estrus and the next ovulation, or they became pregnant. Estrous cycles of regular length (18 to 24 d) were found in 54% of the cases. Prolonged luteal phases (interval from estrus to next ovulation > 28 d) were found in 15.7% of cows. Short estrous cycles (interestrous interval < 18 d) were found in 7.1% of the cases. Periods of acyclicity (basal progesterone levels for periods >/= 15 d) were found in 5.8% of the cases, and one cow exhibited estrus while pregnant and had a high progesterone concentration. Cows with a prolonged luteal phase and those with a short estrous cycle had an interval between ovulations of 35.0 +/- 6.7 d (x +/- SD) and 9.6 +/- 3.1 d, respectively. Signs of estrus were not detected in 33.3% of the ovulations confirmed by progesterone determinations. Low conception rates, failures in estrus detection and a high frequency of abnormal postbreeding luteal phases were found.     

Oxytocin-induced release of prostaglandin F2 alpha in postpartum beef cows: comparison of short versus normal luteal phases

The first postpartum ovulation after early weaning of calves (30 35 days of age) from cows is normally followed by a short luteal phase (6 10 days) unless the animals are pretreated with a progestogen (e.g. norgestomet). Reduced luteal lifespan in cattle is reportedly due to the premature release of a luteolysin (presumably prostaglandin F2 alpha [PGF2 alpha]). Therefore, the objective was to determine if oxytocin-induced release of PGF2 alpha (measured by the stable PGF2 alpha metabolite, 15-keto-13,14-dihydro PGF2 alpha [PGFM]) was greater for cows having a short compared to a normal luteal phase on Day 5 following the first postpartum estrus (Day 0). Thirty postpartum beef cows were randomly assigned into three groups (n = 10 per group) expected to have short (Short d 5) or normal (Norgestomet d 5 and Norgestomet d 16) luteal phases. Cows in Norgestomet d 5 and d 16 groups received Norgestomet (progestogen) implants for 9 days beginning 21 23 days postpartum. On Day 5 (Short d 5 and Norgestomet d 5) or Day 16 (Norgestomet d 16) following first postpartum estrus, each animal was injected (i.v.) with 100 IU oxytocin. In addition, cows in the Short d 5 group were subdivided into two groups following second estrus (normal luteal phase, n = 5 per group) to receive 100 IU oxytocin on Day 5 (Normal d 5) or 16 (Normal d 16), respectively. Estrous cycle length (means +/- SE) for cows in the Short d 5 group (8.7 +/- 0.4 days) was shorter (p less than 0.01) than for cows in all other groups (21.1 +/- 0.3 days).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of intrauterine infection on the function of the corpora lutea formed after first postpartum ovulations in dairy cows

This study was carried out to determine the relationship between postpartum intrauterine infections, endocrine patterns and the function of corpora lutea formed following the first postpartum ovulations in dairy cows. Blood samples were collected daily starting from the day of parturition until 30 d after parturition or until the second postpartum estrus, whichever occurred first. Sera were assayed for progesterone (P(4)), prostaglandin F(2alpha) metabolite (PGFM), and luteinizing hormone (LH) concentrations. Palpations per rectum and real-time ultrasound scanning of the reproductive tracts were carried out in all cows once every 4 d for 1 mo, starting from Day 4 after parturition. In addition, endometrial swabs were collected aseptically from each cow once every 4 d during the first month postpartum. The swabs were cultured for aerobic and anaerobic bacteria. Twelve cows (60%) exhibited short estrous cycles (SC; 6 to 14 d long) following first postpartum ovulations. The mean preovulatory LH surges and LH patterns during the first postpartum cycles were similar in both groups, leading us to believe that lack of luteotrophic stimulation was not a factor in the occurrence of SC. Bacterial isolations were frequent in SC cows. The occurrence of moderate to heavy bacterial growth patterns and the repeated isolations of the similar organisms during postpartum suggests the persistence of uterine infections in SC cows. Increases in PGFM concentrations prior to luteolysis in SC cows were associated with moderate to heavy infection. Thus, postpartum uterine infections do not appear to affect ovulations, but prostaglandin (PGF(2alpha)) released in response to uterine infection may contribute to early demise of the corpus luteum formed after the first postpartum ovulation.     

Biostimulatory effects of estrous cows and bulls on resumption of ovarian activity in postpartum anestrous Zebu (Bos indicus) cows in the humid tropics

Suckled postpartum Zebu (Bos indicus) cows were exposed either to estrous females alone or together with bulls to determine if this regimen would stimulate the resumption of ovarian activity. The study was carried out on 60 Zebu cows. The animals were allocated at parturition to 1 of 3 treatment groups. Group FB cows (n = 14) were exposed to progestogen treated females (approximately 3 cows per progestogen treated cow) and a bull for 42 d. Group F cows (n = 31) were exposed to progestogen treated females and after 21 d a bull was introduced and remained with the group until the end of the experiment 21 d later. Estrus was induced with Syncro Mate B treatment and the cows were in estrus when introduced into Groups FB and F. Group N cows (n = 15) were introduced to a bull 21 d after the treatments had begun in Groups FB and F, and the bull remained with these cows until the end of the study. On average, resumption of ovarian activity occurred in 57% (8/14), 19% (6/31) and 7% (1/15) of the cows in Group FB, F and N, respectively, within 21 d after the start of treatments. The difference was significant between Group FB and Groups F and N (P < 0.05). During the second part of the experiment, in which the bull was introduced to Groups F and N, an additional 32% (10/31) of the cows in Group F and 33% (5/15) in Group N resumed ovarian activity. No cows in Group FB resumed ovarian activity during this period. There were significant differences in body condition between cows that resumed ovarian activity and those that remained in anestrus (P < 0.05). We conclude that biostimulation effectively enhanced resumption of ovarian activity in anestrous suckled Zebu cows. This technique offers a potentially useful and practical way to improve reproductive efficiency in anestrous Zebu cattle in the tropics.     

Plasma progesterone profiles and fertility status of anestrus Zebu cattle treated with norgestomet-estradiol-eCG regimen

Zebu cattle are notorious for poor fertility characterized by late maturity and long intercalving intervals attributed to a variety of factors, including genetic, nutritional and climatic. The aim of the present investigation, therefore, was to induce fertile estrus in acyclic pubertal heifers and postpartum anestrous Zebu cows by hormonal intervention. Pubertal Hariana and Sahiwal anestrous heifers (n=51) and postpartum cows (n=55) were either assigned a placebo (controls, N=6 for each breed and parity) or treated with 10-d norgestomet (3 mg) subcutaneous ear implants, with an initial injection of 3 mg, im norgestomet + 5 mg estradiol valerate, followed by 500 IU eCG at implant withdrawal (NOR-treated groups). Jugular venous plasma samples were obtained from a total of 28 animals (controls : 4 heifers and 4 cows; NOR-treated : 12 heifers and 8 cows) on Days 0 (implant insertion), 3, 7, 9 and Day 10 (implant withdrawal), every 12 h on Days 11 and 12, and then once daily on Days 17, 24 and 31. All the samples were assayed for progesterone. Almost all (97%) heifers and 81% cows were induced to estrus, the majority (92% heifers and 79% cows) within 120 h of implant removal. Synchrony of the induced estrus was better in cows, but interval to estrus and estrus duration were significantly longer in heifers (P<0.05). Post-treatment fertility, based on Day 28 nonretum rate, first service, and overall conception rates, was better in heifers (78.9, 60.5 and 73.7%, respectively) than cows (77.1, 48.6 and 62.9%, respectively), but the differences were significant only for the overall pregnancy rate (71.8% for heifers and 51.2% for cows; P<0.05). Low pre-treatment plasma progesterone values (<0.5ng/mL) were consistent with ovarian inactivity, confirming the true anestrus status of experimental animals. Controls failed to exhibit estrus and maintained low progesterone concentrations throughout the study. In treated animals, high progesterone values from Day 17 onwards suggested ovulatory estrus. These early luteal phase progesterone concentrations in nonpregnant (P=0.06) and nonpregnant, nonretum (P<0.05) animals were low in comparison with those of pregnant animals. Good fertility resulting from breeding according to estrus, inspite of variable intervals to estrus and estrus duration, advocates its advantage over fixed-time insemination in norgestomet-treated anestrous Zebu cattle.     

Bull effect on the reproductive performance of mature and first calf-suckled Zebu cows in the tropics

This experiment was designed to determine if continuous bull exposure of heifers 2 wk post partum to a first calf (30 to 36 m old) or mature (42 to 72 m old) Zebú Brahman suckled cows reduces the interval to first estrus and the number of days open. Post partum first calf cows were randomly assigned to be exposed continuously to epidectomized bulls with surgical ablation of the dorsal ligament of the penis (Group 35 FBE, n = 25) or not exposed to bulls (Group FNE, n = 22). Post partum mature cows were likewise assigned to be continuously exposed (Group MBE, n = 24) or not exposed to bulls (Group MNE, n = 25). Milk samples were collected twice a week for progesterone assays to determine resumption of ovarian cyclic activity. All the cows were artificially inseminated for 120 d while in their respective treatment groups. The first postpartum estrus percentages were 60 < 90 d, 24.4%; and > 90 d, 33.7%. The interval to first estrus f-or Groups FBE and FNE was 75.4 and 104.2 d, respectively, and differed significantly (P < 0.01). For Groups MBE and MNE the interval to first estrus was 76.3 and 95.0 d, respectively (P < 0.05). The number of open days for Groups FBE and FNE was 77.3 and 114.9, respectively (P < 0.01); while for Groups MBE and MNE it was 73.0 and 98.6 d, respectively (P < 0.01). The results of the present study indicate that introduction of bulls to first calving cows or mature Zebú Brahman cows after parturition provides a practical and economical option for reducing the extended post partum anestrus interval and days open under tropical conditions.     

Resumption of ovarian function in autumn lambing Dorset, Rambouillet and Finnish Landrace ewes

The establishment of ovarian activity during lactation was studied in the postpartum period of Rambouillet, Dorset and Finnish Landrace ewes following lambing during the month of October (1981). The mean postpartum intervals to first ovulation and first estrus were 22.7 and 53.0 for Rambouillets, 25.2 and 51.0 for Dorsets, and 22.5 and 49.7 days for Finnish Landrace ewes. Estrus was not associated with the first ovulation postpartum in any breed. The number of silent ovulations prior to the first estrus was highest in the Rambouillet and lowest in Finnish Landrace breeds. Of the 18 ewes in the project, 14 had normal luteal phase lengths, 1 had a possible short luteal phase and 3 had prolonged luteal phases following the first ovulation postpartum. The first service conception rate of all ewes bred was 82% (14 17 ) at an average of 52 days postpartum. The lambing rate following the autumn breeding was higher (2.14 +/- 0.14) than the lambing rate which followed the previous spring breeding (1.28 +/- 0.11).     

Effect of gonadotropin-releasing hormone and prostaglandin F2α on reproduction in postpartum dairy cows

Thirty dairy cows serving as the treated group (Group A) were injected intramuscularly with 100 mcg gonadotropin-releasing hormone (GnRH) at 10 to 16 days postpartum followed by 25 mg prostaglandin F₂α (PGF₂α) 14 days later. Twenty-nine herdmate dairy cows (Group B) serving as controls were treated in a similar manner using saline injections rather than GnRH or PGF₂α treatments. Only cows without obvious uterine infection were assigned to the experimental groups, and any uterine pathology that developed during the treatment interval was treated accordingly following the experimental period. Internal genitalia were evaluated via rectal palpation prior to each injection. Blood samples were collected for progesterone analysis before each injection and at 30 hours following the PGF₂α or the second saline injection. Experimental animals were artificially inseminated at the first detected postpartum estrus starting 35 to 40 days following calving. Results indicated evidence of enhanced cyclicity when Group A cows were compared with those in Group B. However, there were no significant differences between the two groups for interval to first observed estrus, interval to first serive, first serive pregnancy rate, services per pregnancy and days open. Furthermore, no difference in the incidence of follicular or luteal cysts, incidence of repeat breeders or number of reproductive culls was observed. From observations in this study, the GnRH and PGF₂α treatment scheudule might not be economically beneficial in lactating dairy cows as long as reproductive tract abnormalities are promptly diagnosed and subsequently treated by the attending practitioner.     

Reproductive performance of postpartum dairy cows under a highly intervenient breeding program involving timed insemination and combinations of GnRH, prostaglandin F2alpha and human chorionic gonadotropin

Lactating Holstein cows (n=288) were grouped as pairs at parturition and randomly assigned to two treatments (control, C vs intervenient treatment, T). The reproductive management of the Group C cows (n=130) consisted of the intramuscular administration of 500 microg PGF2alpha analogue (PG) on Days 28 and 63 postpartum and breeding on the basis of estrus signs with the a.m.-p.m. rule after Day 63. Cows that were not bred by 77 d postpartum received another injection of PG and were bred at estrus or 84 h after PG treatment. Pregnancy diagnoses were perfomed by palpation of the uterus per rectum 42 to 48 d after AI. Cows in the T group (n=139) received intramuscular injections of 100 microg GnRH 14 d and PG 28 d after calving. On Day 56 postpartum, cows were given a second dose of GnRH followed by PG on Day 63 postpartum and a third GnRH injection 48 h after PG (OvSynch). Cows were inseminated at a fixed time (22+/-1 h) after GnRH. Five days after the fixed-time insemination cows were given 1500 IU hCG i.m.. Group C and T cows that returned to service or were diagnosed as non-pregnant continued to receive PG at intervals of 14 d with breeding at estrus or 84 h after the second PGF2alpha dose. A sustained increase in milk progesterone concentration was observed in 59.0% of T cows after GnRH administration on Day 14. A similar rise in milk progesterone concentrations was observed in 53.8% of C cows. The PG on Day 28 induced luteolysis more in Group T cows (53.2%) than in Group C cows (36.9%). The PG on Day 63 reduced milk progesterone concentrations to basal levels in 50.7% of T and 49.2% of Group C animals. The first service pregnancy rates (T, 40.3% vs C, 36.2%) and the overall pregnancy rates (all services, T, 83.5% vs C, 86.9%) were not different between the two groups. The two treatments did not differ in the interval from first service to pregnancy, calving to pregnancy or in calving interval, number of services per pregnancy or culling rates.     

Effects of 72 hr calf removal and/or gonadotropin releasing hormone on luteinizing hormone release and ovarian activity in postpartum beef cows

A study was conducted to determine the pituitary and ovarian responses to 72 hr calf removal (CR) and/or gonadotropin releasing hormone (GnRH) in beef cows. Forty-eight Angus, Simmental, and Charolais crossbred cows in moderate body condition were allotted to an experiment of 2 x 2 factorial design involving CR and GnRH. At 30 to 32 days postpartum, calves were removed for 72 hr from the CR and CR plus GnRH groups. All cows were injected (i.m.) with saline or 200 mug of GnRH at 33 to 35 days postpartum. Saline or GnRH was injected 5 hr before calf return. Plasma luteinizing hormone (LH) was measured in blood samples collected every 30 min for 5.5 hr beginning 30 min prior to injection of saline or GnRH. Plasma progesterone was measured in blood samples collected 0, 7, and 14 days after GnRH injection and 7 and 14 days following the first detected estrus. There were no differences (P>0.05) in the interval to peak LH release or the magnitude of the LH release between the GnRH and CR plus GnRH groups; however, the GnRH induced release of LH was greater (P<0.05) over time when preceded by CR. Plasma progesterone concentrations were increased on day 7, compared to day 0, after GnRH injection in 57% and 50% of the animals in the GnRH and CR plus GnRH groups, respectively. However, behavioral estrus was not observed in any of the cows between days 0 and 7 after GnRH injection. A higher (P<0.05) percentage of the cows injected with GnRH formed luteal tissue compared to cows injected with saline; however, the luteal lifespan following GnRH injection was decreased relative to the luteal lifespan following the first observed estrus. The mean interval from calving to first estrus was decreased (P<0.05) by 17 days in the CR group relative to the other groups, and calf removal had no detrimental effect on milk production at 80 days postpartum or on calf weaning weights at approximately 7 months of age. In summary, 72 hr CR decreased the postpartum interval and increased the pituitary responsiveness to GnRH. Pretreatment with 72 hr CR did not alter circulating progesterone concentrations or luteal lifespan of corpora lutea induced by GnRH.     

Effect of Chromium Supplementation on Productive and Reproductive Performances and Some Metabolic Parameters in Late Gestation and Early Lactation of Dairy Cows

The objective of this study was to determine the effect of supplemental chromium as chromium-L-methionine (Cr-Met) on productive and reproductive performances and some metabolic parameters in late gestation and early lactation of dairy cows. Sixty multiparous Holstein dairy cows according to prior lactation, parity, body mass (682?±?33?kg), and expected calving date were divided equally (30 cows/treatment) and were randomly allocated to one of the two groups. One group received basal diet without Cr (control group) and another group received Cr-Met supplement added at manufacturer's recommended level (8?mg of "Cr"/head per day) from 21?days before expected calving date until 21?days of lactation. Supplemental Cr tended to increase milk yield (P?=?0.08) while percentage of lactose and lactose yield increased (P??0.05). Percentage of cyclic cows at 36?days postpartum and estrous behavior before AI was higher in the supplemented group.     

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.     

Effect of one spontaneous estrus cycle (after synchronization with PGF2alpha) on reproductive performance in dairy cows

The objective of the study was to analyze the effect of a spontaneous estrus cycle after synchronization of estrus with prostaglandin F2alpha (PGF2alpha) in dairy cows on the degree of synchronization and reproductive performance. We assigned 557 Holstein cows to two treatment groups. In Group 1 estrus was synchronized by two treatments with 25 mg of Dinoprost-Trometamol in 14-day intervals. Cows were treated 27 to 33 days postpartum (dpp) and 41 to 47 dpp, respectively. Cows in Group 2 were treated with 25 mg of Dinoprost-Trometamol three times in 14-day intervals, starting at 34 to 40 dpp. The second and third injections were administered at 48 to 54 dpp and 62 to 68 dpp, respectively. All cows were inseminated on observed estrus after a voluntary waiting period of 65 days post partum. Thus cows in Group 1 were inseminated on spontaneous estrus and cows in Group 2 on induced estrus. Cows not inseminated at 80 days post partum were palpated per rectum and treated according to a predefined protocol. Herd reproductive performance measures did not differ significantly between groups. The proportion of cows with low serum progesterone levels was significantly higher 3 days after synchronization than 24 days after synchronization (97% vs 39%). The first-service conception rate was 34.8% in Group 1 and 30.7% in Group 2 (P > 0.05). Days open were 113.5 in Group 1 and 110.9 in Group 2 (P > 0.05). It is concluded that postponing artificial insemination for one spontaneous estrus cycle after synchronization decreased the degree of synchronization. This procedure, however, had no effect on herd reproductive performance compared to insemination on first observed estrus after synchronization.     

Effects of physiological and/or disease status on the response of postpartum dairy cows to synchronization of estrus using an intravaginal progesterone device

Progesterone treatments are used to increase submission rates in postpartum dairy cows; however, in many cases the protocol is used as a blanket therapy for all cows without regard for physiological or disease state. The objective of this study was to identify the physiological or disease classes of cows that respond well (or not) to synchronization of estrus via progesterone. Dairy cows (n = 402) were monitored peri and postpartum to establish their physiological or disease status. Animals were classified as having negative energy balance, clinical lameness, uterine infection (UI), anovulatory anestrus, high somatic cell counts, and healthy (H). Blood samples were collected at five different time points and analyzed for metabolites. All animals received an 8-day controlled internal drug release protocol, which included GnRH at insertion and PGF_2α the day before removal. Response to the protocol was determined by visual observation of estrus synchronization. Conception rate was determined by ultrasonography between Days 32 and 35 after artificial insemination. Animals without UI were 1.9 times more likely to respond and two times more likely to be confirmed pregnant than those with UI. There was no relationship between negative energy balance and clinical lameness in the visual estrous response, but both conditions were associated with reduced conception rates. Dairy cows in anovulatory anestrus responded successfully to the protocol in both estrous response and conception rates. High glutathione peroxidase concentrations had a positive effect on conception rates, whereas high non-esterified fatty acids and beta-hydroxybutyrate had a negative effect on the estrous response. In conclusion, disease and physiological states of dairy cows determined the response to progesterone-based synchronization. The more disease or physiological problems the cows had, the lower the estrous response and conception rates; cows with these problems were not ideal candidates for synchronization. Both anestrus and healthy dairy cows were good responders to progesterone-based synchronization.     

Reproductive performance of lactating dairy cows treated with cloprostenol, hcg and estradiol benzoate for synchronization of estrus followed by timed AI

In previous studies, we demonstrated that the administration of a luteolytic dose of cloprostenol, followed by 750 IU hCG plus 3 mg estradiol benzoate (EB) 12 h later, synchronized estrus in cows in the luteal phase. Most cows were ready for service 48 h after the beginning of treatment. The objectives of this study were to evaluate the reproductive performance of lactating dairy cows treated with this method of estrus synchronization and to determine the effect of decreasing the hCG-EB dose on synchronization and pregnancy rates after timed AI. Data were obtained from cows first inseminated within an interval of 45 to 70 d postpartum. A total of 2,472 lactating dairy cows in their first to second lactation period were assigned to 4 groups. Cows estimated to be in the luteal phase by rectal palpation were treated with 500 mcg, im, of cloprostenol and assigned to 1 of 3 groups to be intramuscularly injected with hCG-EB 12 h later at the following doses: Group 1 (n=626), 250 IU of hCG and 1 mg of EB; Group 2 (n=592), 500 IU of hCG and 2 mg of EB; and Group 3 (n=664), 750 IU of hCG and 3 mg of EB. Cows displaying natural estrus were inseminated to serve as controls (n=590). The synchronized cows were inseminated 48 h after cloprostenol injection, and control animals visually determined to be in natural estrus during the morning or afternoon were inseminated the following morning. Pregnancy diagnosis was performed by rectal palpation at 34 to 40 d postinsemination. All synchronized cows showed estrous activity within 24 to 36 h after cloprostenol treatment and were considered to be ready for service 48 h after this treatment. There was a significant effect of treatment on the pregnancy rate, either to first AI or to 2 rounds of AI. The pregnancy rate in response to first or second rounds of AI was similar to control rates for cows in Groups 1 and 2, and lower than control rates in Group 3. Cows in Group 1 showed a higher pregnancy rate to first AI than those in Group 3 (P<0.0001), and a higher pregnancy rate to second AI rounds than cows in Groups 2 (P<0.02) and 3 (P<0.0001). The number of cows returning to estrus was unaffected by treatment. However, treatment significantly decreased (P<0.01) the time of return to estrus as the hCG-EB dose increased. These findings indicate that the lowest dose of hCG-EB treatment tested gave the overall best pregnancy results among the treated groups. Furthermore, the synchronization protocol used in this experiment allows effective AI management of lactating dairy cows without the need for estrus detection.