1st Ovulation Research Articles

Improved reproductive performance achieved in tropical dairy cows by dietary beta-carotene supplementation

Dairy farming in tropical climates is challenging as heat stress can impair reproduction in cows. Previous studies have demonstrated the beneficial effects of beta-carotene supplementation on bovine reproductive performance. This study was performed in Thailand, where the temperature-humidity index (THI) during the experimental periods was measured to range from 78.4 to 86.1. Lactating Holstein cows classified as repeat breeders (previous artificial insemination [AI] failures) were randomly assigned into two treatments, control treatment (T1; received placebo, n = 200) and test treatment (T2; received 400 mg/h/day of beta-carotene, n = 200). All cows were subjected to a protocol for synchronization of ovulation and timed artificial insemination (TAI). The day of the 1st ovulation synchronized protocol was defined as day 0, and the total experimental period was 160 days. Daily placebo or beta-carotene supplements were given orally on day 0 and each subsequent day of the experiment. Diagnosis of pregnancy was performed using ultrasound on day 30 after insemination. Non-pregnant cows were subjected to further ovulation synchronizations (maximum of four) and TAI over a period of 160 days. Milk samples were collected every ten days throughout the experiment. The samples were analyzed for beta-carotene concentration, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. The pregnancies per AI of the cows in T2 were significantly greater than that of T1 from the 2nd to 4th TAI. During the entire experimental period, the pregnancies in T2 were significantly greater than that of T1. Cox's proportional hazards regression model data indicated a 44% greater probability of pregnancy for cows receiving beta-carotene. The concentrations of milk beta-carotene in T2 were significantly greater than T1 from the 2nd to 4th TAI. Significantly greater SOD and GPx activities were observed in T2 than T1, suggesting a reduction of oxidative stress in cows treated with beta-carotene. Dietary supplementation with beta-carotene thus improves the reproductive performance of repeat breeders exposed to heat stress, possibly by reducing oxidative stress.

Effect of Toxin Binder Supplemented to Friesian Cows Rations on Stress States and Their Reproductive Performance Under Summer Climatic Conditions in Delta Region تأثیر مضادات السموم الفطریة المضافة لعلائق الأبقار الفریزیان على حالة الاجهاد الحرارى و الأداء التناسلى لها تحت الظروف المناخیة الصیفیة لأقلیم الدلتا

Twenty Holstein cows with an average of 540±17.59 kg LBW and 2-5 parities were used from beginning dry period to 120-days postpartum to study the effect of dietary bentonite and/or zeolite supplementation on reproductive performance under heat stress of Delta region. The experimental cows were distributed into four homogenous groups (5 cows each). All cows were fed a basal ration (BR) according to their production stage and body weight. The first group (G1) was fed (BR) only without any supplementation (control), otherwise groups G2, G3 and G4 were fed control diet plus 2 % bentonite, 1% bentonite and 1% zeolite or 2% zeolite of DM intake, respectively. The obtained results showed that dry matter intake, total proteins, albumin, Albumin/Globulin ratio, progesterone and birth weight of newborns were higher in treatment than in control groups. Rectal temperature, respiratory rate, the interval to 1st ovulation, oestrus and service, days open, and the number of services per conception were lower (P<0.05), while conception rate was higher (P<0.05) in treatment than un-supplemented groups. In conclusion, bentonite supplementation as an antitoxin to ration of lactating Holstein cows at a level of 2% of DM intake under summer months in Delta region had a positive impact on feed intake, health status, and reproductive parameters.

Postpartum hormone and energy profiles and their influence on the resumption of ovarian cyclicity in Curraleiro Pé-Duro cows

The objective of this study was to evaluate hormone and energy profiles in the postpartum period and to correlate these profiles with the resumption of ovarian cyclicity, as well as characterizing the postpartum short estrous cycle of Curraleiro Pé-Duro cows. Twelve Curraleiro Pé-Duro cows were examined via rectal palpation and ultrasound at 10 days postpartum, and subsequently examined daily to evaluate the resumption of ovarian cyclicity as well as every five days in order to evaluate uterine involution. Upon analysis of the data, it was possible to observe the formation of two distinct groups, one of which was comprised of those animals which returned to cyclicity within 60 days postpartum and another comprised of those animals which returned to cyclicity more than 105 days postpartum. Therefore, animals were divided into two groups; precocious, designated Ov Group, and delayed, designated NOv Group, wherein the cut-off time for all tests was 60 days postpartum. Statistically significant differences (P < 0.01) between the groups occurred only regarding the day of 1st ovulation, which in the Ov Group averaged 51.4 ± 9.3 days and in the NOv Group averaged 138.3 ± 19.8 days postpartum. The other postpartum short estrous cycle variables assessed did not show statistically significant differences (P > 0.05) between the groups. NEFA, BHBA and thyroxine concentration levels did not differ (P > 0.05) between the groups in any of the statistical analyses. However, in the analysis comparing growth curves, triglycerides levels were higher for the Ov Group (P = 0.04) and cholesterol levels were higher for the NOv Group (P = 0.02). In this experiment, a small influence of a negative energy balance between the groups was observed, suggesting that these animals can present significant genetic variability due to natural selection, as evidenced by the formation of groups of animals with precocious and delayed reproductive characteristics.

استئناف النشاط المبيضي بعد الولادة في الأبقار الماشية = Resumption of Ovarian Activity in Shami Cows Postpartum

Forty one Shami cows available in Dier-Al-Hajar Station, having 1-5 lactations were used to monitor ovarian activity postpartum (pp), determine the times of the 1st ovulation and estrus, the diameters of dominant follicles and length of ovarian cycle till day 65 pp. Transrectal Ultrasound Echo System (7.5 MHz probe) was used to monitor the daily development and regression of ovarian follicles during the study. Results indicated that the frequency of the first ovulation pp was 19.5, 36.6, 24.4 and 7.3% for cows ovulating the 1st, 2nd, 3rd and 4th dominant follicles, respectively, and there is no ovulation in 12.2% during this study. The first ovulation was determined after 34.6±1.9 day pp, while estrus detected on day 49.1±2.3 pp. There were no effects of parities (primiparous and multiparous), season and suckling on the time of 1st ovulation pp. However, the 1st estrus occurred earlier in primiparous than in multiparous cows and in winter compared to other seasons. The frequency of short (8-13 days), intermediate (17-24 days) and long ovarian cycle (cycles without estrus detected) (25-31days) was 27.8, 58.3 and 13.9%, respectively, with an average length equals to 18.8±1.1 days. It was concluded that Shami cows resumed their ovarian activity quickly pp, this refers to the ability of insemination and fertilization within 2-3 months pp if there is the appropriate of environmental and management.

Follicular Dynamics and Oestrous Detection in Thai Postpartum Swamp Buffaloes (Bubalus bubalis)

This study characterized follicular activity and oestrous behaviour from 5 to 9 days post-calving up to the 4th ovulation postpartum (pp) in 16 multiparous (range 2-7 parities) Thai swamp buffalo cows (Bubalus bubalis), aged 4-12 years and weighing from 432 to 676 kg. Ovarian follicular activity was examined by transrectal ultrasonography (TUS) every morning. Oestrous detection was performed twice daily by direct personal observation of behaviour and for presence of clear cervical mucus discharge and indirectly by video camera recording during 21 h/day. A follicular wave-like pattern was present before the 1st ovulation leading to short oestrous cycles. Growth rates and maximum diameters of the ovulatory follicles did not differ between the 1st and 4th ovulations. However, growth rate for non-ovulatory dominant follicles (DF) before the 1st ovulation was lower than for the ovulatory follicle (p<0.05). In addition, the diameter of all ovulatory follicles (14.3 ± 0.46 mm, n=39) was significantly larger (p < 0.01) than those of the preceding last but one non-ovulatory DF (10.8 ± 0.20 mm, n = 5), but similar to the last preceding non-ovulatory DF diameter (12.92 ± 0.96 mm, n = 14). Short oestrous cycles were most common between the 1st and 2nd ovulations (93.75%, 15/16 cows, 10.2 ± 0.38 days) decreasing in prevalence thereafter (50%, 3/6 buffaloes, 12.0 ± 1.53 days). Oestrous signs were relatively vague around the 1st ovulation pp to become more easily detectable thereafter. This study suggests that properly fed swamp buffaloes could be mated successfully within 2 months pp, at their 2nd spontaneous ovulation, provided oestrous detection is at least performed daily at 06:00-08:00 hour.

Intermittent nutritional stimulus by short-term treatment of high-energy diet promotes ovarian performance together with increases in blood levels of glucose and insulin in cycling goats

The aim of this study was to determine if short-term intermittent treatments of high-energy diet have any stimulatory effects on ovarian function and metabolic status in goat. Cycling Shiba goats were divided into treatment (TG; n = 6) and control (CG; n = 6) groups. After the detection of ovulation (1st ovulation, Day 0) by ultrasonography, a high-energy diet (250% of maintenance) was fed to the TG from Day 12 to Day 15 (4 days) and from Day 18 to Day 21 (4 days). The high-energy diet comprised 1000 g hay-cubes and 300 g of concentrated feed/head/day (approximately 15 MJ of digestible energy/day). The CG was offered maintenance diet throughout the experiment. Transrectal ultrasound examinations were conducted every other day during the luteal phase and were conducted daily during the follicular phase. Blood samples were collected daily from Day −2 to 7 days after ovulation (2nd ovulation) following the nutritional treatment for analysis of follicle stimulating hormone (FSH), progesterone, oestradiol, glucose and insulin in plasma. Two wave-like rises in the concentrations of glucose and insulin appeared in response to the intermittent nutritional stimulus. Mean plasma concentrations of glucose and insulin were significantly ( P < 0.05) higher in the TG than in the CG on almost all days during each treatment period. For ovarian performance, the total number of follicles that developed on the day prior to the 2nd ovulation in the TG (7.5 ± 2.7) was significantly higher than that of the CG (4.5 ± 2.6). Ovulation rate of the 2nd ovulation (4.5 ± 1.0) in the TG was significantly higher than that of the 1st ovulation (3.0 ± 0.6) of the TG and than both 1st (2.5 ± 0.5) and 2nd (2.7 ± 0.5) ovulations of the CG. No significant difference was detected in the concentrations of FSH, progesterone and oestradiol throughout the experiment between TG and CG. The present experiment demonstrated that short-term intermittent nutritional stimulus from the luteal phase increased the total number of ovulatory follicles and the ovulation rate in association with increasing plasma concentrations of glucose and insulin in goats.

Selected Ovarian Ultrasonographic Characteristics During Vernal Transition are Useful to Estimate Time of First Ovulation of the Year

It is important to get mares pregnant as early as possible after vernal transition and thus, identification signs of impending 1st ovulation of the year are warranted. To identify clinical indicators of an approaching first ovulation of the year, mares were teased with a stallion for oestrous detection starting January 3 and subjected to ultrasonographic examination. Day of first appearance of uterus oedema, follicular wall invagination, intrafollicular echogenicity, double contour of the follicle wall, increase in granulosa thickness, follicular wall hyperechogenicity and appearance of pear-shaped follicles was registered, as well as follicle diameter and number. Seventy per cent of the mares had anovulatory oestrous periods of 4.6 ± 3.6 days, with an interoestroual interval of 12.5 ± 12.2 days. Number of anovulatory oestruses per mare was 2.4 ± 2.3. Uterine oedema occurred in 77% of the mares, 32.4 ± 25.6 days before ovulation. Invagination of the follicular wall appeared in 44.4% of the animals, 24.5 ± 18.4 days before ovulation. Intrafollicular echogenicity was seen in all mares and double contour of the follicle was seen in 77% of the animals. Both last two characteristics appeared 1-72 days before ovulation. Increased thickness of the granulosa occurred in 66% of the mares, 1-19 days before ovulation. Pear-shaped follicles and follicular wall hyperechogenicity were detected 3 or less days before the first ovulation, in 44.4% and 55.5% of mares, respectively. Mean number of follicles > 15 mm decreased at least 16 days before ovulation. We concluded that no isolated characteristic was a reliable indicator. However, increase in granulosa thickness, formation of a pear-shaped follicle and follicular wall hyperechogenicity, associated with the reduction of the number of follicles > 15 mm in diameter to < 3, resulted in the first ovulation of the year in 44-67% of the transitional mares, 1-19 days after the characteristics appeared.

Effects of feeding cows in early lactation with soy hulls as partial forage replacement on heat production, retained energy and performance

This study measured the effects of replacing corn silage and vetch hay by soy hulls in total mixed rations (TMRs) fed to 25 pairs of cows through 90 d in milk, on dry matter (DM) intake, in vivo digestibility, milk yield and composition, onset of normal estrous activity, body condition score (BCS), health and the energy balance of lactating cows. The partitioning of metabolizable energy (ME) intake between heat production (HP) and retained energy (RE) in milk and body change of each cow was measured. The two TMRs differed in the content of forage and forage aNDFom [235 g/kg versus 350 g/kg; and 128 g/kg versus 187 g/kg DM, in the experimental (EXP) and control (CON) diets, respectively]. This was reflected by an increase in voluntary DM intake by 7.2% ( P=0.02) in the EXP group as compared with the CON. In vivo DM and aNDFom digestibility were 4.9% ( P=0.03) and 22.7% higher ( P=0.01), respectively, in the EXP group than in the CON. The higher DM intake and digestibility of the EXP TMR were reflected by a concomitant increase of 7.4% in milk yield and 10.8% in RE ( P=0.01) of the EXP cows as compared with the CON. The two dietary groups expressed similar somatic cell counts, and metabolic disorders ( i.e., ketosis and/or lameness), as well as pedometer activity (steps/h) suggesting similar udder health, behavior and animal welfare. A trend to an earlier return to normal ovarian activity occurred in the EXP cows as reflected by fewer days to 1st ovulation and advanced outset of estrous cycle. Despite the higher RE of the EXP cows, the HP of both groups was maintained at an upper level of 141–136 MJ/cow/d during the 90 d of the experiment.

Characteristics of abnormal puerperium in dairy cattle and the rationale for common treatments

AbstractThe abnormalities of the puerperium can be arbitrarily divided into two broad categories. Those which arise following a difficult calving or retained placenta are referred to as “common”, while abnormalities such as sub- and anoestrus, irregular cycles, cystic follicles, absence of ovarian activity, repeat breeding and increased number of inseminations per pregnancy are described as “special”. Since the “common” abnormalities are well understood, this paper deals in greater detail with the “special” abnormalities of the puerperium. Based on the axiom that many facets of the “special” abnormalities can be caused by dysfunction of the liver (as in the case of fatty liver), information is presented based on experiments conducted with the over-conditioned dairy cow model (AM) which suffers from both a severe negative energy balance (NEB) and fatty liver syndrome during early lactation. This cow model guarantees a severe NEB, with body weight loss and clear changes in the body condition score (BCS), lower milk production, a higher milk fat concentration, temporary decline in blood insulin and glucose concentrations, elevated blood concentrations of non esterified fatty acids (NEFAs) and beta-hydroxybutyrate (BHB) as well as elevated liver concentrations of tri-acyl-glycerol (TAG) during the first weeks post partum. Additionally, this model leads to a higher incidence of metabolic and infectious diseases. Particular attention was paid to LH pulse frequency and to its value in predicting the occurrence of first post partum ovulation would occur, to oestrous behaviour and to oocytes quality. Cows with fatty liver (&gt; 50 mg TAG/g liver tissue) had longer intervals between parturition and 1st ovulation and showed fewer standing heats within the first 100 days post partum, but the proportion of detected heats, compared to endocrinological “heats” was higher in confirmed AM-cows. Moreover, when AM cows come in heat, their heats lasted longer and had a higher pregnancy rate following AI. However, the developmental capacity of oocytes in AM cows, and in particular oocytes that were destined to ovulate between 80 and 120 days pp, was adversely affected. We conclude that the fatty liver condition is a trigger for many problems, including metabolic and infectious diseases, and also of reduced fertility. Prevention of over fatness at calving (BCS&gt;3.5) is the best guarantee for a normal puerperium.

Ovarian Activity in Ultrasound Image and Milk Progesterone Concentration in Postpartum Dairy Cows

Dolezel, R., K. Karl berg, E. Ropstad: Ovarian Activity in Ultrasound Image and Milk Progesterone Concentration in Postpartum Dairy Cows. Acta vet. Bmo, 62, 1993: 173-178. Eighteen pluriparous dairy cows were ultrasonographically observed twice a week from day 9-10 post partum to the 2nd ovulation. Milk samples were taken three times a week and progesterone was assayed by RIA. Before the 1st postpartum ovu­ lation and during the 1st sexual cycle, 1.09 ± 1.09 and 1.8 ± 1.11, respectively, subordinate follicles and 1.5 ± 0.52 and 2.4 ± 0.72, respectively, follicular waves were found. The 1st ovulation occurred 17.9 ± 5.04 days after parturition, the length of the 1st sexual cycle was 19.4 ± 4.66 days and clinical involution of the uterus was completed 22.6 ± 4.34 days after parturition. The period from parturition to the time of the 1st postpartum ovulation and the length of the 1st sexual cycle were positively correlated with the number of follicular waves during the periods. About 81 % of the first postpartum follicular waves and 88 % of the 1st ovulations occurred in the ovary contralateral to the previous pregnant uterine hom. The differences disappeared after the 1st postpartum ovula­ tion. Average values of milk progesterone were discovered during the 1st and 2nd sexual cycles at day 5-7 (5.9 ± 4.78 and 6.3 ± 5.16ng/ml) and at day 10-12 (5.6 ± 5.83 and 11.4 ± 7.74 ng/ml).

Post-Partum Ovarian Activity in Finnhorse Mares with Special Reference to Seasonal Effects

In a previous study, times from parturition to the first ovulation were followed in 55 Finnhorse mares on the basis of milk progesterone determinations. Ninety-six per cent of mares had ovulated by day 20 post-partum. If intervals of more than 19 days are excluded from the data, the time from parturition to 1st ovulation was 117 days. However, in cases of foaling before and after the beginning of June the times were 13.0 days and 8.8 days, respectively (p less than 0.001). Long intervals (over 16 days) occurred mainly before 1st May (in 6 out of 7 cases). In a 2nd study, 25 post-partum Finnhorse mares were examined by rectal palpation and ultrasonic scanning. Five and 7 days post partum, but not 2 days post partum there was a statistically significant difference between ovulatory ovaries and non-ovulatory ovaries regarding size of whole ovary and the largest follicle. Six to 8 days before the first post-partum ovulation, the size of the preovulatory follicle was greater in mares which had foaled before the middle of May (32 mm) than in those which had foaled after the middle of May (20 mm) (p less than 0.05). Within 2 days before ovulation there was no statistical difference between the sizes (43 mm and 42 mm, respectively). The growth rate was therefore slower in cases of early foaling (1.8 mm/day) than in cases of late foaling (3.7 mm/day).

A Survey of the Postpartum Reproductive Performance of Dairy Cows with Fertility Problems in Southern Iceland

The purpose of this survey was to evaluate the reproductive performance of dairy cows on problem farms in southern Iceland. In all 229 cows on 6 farms were studied. The animals were examined clinically by rectal palpation, once a month. Blood samples were taken 2–5 and 7–10 weeks after calving. The blood samples were analysed for the contents of glucose, urea, inorganic phosphate, calcium and magnesium. Milk samples for progesterone profiles were taken, by the farmer, every 4th day from day 10 postpartum until first oestrus. Because of this sampling method, 128 cows had no rise in progesterone levels, when milk sampling was stopped. These 128 animals were excluded from the study. The results are based on 101 animals. There was a large variation between cows in postpartum reproductive performance. In the total material 1st ovulation occurred later than reported in many other countries. Fifty percent of the cows had ovulated 35 days after calving and 90 percent 70 days after calving. The first luteal phase was short in about 60 % of the cows. The progesterone values assayed from those short cycles were lower than the values assayed from the following cycle. First artificial insemination (ai) was on the average 77 days postpartum (pp). The conception rate to first service was 49 %. Of 100 milk samples taken at the time of ai, 20 had high progesterone value. This indicates a high frequency of luteal phase inseminations. Clinical ketosis was diagnosed in 35 cows. Of these, 31 had a low glucose value. Cows with clinical ketosis ovulated, on the average, later than other animals and 24 ovulated later than 40 days pp. The results indicated that the fertility problems of these cows studied were late ovulations, low conception rate, probably in part, due to luteal phase inseminations, and a high frequency of ketosis which could be caused by low quality feedstuff.

Postpartum Reproductive Performance in Dairy Cows

The purpose of this study was to evaluate the influence of animal, breed and parity on postpartum reproductive functions in dairy cows. A total of 141 cows were included in the experiment, which was carried out as part of a study on traits affecting longevity in Swedish dairy cows. The cows belonged to 4 different breed-groups and were 1st to 5th calvers. The duration of the study was 3 years and 44 cows were followed during 1 postpartum period, 49 cows during 2 consecutive periods, 43 cows during 3 periods and 5 cows during 4 periods. The cows were clinically examined, by rectal palpation, at 10-day intervals between calving and first AI, which was at first normal oestrus more than 50 days after calving. External signs of heat were checker and recorded three times daily by the herdsmen. Blood samples for progesterone assay were taken at days 10, 15 and 20 after calving and thereafter every 10th day until first AI. Samples taken at days 10, 15 and 20 were also assayed for content of 15-keto-13,14-dihydro-PGF2α. Heat detection records, records from clinical examinations and plasma progesterone assays were chronologically compiled for each postpartum period and based on this, intervals between calving and postpartum ovulations, recorded uterine involution, 1st and subsequent oestrus and regular reproductive functions were estimated. Least-squares methods were used for the statistical evaluation of data. The results indicate a large variation within and between cows in postpartum reproductive performance. In the total material 1st ovulation occurred before recorded uterine involution and there was a close relationship between 1st ovulatory oestrus and the onset of regular reproductive functions. The interval between calving and 1st ovulation significantly influenced the length of the first cycle in the sense that a large proportion of the early ovulating cows had a short interval between 1st and 2nd postpartum ovulations. The large variations were also evident in the plasma levels of 15-keto-13,14-dihydro-PGF2α. There was a marked decline between days 10 and 15 postpartum and most cows were close to basal levels at 20 days postpartum. The individual cow had a significant influence on intervals from calving to recorded uterine involution, 1st ovulatory oestrus, regular reproductive functions and conception. The breed influence was significant for intervals between calving and 1st ovulation and recorded uterine involution whereas the parity of the cow only influenced the interval between calving and recorded uterine involution.

Natural Family Planning

Departamento de Obstetncia. Ginecologia y Pennatologia. Universidad Catolica de Chile, Santiago, Chile

Failure of estrogen-induced discharge of luteinizing hormone in lactating women.

Pituitary-ovarian relationships were studied in seven lactating women by measuring the basal plasma concentrations of pituitary and ovarian hormones and their responses to an estrogen provocation test at 7, 30, and 100 days after delivery. The results were compared to a similar group of seven women who did not breast feed. The first ovulation occurred in five of the nonlactating women beteen 43-87 days after delivery, as judged by the urinary excretion of total estrogen and pregnanediol. In all lactating women, ovarian cyclicity was suppressed for at least 150 days after delivery or until weaning. The basal concentration of PRL in lactating women was significantly higher than in the nonlactating women at all three times measured. At 30 and 100 days, the concentration of estradiol was significantly lower in the lactating women, although the basal concentrations of FSH were similar in the two groups. After an injection of 1 mg estradiol benzoate, the concentrations of FSH and LH in plasma were suppressed to a greater extent in lactating than in nonlactating women. In addition, fewer of the lactating group (one of seven and none of seven at 30 and 100 days, respectively) than the nonlactating group (two of seven and five of seven) subsequently showed a rise in the concentration of LH 58--96 h after the estrogen injection (positive feedback). These results suggest that during lactation the hypothalamic-pituitary system is more sensitive to the negative feedback and relatively insensitive to the positive feedback of estrogen.

Postpartum ovarian activity in suckled and milked buffaloes

Postpartum ovarian activity in suckled and milked buffaloes was investigated. 70 buffaloes were alotted at random to either a suckled group or a milked group. 60 days after calving the 1st ovulation was detected in 52.4 and 69.1% of suckled and milked animals, respectively. After a postparturient period of 3 months, corresponding figures for the 2 respective groups were 76.2 and 90.5%. The percentage of animals with postpartum ovulation interval (PPOI) of more than 3 months was 23.8% for sucklers and 9.5% for milkers. Average PPOI length for suckled and milked animals was significantly different (p less than .01, 87 vs. 51 days, respectively). Percentages of animals that came into heat 2 months after calving were 19.1% for sucklers and 31% for milkers. 90 days' postpartum, 35.1% of sucklers and 66.7% of milkers showed their 1st estrus. 61.9% of nursed animals and 33.3% of the milked animals came into heat after a long postpartum estrous interval (PPEI) of more than 3 months. Average PPEI length for sucklers was significantly different from that for milkers (131.5 vs. 77.9 days, p less than .01). PPEI lengths for primipara and pluripara were 108.6 and 100.8 days, respectively. These data show that suckling in buffaloes delayed the 1st postpartum ovulation and lengthened the period of time to the 1st postpartum heat.