Postpartum Estrous Cycles Research Articles

Prevalence and Associated Risk Factors of Postpartum Anestrus in Dairy Cows of Sylhet District, Bangladesh

The objectives of current study were to assess the prevalence and risk factors associated with postpartum anestrus in lactating dairy cows in Sylhet region, Bangladesh. A total of 420 postpartum cows of different breed and age were selected randomly from different dairy farms in studied area. Structured questionnaire was used to collect data from farm owner on prevalence and risk factors for postpartum anestrus. Observed heat within 60 days after parturition was considered as normal cyclic cows and others were considered as postpartum anestrus. The prevalence of postpartum anestrus was 36.20%. The study shows that older cows take relatively more time for ovarian resumption. Cow’s having first parity shows cyclicity within 60 days of parturition, and postpartum anestrus increases significantly with the advancement of parity. Postpartum anestrus was significantly higher (P< 0.001) in cows with poor (≤1.0) and excessive (>3) body condition scores (BCS), respectively, compared to those with moderate/optimal BCS (2–3). The postpartum cyclicity in cows within 60 days with a history of normal placental expulsion was significantly higher than in the cows with RFM. Ovarian cyclicity was highest (75.92%) among the cows that were maintained in adequate hygienic conditions and lowest (43.51%) in a poor environment. The highest percentage (88.10%) of cows showed postpartum cyclicity with a history of short lactation length (0-150 days) and resumption of postpartum estrous cycle increases significantly with lactation length. Resumption of postpartum estrus cycles in cows takes more time with a history of minimal (<15 liters) daily milk production than the cow with medium (>15-25 liters) daily milk production. Cows get an adequate feed supply (both concentrate and green grass), which shows a positive effect on postpartum cyclicity. Pre and postpartum complications have a significant (p<0.001) effect on the postpartum cyclicity of cows. Endometritis (81.25%) followed by pyometra (75.76%) were recorded as major reproductive obstacles in ovarian resumption, whereas uterine prolapse (70.59%) followed by abortion (61.54%), milk fever (58.33%), stillbirth (58.33%) and dystocia (57.63%) were the major recorded complications in post-partum phase. The study also revealed that the non-restricted suckling period has a significant (p<0.001) negative effect on ovarian resumption. The risk factors including parity, BCS, placental expulsion, hygienic condition, lactation length, daily milk production and management system were significantly (P<0.01) influenced the postpartum cyclicity. Maintaining optimal BCS of cows, proper hygienic and good management practice, and farmer's training on management of cattle reproduction would improve the number of cows for breeding by 60 days postpartum.

Transition cow metabolites and physical traits influence days to first postpartum ovulation in dairy cows

Physical activities are associated with the health of transition dairy cows and pregnancy outcomes are positively related to early resumption of postpartum estrous cycles. The objective was to assess key metabolites and patterns of prepartum and postpartum physical activity as they relate to the onset of first postpartum ovulation in lactating dairy cows. Close-up dry Holstein cows (n = 82) and late gestation heifers (n = 78) were enrolled beginning 3 wk before expected calving date (Day 0). Cows were fit with Cow SensOor ear tags to assess transitional changes in eating, resting, rumination, high activity, and ear-surface temperatures. Rectal temperatures were assessed and blood samples were collected on Days 0, 3, 7, and 14 to measure concentrations of glucose, free fatty acids (FFA), β-hydroxybutyrate (BHB), calcium, and haptoglobin. Body condition scores (BCS) and body weights (BW) were measured weekly, and blood samples were collected weekly from Day 21 ± 3 through 70 ± 3 to quantify changes in progesterone to detect luteal function after ovulation. Cows first ovulating before median Day 33 were classified as early (n = 76), whereas those first ovulating after Day 33 were classified as late (n = 84). Early ovulating cows first ovulated earlier (P < 0.001) than the late ovulation cows (24.3 ± 1.2 d [range: 16–32 d] vs. 48.8 ± 1.2 d [range: 33–74 d]), respectively. Mean days to first ovulation excluded seven cows that failed to ovulate before insemination. Compared with late ovulating cows, early ovulating cows had lesser (P < 0.05) concentrations of FFA, BHB, and haptoglobin on Days 0, 3, 7, and 14 in addition to having lesser (P < 0.05) rectal temperatures and ear-surface temperatures. Ear-surface temperatures began to decrease 4 d before parturition and remained less (P < 0.05) after calving than cows that subsequently ovulated late. Early ovulating cows tended (P = 0.07) to spend more time eating, and less (P = 0.02) time resting and being active during the first 3 wk after calving, and lost less (P = 0.03) BW and BCS during the first 9 wk compared with late ovulating cows. Although no differences were detected in yields of milk or energy-corrected milk during the first 9 wk after calving, early compared with late ovulating cows produced more (P < 0.01) milk protein. We concluded that metabolic measures during the first 2 wk after calving, and physical and behavioral traits are associated with the onset of postpartum ovarian activity.

Control of Puerperium in a Dairy Farm using an Intrauterine Suspension

The purpose of this research was to evaluate a product developed at the Faculty of Veterinary Medicine of Cluj Napoca and his efficiency in the control of the puerperium at cows. The study was carried out between January 2017 to December 2018 in a dairy farm from Mures county, Romania. In this study were enclosed 60 cows, randomly divided in 3 groups: Puerperal group (group 1), Puerperal and Estrumate group (group 2), and control group (group 3). For each group the treatment applied for the control of puerperium was different. For each group were followed: the evolution of puerperium, the appearance of the first postpartum estrous cycle, the interval of service period and the number of artificial inseminations necessary for one gestation. For the puerperium control and to avoid the postpartum complications Puerperal intrauterine suspension it’s a good option.

Luteal Blood Flow and progesterone concentration during first and second postpartum estrous cycle in lactating dairy cows

The aim of the present study was to determine the differences in corpus luteum (CL) functionality between the first postpartum estrous cycle and the following cycle in lactating dairy cows. Luteal blood flow (LBF), luteal size and blood progesterone (P4) concentration were monitored during the first and second postpartum estrous cycle. During the first and second postpartum estrous cycle, the mean LBF value increased (p<.05) from early to late dioestrus, while it decreased rapidly in proestrus, resulting statistically lower (p<.05) than those registered in all previous phases. Statistically significant differences were not observed between overall LBF during first and second postpartum estrous cycle (p>.05). During the first postpartum estrous cycle, P4 blood concentrations showed a significant reduction (p<.05) from dioestrus to proestrus. A different trend of P4 concentrations was observed during the second postpartum estrous cycle, where mean P4 value registered in proestrus resulted statistically lower than those registered in the previous cycle phases (p<.05). The mean P4 concentration registered over the first postpartum estrous cycle resulted statistically lower (p<.05) than that registered during the second one. A significant correlation between P4 concentrations and LBF was registered only during the second postpartum estrous cycle. Results indicate that during the first postpartum estrous cycle, P4 concentration was independent of luteal blood flow and luteal size.

Contrasting effects of progesterone on fertility of dairy and beef cows

The role of progesterone in maintaining pregnancy is well known in the bovine. Subtle differences exist between dairy and beef cows because of differing concentrations of progesterone during recrudescence of postpartum estrous cycles, rate of follicular growth and maturation, proportions of 2- and 3-follicular wave cycles, and other effects on pregnancy outcomes per artificial insemination (P/AI). Because proportions of anovulatory cows before the onset of the artificial insemination (AI) period are greater and more variable in beef (usually ranging from 30 to 70%) than dairy (25%) cows, AI programs were developed to accommodate anovulatory and cycling beef cows enrolled therein. Incorporating a progestin as part of an AI program in beef cows improved P/AI by reducing the proportion of cows having premature luteal regression and short post-AI luteal phases. In both genotypes, prolonged dominant follicle growth in a reduced progesterone milieu resulted in increased (1) LH pulses, (2) preovulatory follicle diameter, and (3) concentrations of estradiol and a subsequently larger corpora lutea (CL). In contrast, the progesterone milieu during growth of the ovulatory follicle in an ovulation control program does not seem to affect subsequent P/AI in beef cows, whereas in dairy cows follicle development in an elevated compared with a low progesterone environment increases P/AI. Progesterone status in beef cows at the onset of ovulation synchronization is not related to P/AI in multiparous cows, whereas P/AI was suppressed in primiparous cows that began a timed AI program in a low-progesterone environment. In timed AI programs, elevated concentrations of progesterone just before PGF2α and reduced concentrations at AI are critical to maximizing subsequent P/AI in dairy cows, but seemingly much less important in beef cows. By inducing ancillary CL and increasing concentrations of progesterone, human chorionic gonadotropin may increase P/AI when administered to beef cows 7d after AI or at embryo transfer, and its success seems to depend on induction of ancillary CL, whereas in dairy cows increased fertility was detected in cows with multiple CL, human chorionic gonadotropin-enhanced progesterone from original CL, or both. Pregnancy losses after AI are less frequent in beef cows and are not associated with pre-AI progesterone or cycling status, whereas losses in dairy cows are inversely related to progesterone and adversely affected in anovular dairy cows. Genotype and nutritional management likely influence several physiological differences including circulating concentrations of progesterone and responses to supplemental progesterone.

Effects of breed, age, season, and multiple ovulations on cyclic, PGF2α-induced, and postpartum estrus characteristics in Spanish jennies

This retrospective, population-based, cross-sectional study analyzed data for a total of 104 jennies reared in southern Spain over the period 1995 to 2014. Intervals to ovulation and incidence of multiple ovulation and pregnancy were charted for spontaneous, PGF2α-induced, and postpartum estrous cycles. In spontaneous estrous cycles, the interovulatory interval varied as a function of breed (P < 0.03) and month of ovulation (P < 0.01), and duration of estrus signs was longer in older jennies (0.04). Spontaneous cycles were also associated with higher ovulation rates from September to January (P < 0.006). When PGF2α was used to induce the estrus, not only did estrus signs last longer in old (P < 0.004) and in polyovular (0.02) jennies but old jennies also displayed significantly higher ovulation rates (P < 0.03). In postpartum jennies, no variations were observed as a function of any of the independent variables analyzed. Comparison of ovulation rates between different types of cycle revealed that postpartum jennies exhibited significantly lower ovulation rates (1.32 ± 0.07) and a lower incidence of multiple ovulation (30.4%) than spontaneous (1.62 ± 0.04, 55.0%) and PGF2α-induced (1.74 ± 0.08, 65.5%) groups. No differences were observed in the incidence of ovulation or pregnancy depending on the location of ovulation in polyovular cycles, and ovulation occurred at similar rates in the right and left ovaries. These findings shed further light on reproductive physiology in jennies and may be of value in improving animal management.

Starting Ovsynch protocol on day 6 of first postpartum estrous cycle increased fertility in dairy cows by affecting ovarian response during heat stress

The objective was to compare fertility in cows using an Ovsynch protocol starting on day 6 of first postpartum estrous cycle with an Ovsynch protocol initiated at random stages of the estrous cycle during heat stress (temperature-humidity index (THI)=77–83). Cows (n=459) at the beginning of the lactation period were randomly assigned to time-of-ovulation synchronization treatments: (1) control, Ovsynch (first GnRH treatment, PGF2α treatment 7 days later, second GnRH treatment 56h later, and TAI 16h later), initiated at random stages of the estrous cycle (40±2days postpartum, n=224) and (2) Ovsynch initiated on day 6 of first postpartum estrous cycle (estrus=day 0) based on detection of the first estrus after day 30 postpartum (O6, 35±2 postpartum, n=235). Statistical analyses were conducted using SAS. The percentage of cows responding to the initial GnRH injection using the Ovsynch protocol was greater with the O6 treatment compared to the control treatment (60.4% compared with 52.6%). The percentage of cows having a corpus luteum (CL) on the day of the PGF2α injection was not different among treatments (control=87.0% and O6=90.2%, respectively). Also more cows in the O6 treatment group responded to the second GnRH injection of the Ovsynch protocol compared with control treatments (82.5% compared with 75.8%). Treatment affected the percentage of cows diagnosed pregnant at 32±0.7days and 60±3days after the resynchronized timing of AI but pregnancy losses (5.3% compared with 6.8%) did not differ between treatment groups. It is concluded that initiating the Ovsynch protocol 6 days after estrus during the first 40 days postpartum resulted in a greater pregnancy rate at the synchronized estrus and increased fertility compared with control cows during heat stress.

Effects of body condition and leptin on the reproductive performance of Lusitano mares on extensive systems

The aim of this study was to investigate the effects of body condition (BC), BC changes, and plasma leptin concentrations on the reproductive performance of Lusitano broodmares on extensive systems. Data from 119 mares (ranging from 4 to 22 years of age) were collected over a period of four consecutive breeding seasons. Each case was considered as one foaled mare bred in 1 year. Body condition changes at conception (ΔBCScon) showed a strong effect on fertility at the first two postpartum estrous cycles and a significant interaction with body condition score at conception (BCScon) was observed (P < 0.01). The best fertility results were obtained with positive and greater ΔBCScon. The best predictive value of fertility (91%) was achieved when the BCScon was 3.0 and ΔBCScon was 0.375. Global foaling rate for the 4-year period was 74.5%. Mean foaling interval and gestation length were, respectively, 368.0 ± 2.8 and 340.3 ± 1.0 days. Gestation length was influenced by the month of foaling (P < 0.05) and decreased as mares got older (P < 0.01). The number of estimated estrous cycles per live foal was 1.78 ± 0.12, including foal heat ovulation. Leptin was correlated with BCS (0.41; P < 0.001), but in the present study, plasma leptin concentrations on late gestation and early lactation did not influence fertility results. At 90 days of age, lower growth performances were obtained in foals which dams presented negative BCS changes on the first 3 months of lactation (P < 0.05). In conclusion, BC changes at early postpartum period influence the reproductive efficiency of broodmares and the growth of their suckling foals. These findings are important to help breeders on management options concerning feeding strategies in the Lusitano production systems and others under similar conditions.

The effect of metritis on luteal function in dairy cows

BackgroundDisturbed uterine involution impairs ovarian function in the first weeks after calving. This study analyzed the long-term effect of metritis on luteal function of 47 lactating Holstein-Friesian cows during the first four postpartum estrous cycles. Cows with abnormal uterine enlargement and malodorous lochia were classified as having metritis (group M, n = 18), and all others were considered healthy (group H, n = 29). Luteal size was measured once between days 9 and 13 of the first (group H, n = 11; group M, n = 12), second (group H, n = 23; group M, n = 18) and fourth (group H, n = 11; group M, n = 7) postpartum luteal phases. Serum progesterone concentration was measured at the same time. Sixteen cows (group H, n = 9; group M, n = 7) underwent transvaginal luteal biopsy for gene expression analysis of steroidogenic regulatory proteins during the second and fourth cycles. Cows with persistence of the corpus luteum (CL) underwent determination of luteal size, luteal biopsy and serum progesterone measurement once between days 29 and 33, followed by prostaglandin treatment to induce luteolysis. The same procedures were repeated once between days 9 and 13 of the induced cycle.ResultsThe cows in group M had smaller first-cycle CLs than the cows in group H (p = 0.04), but progesterone concentrations did not differ between groups. Luteal size, progesterone concentration and gene expression did not differ between the two groups during the second and fourth cycles. Compared with healthy cows (10%), there was a trend (p = 0.07) toward a higher prevalence of persistent CLs in cows with metritis (33%). Persistent CLs were limited to the first cycle. Persistent CLs and the induced cyclic CLs did not differ with regard to the variables investigated.ConclusionsAn effect of metritis on luteal activity was apparent in the first postpartum estrous cycle. However, after the first postpartum cycle, no differences occurred in analyzed parameters between metritis and control cows. Therefore, a metritis is able to impair luteal activity transiently, but does not seem to have a long-term effect on luteal function.

Efeito da frequência de amamentação sobre a taxa de ovulação após tratamento com desmame temporário + GnRH, sobre a incidência de luteólise prematura no primeiro ciclo estral pós-parto e sobre o desempenho da progênie de vacas Nelore

Avaliou-se o efeito da restrição na frequência de amamentação sobre o diâmetro folicular no dia 0 (DFOL), sobre a taxa de ovulação (TO), e sobre a incidência de luteólise prematura no primeiro ciclo estral pós-parto (ILP) de vacas Nelore multíparas, em anestro, submetidas à amamentação ad libitum (controle; n= 115) ou amamentação uma vez ao dia (restrito; n= 109), entre os dias -14 e 9 do experimento, e estudou-se o efeito desses tratamentos sobre o peso à desmama da progênie dessas vacas. Induziu-se ovulação com remoção de bezerros entre os dias -2 e 0 e aplicação de 100μg de GnRH no dia 0. Somente animais que ovularam foram mantidos no experimento (n= 125). A ocorrência de luteólise prematura foi avaliada por meio da dosagem da concentração sérica de progesterona nos dias 5 e 9. A TO não foi influenciada pelos tratamentos (55,8%; P&gt;0,1), e as vacas do tratamento restrito apresentaram maior DFOL (10,90±0,26 vs. 10,18±0,21mm; P&lt;0,05) e menor ILP (21,4% vs. 43,5%; P&lt;0,05). Os bezerros do tratamento controle foram mais pesados (162,32±2,08 vs. 155,91±4,12kg; P&lt;0,05). Conclui-se que a restrição na frequência de amamentação em vacas Nelore reduz a ILP, porém com possível efeito negativo no desenvolvimento dos bezerros.

Nutrition, Metabolism, and Fertility in Dairy Cows: 1. Dietary Energy Source and Ovarian Function

In previous studies, high plasma insulin was associated with earlier resumption of postpartum estrous cycles in dairy cows. The objective of this experiment was to quantify hormonal and ovarian responses to dietary starch and fat contents. Thirty cows were fed on a standard diet from calving until 40 d in milk (DIM) and then 6 cows were allocated to each of 5 isoenergetic diets containing 231, 183, 159, 135, and 87g of starch and 39, 42, 43, 45, and 48g of fat/kg of dry matter (DM) for diets 1 to 5, respectively, until 70 DIM. Estrus was synchronized at 60 DIM. Between 60 and 70 DIM, energy intake, milk yield, and energy balance were similar among diet groups. Plasma insulin-to-glucagon ratio increased with increasing dietary starch and decreasing dietary fat concentrations, reaching a break point at 159g of starch, 43g of fat/kg of DM (diets 1 to 5: mean 3.86, 3.78, 3.59, 2.98, 2.06±standard error 0.22). Growth hormone, insulin-like growth factor-I, and leptin did not vary among diets. The greatest dietary starch concentration was associated with elevated plasma urea-N (diets 1 to 5: mean 3.69, 3.01, 2.94, 2.95, 2.75,±standard error 0.13mmol/L, respectively) and delayed postovulatory progesterone increase (progesterone at 3 to 5 d postovulation for diets 1 to 5: mean 2.7, 5.9, 4.2, 5.6, 4.3±standard error 0.9ng/mL, respectively). The number of small (<5mm) ovarian follicles was positively related to starch intake (r=0.381) and plasma insulin concentration (r=0.402). It is concluded that to maintain adequate insulin-to-glucagon ratio in cows at the start of the breeding period, dietary starch concentration should be above 160g/kg of DM and dietary fat below 44g/kg of DM, and this should have a positive effect on ovarian function.

Risk factors for resumption of postpartum estrous cycles and embryonic survival in lactating dairy cows

The objectives of this study were to evaluate factors associated with resumption of postpartum estrous cycles and embryonic survival in lactating dairy cows. Holstein cows, 6396 from four dairy farms were evaluated to determine the relationships among parity, body condition score (BCS) at calving and at AI, season of year when cows calved, and milk yield on resumption of postpartum estrous cycles by 65 days postpartum, and all the previous variables, estrual or anestrus and AI protocol on conception rates and embryonic survival at the first postpartum insemination. Cows had their estrous cycle pre-synchronized with two PGF 2α injections given 14 days apart and were inseminated between 69 and 82 days postpartum following either an estrous or ovulation synchronization protocol initiated 12–14 days after the presynchronization. Blood was sampled and analyzed for progesterone twice, 12–14 days apart, to determine whether cows had initiated onset of estrous cycles after calving. Cows were scored for body condition in the week after calving, and again at AI, between 69 and 82 days postpartum. Pregnancy was diagnosed at 30 ± 3 and 58 ± 3 days after AI. Farm influenced all reproductive outcomes evaluated. More ( P < 0.0001) multiparous than primiparous cows had initiated estrous cycles. Onset of estrous cycles was also influenced ( P < 0.01) by BCS at calving and at AI, BCS change, season, and milk yield. More ( P < 0.001) cows that had initiated estrous cycles than anestrous cows were pregnant at 30 and 58 days after AI, but anestrus did not affect pregnancy loss. Conception rates were also influenced ( P < 0.01) by parity, BCS at calving and AI, BCS change, and season; however, milk yield and insemination protocol were not associated with conception rates at 30 and 58 days after AI. Factors that reduced conception rate on day 30 after AI also increased pregnancy loss between 30 and 58 days of gestation. Improving BCS at calving and AI, minimizing losses of BCS after calving, and hastening onset of estrous cycles early postpartum are all expected to increase conception because of enhanced embryonic survival.

Nutrition, synchronization, and management of beef embryo transfer recipients

A commercially viable cattle embryo transfer industry was established during the early 1970s. Initially, techniques for transferring cattle embryos were exclusively surgical. However, by the early 1980s, most embryos were transferred nonsurgically. For an embryo transfer program to be effective, numerous factors need to be in place to ensure success. Nutrition, estrous cycle control, and recipient management are all responsible for the success or failure in fertility for a given herd. Utilization of body condition scores is a practical method to determine nutritional status of the recipient herd. Prepartum nutrition is critical to ensure that cows calve in adequate body condition to reinitiate postpartum estrous cycles early enough to respond to synchronization protocols. Estrus synchronization for embryo transfer after detected estrus or for fixed-time embryo transfer without estrus detection are effective methods to increase the number of calves produced by embryo transfer. In addition, resynchronization of nonpregnant recipients effectively ensures that a high percentage of recipients will return to estrus during a 72 h interval and are eligible for subsequent embryo transfers. Numerous additional factors need to be assessed to ensure that the recipient herd achieves its reproductive potential. These factors include assessing the merits of nulliparous, primiparous, or multiparous cows, ensuring that facilities allow for minimal stress, and that the herd health program is well-defined and followed. Numerous short- and long-term factors contribute to recipients conceiving to a transferred embryo, maintaining the embryo/fetus to term, delivering the calf without assistance and raising and weaning a healthy calf.

Postpartum Reproductive Management Based on the Routine Farm Records of a Dairy Herd: Relationship between the Metabolic Parameters and Postpartum Ovarian Activity

The aim of this study was 1) to confirm the practical efficiency of a routine milk P4 monitoring system for postpartum reproductive management of a dairy herd, and 2) to evaluate the relationship between the blood metabolic profiles, milk quality and body weight of individual cows in the farm records, which may reflect the postpartum nutritional condition, and the time of postpartum resumption of ovarian activity of dairy cows. A total of 116 Holstein cows was used in the present study. First, during the period of Experiment 1, postpartum reproductive management based on weekly measured milk P4 concentration from individual cows was conducted. Compared with the reproductive records of the past two years without P4 monitoring, although the day from calving to first AI did not change, both the number of AI until pregnant (with P4; 1.9 times vs. without P4; 2.9 times) and the days open (with P4; 95.1 days vs. without P4; 135.8 days and 133.8 days) were significantly decreased. In Experiment 2, the measurement of blood constituents such as albumin, blood urea nitrogen, packed cell volume, ammonia, glucose, total cholesterol, non-esterified, AST and γ-GTP was performed on the blood samples taken once approximately 14 days postpartum, to monitor both health and nutritional conditions. The milk constituent parameters, such as milk protein (MP), milk fat (MF), SNF and lactose, collected from the monthly progeny test of individual cows, were used to monitor the postpartum nutritional status. Furthermore, the data obtained from the routine measurements of body weight were used to calculate the rate of peripartum body weight loss. The resumption day of the postpartum estrous cycle was assumed from the milk P4 profiles of individual cows. There was no clear relationship between each parameter from blood examination and those from resumption time. However, the cows had low values of MP, and SNF, which significantly affected the resumption of the postpartum estrous cycle. Similarly, a higher rate of body weight loss indicated a significant delay (more than 1 month) in the resumption of the postpartum estrous cycle, compared with the groups that had a medium or lower rate of body weight loss. The results of the present study demonstrated that the implementation of routine milk P4 monitoring-based postpartum reproductive management, together with milk quality parameters and routine BW data available in field conditions may be utilized as a practical approach for increasing the postpartum reproductive efficiency of a high yielding dairy herd. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 6 : 787-

Influence of plasma estradiol 17-β and progesterone levels on estrous behaviour in mithun ( Bos frontalis)

The study was conducted on 10-adult mithun ( Bos frontalis) cows during the third or fourth postpartum estrous cycle to investigate the influence of plasma estradiol 17-β (E2) and progesterone (P4) levels on the expression of behavioural estrus. The estrus was detected in the mithun cows by bull parading and the patterns of behavioural estrus were recorded. The estrous intensity score (EIS) was assigned according to the visible signs in cows and bull activities. The daily blood samples throughout the estrous cycle were collected by jugular venipuncture and were analysed for E2 and P4 through ELISA. The variations in E2 and P4 concentrations were analysed by repeated measurement ANOVA. The model included the day of estrous cycle and EIS as source of variation. The association of EIS with E2 and P4 was established by the partial correlation analysis. The average estrous cycle length was found 21.3 ± 0.4 days. The average duration ( h) of estrus and standing heat were recorded 67.2 ± 7.2 and 10.5 ± 2.7, respectively. The expression of behavioural estrus was found silent. In the entire estrous cycle, two prominent E2 peaks were observed approximately on day 1 and 17. The peak E2 concentration on day 17 was found significantly ( p < 0.01) higher than the peak E2 concentration on day 1. The P4 concentration was found to be lowest ( p < 0.01) on the day of estrus. The P4 concentration was increased gradually from day 1 to 6 of the cycle. The P4 concentration was increased sharply and from day 7, attained peak concentration on day 11 and decreased thereafter. The EIS was found to be associated more closely with the basal concentrations of E2 and P4, and with the E2:P4 ratio of the cycle. The study revealed that the P4 concentration was instrumental in relation to the E2 concentration for the behavioural expression of estrus in this species. The low expression of behavioural estrus was probably due to the overall low P4 concentration during the entire estrous cycle.

Endocrine control of estrous cycle in mithun ( Bos frontalis)

The objective of the present study was to establish the profiles of luteinising hormone (LH), follicle stimulating hormone (FSH), estradiol 17β (E2) and progesterone (P4) secretion and their interrelationships during the natural estrous cycle of mithun ( Bos frontalis). Daily blood samples were collected from second or third postpartum estrous cycles for determination of plasma concentrations of LH, FSH, E2 and P4. Concentration of P4 was found to be lowest on the day of estrus. It increased following estrus, attained the highest concentration on day 11 and decreased thereafter. Concentrations of LH and FSH varied significantly ( p < 0.01) during the first and last 6 days of the cycle and their variations were found to be synchronised. Both LH and FSH attained a biphasic peak during the estrous cycle. This biphasic peak lasted on from day −5 to day 3 of the cycle. The variations in maximum LH and FSH concentrations of both the phases did not differ significantly. During the entire estrous cycle, the E2 concentrations attained either one peak or two peaks. The first peak, approximately on day 4 before estrus was common in all animals. One additional peak was found on the day of estrus in 45% animals. A significant ( p < 0.01) negative relationship was found between P4 and, LH and FSH during the first and last 6 days of cycle. But a significant ( p ≤ 0.01) negative relationship between E2 and, LH and FSH was found only during the last 6 days of cycle. The results suggest a negative feedback mechanism on LH and FSH release by E2 and P4 during the respective phases of cycle. A sustained increase in LH and FSH levels during the period before estrus was probably necessary for the final maturation of ovulatory follicle and subsequent ovulation.

Effect of biostimulation on uterine involution, early ovarian activity and first postpartum estrous cycle in beef cows

The objective was to determine the effect of biostimulation (bull-exposure) on uterine involution (UI), plasma progesterone concentration (P 4), size of largest follicle (LF), number of follicles larger than 5 mm ( F≥5), presence of fluid in uterine lumen (PF), presence of luteal tissue (LT), and length of the first estrous cycle postpartum (LEC). Ninety Angus cows with calves were allocated by parity and body frame into three groups (30 per group) 1 week postpartum. Two groups were exposed to bulls (BE) and one non-exposed group (NE) served as a control. Data were collected during weekly sessions of palpation per rectum, ultrasonography and bleeding on a subgroup of 30 cows (10 cows per group) for 6 weeks, and permanent surveillance of estrus with HeatWatch ® on all 90 cows. There were no significant differences between BE and NE cows for UI (17.1±1.1 days versus 20.1±1.6 days), LF (9.5±1.7 mm versus 11.0±2.4 mm), F≥5 (1.20±0.3 versus 1.47±0.09), and PF. However, LT was detected in more BE than NE cows (13 versus 2; P<0.001). Overall differences in P 4 were found between BE and NE cows with detected LT (2.00±0.3 ng/ml versus 1.05±0.4 ng/ml, respectively; P<0.05). More BE cows resumed reproductive cyclicity with estrous cycles normal in length compared with NE cows (16/30, 53%; 16/30, 53%; and 8/30, 26.6%, for the two BE groups and the NE group, respectively; P<0.01). In conclusion, BE hastened luteal function but did not affect uterine involution.

Follicular dynamics during postpartum anestrus and the first estrous cycle in suckled or non-suckled Brahman ( Bos indicus) cows

Brahman ( Bos indicus) cows, were selected at 28±10 days after calving and analyzed by real time rectal ultrasonography three times a week, in order to evaluate and compare follicular and corpus luteum development during postpartum (PP) anestrus and the first PP estrous cycle under sylvopastoril conditions. Suckling (S, n=11) or non-suckling (NS, n=5) cows were evaluated in a zone of tropical dry forest (450 m of altitude, mean temperature=27°C, annual rainfall=1000 mm). Estrous detection was performed twice daily by direct observation. Progesterone was quantified using RIA. From 28±10 days postcalving to resumption of estrous cycles, there were no differences ( P>0.05) between NS and S cows for diameter of the dominant or first subordinate follicle, follicular growth rate, or interdominance interval. Silent ovulation, corpus luteum formation and subsequent progesterone concentrations ranging from 0.3 to 9.7 ng/ml, were found in both groups. The first calving to ovulation and calving to standing estrus intervals were shorter ( P<0.01) in NS (34.8±5.81 and 41.2±9.03 days) than in S (65±4.82 and 81±6.21 days) cows. Follicular development and progesterone concentrations during the first PP estrous cycle did not differ ( P>0.05) between NS and S cows. These results suggest that Brahman cows could have an early PP resumption of follicular recruitment if fed under sylvopastoril system conditions. However, non-suckled cows did have an earlier standing estrus and ovulation than did suckled cows.

Dinâmica folicular ovariana de vacas leiteiras no pós-parto após tratamentos com buserelina (GnRH) e cloprostenol (PGF2alfa)

O objetivo deste trabalho foi verificar os efeitos da administração de 10 mig de buserelina (GnRH), mediante a presença de um folículo ovariano com diâmetro ³ 10 mm, associada a uma dose de 500 mig de cloprostenol seis dias após, ou de duas doses de 500 mig de cloprostenol (PGF2alfa) no 12º 26º dia após o parto, sobre a dinâmica folicular e o restabelecimento da atividade ovariana cíclica em 15 vacas mestiças holandês-zebu, eqüitativamente e aleatoriamente distribuídas em três grupos de tratamento. Realizou-se a ultra-sonografia em dias alternados do 14º ao 26º dia pós-parto e em dias consecutivos até o final do segundo ciclo estral e coletaram-se amostras de sangue, duas vezes por semana, para determinação das concentrações de progesterona, pelo método de radioimunoensaio. Observou-se que, independente do tratamento hormonal, os segundos ciclos estrais pós-parto apresentam como padrão duas ondas de crescimento folicular, em que a emergência da primeira e da segunda onda ocorreu nos dias 0 e 10, respectivamente, e folículos dominantes da primeira onda podem persistir durante todo o intervalo inter-ovulatório, sem influenciar a dinâmica folicular. O tratamento com duas doses de PGF2a reduziu em 20 dias o período de serviço e tendeu a melhorar o índice de concepção ao primeiro serviço, o que sugere possível efeito deste hormônio no eixo hipotalâmico-hipofisário-ovariano de vacas pós-parto.

Effects of Grain Processing and Bovine Somatotropin on Metabolism and Ovarian Activity of Dairy Cows During Early Lactation

This study compared the effects of exogenous bovine somatotropin (bST) on the metabolism and ovarian activity of cows fed diets differing in ruminally degradable starch. Twenty-four multiparous and eight primiparous Holstein cows in early lactation were divided into four groups and fed diets containing 39% grain as steam-flaked sorghum or steam-rolled corn with or without bST for 90 d in a 2 x 2 factorial design. Flaked sorghum improved energy status of cows during early lactation, tending to increase plasma glucose and insulin. Administration of bST decreased plasma urea nitrogen and increased nonesterified fatty acids (NEFA). Plasma levels of β-hydroxybutyrate (BHBA) and hepatic concentrations of triglycerides were not altered by treatments. Temporal changes in plasma glucose, urea nitrogen, NEFA, and BHBA were detected in a quadratic manner and insulin increased linearly with time, but treatments did not affect postpartum changes in these metabolites. There were greater decreases in body weight and net energy balance in cows on bST during the first 7 wk of treatment. Cows receiving bST took longer to reach the nadir of negative energy balance, and bST tended to delay the period to reach a positive energy balance. Follicular populations and incidence of cystic ovaries were not affected by treatments, but cows receiving bST had fewer double ovulations. Flaked sorghum increased plasma progesterone during the early luteal phase of the first two postpartum estrous cycles. Feeding more ruminally degradable starch improved the energy status and luteal activity of cows in early lactation.