Silent Ovulation Research Articles

Unlocking the Secrets of Pheromones: Reproductive and Social Communication in Domestic Mammals

Pheromones play a pivotal role in the reproductive and behavioural management of livestock, influencing various physiological and behavioural responses within and across species. This review explores the application of pheromones in cattle, buffalo, sheep, goats, pigs, and equines, highlighting their significant impact on reproductive efficiency, stress reduction, and animal welfare. In cattle, pheromones are essential for estrus detection and the enhancement of maternal bonding. Similarly, in buffaloes, urinary pheromones have been identified as markers for estrus detection, aiding in overcoming the challenge of silent ovulation, while also contributing to penis erection and sperm quantity enhancement. In small ruminants such as sheep and goats, the "male effect" accelerates puberty and synchronizes estrus, which is crucial for optimizing breeding cycles. In pigs, the presence of boars accelerates puberty in gilts and reduces postpartum anestrus in sows, enhancing reproductive outcomes. Equines benefit from appeasing pheromones, which alleviate stress in foals and adult horses, particularly during transportation and other stressful events. The synthesis and application of synthetic analogs of these pheromones have demonstrated practical benefits in animal husbandry, offering promising avenues for improving reproductive performance and animal welfare. However, despite these advancements, the identification and characterization of specific pheromones across different species remain incomplete. Future research should focus on the molecular identification of these pheromones, their mechanisms of action, and the development of innovative applications to further enhance their utility in animal management.

Efficacy of an automated technology at detecting early postpartum estrus events: Can we detect resumption of cyclicity?

The objective of this observational study was to evaluate the efficacy of a neck-mounted automated activity monitor (AAM) at detecting early postpartum resumed ovarian cyclicity. A total of 192 lactating cows (primiparous = 73 and multiparous = 119) were enrolled in this study. Cows were continuously monitored by a neck-mounted AAM early postpartum (7 to 30 d in milk; DIM). Calving was classified as assisted (forced extraction of a calf) or unassisted (normal calving). Retained fetal membrane, metritis, hyperketonemia, clinical mastitis, and milk production were recorded. Cows were classified as healthy (i.e., no disease events) or sick (i.e., any disease event). Estrus events were alerted by the AAM using a proprietary algorithm set by the AAM company. Blood samples, from the coccygeal vein, were collected at 15, 18, 21, 24, 28, and 30 DIM for progesterone (P4) analysis. Resumption of cyclicity was considered when P4 concentration was ≥1 ng/mL on any collection day. Cows were considered anovular when P4 concentration was <1 ng/mL on all collection days. Cows were classified as true positive: P4 ≥ 1 ng/mL and at least one estrus alert; false positive: P4 < 1 ng/mL and at least one estrus alert; true negative: P4 < 1 ng/mL and no estrus alerts; and false negative: P4 ≥ 1 ng/mL and no estrus alerts. Statistical analyses were performed by frequency distribution and mixed effects logistic regression procedures on SAS (SAS Institute Inc.). The specificity, sensitivity, accuracy, and positive predictive value of the sensor to detect cows that had resumed cyclicity were 84.0%, 34.1%, 52.1%, and 79.2%, respectively. Out of the 192 cows, 35.9% (69/192) were anovulatory and 37.5% (72/192) had no estrus events between 7 to 30 DIM. Healthy cows were more likely to resume cyclicity in early lactation compared with cows that were sick (78.3 ± 1.9 vs. 32.8 ± 3.1%, respectively) independent of parity. In conclusion, the sensor had a high specificity for detecting anovular cows, but it had lower sensitivity, and thus was not effective at detecting cyclic cows, perhaps due to silent ovulation early postpartum.

Gene expression in the amygdala and hippocampus of cyclic and acyclic gilts.

Age at first estrus is the earliest phenotypic indicator of future reproductive success of gilts. Prebreeding anestrus is a major reason for reproductive failure leading to culling of replacement gilts. The two types of prebreeding anestrus are delay in attaining puberty (prepubertal anestrus, PPA) and silent ovulation (behavioral anestrus, BA). Neural tissues such as amygdala and hippocampus play a major role in regulating sexual behavior, social interactions, and receptivity to males. Differences in gene expression in the amygdala and hippocampus of gilts were analyzed in three comparisons: 1) PPA cases and cyclic controls at follicular phase of estrous cycle, 2) BA cases and cyclic controls at luteal phase of estrous cycle, and 3) gilts at different stages of the ovarian cycle (cyclic gilts at follicular phase and luteal phase of estrous cycle) to gain functional understanding of how these rarely studied tissues may differ between pubertal phenotypes and different stages of the estrous cycle of gilts. Differentially expressed genes (DEG) between PPA and BA cases and their respective cyclic controls were involved in neurological and behavioral disorders as well as nervous system functions that could directly or indirectly involved in development of behaviors related to estrus. The comparison between cyclic follicular and luteal phase control gilts identified the greatest number of DEG in the hippocampus and amygdala. These DEG were involved in adult neurogenesis and neural synapse (e.g., GABAergic, dopamine, cholinergic), suggesting that these tissues undergo structural changes and synaptic plasticity in gilts. This is the first report to demonstrate that the stage of estrous cycle is associated with dynamic changes in gene expression within porcine hippocampus and amygdala and indicates a role of gonadal steroids in regulating their biology.

Estrus Detection Methods in Dairy Animals- Advances and the Prospects: A Review

Fertility over the past few decades is of serious concern in the dairy industry. Fertility of a dairy herd is determined by composite factors, which in turn depends upon effective management strategies. The reproductive potential of the animals need to be exploited to its maximum to achieve optimum production in a herd. The single most important factor that limits the establishment of pregnancy and survival of the embryo in dairy cattle and buffaloes and thereby reproductive efficiency of a herd is proper estrus detection, Pedometer or activity meter is a motion switches devices within which steps followed by animals are recorded. Activity meters can be attached to the neck or leg of cows and they may be read by a receiver and processed by computer in a milking parlour. By implementing automatic detection system, heat detection rates can be improved, for improving reproductive efficiency. The activity monitoring techniques can also be used to detect the silent ovulation which is helpful for improving efficiency and accuracy of estrus.

Ovarian Follicular Dynamics, and Hormonal and Biochemical Profile in Post-Pubertal and Postpartum Jaffrabadi Buffaloes

Jaffrabadi buffalo is one of the heaviest buffalo breeds of the world (800 kg) and is known for poor reproductive efficiency. There is a scarcity of normal physiological data regarding reproductive parameters of Jaffrabadi buffalo. The primary objective of this study was to elucidate ovarian follicular dynamics, hormonal and biochemical profiles in 10 post-pubertal heifers (n=5 each of age 42±2 and 48±2 months) and five &gt;90 days postpartum lactating buffaloes. Ultrasound monitoring of ovaries of animals was done at weekly interval and all follicles with diameter less than 4 mm (small follicles), 4-8 mm (medium follicles) and greater than 8 mm (large follicles) as well as CLs identified were recorded. Blood samples were also collected soon after each USG from all animals for assay of hormonal and biochemical profiles. The findings revealed that the average number of small, medium and large follicles, total number of follicles per ovary as well as diameters of largest and subordinate follicles varied greatly among periods between three groups. The size of corpus luteum ranged from 13.7 to 21.2 mm, 13.7 to 23.9 mm and 15.3 to 22.7 mm, respectively, in Group-I, II and III. In the first week of study, significantly higher (p less than 0.05) average numbers of small follicles in Group-I and III, and medium follicles and total numbers of follicles in Group-III were observed as compared to other groups. The diameter of largest follicles and subordinate follicles were non-significantly different among all groups at all periods of the study. Plasma estrogen levels were significantly higher (p less than 0.05) in Group-I as compared to Group-III and Group-II on first and second week, however, it increased significantly (p less than 0.05) in Group-II and I on fourth week of study period. Plasma insulin concentrations were significantly (p less than 0.01) lower in buffaloes (Group-III) than in heifers (Group-I and II) throughout the study period, while plasma total cholesterol and total protein levels were higher in Group-III on 3rd to 5th weeks of study. Further, there were no significant differences in the plasma FSH, LH, progesterone and blood glucose levels in animals of three groups between periods at any of the week. The ultrasonographic and endocrine profile suggested establishment of cyclicity with silent ovulation. However, the behavioural estrus was still not manifested by these post-pubertal heifers and postpartum lactating buffaloes. These results are helpful to diagnose anovulatory conditions and/or true anestrus and initiate estrus synchronization protocols for early conception in Jaffrabadi buffaloes.

Body Weight and Blood Biochemical Changes Following Nutritional Supplementation in Prepubertal Jaffrabadi Buffalo (Bubalus bubalis) Heifers

The high plan of nutrition right from an early age is believed to enhance ovarian activity and early onset of puberty in heifers. This study was therefore conducted to know the body weight, ovarian and blood biochemical changes in nutritionally supplemented and control groups of prepubertal Jaffrabadi buffalo (Bubalus bubalis) heifers. A total of 12 animals of 30 ± 2 month's age and the identical body weight of 380–410 kg from Cattle Breeding Farm, JAU, Junagadh were utilized for this study. They were randomly divided into two equal groups of 6 animals in each treatment and control groups. The heifers of the treatment group were supplemented with bypass fat (100 g), bypass protein (950 g) and chelated mineral mixture (50 g) over the routine farm feeding practices of control group, and its effect on body weight gain and blood biochemical profiles were studied at a monthly interval during 6 months of experimental period. The overall effect of nutritional supplementation on animals body weight, blood glucose and total cholesterol over the control group was statistically non-significant (p greator than 0.05) yet beneficial. The plasma total protein levels in the supplemented group increased with a duration of supplement and levels were significantly (p less than 0.05) higher over the control group. The ovarian dynamics evaluated by transrectal ultrasound during last three months of the study revealed an increasing number of growing follicles greator than 4 mm in diameters (5.00 ± 0.13 to 6.67 ± 0.40), without significant variation in diameters of largest follicles (9.14 ± 0.45 to 10.27 ± 0.85 mm) between groups or periods. However, none of the heifers exhibited behavioral signs of estrus during 6 months study, in spite of the establishment of cyclicity with the presence of developed follicles, or CLs suggesting silent ovulation, at 36 ± 2 months of age in this breed.

Resumption of cyclic ovarian activity in postpartum ewes: a review

The reproduction rate is considered a crucial factor that affects the ability of producers to meet the growing demand for ovines meat, and optimizing this factor will maximize the production rate and increase the efficiency of livestock. A reduction in the length of the postpartum anestrus period results in a shorter interval between lambing and conception and enables more lambs to be produced throughout the life of a ewe. This review discusses the current knowledge of several factors associated with the resumption of cyclic ovarian function in postpartum ewes and how the suckling management of ewes may affect this process. Factors that influence the resumption of cyclic ovarian activity include uterine involution, follicular development, occurrence of silent ovulation and short estrous cycles, breed, reproductive seasonality, nutrition and lactation. Controlled suckling and early weaning are management practices that may be used to obtain three lambings in a 24-month period. In the majority of the studies the interval between lambing and first estrus was reduced when a controlled suckling management strategy was used, therefore the controlled suckling appears to be the best alternative because it has produced good results and is easy to implement. Currently, however, this practice is still not widely used.

Body condition loss and increased serum levels of nonesterified fatty acids enhance progesterone levels at estrus and reduce estrous activity and insemination rates in postpartum dairy cows

Data from 96 Holstein Friesian cows on a commercial dairy farm were used to investigate whether body condition and serum levels of nonesterified fatty acids (NEFAs) postpartum (pp) affect progesterone (P4) levels, estrous activity, and fertility in dairy cows. The examination period started 14 days before the expected calving date and ended either when a cow was inseminated or at a maximum of 90 days pp. Body condition score (BCS; 1–5 scale) and backfat thickness (BFT) were determined every 2 weeks. Blood for analysis of NEFA and P4 concentrations was sampled weekly during the first 35 days pp and then every 48 hours until an ovulation was observed. Transrectal ultrasonography of the ovaries started at 21 days pp and was performed after blood sampling. If cows were not inseminated because of silent ovulation, sampling and ultrasonography continued on Days 7, 14, and 18 after ovulation and again every 48 hours until the next ovulation. Estrous activity was continuously measured with the Heatime estrus detection system. Pregnancy controls were performed ultrasonographically 28 and 42 days after AI. Cows with increased NEFA levels at 28 days pp had an increased risk of maintaining minimum P4 levels above 0.4 ng/mL at first recognized estrus (P = 0.03). Higher NEFA levels at Day 7 were associated with lower probability for a cow to have elevated P4 levels (≥2 ng/mL) by Day 35 pp, indicating delayed commencement of luteal activity (C-LA). Estrous activity was not influenced (P > 0.10) by minimum P4 concentrations at estrus, but more animals with C-LA until Day 35 pp showed estrous activity compared to cows without C-LA throughout this period (P = 0.006). Estrous activity was lower in cows with a low BCS 14 days pp (P = 0.02) and with a low BFT 42 days pp (P = 0.03). Moreover, the probability to exhibit estrus was reduced with higher NEFA levels at 21 days pp (P = 0.01). Eighty-five cows were inseminated and 37 (44%) got pregnant after insemination. Higher NEFA levels, especially 14, 28, and 42 days pp, were associated with lower probability to inseminate a cow. Regarding the cows that were inseminated, no influence of BCS, BFT, or NEFA levels on pregnancy per artificial insemination was found. In conclusion, cows with higher loss of body condition and elevated NEFA concentrations had higher P4 concentrations during estrus, a reduced estrous activity and insemination rate, but no depression in pregnancy per artificial insemination.

A Three-day PGF&lt;sub&gt;2α&lt;/sub&gt; Plus eCG-based Fixed-time AI Protocol Improves Fertility Compared with Spontaneous Estrus in Dairy Cows with Silent Ovulation

This study was designed to test the treatment with prostaglandin F2α (PGF2α) plus equine chorionic gonadotrophin (eCG) and GnRH 48 h later (PEG protocol) followed by fixed-time AI (FTAI) in dairy cows with silent ovulation (cows with a mature corpus luteum and no signs of estrus detected in the preceding 21 days). In Experiment I, ovulation following the PEG protocol monitored in 24 cows with silent ovulation was recorded in 83% of the cows 36 h after GnRH treatment. In Experiment II, control cows were artificially inseminated during spontaneous estrus (4615 AI), while cows in the PEG group (1266 AI) were subjected to FTAI 24 h after GnRH treatment. Binary logistic regression revealed a significant effect of the interactions of treatment by season, by parity or by repeat breeding syndrome (>3 AI) on the conception rate. The conception rate was negatively affected by the warm season and age in controls but not in treated cows, whereas repeat breeder cows in the control and PEG groups were less (by a factor of 0.7) or more (by a factor of 1.5) likely to become pregnant, respectively, than the remaining animals. Moreover, the likelihood of twin pregnancy was lower in multiparous PEG (by a factor of 0.4) cows than in the remaining cows. This protocol, besides overcoming the negative effects of heat stress and age on the conception rate, increased fertility in repeat breeder cows compared with spontaneous estrus. Moreover, this treatment regimen reduced the twin pregnancy rate in multiparous cows.

Exposure to Estrogen Mimicking the Level of Late Pregnancy Suppresses Estrus Subsequently Induced by Estrogen at the Level of the Follicular Phase in Ovariectomized Shiba Goats

A high-estrogen environment during late pregnancy is suspected to cause postpartum silent ovulation, and progesterone (P4) is suggested to recover estrus. However, few attempts have been undertaken to elucidate the influence of these steroids on estrus by analyzing hormonal profiles. We investigated estrus and luteinizing hormone (LH) surges in ovariectomized goats (n=6) assigned to three treatments in a cross-over design. In groups 1 and 2, 200 µg/kg body weight/day estradiol benzoate (Dose-200 E2B) was administered for 14 days concurrent with P4 for 11 days, while in the control, saline solution and P4 were administered likewise. Ten days after the final administration of Dose-200 E2B, group 2 was treated with P4 for 8 days, and all groups were treated with 2 µg/kg body weight E2B (Dose-2 E2B) 20 days after the final administration of Dose-200 E2B (or saline solution). The proportion of cases expressing estrus after the administration of Dose-2 E2B was smaller (P<0.01) in group 1 than in the control (1/6, 3/6 and 6/6; groups 1 and 2 and the control, respectively). The proportions of cases generating LH surges did not differ (P>0.1) among the groups (5/6, 5/6 and 6/6; groups 1 and 2 and the control, respectively), but the peak concentrations in groups 1 and 2 (26.2 ± 14.7 and 11.3 ± 6.7 ng/ml) were lower (P<0.01) than those in the control (67.8 ± 19.4 ng/ml). These results demonstrated that elevation of plasma estrogen mimicking late pregnancy inhibits the subsequent estrus induced by estrogen simulating the follicular phase.

Relationship Between Postpartum Disorders And Pregnancy Losses and Subsequent Fertility of Dairy Cows

Abstract The aim of the study was to find the relationship between some postpartum disorders and pregnancy losses (PL), and the influence of PL on further fertility of Holstein-Friesian dairy cows. The 1,056 pregnancies and 906 calving intervals (CI) of 378 cows during the nine-year observation period were analysed. The average milk yield during this period increased from 7,500 to 10,500 kg/305 d of lactation. All cows up to 4 weeks after calving were gynecologically examined and cases of genital tract disorders were recorded and treated. Artificial inseminations (AI) were made using commercial frozen/thawed semen. In cows with silent ovulation, oestrus was induced by injection of PGF2α or programmes using PGF2α and GnRH, or hCG were applied. Pregnancy was diagnosed with the use of ultrasonography or foetal membrane slip only from 30 and 42 d after service, respectively, and re-diagnosed between 70 and 90 d after AI. The cases of „early foetal loss” up to 90 d and „mid-to-late PL” between 91 and 260 d after AI were recorded. Endometritis was noted in 31.8%, ovarian cysts in 8.5%, whereas ovarian inactivity in 4.6% of cows. Early PL was observed in 5.2%, whereas mid-to-late PL in 6.8% of cows (total 12%). From all analysed factors, the influence of delayed or periodical lack of ovarian activity was significant with regard to early PL (P=0.029). The probability of early PL increased when besides the diagnosis of ovarian inactivity, AI was made following an induced oestrus (P=0.003). CI for cows, which did not lost pregnancy amounted 442.9 d. The early, mid-to-late and multiple PL extended the CI to 579.6, 661.1 and 657.7 d, respectively (P&lt;0.05). Concurrently, CI for cows with “early foetal loss” was significantly shorter comparing to cows with “mid-to-late foetal loss” (579.6 d vs.661.1 d; P&lt;0.05). On average 2.6 inseminations for one pregnancy were needed, and each PL increased the AI index. Significant differences were stated after early and multiple foetal losses (5.2 and 5.1 vs. 2.6; P&lt;0.05).

Resumption of ovarian cyclicity and fertility response in bull-exposed postpartum buffaloes

A study was undertaken to evaluate the effect of bull exposure on resumption of ovarian cyclicity and fertility response in postpartum buffaloes raised under standard farm conditions. A total of 24 Murrah buffaloes was randomly grouped to receive one of the following treatments: (1) exposure to a vasectomised bull from 40th to 90th day postpartum (bull-exposed, BE, n = 11) and (2) isolated from bull (non-exposed, NE, n = 13). Changes in the progesterone concentration were used to assess the resumption of ovarian cyclicity. Postpartum interval to resumption of ovarian cyclicity (47 ± 2.58 days vs. 56 ± 2.37 days, p < 0.05) as well as behavioral estrus (57 ± 3.61 days vs. 71 ± 5.13 days, p < 0.05) was shorter in bull-exposed animals than control animals. Similarly, animals in the BE group had significantly shorter interval to postpartum ovulation (48 ± 2.69 days vs. 57 ± 2.37 days, p < 0.05). Reduced incidence of silent ovulation was observed in BE group compared to NE group (18.18% vs. 50%). More than half proportion of animals in BE group conceived by 60 days postpartum compared to a very low proportion of animals in NE group (54% vs. 15%, p < 0.05). Furthermore, first service conception rate in BE animals was significantly greater than NE animals (100% vs. 37.50%, p < 0.05). In conclusion, continuous bull exposure to buffaloes during later postpartum period accelerates resumption of ovarian cyclicity, reduces incidence of silent ovulation and enhances first service conception rate. These results indicate that introduction of bulls to buffalo herd could be a rational management strategy for reducing the postpartum anestrus by enhancing reproductive function in buffaloes.

Silent ovulation, based on walking activity and milk progesterone concentrations, in Holstein cows housed in a free-stall barn

The objectives of the current study were to determine the incidence of silent ovulation (based on walking activity and milk progesterone profiles), identify risk factors for silent ovulation, and investigate its impact on reproductive performance in high-yielding dairy cows in free-stall housing. Overall, 277 lactations in 161 Holstein Friesian cows from a commercial dairy herd in northern Japan were studied. Walking activity (measured with pedometers) >80% above the mean for the preceding 2 d was defined as estrus, whereas day of ovulation was estimated using milk progesterone concentrations. Ovulation not preceded by increased walking activity was considered silent ovulation; the incidence was 55.2%, 23.8%, 21.3%, and 10.5% at the first, second, third, and fourth ovulations postpartum, respectively. Moderate and high milk yield significantly increased the risk of silent ovulation at second (odds ratio [OR] = 2.7 and 1.2; P = 0.04) and third and/or fourth ovulations (OR = 6.7 and 12.9; P = 0.03). Based on survival analysis, silent ovulations at the first, second, third, and/or fourth ovulations were associated with 28% (hazard ratio [HR] = 0.72), 55% (HR = 0.45), and 47% (HR = 0.53) reductions in pregnancy rate, respectively, and 41% (HR = 0.59), 66% (HR = 0.34), and 65% (HR = 0.35) reductions in artificial insemination (AI) submission rate. Cows with at least one silent ovulation (with the exception of the first ovulation) had a longer interval from calving to first AI (72 vs. 54 d, P < 0.001) and to achievement of pregnancy (133 vs. 80 d, P < 0.001). In conclusion, approximately one third of the ovulations (based on milk progesterone concentrations) in Holstein cows within 90 d postpartum were silent. Silent ovulations at the second to fourth ovulations were associated with high milk yields and at all ovulations were associated with impaired reproductive performance.

A Clinical Study of Anestrus Buffaloes in Southern Nepal

Anestrus is one of the most important reproductive disorders in dairy buffaloes. The clinical features of anestrus in buffaloes, however, have not been well described. The objectives of this study were to describe the causes of anestrus in buffaloes and their reproductive performance after treatment under field conditions in southern Nepal. Of 135 anestrus buffalo cows, 61.4% had true anestrus with ovarian dysfunction and 33.3% had silent ovulation. In 111 buffalo heifers, 76.6% were in true anestrus and 18.9% had silent ovulation. The duration of anestrus after calving was longer than 6 months in 83% of buffalo cows and 61.5% of the buffalo cows had durations longer than 10 months. The interval between the last breeding and diagnosis of anestrus was more than 5 months in 67.4% of cows and heifers. Treatment of anestrus with prostaglandin F(2)alpha in cows and heifers with a corpus luteum resulted in higher pregnancy rates within one (P<0.01) and two months (P<0.05) after treatment as compared with treatment with a vitamin/mineral mixture. Buffalo cows and heifers with inactive ovaries bearing a dominant follicle were also successfully treated with gonadotropin releasing hormone, resulting in higher pregnancy rate within one month after treatment (P<0.05). In conclusion, the predominant cause of anestrus in dairy buffaloes in this region was true anestrus with inactive ovaries, and the duration of anestrus after calving as well as breeding was extremely long. Routine reproductive examination and adequate hormone treatment may improve the reproductive performance of these buffaloes.

Incidence of silent ovulation in a free-stall Holstein herd based on walking activity and milk progesterone profiles

Incidence of silent ovulation in a free-stall Holstein herd based on walking activity and milk progesterone profiles

Relationships between Milk Production, Ovarian Function and Fertility in High‐producing Dairy Herds in North‐eastern Spain

In the dairy industry worldwide, reproductive disorders are a major cause of economic losses and a challenge to scientists and technicians. In recent decades, declining fertility and increasing milk production have been widely reported in dairy cattle. In this article, the relationships between milk production, ovarian disorders and fertility in high-producing dairy herds are briefly described. We carried out a retrospective study of 23 204 lactations included in a reproductive control programme in north-eastern Spain, a geographical area experiencing both warm and cool conditions. The data were collected between 1991 and 2007 and refer to cows first inseminated or examined 45-80 days postpartum in five well-managed, commercial, Holstein-Friesian high-producing dairy herds. Ovarian disorders were classified as ovarian inactivity or hypofunction, cystic ovarian disease, sub-oestrus or silent ovulation and sub-luteal function. Ovarian hypofunction and milk production increased throughout the study period and there was a decrease in the pregnancy rate to first artificial insemination (AI). Cows suffering ovarian hypofunction were efficiently treated using combined progestagen-prostaglandin treatments. The incidence of ovarian cysts showed little variation with time. Treatment of this syndrome may include different GnRH-based treatments or manual rupture. During the last 5 years, sub-oestrus was the predominant dysfunction (42.1%) compared with the cystic (6.3%) and ovarian hypofunction (12%) forms. Response of sub-oestrous cows to treatment with luteolitic agents was usually higher than 60%. Ovarian function and fertility were dramatically impaired during the warm period. However, during the later years of the study, the inclusion of fans and water sprinklers for the warm season appeared to overcome the seasonal effect on fertility.

Factors affecting the response to the specific treatment of several forms of clinical anestrus in high producing dairy cows

This study was designed to examine estrous response rates to the therapeutic treatment of clinical anestrus in high producing dairy cows and to identify the factors that could affect these rates. Cows with silent ovulation (Subestrus group), cystic ovarian disease (Cyst group) or ovarian hypofunction (OH group) were given specific treatment for their disorder. Data were derived from 1764 treatments in cows producing a mean of 45.4 kg of milk upon treatment including: 889 subestrous cows, 367 cystic cows and 508 cows with ovarian hypofunction. Cows showing estrus following treatment exhibited a similar pregnancy rate to cows attaining natural estrus used as reference: 33% (337/1006) and 35% (626/1796), respectively. No significant differences in pregnancy rates were observed among the Subestrus, Cyst and OH groups (34% (196/571), 34% (44/130), 32% (97/305), respectively. Based on the odds ratio, an estrous response for all groups was less likely to occur in cows that had suffered previous anestrus, compared to cows that were anestrous for the first time, whereas the likelihood of an estrous response increased in cows treated after 90 days in milk. Our results indicate that previous anestrus and a late stage of lactation can have a negative and positive effect, respectively, on the estrous response to the specific treatment of clinical anestrus shown by high producing dairy cows. Treatment targeted at each type of clinical anestrus can render similar pregnancy rates to those shown by cows in natural estrus.

Annual characteristics of estrous activity in wool and hair ewe lambs under subtropical conditions

The increased emphasis placed on lamb production in Brazil points to the need for a better knowledge of the annual pattern of reproductive activity in ewe lambs. This study evaluates the annual estrous activity pattern of hair and wool ewe lambs raised in southeast Brazil. Estrous characteristics were recorded for 12 months in ten Santa Inês and 21 Romney Marsh and Suffolk ewe lambs. Santa Inês ewe lambs exhibited a greater length of the normal estrous cycle (14 to 19 days) than Romney Marsh and Suffolk ewe lambs (17.0 ± 0.1 days vs. 16.5 ± 0.2 and 15.9 ± 0.2 days). All the ewe lambs presented a greater number of periods of estrus per animal per month for single estrous cycles (up to 26 days) during autumn and winter. During spring and summer there was a reduction of this number but this decline varied according to the breed. For Santa Inês ewe lambs the reduction was only significant in the summer. For wool ewe lambs the reduction was significant in both seasons but was more accentuated for Romney Marsh. The Romney Marsh ewe lambs had a more restricted breeding season than Suffolk and both presented optimal estrus activity in autumn and winter. Santa Inês ewe lambs had a continuous distribution of estrous cycles along the year, although presenting a reduction in the number of estrous periods in the summer. The ewe lambs of three breeds presented characteristics of sexual immaturity, like irregular estrous cycles and silent ovulations.

Non-invasive assessment of reproductive status in Chinese water deer ( Hydropotes inermis): Correlation with sexual behaviour

The annual reproductive cycle of Chinese water deer ( Hydropotes inermis), a nearly threatened small cervid species, was studied by means of fecal steroid analysis coupled with behavioural observations. Data showed a clearly seasonal reproductive pattern. In adult males, the onset of androgen secretion, in October, was concomitant with the first manifestations of territoriality. Androgen metabolites concentrations reached significant peak values in December, when matings occurred. In mature females, there was a close synchrony in reproductive states: lactational/seasonal anoestrus from June to November, pregnancy from December to May. Fecal progesterone metabolites profiles suggested that silent ovulations occurred at the onset of breeding season and that females conceived at their first ovulation with behavioural estrus. The female sexual receptivity state might last only a few hours. High levels of sniffing, parades and pursuits, concomitant of the highest concentrations of androgen, could allow the males to detect the furtive estrus in the females present in their territory. We concluded that the non-invasive method applied for the first time in this species was useful for the evaluation of the endocrine status and its relation with behaviour.

The effect of melatonin treatment on the ovarian response of ewes to the ram effect

To determine the ovarian response to the ram effect after treatment with melatonin, on 8 March, 71 Rasa Aragonesa ewes were randomly assigned to either the treatment group and given an 18 mg melatonin implant or the untreated group. On 19 April (day 0), rams were introduced into the flock. Melatonin treatment produced a significantly higher percentage of cyclic ewes at ram introduction ( P < 0.05). Melatonin-treated ewes had their first oestrus after ram introduction significantly earlier than did untreated ewes ( P < 0.0001), and the groups differed in the distribution of their ovarian response. Most (80%) of the treated ewes exhibited a silent ovulation followed by a cycle of normal duration, whereas about half (52%) of the untreated ewes exhibited a silent ovulation, a short cycle, and another silent ovulation followed by a cycle of normal duration ( P < 0.05). At ram introduction, melatonin-treated ewes, cyclic and non-cyclic, had higher mean plasma progesterone concentrations than did untreated ewes. The proportion of ewes that mated within the first 17 days of the mating period was significantly higher among the treated ewes than in the untreated ewes ( P < 0.0001). Furthermore, at lambing, 39% of the melatonin-treated ewes lambed within the first 17 days of the lambing period, while none of the untreated ewes lambed in that period. The untreated group exhibited peaks in mating between days 18 and 21, and particularly, between days 22 and 25, when the majority of ewes lambed; peaks did not occur in the treatment group. Treated and untreated ewes did not differ significantly in fertility, litter size and fecundity. In conclusion, melatonin treatment modifies the ovarian response to the ram effect in ewes, which leads to modifications in mating patterns, and consequently, the lambing curve.