Factors in the resumption of ovarian activity and uterine involution in postpartum dairy cows

Risk factors for ultrasound-diagnosed endometritis and its impact on fertility in Scottish dairy cattle herds

BACKGROUND

The aim of this study was to investigate the risk factors for and the impact of ultrasound-diagnosed endometritis (UDE) on lactating dairy cows' reproductive performance.

METHODS

Data were analysed from 1123 Holstein and Holstein-Friesian cows from two Scottish dairy farms. A reproductive ultrasound examination was conducted on two occasions, at 43 ± 3 and 50 ± 3 days in milk (DIM), to screen for hyperechoic fluid in the uterus. Statistical analyses were performed using multivariable logistic regression modelling and Cox proportional hazards models.

RESULTS

The overall incidence of UDE was 8.8% (99/1123). Risk factors for UDE included calving during autumn/winter seasons, increased parity and the presence of two or more diseases in the first 50 ± 3 days postpartum. The presence of UDE was associated with a reduced odds of pregnancy after all artificial inseminations up to 150 DIM.

LIMITATIONS

The retrospective design of this study led to some inherent limitations with the quality and quantity of data collected.

CONCLUSIONS

The findings of this study indicate which risk factors should be monitored in postpartum dairy cows to limit the impact of UDE on future reproductive performance.

[Influence of an eCG administration on puerperal involution and fertility in Simmentaler cows]

SUBJECT AND AIM

In the literature, various methods aiming for a promotion of uterine involution and ovarian function in post-partum dairy cattle have been described. Recently, successful use of equine choriongonadotropin (eCG) in this context has been repeatedly reported, while other studies have failed to demonstrate positive effects of eCG administration on puerperal involution in cows. Due to the contradictory results described in the literature, the aim of this field study was to verify whether the administration of eCG on day 10 post-partum exerts a positive effect on uterine involution, ovarian activity and fertility indices in Simmental cows.

MATERIAL AND METHODS

In nine dairy farms, 205 Simmental cows were divided by lot into three groups: Group 1 animals received 500 I.U. eCG, group 2 received 50 µg gonadorelin, and group 3 animals received 250 mg butafosfan and 125 µg cyanocobalamin (control group). Treatment was administered on day 10 post-partum in each case. The animals were examined clinically and ultrasonographically on the 10th, 25th and 42nd day post-partum and the time to insemination and pregnancy were recorded. Group comparison with respect to the recorded parameters was initially performed without considering confounding factors by analysis of variance. In the second step, potential influencing variables (lactation, milk yield, change in backfat thickness, retentio secundarium and serverity of the obstetric intervention) were taken into account, as well as the combination of the random factors "farm" and "individual animal within the farm".

RESULTS

The administration of eCG exhibited no significant effect on uterine involution, however, the cervical involution was influenced significantly. In the group of cows with eCG treatment, ovarian cysts were detected significantly more frequently on day 25 post-partum (p=0.04). This difference did not persist on the 42nd day post-partum. Neither voluntary waiting period nor the days open were significantly shortened by eCG administration. Lactation number showed a significant effect on uterine involution. Heifers exhibited more rapid involution by day 42 post-partum than cows.

CONCLUSION

Administration of eCG in Simmentaler cows at day 10 post-partum showed no positive effect.

CLINICAL RELEVANCE

The use of eCG in early puerperium to promote fertility in the cow should be avoided.

Incidence, clinical patterns, and risk factors of postpartum uterine diseases in dairy cows from high-altitude tropical herds

The cow's uterus sustains bacterial contamination and active inflammation after calving as part of the normal physiological process of uterine involution. Although the definition, incidence, and risk factors for postpartum uterine diseases (PUD) have been documented in annual calving systems with high-producing cows on total mixed ration, the literature contains little information for other production systems. The objective of this study was to quantify the incidence risk and factors associated with metritis, clinical endometritis, and cytological endometritis in high-altitude tropical dairy herds in a pasture-based system. A total of 248 cows from 5 commercial dairy herds in northern Antioquia, Colombia, were enrolled in this prospective observational longitudinal cohort study. Data collection and PUD diagnosis were performed at d 0, 3, 10, 17, 24, 31, 38, 45, and 52 (±1) after parturition. Between 60 and 70 d, cows were systematically enrolled in a synchronization protocol, and herds were visited monthly for pregnancy diagnosis until 180 ±15 d. The multivariable logistic regression model of variables associated with PUD occurrence included (a) parity, season of calving, transition diet, and body condition score at calving; (b) blood calcium, phosphorus, and magnesium concentrations, and milk urea nitrogen, β-hydroxybutyrate and fat-to-protein ratio; and (c) dystocia, retained placenta, and delayed uterine involution. The incidences of puerperal metritis, clinical metritis (MET), clinical endometritis (CE), and cytological endometritis (CYTO) were 2.8, 25, 29, and 26%, respectively. Retained placenta and dystocia were associated with MET, and MET was associated with CE. Low blood calcium concentration at calving was associated with CYTO. Overall, 51.2% of the cows suffered at least 1 category of PUD during the first 60 d postpartum (DPP). However, cows also suffered from different consecutive clinical events of PUD (MET, CE, and CYTO) during the follow-up period (0 to 180 ±15 DPP). These events could be grouped into 4 types (which were referred to as "clinical patterns") based on interactions between MET, CE, and CYTO.

Postpartum Uterine Involution and Embryonic Development Pattern in Chinese Holstein Dairy Cows

Understanding the postpartum uterine involution pattern and embryonic development could facilitate bovine reproduction management, improve reproductive efficiency, and diagnosis of the reproductive disorder, which would contribute to the success of the dairy business. This study aimed to investigate postpartum uterine involution and embryonic developmental patterns or postconceptional marks of embryonic fetal development in Chinese Holstein dairy cows using B-mode ultrasonography. The results revealed a significant decline in the involution period with an increase of parity and age. The uterine involution period was shorter in multiparous cows when compared with cows with lower parities. Consistently, cows over 4 years old recovered faster than younger cows (2 or 3 years). Besides, the elder cows (over 4 years) had a relatively larger size of resumed cervix uteri and horns. Postpartum uterine involution pattern analysis revealed that the reproductive tract recovered very fast during the first 16 days postpartum for all the parity. Results of postconceptional marks of embryo development revealed a slow increase in diameter of the gravid uterine horn and crown-rump length (CRL) before day 60. In contrast, this increase was dramatic and rapid after the 60th day. We also established two models to estimate gestational age based on gravid uterine horn diameter or CRL. A formula was established to determine the gravid uterine horn size during postconceptional on day 30th–day 90th (r = 0.8714, P < 0.01). In addition, a significant positive correlation between CRL and gestational age (r = 0.98151, P < 0.01) was built. In conclusion, these results illustrated that parity and calving age had significant effects on uterine involution in Chinese Holstein cows. Crown-rump length and gravid uterine horn diameter are both efficient for evaluating the embryo growth. These current findings broaden the understanding of basic reproductive pattern in Chinese Holstein cows and could benefit bovine reproductive management primarily in postpartum and early pregnant cows to reduce the calving interval and avoid periparturient metabolic diseases.

Impact of endometritis on post-partum ovarian cyclicity in dairy cows

Endometritis in dairy cows is a major global issue and has been associated with a decrease in reproductive performance. The aim of this study was to quantify the effect of endometritis (as defined by the presence of any abnormal vaginal discharge after 21 days post-partum) on post-partum ovarian cyclicity in dairy cows. Milk progesterone analysis was used to monitor reproductive cyclicity in 170 dairy cows across three different commercial herds. Associations between the occurrence of endometritis and the incidence risk of a variety of atypical cycle profiles during the calving to conception period were investigated to establish the importance of endometritis on post-partum ovarian activity. Endometritis increased the incidence odds of atypical ovarian profiles (P < 0.05) with prolonged luteal activity being the most affected (P < 0.05), but also showed prolonged time (3 days) to onset of luteal activity after parturition (P < 0.05). Using milk progesterone analysis, we found a relatively low incidence odds for reproductive cycle problems in healthy cows during the calving to conception period. However, the incidence odds of cycle problems, in particular prolonged luteal activity, were high in cows that had experienced endometritis, which would have significantly impaired reproductive function.

Effect of equine chorionic gonadotropin administration on day 8 post-partum on ovarian follicular development, uterine health and uterine involution in lactating dairy cows

The objective was to evaluate the effect of equine chorionic gonadotropin (eCG) injection on day 8 postpartum on ovarian cyclicity, uterine health and uterine involution in lactating dairy cows. Lactating dairy cows [n = 34, (21 primiparous and 13 multiparous)] were enrolled in the study. Animals were stratified by calving date, parity and BCS, and randomly assigned to either control (CON n = 18) or eCG treatments (n = 16). On day 8 ± 0.9 post-partum (pp), eCG treatment cows received a 2 ml i.m. injection (500 IU) of eCG and control treatment cows received a 2 ml i.m. injection of 0.9% sodium chloride. Ovaries were examined by transrectal ultrasound every second day from day 10 pp until ovulation or regression of the first follicle wave, and the diameter of the dominant follicle was recorded at each exam. Ultrasound exams were conducted on days 21, 28, 35 and 42 pp to measure the diameter of the cervix and the uterine horns. Vaginal discharge score (VDS) was recorded on a 1 to 5 scale on days 14, 21, 28, 35 and 42 pp. Endometrial cytology samples were collected on day 42 pp, and the percentage of polymorphonuclear neutrophils (PMN) determined. Milk samples were collected three times per week from day 14 pp until day 60 pp for P4 determination. Ovarian follicular development variables, ovarian function variables analysed and incidence of subclinical endometritis were not affected by treatment. There was a treatment by parity interaction for pp interval to commencement of luteal activity (P = 0.04) and number of luteal phases (P = 0.05), whereby eCG treatment caused an earlier pp commencement of luteal activity and a greater number of luteal phases in multiparous cows, but not in primiparous cows. A significant effect of treatment on uterine involution was observed (previously gravid horn: P = 0.03; previously non-gravid horn: P = 0.01) and uterine health status (P = 0.03), whereby eCG cows had smaller mean horn uterine diameter and lesser VDS than CON cows. In summary, parenteral administration of 500 IU eCG on day 8 post-partum did not affect resumption of ovarian cyclicity in all cows but did enhance uterine involution and VDS. In multiparous cows, eCG advanced commencement of luteal activity and increased the number of luteal phases.

Cytological endometritis in dairy cows: diagnostic threshold, risk factors, and impact on reproductive performance

We determined the threshold proportion of polymorphonuclear leukocytes (PMNs) for a diagnosis of cytological endometritis (CEM), the risk factors for this condition, and its impact on reproductive performance in dairy cows. Uterine cytology was performed on 407 Holstein cows 4 weeks postpartum to determine the proportions of endometrial cells and PMNs. A receiver operator characteristics curve was used to determine the threshold above which the PMN proportion affected the likelihood of cows conceiving by 200 days postpartum. The optimal threshold was ≥ 14% PMN (sensitivity, 31.3%; specificity, 81.7%; p ＜ 0.05). The farm identity, retained placenta (odds ratio [OR] = 1.87), and septicemic metritis (OR = 3.07) were risk factors for CEM (p ＜ 0.05). Cows with CEM were less likely to resume cyclicity (OR = 0.58) and to conceive by 200 days postpartum (hazard ratio = 0.58). Cows with CEM tended (p ＜ 0.1) to be less likely to become pregnant after their first insemination (OR = 0.65) and to require a greater number of inseminations per conception (2.3 vs. 2.2). In conclusion, a PMN threshold of 14% defined the presence of CEM at 4 weeks postpartum. The farm, retained placenta, and septicemic metritis were risk factors for CEM, which reduces subsequent reproductive performance.

Effects of parity on productive, reproductive, metabolic and hormonal responses of Holstein cows

The objective of this study was to determine the effects that parity may have on production, reproduction and the metabolic status of Holstein cows managed in a production system based on total mixed ration and pasture. Primiparous (n = 22) and multiparous (n = 24) cows from a dairy farm research station in Uruguay were used in a completely randomized design. Body weight (BW), body condition score (BCS) and backfat thickness (BFT) were recorded weekly from -30 to 70 days postpartum. Milk production was measured daily, and milk composition was determined weekly. Resumption of postpartum ovarian activity and progesterone profiles were measured three times a week based on milk progesterone. Blood was collected to determine the levels of glucose, insulin-like growth factor I (IGF-1), insulin, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), albumin, total protein and cholesterol. Milk production and components were lower for primiparous cows (p < 0.01) than multiparous cows. Body weights were also lower in primiparous cows than in multiparous cows (p < 0.05); however, BCS and BFT were greater (p < 0.01) in primiparous cows than in multiparous cows. Primiparous cows had greater levels of glucose, insulin and IGF-1 and lower concentrations of NEFA and BHB (p < 0.01) than multiparous cows. The intervals from calving to first ovulation were not affected by parity; however, primiparous cows showed less abnormal cycles (27.2%) than multiparous cows (50.0%) (p < 0.01). The present study found that a feeding system based on TMR and pasture was sufficient to produce over 25 L of milk per day without extending their calving to first ovulation interval in primiparous and multiparous cows. However, multiparous cows showed a greater imbalance in metabolic and hormonal profiles than primiparous cows, causing abnormal ovarian activity.

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.

Factors associated with ovarian structures and intrauterine fluid in the postpartum period in dairy cows

The objective was to examine risk factors for the interval to resumption of ovarian cyclicity (ROC), multiple ovulations (MCL), ovarian follicular cysts (OC), and presence of intrauterine fluid (IUF) at 22 to 28 [visit (V) 1] and 36 to 42 (V2) days in milk (DIM) in dairy cows. The study was conducted retrospectively by evaluating records from 1,155 Holstein cows from 3 herds. Ovaries and uteri were examined at V1 and V2 by transrectal ultrasonography to determine ovarian structures and IUF. Based on the odds ratio, multiparous cows were more likely to have ROC at V1 by a factor of 1.79 compared with primiparous cows. The likelihood of ROC at V1 was lower in cows with higher milk production, in cows with retained fetal membranes (RFM) or cows with IUF at V1 by factors of 0.98 (for each kg of milk increased), 0.52, and 0.61, respectively. Based on the odds ratio, cows diagnosed with IUF at V2 were 2.85 times more likely to have attained ROC at V2. Multiparous cows and cows that delivered twins were 2.73 and 2.16 times, respectively, more likely to have MCL at V1, whereas cows with RFM were 0.38 times less likely to have MCL at V1. The likelihood of MCL at V2 was higher in cows with MCL and OC at V1 by factors of 2.67 and 1.91, respectively. Multiparous cows were 8.51 times more likely to have OC at V1 than primiparous cows. Higher producing cows were more likely to have OC at V2 by a factor of 1.04 compared with lower producing cows. Parity, stillbirth, RFM, and ROC at V1 were all identified as risk factors for IUF at V1. Cows with RFM and delivering twins were more likely to be diagnosed with IUF at V2 by a factor of 3.43 and 4.07, respectively. In summary, parity, twinning, RFM, metritis, IUF, and milk production were all associated with altered ovarian structures, and the presence of IUF was related to parity, twinning, RFM, and ROC in postpartum dairy cows.

Intravaginally administered lactic acid bacteria expedited uterine involution and modulated hormonal profiles of transition dairy cows

The objective of this investigation was to evaluate whether intravaginal infusion of lactic acid bacteria (LAB) around parturition could expedite involution rate of the uterus and improve reproductive performance of postpartum dairy cows. One hundred pregnant Holstein dairy cows were assigned to 1 of 3 experimental groups: (1) 1 dose of LAB in wk -2 and -1 and 1 dose of carrier in wk 1 relative to the expected day of parturition (TRT1); (2) 1 dose of LAB in wk -2, -1, and 1 (TRT2); and (3) 1 dose of carrier in wk -2, -1, and 1 (CTR). The LAB treatment was a lyophilized mixture of Lactobacillus sakei FUA3089, Pediococcus acidilactici FUA3138, and Pediococcus acidilactici FUA3140 with a cell count of 10(8) to 10(9) cfu/dose. Uterine involution and ovarian activity was evaluated by transrectal ultrasonography weekly from d 7 to 49 postpartum. Blood samples were collected from a subset of cows to quantify prostaglandin (PG) F2α metabolite (PGFM), PGE2, and progesterone. Cows treated with LAB had smaller cross-sectional areas of gravid horn and uterine body on d 14 postpartum. Cows in TRT2 resumed ovarian cyclicity earlier, as indicated by increased concentrations of serum progesterone. Cows in TRT1 had fewer days open than those in the CTR (110 vs. 150 d), whereas cows in TRT2 and CTR did not differ in days open. In addition, both TRT1 and TRT2 increased the concentrations of PGFM at calving week, and cows in TRT2 also had greater concentrations of PGE2 on d 14 and d 21 postpartum relative to CTR. Overall, cows treated intravaginally with LAB had smaller gravid horn and uterine body on d 14 postpartum than those in the CTR group. Treatment with LAB also increased concentrations of serum PGFM (3,533±328pg/mL in TRT1, 4,470±372pg/mL in TRT2, and 2,000±328pg/mL in CTR on d 0, respectively), with the TRT1 group having fewer cows that resumed ovarian cyclicity but fewer days open compared with both TRT2 and CTR groups. More research is warranted to better understand the mechanism(s) by which intravaginal LAB expedited uterine involution and affected hormonal profiles.

The effect of metritis on luteal function in dairy cows

Background

Disturbed 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.

Results

The 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.

Conclusions

An 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.

Aspectos reprodutivos e produtivos de vacas da raça Holandesa com puerpério normal ou patológico

Foram avaliadas 103 vacas da raça Holandesa de primeira, segunda ou terceira ordens de lactação, com o objetivo de comparar aspectos reprodutivos e produtivos dos animais com puerpério normal ou patológico. Exames ginecológicos foram realizados semanalmente, do parto ao final do puerpério, por meio de palpação transretal, ultrassonografia e vaginoscopia. As incidências de partos gemelares, partos auxiliados, retenção de placenta e infecções uterinas até o primeiro serviço foram de 11,7%, 20,4%, 38,8% e 75%, respectivamente. A involução uterina e a primeira ovulação ocorreram aos 33,5±11,1 e 43,6±21,5 dias após o parto, respectivamente, com diferenças (P<0,001) entre vacas com ou sem infecção uterina. O primeiro serviço ocorreu aos 75,9±31,0 dias após o parto e a taxa de gestação foi de 20,7%. A produção de leite diária foi de 27,9±7,3 litros por vaca até 42 dias após o parto. O prejuízo com a redução na produtividade e o descarte do leite contaminado com resíduos de antibiótico foi equivalente a 598 litros de leite por vaca com retenção de placenta e infecção uterina. A alta incidência de transtornos puerperais interferiu na fertilidade e na produção de leite, causando elevado impacto econômico para a propriedade.

The effect of lactation on post-partum uterine involution in Holstein dairy cows

The objective was to examine the effect of lactation on uterine involution in post-partum dairy cows. Holstein primiparous cows were used (n = 19, mean age: 3.9 ± 0.1 years). At calving, cows were randomly assigned to one of two treatment groups, lactating (n = 11) or non-lactating (i.e. dried off at calving, n = 8). Examination of the reproductive tract was carried out by ultrasonography twice weekly until week 7 post-partum. Blood samples were collected twice weekly for the analysis of progesterone to indicate the resumption of cyclicity and metabolites indicative of energy status. Uterine involution was assessed in terms of size of the uterine horns, uterine body diameter and uterine fluid volume as assessed by the amount of non-echogenic material measured by ultrasound and position of the uterus. Vaginal mucous score was taken on day 28 post-partum for the assessment of uterine inflammation. Resumption of cyclicity (serum progesterone > 1 ng/ml) had occurred in both groups on average by day 21 post-partum. Concentrations of non-esterified fatty acids and beta-hydroxybutyrate were higher, whereas concentrations of glucose, insulin and IGF-1 were lower (p < 0.05) in lactating compared to non-lactating cows. Lactating cows had a smaller mean uterine body diameter (p < 0.05) than non-lactating cows from days 28 to 42 post-partum (day 28: 20.2 ± 1.3 vs 24.9 ± 1.5 mm, respectively) and had a lower mean uterine fluid volume up to day 49 (p < 0.05). By day 49, there was no difference in uterine diameter (15.2 ± 1.8 vs 15.2 ± 1.6 mm) or uterine fluid volume (0.11 ± 0.38 vs 0.18 ± 0.46) between lactating and non-lactating cows, respectively. Vaginal mucous score revealed no evidence of uterine inflammation in either group. In conclusion, while lactation induced significant alterations in metabolic status, it did not have a major effect on the rate of uterine involution as defined in this study.

The influence of genital tract status in postpartum period on the subsequent reproductive performance in high producing dairy cows

The aim of the present study was to characterize the early postpartum period in clinically healthy dairy cows by ultrasonography (US), endometrial cytology (EC), and white blood cell counts, and determine possible relationships between postpartum findings and subsequent reproductive performance. Fifty-three dairy cows were examined on Days 15 to 21 (Visit 1), 22 to 28 (Visit 2), and 29 to 35 (Visit 3) postpartum. The clinical examination included: examination of vaginal fluid, EC, transrectal palpation and ultrasonography of the genital tract (cervical diameter, endometrial thickness, presence of a corpus luteum [CL] or intrauterine fluid [IUF] and its echogenicity). Luteal activity (presence of a CL in a single visit), return to cyclicity (presence of a CL in 2 consecutive visits), and conception rate at 70 and 120 days postpartum were considered as the dependent variables in four consecutive binary logistic regression analyses. Factors affecting leukocyte counts were established by general linear model (GLM) repeated measures analysis of variance. Based on the odds ratio (OR), the likelihood of luteal activity was higher in multiparous than primiparous cows (OR = 3.75) and tended to diminish in cows showing increased endometrial thickness in Visit 1 (V1) (OR = 0.06). The likelihood of returning to cyclicity decreased for each centimeter increase in cervical diameter in V1 (OR = 0.14) and that of conception on Day 70 was lower in cows showing the presence of echogenic or anechogenic IUF in V1 (OR = 0.09 or OR = 0.13, respectively) compared with cows lacking IUF. Effects of parity and IUF were observed on neutrophil counts. Positive EC results were unrelated to the cumulative conception rate at 70 and 120 days in milk, whereas cows returning a positive EC result in V1 showed a greater likelihood of increased endometrial thickness. In conclusion, measuring cervical diameter, endometrial thickness, and detecting the echogenicity of IUF by ultrasonography from Days 15 to 21 postpartum in clinically normal cows is an appropriate tool to predict subsequent reproductive performance. Vaginal examination and transrectal palpation alone did not emerge as valuable predictors.

Influence of postpartum cloprostenol treatment in sows on subsequent reproductive performance under field conditions

During the previous decade several studies focused on postpartum treatment with prostaglandin for improvement of reproductive performance in sows. The aim of the study was to investigate the effect of administration of a prostaglandin F(2 alpha) (PGF(2 alpha)) analogue in sows within 24-48 h after farrowing on sow and litter performance. In five commercial farms, the sows were randomly assigned to either treatment A (2 ml cloprostenol, Planate) or treatment B (2 ml physiological saline solution, i.m.). Fifteen per cent of all sows were at random selected for progesterone analysis. Litter performance was assessed by measuring pre-weaning mortality and average daily weight gain (ADG). Sow performance was assessed by measuring weaning-to-oestrus interval (WOI), the percentage of sows returning to oestrus and litter size during subsequent farrowing. Administration of a PGF(2 alpha) analogue within 24-48 h postpartum had no effect on the rate of progesterone decline measured over 24 h compared with that of the controls. Litter performance and WOI were not affected by treatment. The subsequent litter size in sows of parity seven and more showed a significant difference of 1.98 piglets (p < 0.01) between both groups, to the benefit of the cloprostenol group. In conclusion, administration of a synthetic PGF(2 alpha) analogue, cloprostenol, within 24-48 h after farrowing improved litter size at next farrowing in older (>or=7 parity) sows.

Identification of a female-pig profile associated with lower productivity on commercial farms

At-risk female pigs were defined as females having characteristics of at least one of the four subgroups: females with reservices, lactation length (LL) 0-13 days, weaning-to-first-mating interval (WMI) > or = 8 days, and abortion records. These females may have suboptimal reproductive performance. This study examined reproductive performance in at-risk females, and the relationships between at-risk females, parity, season of mating, and the four subgroups. From 117 farms, 102,494 parity records were categorized into at-risk females and non-at-risk females. Statistical mixed models were used to analyze reproductive performance. Of the 102,494 records, 19.6% were at-risk females. At-risk females had at least 11.1% lower farrowing rates than non-at-risk females among all parities and seasons of mating (P<0.05). As parity increased from 1 to > or = 6, farrowing rate in at-risk females decreased from 74.1 to 62.9%, while the farrowing rate in non-at-risk females decreased from 87.3 to 82.0% (P<0.05). There was no difference in the number of pigs born alive between at-risk females and non-at-risk females (P=0.810). Females at Parity 1 and those that mated during summer had the highest proportion of becoming at-risk females (P<0.001). Gilts and sows with abortion records had at least 39.3% lower farrowing rates than those with non-abortion records (P<0.001). Among the LL 0-13 days, the farrowing rate was below 70% regardless of WMI. Monitoring and reducing at-risk females is an opportunity for producers to improve herd productivity.

Milk progesterone profiles and their relationship with fertility, production and disease in dairy cows in Northern Ireland

A detailed investigation was conducted to identify the main factors influencing the current poor reproductive performance in dairy herds in Northern Ireland. Nineteen herds were selected and a comprehensive database was established, comprising detailed information collected over a 2-year period. Milk progesterone monitoring (no.=1423 cows), based on twice weekly sampling, was included in this on-farm investigation. The mean interval from calving to commencement of luteal activity was 30·1 days and 13·4% (184/1378) of these cows had not commenced luteal activity by day 50post partum. In addition, there was a high incidence of abnormal progesterone profiles: delayed ovulation type I; 15·6% (242/1388), delayed ovulation type II; 11·7% (125/965), persistent corpus luteum type I; 19·4% (212/1121) and persistent corpus luteum type II; 11·9% (70/619). Delayed commencement of luteal activity and abnormal profiles were associated with reduced fertility performance manifested as increased interval to first AI service and ultimately prolonged calving interval. Delayed commencement of luteal activity and abnormal progesterone profiles, with the exception of ‘delayed ovulation type II’ profiles, were not associated with lower conception rates. Assistance at calving was associated with delayed commencement of luteal activity. Delayed commencement of luteal activity and delayed ovulation types I and II profiles were associated with indicators of nutritional stress and poorer production performance in early lactation. Retained foetal membranes were strongly associated with prolonged luteal phases (persistent corpus luteum types I and II profiles). While hormonal therapy may prove useful in treating cows with abnormal milk progesterone profiles, the prevention and treatment of associated diseases and the implementation of good management practices are likely to be more rewarding.

Endocrine and behavioral observations during transition of non-breeding into breeding season in female American bison (Bison bison)

This study provides endocrine data in relation to behavioral events during the transition of the non-breeding into the breeding season in American bison (Bison bison). Fecal progesterone metabolite patterns (20-oxo-P) were obtained in 13 adult female American bison and hormonal data were correlated with behavioral observations; i.e. copulation, male tending, female tail-up behavior and gestation length. Based on fecal progesterone metabolite patterns, the breeding season started between the middle of July and early August. Predictable short cycles reflected the transition from non-breeding to the breeding season; the luteal phase of these cycles was 4.10+/-0.86 days. Copulations and female tail-up behavior were reliably associated with the hormonally detected ovulation. Male tending behavior was more loosely associated with hormonally detected ovulation. The observed hormonal pattern in the study females indicated that 9 of 10 pregnant cows conceived during the second ovulatory period in the breeding season. One other cow conceived during her third ovulatory period, and one cow did not conceive until later in the breeding season by beginning of October. Gestation duration was on average 266.30+/-1.00 days. In summary, this study confirmed that the bison is a seasonally polyestrous species; the transition from the non-breeding into the breeding season was characterized by short cycles with low progesterone metabolite values.

Associations between energy metabolism, LH pulsatility and first ovulation in early lactating cows

This study was designed to elucidate associations between energy metabolism and LH pulsatility characteristics in early lactation, and days to first ovulation, in order to explain the relationship between energy balance and fertility observed in epidemiological studies. To this end, 10 multiparous HF cows were monitored during lactation, after the application of two different feeding strategies during the dry period. Days to first ovulation was assessed using blood progesterone measurements and LH pulsatility was measured in 8-h windows in the third week postpartum. The association between depth of negative energy balance and days to ovulation was confirmed. However, this study does not support the idea that LH pulsatility characteristics in early lactation are predictive for the interval between parturition and first 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 (P4), size of largest follicle (LF), number of follicles larger than 5 mm ( F > or = 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 > or = 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 P4 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.

Administration of prostaglandin F2alpha after farrowing alters the association between lactation length and subsequent litter size in mid- or old-parity sows

A 4000 sow farm in the US using early weaning and a computerized record system was recruited. Farrowed sows were assigned into two experimental treatments: prostaglandin F2alpha injection or control. Sows were assigned by a farm worker to obtain even parity distributions between two groups in each farrowing group. A single i.m. injection of 2 ml of prostaglandin F2alpha between 24 and 48 h after farrowing was administered in the muscle immediately lateral to the vulva. Control sows received no treatment. Of 3562 farrowed sows, 1592 were administered with prostaglandin F2alpha. Parity distributions were not different between control and treatment groups. Parity was categorized into two groups: parity 1-2 or > or = 3. Mean lactation length was 18 days and there was no difference between the control and treatment groups. No main effects of prostaglandin F2alpha administration were found in either parity group on adjusted 21-day litter weight, weaning-to-first-mating interval or weaning-to-conception interval. In parity > or = 3 sows, a two-way interaction between the association of lactation length and treatment with pigs born alive at subsequent farrowing was found (P = 0.044), while no such interaction was found in parity 1-2 sows (P = 0.14). The prediction line for subsequent pigs born alive indicates that prostaglandin F2alpha administration alters the relationship between lactation length and subsequent litter size on mid- or old-parity sows.

Reproductive effects of estradiol cypionate in postparturient dairy cows

OBJECTIVE

To determine the effects of estradiol cypionate (ECP) on measures of reproductive efficiency in postparturient dairy cows.

DESIGN

Randomized clinical trial.

ANIMALS

273 cows in a single herd in California.

PROCEDURE

Twenty-four hours after parturition, 122 cows were treated with ECP (4 mg, IM); the remaining 151 cows were untreated controls. Percentages of cattle with abnormal findings during uterine palpation 27 to 40 days after parturition were compared between groups, along with days to first artificial insemination (AI), percentages of cows that were not pregnant after the first AI, and days to pregnancy.

RESULTS

Treatment with ECP did not have a significant effect on whether results of uterine palpation 27 to 40 days after parturition were abnormal, days to first AI, or odds that a cow would be pregnant after the first AI. Treatment with ECP appeared to have a negative effect on days to pregnancy (hazard ratio, 0.72)

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that prophylactic administration of ECP during the early postparturient period in dairy cows did not have measurable beneficial effects on reproductive efficiency.

Risk factors for post partum ovarian dysfunction in high producing dairy cows in Belgium: a field study

An epidemiological study of risk factors for postpartal ovarian disturbances was carried out on 334 high-yielding dairy cows in 6 well-managed Belgian herds. Ovarian activity was closely monitored using progesterone profiles, based on twice weekly RIA-analysis for progesterone in milk fat, starting at 10 d after calving and continuing until the confirmation of a new pregnancy. Attention was focused on abnormal cyclicity during the preservice, postpartum period; cows were divided into 6 different categories. Three of these categories (normal profile, delayed cyclicity, and prolonged luteal phase) were of major importance and were analyzed using a multiple variable logistic regression model. Season of calving (stable vs pasture, odds ratio (OR)=5.7), an extended length of the previous dry period (> 77 vs < or = 63 d, OR=2.9), problem calvings (OR=3.6), abnormal vaginal discharge (OR=4.5), health problems during the first month of lactation (clinical disease, OR=5.4; ketosis, OR=11.3), and clinical parameters illustrating the appearance of a severe negative energy balance significantly increased the risk for delayed cyclicity before service. Parity (> or = 4 vs 1, OR=2.5), problem calvings (OR=2.9), occurrence of puerperal disturbances (OR ranged from 3.5 to 11.0), health problems during the first month of lactation (OR=3.1), and an early resumption of ovarian cyclicity after calving (< 19 d vs > 32 d, OR=2.8) increased the risk for prolonged luteal cycles before service.

Interactions between the associations of parity, lactation length, and weaning-to-conception interval with subsequent litter size in swine herds using early weaning

Sixteen farms having an average lactation length between 14.9 and 18.9 days were selected based upon producers' willingness to keep records of production and lactation feed intake. Data contained 9162 subsequent litter-size records abstracted from computerized production information-system files and lactation feed-intake records. Two-way interactions between the associations of parity and lactation length, and parity and weaning-to-conception interval with subsequent litter size were found in the same statistical model. Subsequent litter size did not increase in parities 1 and 2 as lactation length increased--but subsequent litter size in sows of parities 3-6 increased. In only parity 1, sows with weaning-to-conception interval 6-12 days produced 0.5 fewer pigs at subsequent farrowing than those with weaning-to-conception interval 1-5 days. However, in multiparous sows, no difference in subsequent litter size was found between weaning-to-conception intervals 1-5 and 6-12 days.

Postpartum adrenal, pituitary and ovarian functions in dairy cows

Postpartum stress and the resumption of pituitary and ovarian functions were investigated in 29 dairy cows during the first month after calving. Adrenocorticotropic hormone (ACTH, 25 i.u., IM) challenge tests for adrenal function at 8 and 22 days postpartum and gonadotropin releasing hormone (GnRH, 50 micrograms IM) challenge tests for pituitary function at 7 and 21 days postpartum were conducted. Ovarian function, particularly the interval to first ovulation, was evaluated through weekly rectal palpation and ultrasonographic examination, as well as thrice weekly milk progesterone levels. Elevated basal cortisol levels were found in 24.1% and 20.7% of cows at 8 and 22 days postpartum, respectively. Adrenal response to ACTH was similar at 8 and 22 days postpartum with low, medium and high peak responses in 13.8%, 62.1% and 24.1% of cows, respectively. A moderate correlation was observed between basal and peak cortisol levels. Peak pituitary luteinizing hormone (LH) response was low in 65.5%, medium in 27.6% and high in 6.9% of cows at 7 days postpartum. Pituitary responsiveness improved by day 21 with low in 34.5%, medium in 37.9% and high in 27.6% of cows. About a week after calving, a negative correlation between peak cortisol and peak LH levels was observed. First ovulation occurred in 28%, 48% and 17% of postpartum cows during the second, third and fourth week, respectively. These results indicate a negative effect of peak cortisol levels on pituitary responsiveness to GnRH stimulation during the first week, altered adrenal and pituitary function in a third of the cows until the third week and restoration of ovarian function in most cows (93%) a month after parturition.