Cycle In Dairy Cows Research Articles

Induction of cyclicity in dairy cows using GnRH (Gonadotropin releasing hormone) in the region of Batna, Algeria

ABSTRACTThe objective of this study was to evaluate the effect of the GnRH induction of cyclicity in dairy cows during the postpartum period, and to contribute to solve some breeding problems.A total of 96 dairy Holstein cows were randomly divided into two groups to evaluate the effect of a single injection of GnRH on the return of the cyclic activity of cows during the post partum period. During this study, the cows were submitted to rectal palpation at regular intervals to evaluate the uterine involution and check the return of estrus.The results have shown that 90% of the cows have a pelvic uterine position for the treated group against 60% in the group untreated. Additionally, we found that gonadotropin treatment has a positive impact on the reduction of the interval calving-estrus by 66 days compared to the control group.These findings confirm the beneficial effect of the GnRH during the post partum on the reproductive parameters in treated cows, giving particularly a shorter calving to first estrus interval, calving to conception/pregnancy interval, and calving interval.

Associations between serum calcium concentration and postpartum health and reproductive performance in dairy cows

In the present study, the aim was to evaluate the associations between serum calcium concentration after calving and serum metabolites, postpartum disorders, and reproductive performance in dairy cows. Blood samples were collected from 200 Holstein cows immediately and 1, 2, 4, 6, and 8 weeks after calving to measure serum metabolites and progesterone concentrations. Cows were divided into three groups on the basis of the mean serum calcium concentration after calving: a Low group (<7.9 mg/dL, n = 52), a Moderate group (7.9–9.6 mg/dL, n = 100), and a High group (≥9.7 mg/dL, n = 48). Total cholesterol (TCH) concentration was greater in the High group than in the Moderate group during the postpartum period (P < 0.01). The High group had greater albumin concentrations during the postpartum period (P < 0.01) and glucose concentrations after calving and 1 week postpartum (P < 0.05) than the Low and Moderate groups. The High group had a lesser incidence of retained placenta than the Low (P < 0.1) and Moderate (P < 0.01) groups, and a lesser incidence of clinical endometritis than the Moderate group (P < 0.05). The probability of resuming estrous cyclicity by 8 weeks postpartum was greater in the High group than in the Low group (hazard ratio = 3.71, P < 0.05). In conclusion, greater serum calcium concentration after calving is associated with greater serum TCH, albumin, and glucose concentrations, a lesser incidence of retained placenta, and clinical endometritis, and earlier resumption of estrous cyclicity in dairy cows.

Changes in milk characteristics and fatty acid profile during the estrous cycle in dairy cows

The relationship of the estrous cycle to milk composition and milk physical properties was assessed on Holstein (n = 10,696), Brown Swiss (n = 20,501), Simmental (n = 17,837), and Alpine Grey (n = 8,595) cows reared in northeastern Italy. The first insemination after calving for each cow was chosen to be the day of estrus and insemination. Test days surrounding the insemination date (from 10 d before to 10 d after the day of the estrus) were selected and categorized in phases relative to estrus as diestrus high-progesterone, proestrus, estrus, metestrus, and diestrus increasing-progesterone phases. Milk components and physical properties were predicted on the basis of Fourier-transform infrared spectra of milk samples and were analyzed using a linear mixed model, which included the random effects of herd, the fixed classification effects of year-month, parity number, breed, estrous cycle phase, day nested within the estrous cycle phase, conception, partial regressions on linear and quadratic effects of days in milk nested within parity number, as well as the interactions between conception outcome with estrous cycle phase and breed with estrous cycle phase. Milk composition, particularly fat, protein, and lactose, showed clear differences among the estrous cycle phases. Fat increased by 0.14% from diestrus high-progesterone to estrous phase, whereas protein concomitantly decreased by 0.03%. Lactose appeared to remain relatively constant over diestrus high-progesterone, rising 1 d before the day of estrus followed by a gradual reduction over the subsequent phases. Specific fatty acids were also affected across the estrous cycle phases: C14:0 and C16:0 decreased (-0.34 and -0.48%) from proestrus to estrus with a concomitant increase in C18:0 and C18:1 cis-9 (0.40 and 0.73%). More general categories of fatty acids showed a similar behavior; that is, unsaturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, trans fatty acids, and long-chain fatty acids increased, whereas the saturated fatty acids, medium-chain fatty acids, and short-chain fatty acids decreased during the estrous phase. Finally, urea, somatic cell score, freezing point, pH, and homogenization index were also affected indicating variation associated with the hormonal and behavioral changes of cows in standing estrus. Hence, the variation in milk profiles of cows showing estrus should potentially be taken into account for precision dairy farming management.

Determination of progesterone concentration during the estrous cycle in dairy cows using a chemiluminescence assay

The study aimed to determine the patterns of serum progesterone concentration in estrous cycle in dairy cows by a chemiluminescence assay (CLIA). Four non-lactating multiparous Jersey cows were used. Animals with a corpus luteum (CL) in any of the ovaries were induced into estrus. Day zero (d0) of the estrous cycle was defined as the day of visible estrus. Blood samples were collected and ultrasonography (US) of the ovaries were performed until a new manifestation of visible estrus was observed. The lengths of the estrous cycles (estrus to estrus) of the four cows were 20, 21, 22, and 23 days. The mean serum concentrations of P4 (x ± s) were 2.8 ± 1.4 ng/mL in proestrus, 2.4 ± 1.5 ng/mL in estrus, 2.0 ± 1.8 ng/mL in metestrus, and 11.9 ± 5.7 ng/mL in diestrus. The follicular and luteal phases of the estrous cycle were established based on P4 concentrations. P4 serum concentrations ≥5.48 ng/mL indicated the presence of functional CL, which was observed from d3 to d12 of the cycle. P4 concentrations decreased from d13 until next estrus. Thus, the previously mentioned P4 serum concentration was established as the limit for a predominantly functional CL. P4 concentrations < 5.48 ng/mL indicated a nonfunctional CL or CL that is not yet fully formed, which is observed in metestrus. A P4 standard curve, constructed based on the Lorentz distribution, was used to determine values of < 5.48 ng/mL of serum P4 concentration for the follicular phase and ≥ 5.48 ng/mL for the luteal phase. Data obtained from US examinations were consistent with P4 concentrations determined using CLIA. In conclusion, the automated CLIA was efficient in determining the P4 concentrations during the various stages of estrous cycles in dairy cows. The findings of the study will help researchers in the animal reproduction field. We recommend the use of CLIA because it´s available in many laboratories worldwide with the ability to process thousands of samples per day.

New Approach for Improvement of the First Insemination Conception rate in Ovsynch Treated Holstein Dairy Cows by Use of Estradiol Benzoate and Antioxidants

The aim of the current study was conducted to improve the first insemination conception rate in Holstein dairy cows by the use of estradiol benzoate and antioxidants in conjunction with ovsynch program. A total number of 160 cyclic dairy cows 55-67 day in milk, 4-10 years old, 2nd to 5th lactations were divided into 4 groups: G1 (n=40) treated with ovsynch program (control group). G2 (n=40) injected with 1mg estradiol benzoate i.m at the time of estrumate injection in ovsynch protocol, G3 (n=40) injected with 15ml of vitesel i.m at the time of estrumate injection in ovsynch protocol, G4 (n=40) injected with 1mg of estradiol benzoate plus 15ml vitesel i.m at the time of estrumate injection in ovsynch protocol. The expression ad intensity of estrus signs were studied using behavioral and physiological changes. The conception rate after first insemination examined using transrectal ultrasonography on the 30th day from insemination and pregnancy rate was confirmed rectally after 60 days from insemination. The obtained results showed that total cows expressed estrus in G2 (ovsynch plus estradiol benzoate) and G4 (ovsynch plus estradiol benzoate and E-selenium) had highly significantly incidence (87.5% and 95.0%) compared with the cows of G1 (ovsynch group) and G3 (ovsynch plus E-selenium) 52.5% and 60%) P < 0.0001. The G2 and G4 had significant incidence of intense estrus signs (82.9% and 84.2%) compared with cows of G1 and G3 (57.1% and 62.5%) p = 0.040. also, it was noted that the G2 and G4 had highly significant incidence of first insemination conception (75.5% and 80%) versus (32.5% and 40%) in cows of G1 and G3 P < 0.0001. the pregnancy rate in G2 and G4 had highly significant incidence (67.5% and 80%) versus (30% and 40%) in cows of G1 and G3 P < 0.0001 as shown in table 2. Moreover, all cows showed intense estrus signs had 100% first insemination conception rate compared with 6.7% in weak estrus signs as in (table 3 and figure 1). It can be concluded that the beneficial effects of injection of estradiol benzoate and antioxidant with ovsynch program improve the reproductive efficiency through intensified signs of estrus and increase secretary activity of the tubular tract. These drugs improve the first insemination conception, pregnancy rates and enhances fertility in postpartum Holstein dairy cows.

Changes in the concentrations of somatic cell counts, lingual antimicrobial peptide and lactoperoxidase activity in milk at periovulatory period in dairy cows.

The objective of the present study was to examine the changes in innate immune factors in milk during the estrous cycle in dairy cows. Milk was collected from cows with a normal ovulatory cycle and cows subjected to the OVSYNCH protocol, and somatic cell counts (SCC), lingual antimicrobial peptide (LAP) concentrations and lactoperoxidase (LPO) activity in milk were measured. In cows with a normal ovulatory cycle, there was no significant change in LAP concentrations and SCC during the ovulatory cycle. However, LPO activity at days 0 and 19 (day 0 = day of ovulation) were significantly higher than those at days 10, 12 and 15. In cows subjected to the OVSYNCH protocol, a significant increase in SCC was observed at day 9 (2 days after prostaglandin treatment) compared with that at day 11 (2 days after second administration of gonadotropin). There were no significant changes in LAP concentrations and LPO activity during the OVSYNCH protocol. These results indicate that LPO activity, an innate immune factor, was enhanced in the preovulatory period.

Seasonal and parity effects on ghrelin levels throughout the estrous cycle in dairy cows

In dairy cows, heat stress depresses appetite, leading to decreased food intake, a negative energy balance, and modifies ghrelin levels. Ghrelin is a gut–brain peptide with two major forms: acylated, with an O-n-octanoylated serine in position 3, and nonacylated. To date, the effect of heat stress and estrous cycle on ghrelin secretion in dairy cows has not been studied. We characterized ghrelin secretion during the estrous cycle in each, the winter and the summer seasons. We further examined the effects of parity on ghrelin secretion. Blood was collected from 10 primiparous or multiparous Israeli-Holstein dairy cows throughout the estrous cycle, in both, the hot and cold seasons. The levels of acylated and total ghrelin were measured in the blood samples. We found that both acylated and total ghrelin levels during heat stress were lower than their respective levels in the winter in both, primiparous and multiparous cows. No differences in acylated and total ghrelin levels were found between primiparous and multiparous cows in both seasons. We further found that in multiparous but not primiparous cows acylated ghrelin secretion oscillated during the estrous cycle in both seasons. Its levels peaked on the last days of the first follicular wave and on the days before and during ovulation. Interestingly, we found that elevated acylated ghrelin levels correlated with conception success and increased total ghrelin levels were associated with successful conception from first insemination. Our data is the first to demonstrate seasonal variation in ghrelin secretion. This study provides evidence for the yet unfamiliar link between heat stress, ghrelin and fertility. Increased circulating acylated ghrelin may contribute to improved fertility in dairy cows. It further raises the possibility of a link between ghrelin levels and successful inseminations. Further research is required to determine the effects of ghrelin on dairy cow performance.

Relationship of blood metabolites with reproductive cyclicity in dairy cows

A total of 40 dairy cows in early lactation (60 to 90 days) of four different breeds were selected, comprising 10 animals each from Holstein Friesian (HF), Jersey (J), Achai (ACH) and F&lt;sub&gt;1&lt;/sub&gt; (HF x Sahiwal). All cows were multiparous with body weight 250-400 kg and milk production ranged from 3 to 12 kg/day. Blood samples were collected from each animal at fortnight intervals for 90 days. In the present study, 65 % of cows reestablished estrus while 35 % cows remained anestrous, 80 % of Holsteins showed estrus followed by 70 % of Jersey and F&lt;sub&gt;1&lt;/sub&gt; cows while in Achai breed showed only 40 % and 60 % cows remained anestrous. Blood glucose and daily milk yield significantly affected post partum estrus (P&lt;0.01) while serum total protein and triglycerides concentration in blood did not affect post partum estrus. The serum glucose level was lower (39.93 ± 3.14 mg/dl) two months before and showed an increasing trend (49.63 ± 2.47 mg/dl) towards commencement of estrus as well as during estrus (48.20 ± 2.42 mg/dl) and then a declining trend was observed. Mean concentration of serum glucose was significantly higher in Jersey (52.50 ± 2.09 mg/dl) followed by F&lt;sub&gt;1&lt;/sub&gt; (39.68 ± 1.45 mg/dl), HF (38.85 ± 1.77 mg/dl) and Achai (33.30 ± 2.17 mg/dl) respectively. Breed type significantly affected blood glucose (P &lt; 0.05) in jersey cows whereas both blood glucose and triglycerides were significantly affected (P &lt; 0.001 and P &lt; 0.05, respectively) in F&lt;sub&gt;1&lt;/sub&gt; cows.

Targeted Analysis Reveals an Important Role of JAK-STAT-SOCS Genes for Milk Production Traits in Australian Dairy Cattle.

The Janus kinase and signal transducer and activator of transcription (JAK-STAT) pathway genes along with suppressors of cytokine signalling (SOCS) family genes play a crucial role in controlling cytokine signals in the mammary gland and thus mammary gland development. Mammary gene expression studies showed differential expression patterns for all the JAK-STAT pathway genes. Gene expression studies using qRT-PCR revealed differential expression of SOCS2, SOCS4, and SOCS5 genes across the lactation cycle in dairy cows. Using genotypes from 1,546 Australian Holstein-Friesian bulls, a statistical model for an association analysis based on SNPs within 500 kb of JAK-STAT pathway genes, and SOCS genes alone was constructed. The analysis suggested that these genes and pathways make a significant contribution to the Australian milk production traits. There were 24 SNPs close to SOCS1, SOCS3, SOCS5, SOCS7, and CISH genes that were significantly associated with Australian Profit Ranking (APR), Australian Selection Index (ASI), and protein yield (PY). This study supports the view that there may be some merit in choosing SNPs around functionally relevant genes for the selection and genetic improvement schemes for dairy production traits.

Relationship between serum metabolites, body condition, peri- and postpartum health and resumption of postpartum cyclicity in dairy cows

Earlier postpartum cyclicity is associated with greater reproductive efficiency, which can result in increased dairy product yields. We determined the relationship between blood metabolites, body condition, and peri- and postpartum health and resumption of postpartum cyclicity in dairy cows. Blood samples were collected from 145 dairy cows at 4 and 2 weeks prepartum, after calving, and at 1, 2, 4, and 6 weeks postpartum to measure serum non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), glucose, total cholesterol, albumin, urea nitrogen, aspartate aminotransferase, γ-glutamyltransferase, calcium, magnesium, phosphorus, and progesterone. Body condition score (BCS) was assessed at the same time points. Uterine inflammation was evaluated 4 and 6 weeks postpartum by measuring uterine discharge using a metricheck instrument and uterine cytology using neutrophil levels. Cows were grouped based on progesterone concentration (resumption of ovarian cyclicity, ≥1ng/mL) at 2, 4, and 6 weeks postpartum into a non-cycling (NCY) group (n=61) and a cycling (CY) group (n=84). NEFA concentration was higher in the NCY group than in the CY group throughout the study period (P<0.0001), whereas BHBA concentration was higher in the NCY group immediately after calving (P<0.05). Total cholesterol concentration was lower in the NCY group throughout the pre- and postpartum period (P<0.05 to 0.0001). Concentrations of albumin, urea nitrogen, and magnesium were lower during postpartum (P<0.05 to 0.0001). BCS was lower in the NCY group at 6 weeks postpartum (P<0.001). Metricheck score (P<0.05) and neutrophil levels (P<0.005) were higher in the NCY group at 4 weeks postpartum. The NCY group had a higher prevalence of dystocia (P<0.05) and metabolic disorders (P<0.005). In conclusion, our results indicate that minimizing the extent of a negative energy balance, as well as implementing prophylactic measures for dystocia, uterine inflammation, and metabolic problems are important factors for hastening the resumption of postpartum cyclicity, which is crucial to improve reproductive efficiency in dairy cows.

Relationship between metabolism and ovarian activity in dairy cows with different dry period lengths

The objectives of the present study were to evaluate the effects of dry period length on ovarian activity in cows fed a lipogenic or a glucogenic diet within 100 days in milk (DIM) and to determine relationships between ovarian activity and energy balance and metabolic status in early lactation. Holstein-Friesian dairy cows (n = 167) were randomly assigned to one of three dry period lengths (0, 30, or 60 days) and one of two diets in early lactation (glucogenic or lipogenic diet) resulting in a 3 × 2 factorial design. Cows were monitored for body condition score, milk yield, dry matter intake, and energy balance from calving to week 8 postpartum, and blood was sampled weekly from 95 cows from calving to week 8 postpartum. Milk samples were collected three times a week until 100 DIM postpartum for determination of progesterone concentration. At least two succeeding milk samples with progesterone concentration of 2 ng/mL or greater were used to indicate the occurrence of luteal activity. Normal resumption of ovarian cyclicity was defined as the onset of luteal activity (OLA) occurring at 45 DIM or less, followed by regular ovarian cycles of 18 to 24 days in length. Within 100 DIM postpartum, cows with a 0-day dry period had greater incidence of normal resumption of ovarian cyclicity (53.2%; 25 out of 47 cows) compared with cows with a 60-day dry period (26.0%; 13 out of 50 cows, P = 0.02). Independent of dry period length or diet, cows with OLA at less than 21 DIM had a greater body condition score during weeks 1 and 2 (P = 0.01) and weeks 1 through 8 (P = 0.01) postpartum compared with cows with OLA at greater than 30 DIM. Cows with the first ovarian cycle of medium length (18–24 days) had greater energy balance (P = 0.03), plasma concentrations of insulin (P = 0.03), glucose (P = 0.04), and insulin-like growth factor I (P = 0.04) than cows with long ovarian cycle lengths (>24 days) but had lower plasma β-hydroxybutyrate (P < 0.01) and liver triacylglycerol (P = 0.02) concentrations than cows with short ovarian cycle lengths (<18 days) during weeks 1 through 8 postpartum. Diet did not affect the measured ovarian activity variables within 100 DIM. In conclusion, omitting the dry period (0 days) increased the incidence of normal resumption of ovarian cyclicity in dairy cows within 100 DIM compared with a conventional dry period (60 days). Short (<18 days) or long (>24 days) ovarian cycles during the first ovarian cycle postpartum were associated with severe negative energy balance and poor metabolic status in early lactation.

Two Possibile Hormonal Treatment Methods for Inducing Follicular Growth in Dairy Cows With Inactive-Static Ovaries

Abstract Postpartum anestrus is a physiological phenomenon in high-producing dairy cows. Static ovaries have been related as major contributors for its occurrence causing a significant reproductive problem to the dairy industry. Different treatment methods have been employed with inconsistent rate of success in initiation of cyclicity, requiring further investigations in order to achieve satisfactory results. The aim of the present study was to compare the ovarian response in cows diagnosed with static ovaries, more than 60 days postpartum using two different hormonal treatment (GnRH and eCG) methods. A total of 58 acyclic cows (no CL, follicles&lt;8mm, P4&lt;0.5ng/mL) were randomly divided into three groups: GnRH (Group 1, n=23), eCG (Group 2, n=23) and Controls (n=12), and allocated thereafter, into subgroups according to the applied doses of GnRH (100μg or 250μg); eCG (750 IU or 1000 IU) whilst control group cows were left untreated. Daily follicular growth rate and treatment respond interval were estimated based on repeated ultrasound examinations. Blood serum P4 sampling was done on d -7, d-0 (start of the experiment) and on d 7 after ovulation. Resumption of cyclic activity occurred in 55.17% (32/58) of the treated cows, 56.52% in Group 1; 60.86% in Group 2 and 41.66% in the control group. Overall, the follicular growth rate was similar between the trials group and significant with regard to the cows in the control group (p&lt;0.05). eCG or GnRH treated cows responded significantly faster 6.85±0.2 and 7.84±0.2 days, respectively, in comparison to the control group cows (17±0.7 days, p&lt;0.001). Treatment with a single dose of GnRH or eCG caused resumption of follicular growth and ovulation following luteogenesis (forming CL) without significant changes in P4 concentrations on day 7 after ovulation (p&gt;0.05). Cows in Group 2 had significantly higher incidence of multiple ovulations than cows in Group 1 (p&lt;0.05). The eCG treatment resulted in a faster response and higher ovulation rate compared to GnRH treatment. In conclusion, both treatments have shown acceptable results in resumption of cyclicity in dairy cows with static ovaries.

The effect of corpus luteum on hormonal composition of follicular fluid from different sized follicles and their relationship to serum concentrations in dairy cows

ObjectiveTo investigate the effect of the presence or absence of corpus luteum on hormonal composition of follicular fluid (FF) from different sized follicles and their relationship to serum concentrations in dairy cows. MethodsOvaries were collected from 30 clinically healthy adult female cows (Holstein Friesian) 4–7 years of age with clinically normal reproductive tracts after slaughtering. Blood samples were collected from the jugular vein before slaughter from each cow. The stage of the cycle in the cows was determined postmortem. The ovaries collected from per cow were classified with corpus luteum (CL+) and without corpus luteum (CL−). FF was aspirated from small (3-5 mm), medium (6-9 mm), and large (10-20 mm) follicles in CL+ and CL− ovaries. Serum and FF samples were analyzed for estradiol-17β, progesterone, testosterone, T3 and T4 concentrations. ResultsResults demonstrated that the FF concentrations of estradiol-17β, progesterone and testosterone in different sized follicles categories (small, medium and large follicles in CL+ and CL− ovaries) were significantly higher (P≤0.05) when compared with the serum. The FF concentrations of estradiol-17β and testosterone in same follicle size categories in CL+ and CL− ovaries were also significant (P<0.05). Indeed, concentrations of these hormones in the CL− ovaries were higher than those of the CL+ ovaries. However, there was a statistically significant difference between medium and large follicles for progesterone concentration in CL+ and CL− ovaries (P<0.05). There was a significant correlation between concentration of hormones in serum and FF with increased follicular diameter. ConclusionsThese results indicated that the levels of hormonal composition in the FF were related to follicular size and interestingly to the presence or absence of a corpus luteum. Indeed, the corpus luteum locally affects neighboring follicular compositions during the luteal phase of the estrous cycle in dairy cows.

Comparison of synchronisation and fertility after different modifications of the ovsynch protocol in cyclic dairy cows

The objectives of this study were to evaluate the effects of (1) double doses of PGF2α administration or (2) an exogenous progesterone (CIDR) applied concurrently with, or (3) the day after, first GnRH of Ovsynch (GnRH-1), on synchronisation and fertility during the Ovsynch protocol. All cows (n = 378) received the Ovsynch protocol (GnRH-7d-PGF2α-56h-GnRH-18h-TAI). The 'OVS' group (n = 105) received only the Ovsynch protocol. The 'OVS-PGF' group (n = 118, GnRH-7d-PGF2α-12h-PGF2α-44h-GnRH-18h-TAI) received an extra dose of PGF2α 12 h later on Day 7. The 'OVS-7CIDR' group (n = 78, GnRH+CIDR-7d-PGF2α-56h-GnRH-18h-TAI) received a CIDR for 7 days between GnRH-1 and PGF2α. In the 'OVS-6CIDR' group (n = 77, GnRH-24h-CIDR-6d-PGF2α-56h-GnRH-18h-TAI), CIDR was applied one day after GnRH-1 and removed 6 days later. When all cows were evaluated, the responses to GnRH-2 were higher (P = 0.005) in cows that responded to GnRH-1 (95.4%) compared to the cows that did not respond (87.6%). The pregnancy rates at 31 and 62 days for each group were 48.6% and 42.9% in the OVS, 54.2% and 52.5% in the OVS-PGF, 52.6% and 48.7% in the OVS-7CIDR, and 55.8% and 49.3% in the OVS-6CIDR groups. Thus, none of the three different treatments has an effect on increasing the out-comes of the Ovsynch protocol in cyclic lactating dairy cows.

Endometrial expression of progesterone, estrogen, and oxytocin receptors and of 20α-hydroxysteroid dehydrogenase and cyclooxygenase II 2 and 5 days after ovulation in induced short and normal estrous cycles in dairy cows

The aim of this study was to investigate causes of the short estrous cycles that occur frequently in dairy cows after estrus synchronization using PGF2α and GnRH. Expression of oxytocin receptor (OR), progesterone receptor (PR), and estrogen receptor (ER); of cyclo-oxygenase II (COX-II) and 20α-hydroxysteroid dehydrogenase (20α-HSD); and of peripheral blood estradiol-17ß and progesterone (P4) concentrations were analyzed in estrous cycles of normal length and in induced short estrous cycles. On Day 8 (ovulation = Day 0), presynchronized dairy cows (n = 14) were given 0.15 mg of dexcloprostenol and 0.1 mg of gonadorelin 24 hours later. Animals were bled once daily for P4 and estradiol-17ß analyses, and endometrial biopsy specimens were taken on Days 2 and 5 for PR, ER, OR, 20α-HSD, and COX-II determinations with immunohistochemistry and/or real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Ovulations and ovarian structures were monitored with transrectal ultrasound daily until the next ovulation. After excluding one case of incomplete luteal regression, short estrous cycles occurred in 8 of 13 cases (length from 8 to 12 days). No differences were established in endometrial ER, PR, or COX-II expression between the normal and short cycle groups in the semi-quantitative immunohistochemistry analysis. In qRT-PCR analysis, no differences were found in relative gene expression of endometrial ER, PR, OR, 20α-HSD, or COX-II between normal and short cycles. Despite evidence from previous studies that short estrous cycles are induced by premature prostaglandin release, differences in these receptors or in enzyme expression do not explain the release.

Investigation on some biochemical parameters and effect of hormonal treatment in anoestrous dairy cows with cystic ovarian follicle

To investigate some blood biochemical parameters in anoestrous dairy cows with cystic ovarian follicles (COF) during the first two months post partum and the effect of hCG-PGF2α -GnRH treatment on their reproductive response. The investigation was performed on 20 lactating Holstein cows, divided into two groups: control group (n=8) and treated group (n=12). All animals had cystic ovarian follicles, detected during the two consecutive transrectal ultrasound examinations at 7-day interval. Blood samples from each animal were collected on the day of second ultrasonography (Day 0) and subjected to a hormonal and biochemical analysis. Treated cows were subjected to another ultrasound examination on day of prostaglandin injection and the presence of corpus luteum was recorded. The control animals were not treated, while the treated group received 1 500 IU hCG on day 0, PGF2α 500 mg on day 7 and 100 μg GnRH 48 hours latter. Eighteen hours after GnRH administration animals bearing corpus luteum on Day 7 were artificiallly inseminated. The last ultrasound examination was made forty days after start of the threapy. On the base of the obtained results, cumulative oestrous activity, cumulative ovulation rate, pregnancy rate and COF persistence were determined. The blood analysis in the both groups on Day 0 showed significantly (P<0.05) lower mean concentration of progesterone, glucose and inorganic phosphate compared to the reference range values for cyclic dairy cows. Cumulative oestrous activity (91.7%) and cumulative ovulation rate (75.0%) were considerably higher (P<0.05) in treated group than control group, whereas the cystic follicle persistence (25.0%) was lower (P<0.05) in the treated group than control group. The present study confirmed the thesis for low blood levels of glucose and inorganic phosphate in cows presenting cystic ovarian follicles. It also indicated significant improvement of cumulative oestrous activity and ovulation rate in animals subjected to hCG-PGF2α -GnRH administration than non-treated animals. The used hormonal protocol could decrease cystic ovarian follicle persistence in dairy cows.

HORMONAL METHODS FOR ESTROUS CYCLE MANIPULATION IN DAIRY COWS

SUMMARY: Reproduction efficiency in dairy cows is declining all over the world. Epidemiologic studies suggest that diseases have greater effect on herd fertility compared to the parameters like milk production. Immediate solution to the problem of infertility may bethe application of some method of hormonal manipulation of estrous cycle in dairy cows. Reproductive system ultrasound examination enables today’s veterinarians to visualize ovarian changes during the estrous cycle, giving them a chance to intervene with exogenous hormonal inhibition and/or stimulationof temporary ovarian structures at the appropriate time. Summarizing possible hormonal methods for estrous cycle manipulation we have analyzed following protocols: prostaglandin based protocols, prostaglandin + progestagensin combination, regimes using prostaglandin + gonadotropin-releasing hormone (GnRH) and prostaglandin + GnRH+ estradiol protocols. In dairy herds where estrus detection does not represent a significant problem, prostaglandin based or Select Synch protocols are methods of choice for the hormonal manipulation of estrous cycle. However, if there are problems regarding estrus detection Ovsynch or Presynch + Ovsynch could be an effective alternative for the hormonal manipulation of estrous cycle. Furthermore, fixed time artificial insemination (TAI) could be modified to coincide with the second GnRHinjection, thus reducing the time and number of visits.

Influence of repeated dinoprost treatment on ovarian activity in cycling dairy cows

To study the ovarian response to the long-term effect of PGF2α, 16 cows were treated with 25 mg tromethamine dinoprost (Pronalgon F; Pfizer, Tokyo, Japan) for 21 days after natural ovulation. Five control cows were treated with sterile physiological saline. The follicle and corpus luteum (CL) development were monitored using a real-time ultrasound instrument. In addition, the plasma concentration of progesterone (P4) was determined. In nine of the 16 Pronalgon-treated cows, the first dominant follicle (1st DF), second dominant follicle (2nd DF), and third dominant follicle ovulated consecutively (group A). In five cows, the 1st and 2nd DFs ovulated consecutively (group B). The developing CL started to regress approximately 5 days after each ovulation without maturation in groups A and B. In the two remaining Pronalgon-treated cows, there was no further ovulation after natural ovulation (group C). In one cow in group C, the 1st DF became atretic and the 2nd DF became cystic with the diameter of the cystic follicle reaching 31.2 mm on Day 30. In another cow, the 1st DF became cystic with a diameter of 30.9 mm on Day 18. Although P4 began to increase after each ovulation in all of the Pronalgon-treated cows, it decreased immediately after each ovulation without a large increase, peaking at approximately 1 ng/mL. Furthermore, the number of days when P4 was >1 ng/mL from natural ovulation to Day 21 was 2.6 ± 0.7 days, which was significantly less than that in the control cows (16.0 ± 0.6 days). These results indicate that the long-term effect of PGF2α has an important role in ovulation of all dominant follicles and might induce cystic ovaries in cows.

Associations of prepartum body condition score with occurrence of clinical endometritis and resumption of postpartum ovarian activity in dairy cattle

This study was performed to investigate the effect of periparturient body condition score on the occurrence of clinical endometritis and postpartum resumption of ovarian activity in dairy cows. Eighty-seven lactating Holstein cows, fed with a total mixed ration diet, were included into the study. Body condition scoring (using a 5-point scale with quarter-point divisions) was performed by the same investigator using the visual technique every 2weeks, from 2weeks before until 6weeks after calving. Palpation of the reproductive tract and ultrasonographic assessment of ovaries for detection of corpus luteum using a rectal linear probe was also performed at 2, 4, and 6weeks after calving. Cows with clinical endometritis had significantly lower body condition score (BCS) than normal cows at all weeks pre- and postcalving, and cows that did not ovulate until 45days after calving had a significantly lower BCS pre- and postpartum. Cows that did not ovulate until 45days after calving also lost more BCS from 2weeks before to 4weeks after calving. Besides, first ovulation after calving take occurred later in cows with clinical endometritis compared to normal cows (P < 0.05). In conclusion, low BCS is a risk factor for postpartum endometritis and delayed cyclicity in dairy cows. BCS loss from dry-off to early lactation and occurrence of clinical endometritis can significantly affect postpartum ovarian activity.

The relationship between endometrial cytology during estrous cycle and cutoff points for the diagnosis of subclinical endometritis in grazing dairy cows

The objectives of this study were to assess the effect of the stage of estrous cycle on the percentage of endometrial polymorphonuclear cells (PMN) obtained by cytobrush to determine cutoff values for the diagnosis of subclinical endometritis under pastoral conditions, to measure the prevalence of subclinical endometritis 21 to 62d in milk (DIM), and to evaluate the effect of subclinical endometritis on reproductive performance in grazing dairy cows. The first experiment was conducted on a commercial dairy farm in Buenos Aires province (Argentina), where 17 postpartum cyclic dairy cows without clinical endometritis were selected and synchronized by Ovsynch protocol. Endometrial cytology (cytobrush technique) and blood (tail vessels) samples were obtained on d0, 4, 11, and 18 of the estrous cycle (corresponding to estrus, metestrus, diestrus, and proestrus, respectively) and used for measuring percentage of PMN and P4 concentration, respectively. The percentage of PMN was determined 3times by blinded count by 2 operators. Data were analyzed with PROC MIXED, PROC GENMOD, and PROC FREQ from SAS 9.1. The percentage of PMN did not vary with the stage of the estrous cycle. In addition, PMN counts were below any of the reported thresholds in this study (4%) for most of the cows. Therefore, the risk for false positive test results as a consequence of physiological changes in the counts of PMN during estrous cycle is low. The second experiment was conducted on 4 commercial dairy farms in Buenos Aires province (Argentina), where lactating Holstein dairy cows (n=418) 21 to 62 DIM without clinical endometritis were studied. Samples of endometrial cytology were collected with the cytobrush technique. Data were analyzed with receiver operator characteristic curves with Sigmaplot 10.0, and with PROC GLIMMIX, PROC PHREG, and PROC LIFETEST from SAS 9.1. Cutoff values for the diagnosis of subclinical endometritis in grazing dairy cows are 8% PMN for 21 to 33 DIM, 6% PMN for 34 to 47 DIM, 4% PMN for 48 to 62 DIM, and overall 5% PMN for 21 to 62 DIM; the prevalence of subclinical endometritis 21 to 62 DIM was 17%. Finally, subclinical endometritis diagnosed at 21 to 62 DIM decreases the hazard for pregnancy (hazard ratio=0.668; 95% confidence interval=0.492–0.909) and increases the calving to conception interval by d30 compared with normal cows (median 95% confidence interval=133 vs. 93, respectively).