Behavioral and hormonal pattern of repeat breeder cows around estrus

Seasonal distribution of repeat breeder cows and evaluation of modified protocols for post AI treatment during summer

An important problem of dairy industry worldwide is repeat breeder cows (RB). In this study, one farm in Northern Greece was chosen on the basis of subfertility. First, the available reproductive data of the previous year were evaluated; then, the farmer was advised to use the most common treatments for RB [GnRH with the third artificial insemination (AI+GnRH) or ovsynch in cows found empty after the second AI], and their efficacy was monitored throughout the year. Cows (n = 147) 2.5 to 4.5 years old were included. During the next year, post AI treatments (meta-ovsynch and meta-AI) were used during summer; GnRH (100 μg of gonadorelin) alone or in combination with meloxicam (0.5 mg/kg BW) was used during summer. Meta-ovsynch protocols were administered to 29 cows detected as non-pregnant after 3 AIs; cows were divided randomly into 3 meta-ovsynch (OS) groups: group OS (controls, n = 10), standard ovsynch protocol; group OS+GnRH (n = 10), OS plus GnRH 10 days after AI; and group OS+GnRH+NSAID (n = 9), OS plus GnRH 10 days after AI plus meloxicam 15 days after AI. Meta-AI protocols were tested in 27 RB cows; cows were divided randomly into 3 AI groups: GnRH (n = 9), 1 dose of GnRH with AI; GnRH-GnRH (n = 9), two doses of GnRH, one with AI and another 10 days later; and GnRH-GnRH-NSAID (n = 9), two doses of GnRH as in GnRH-GnRH group and one dose of meloxicam 15 days after AI. Pregnancy diagnosis was performed by ultrasound 38 days after AI. During the 1st year of evaluation, 53.79% of cows had received ≥ 3 AIs; the highest percentage (38.48%) of RB cows was recorded during autumn. After treatment for RB, the lowest (P < 0.05) pregnancy rate (PR) was recorded in August (18.18%) compared to January (75.0%), May (53.33%), and December (50.0%, P < 0.1). The efficacy of ovsynch during winter was significantly higher compared to all the other seasons. The percentage of cows with increased estrous cycle duration (24-37 days) after RB treatment and AI was the highest (P < 0.05) in spring and summer after AI+GnRH and the lowest (P < 0.05) during winter after ovsynch. Concerning the post AI treatments during summer, significantly higher pregnancy rate was recorded in the OS+GnRH+NSAID group (55.55%) compared to OS+GnRH (10%) and OS (10%) groups. Pregnancy rates did not differ among AI groups. It seems that OS+GnRH+NSAID is a promising protocol for RB cows during summer although further research is needed to support the present results.

Current Insights in the Repeat Breeder Cow Syndrome

Cows can have difficulties becoming pregnant, and in certain cases, these reproductive failures do not have an evident cause. Furthermore, when these failures are repeated three or more times with estrous cycles of normal duration and in the absence of evident clinical signs, it is considered repeat breeder cow (RBC) syndrome. A substantive incidence of RBC syndrome has been reported all over the world, which severely affects the farm economy. This paper reviews those studies particularly focused on RBC syndrome from 2000 to 2023 but also includes consolidated information until this date. Hormonal imbalances, undetectable oviductal or uterine defects, or poor oocyte or embryo quality have been reported as causes of RBC syndrome, while subclinical endometritis has been considered a relevant causal agent. However, it is unresolved why this condition is recurrent in certain animals, despite the implementation of corrective management actions or treatments. Recent studies evaluate the putative role of certain genes, factors, hormones, or proteins in the pathogenesis of RBC syndrome. Numerous risk factors contribute to the appearance of this syndrome, and some of them could be mitigated to partially prevent this infertility, while others cannot be changed. Due to the complexity of this syndrome, it is important to increase knowledge about the mechanisms involved, develop new diagnostic tools to differentiate causal agents, and implement new treatments to restore fertility. There is consensus about the huge repercussions of this syndrome on farm profitability, but further studies are now needed to describe its economic impact.

Heamatological parameters, endocrinological profiles, antioxidant and oxidative stress profiles of repeat breeding crossbred cows in Andaman and Nicobar Islands

The present study was carried out to assess the effect of repeat breeding syndrome (RBS) on heamatological, antioxidant, oxidative stress and endocrinological profiles in crossbred cows under tropical island ecosystem of Andaman and Nicobar Islands. Each of the twelve number of cows was selected (which were affected with repeat breeding syndrome) as Group 2 and normal cyclic breeding cows as Group 1. These cows were maintained under similar type of managemental conditions. Heamatological profiles, antioxidant and hormone profiles were estimated by automatic blood analyser and commercial diagnostic kits, respectively. The result revealed that the crossbred cows with RBS suffered severe anaemia. The RBS affected animals showed significantly lower level of antioxidant profiles and significantly higher malondialdehyde (MDA) than the unaffected animal groups. Similarly, endocrinological profiles revealed that the RBS affected animals had significantly higher level of cortisol, prolactin and lower level of 17 β-estradiol (E2), progesterone (P4), follicle stimulating hormone (FSH), luteinizing hormone (LH), thyroxine (T4) and insulin like growth factor-1 (IGF-1) than the unaffected crossbred cows. The study concluded that the RBS was due to anaemia, lack of antioxidants, overproduction of free radicals and disturbances of endocrinological profiles in crossbred cows of Andaman and Nicobar Islands.

Effect of variable interservice interval on conception in crossbred cows

Reducing number of services per conception holds the key for profitable dairying. The widely considered estrous cycle length of 21 d has been refuted, a change that can seriously implicate fertility. The present investigation evaluated association amongst interservice interval (ISI, the period intervening two successive inseminations) and services per conception alongwith certain cow related variables (age, lactation number, days in milk to AI, days in milk at conception, age at conception and 305 d lactation yield). Data on 768 ISIs (range: 17 to 24 d) from 1,479 AIs (600 in normal; 879 in repeat breeders) in 193 lactating Jersey crossbred cows conceiving to different number of inseminations, was utilized. The ISI data in form of average, immediately prior to conception and pattern (regular – if ISI between AIs was of same duration; irregular – if ISI between AIs was of different durations) was considered for analysis. Nearly 84% of ISI ranged from 19 to 22 d, merely 22.6% being of 21 d (overall average of 20.3±0.44 d). Correlation matrix revealed a solitary, significant and negative relation of ISI, both average and prior to conception, with services per conception. The ISI of ≥21 d culminated consistently into more number of pregnant cows as well as lesser services per conception. The forward selection regression model predicted reduction in ISI by 0.17 d with each additional insemination. Irregular pattern of ISI was also unfavourable for conception. The probable mechanisms for variable ISI in light of conception have been exhaustively elaborated, which could pave potential future studies aiming reduced reproductive wastage.

Effects of human chorionic gonadotropin and intravaginal progesterone device treatment after artificial inseminations on the reproductive performance of normal and repeat breeder lactating dairy cows

We examined the effects of human chorionic gonadotropin (hCG) treatment on Day 5 (Day 0 = day of artificial insemination: AI) and intravaginal progesterone device (IVPD) treatment from Day 5 to 19 on the conception and detection rates of return to estrus (re-estrus) in lactating dairy cows. A total of 306 cows from a commercial dairy farm were divided into the following three groups on Day 5: non-treatment group (n = 128), untreated; hCG group (n = 71), 3,000 IU hCG was administered (intramuscularly); IVPD group (n = 107), IVPD was inserted into the vagina from Day 5 to 19. Re-estrus detection was performed up to Day 25. Pregnancy was diagnosed by rectal palpation between Day 50 and 60. There was an interaction between treatment and AI number (P < 0.01) on the conception rate of first-AI. For cows with more than three AIs, the IVPD treatment (66.7%) was more effective than the non-treatment (23.1%) (P < 0.05). The re-estrus detection rate was significantly (P < 0.05) higher in the IVPD group (60.7%) than that in the non-treatment group (41.4%) and tended (P < 0.1) to be higher than that in the hCG group (37.8%). Our results suggested that the conception rate can be improved by IVPD treatment, especially in cows with more than three AIs. In addition, IVPD treatment can induce higher estrus expression up to 25 days after AI in non-pregnant cows.

Moosense pedometer activity and periestrual hormone profile in relation to oestrus in crossbred cattle

The objective of the study was to establish the characteristics of pedometer activity in crossbred cows (20) and to determine the relationships between the pedometer activity and the serum concentrations of periestrual hormones. Animals in oestrus were detected by trained personnel based on oestrus behaviour by visual observation twice daily. Further oestrus was detected by pedometer activity and it was confirmed by serum progesterone and estradiol concentration. Individual animal daily activity data were collected and transformed into hourly activity in Excel sheet and arranged for statistical analysis. The relationship of pedometer activity with E2, E2: P4 and progesterone level on the day of oestrus was determined. Pearson correlation analysis was performed using the statistical package SPSS (SPSS Inc. USA). Activity count per hour (ACPH) increased from 248.51±22.46, 312.51±37.16, 323.52±49.24 and 423.42±47.77 from -3 day, -2 day and -1 day of proestrus, respectively to estrus day. After estrus, the activity decreased from 313.76±46.62 and 271.36±36.06 on the 1st day and 2nd day of metestrus, respectively. A similar trend was observed for serum E2 and E2: P4 which increased from 3 days before estrus to reach a peak level on the day of estrus (31.40±2.34 pg/ml) and declined after that to the basal level (2 pg/ml) after estrus. Contrary to this, P4 concentration showed a decreasing trend from –3 day proestrus to estrus (0.46±0.05) and then a gradual increase after estrus day. ACPH showed positive correlation with estradiol concentrations (r = 0.34; P = 0.0779) and E2:P4 ratio (r=0.50; P=2.077) but, negative correlation with progesterone concentration on day of oestrus (r=–0.73; P=2.74). In conclusion, our results suggested that the concentration of E2, E2:P4 ratio and P4 concentration during proestrus and on the day of estrus are the important factors contributing the behavioral manifestation of estrus in terms of ACPH in crossbred cows.

Lame cows have a subdued hypothalamus-pituitary axis as revealed by LH release in response to exogenous endocrine challenges

Lameness is a serious concern in cows due to its multilevel effects and increasing incidences. The ability of anterior pituitary and hypothalamus to release LH, a prime reproductive hormone, is unknown in lame cows. Our study tested this ability by exogenous endocrine challenge using Buserelin acetate (GnRH analogue) and estradiol valerate (EV). The study included moderately lame (L; n=7) either cyclic (LC; n=3) or anestrus (LA; n=4); and normal cyclic, non–lame (NL; n=5) cows. Progesterone blocks LH release, so it was lowered by injecting PG in cyclic cows. After 14 h, all cows were given a walk for 5 min and immediately thereafter injected with 0.008 mg GnRH and 4 h later with 1 mg of EV. Blood plasma progesterone, cortisol and LH were quantified, periodically. There was a significant delay in the onset (105.0 vs 75.0±7.0 vs 54.0±9.0 min) and duration (22.5±5.3 vs 80.0±10.8 vs 117.0±2.7 min) of LH surge in LA vs LC vs NL cows; the surge was absent in two LA cows. The altered LH profile was attributed to a 3 fold (in L) vs 1.6 fold (in NL) rise in cortisol. LH released (ng/ml) in response to EV was also low in LA (31.5±2.4) and LC (69.9±7.2) than NL (79.2±7.0) cows. In conclusion, lame cows subjected to walk exhibited reduced pituitary response to release LH following exogenous GnRH as also a reduced ability of hypothalamus to stimulate LH release in response to exogenous estradiol.

Inherent inferior quality of follicular fluid in repeat breeder heifers as evidenced by low rates of in vitro production of bovine embryos

The aims of the present study were to determine the effect of follicular fluid obtained from the ovulatory follicle of repeat breeder heifers on in vitro oocyte maturation (Experiment 1), fertilization (Experiment 2) and production of bovine embryos (Experiment 3). Holstein virgin heifers (VH, n = 5) with normal fertility or repeat breeder syndrome (RBH, n = 5) were used in the present study. Follicular fluid of VH and RBH was aspirated from ovulatory follicles and used as maturation medium. Bovine oocytes were aspirated from follicles of slaughterhouse ovaries and randomly allocated in three groups; in Group 1, oocytes cultured in TCM-199 supplemented with 10% heat-treated fetal calf serum and hormones (5 IU/mL hCG plus 0.1 IU/mL rFSH); in Group 2, oocytes cultured in TCM-199 supplemented with 10% filtered follicular fluid of VH without hormones; in Group 3, oocytes cultured in TCM-199 supplemented with 10% filtered follicular fluid of RBH without hormones. The mean (±SEM) percentage of matured oocytes was different between VH and RBH groups (72.2 ± 4.0 vs 56.4 ± 4.6%; P < 0.05, respectively). Further, the mean (±SEM) percentage of normal oocyte fertilization was higher in the VH than the RBH group (49.3 ± 2.1 vs 32.0 ± 4.2; P < 0.05, respectively). The mean percentage of embryos developed to the blastocyst stage was higher in the VH than the RBH group (12.0 ± 1.3 vs 7.0 ± 1.6; respectively; P < 0.05). In conclusion, our findings support our hypothesis that the ovulatory follicle microenvironment of Holstein repeat breeder heifers places their oocytes at a developmental disadvantage compared with Holstein fertile virgin heifers and that this suggest the existence of an inherent inferior quality of the ovulatory follicle microenvironment in repeat breeding Holstein heifers.

Proteomic analysis of preovulatory follicular fluid reveals differentially abundant proteins in less fertile dairy cows

The follicular fluid (FF) proteome can provide an indication of follicular quality. High-yielding dairy cows suffer from low fertility, which could be related to follicular function. However, the proteome of preovulatory follicles has never been described in cows. Our objectives were to: 1) define the bovine preovulatory FF proteome, and 2) examine differentially abundant proteins in FF of controls (CTL, n=10) and less fertile cows (LFC; failed to conceive following ≥6 inseminations, n=8). Follicles ≥7mm in diameter were aspirated in vivo, and estradiol (E2) and progesterone (P4) were examined. The FF from 10 preovulatory follicles (E2/P4>1) was analyzed; E2 was higher and follicle diameter tended to be larger in LFC. As aspirations were conducted at a fixed time, this suggests accelerated follicular growth in LFC. The 219 identified and quantified proteins consisted mainly of binding proteins, proteases, receptor ligands, enzymes and transporters. Differential abundance of 8 relevant proteins was found in LFC compared to CTL: SERPINA1, TIMP2, ITIH1, HSPG2, C8A, COL1A2, F2, and IL1RAP. These proteins could influence follicular function-e.g., decreased SERPINA1 may be related to accelerated follicular growth-and therefore, further examination of their roles in the etiology of LFC is warranted.

SIGNIFICANCE

High yielding dairy cows suffer from infertility that leads to major economic losses worldwide. In Israel, about 30% of dairy cows fail to conceive following ≥4 inseminations. The etiology of this low fertility is multifactorial and remains a serious challenge. Follicular fluid proteome can provide indication to follicular quality, yet the proteome of pre-ovulatory follicles has not been described in cows. This work examined the differential abundance of proteins in less fertile dairy cows compared to controls, and found 8 relevant novel proteins that could influence follicular function. The role of these proteins in the etiology of less fertile cows should be further examined.