Repeat Breeding Syndrome Research Articles

Repeat breeding in dairy heifers: follicular dynamics and estrous cycle characteristics in relation to sexual hormone patterns

Repeat breeding occurs at an incidence of 10% in the Swedish dairy cow population. Evidence is available for a hormonal asynchrony around estrus in repeat-breeder heifers (RBH). This asynchrony seems to be the underlying cause for a series of dysfunctions such as prolonged standing estrus and delayed ovulation, leading to fertilization failure. For further determinations of repeat-breeder estrous cycle characteristics, seven strictly selected RBH and six virgin heifers (VH) were studied during 3–7 consecutive cycles, with particular attention paid to the estrous period. Follicular dynamics were studied by ultrasonography and related to estrous behavior and pattern of sexual hormones (progesterone, estradiol-17β, and LH) in peripheral circulation. Mean group data were compared and a classification model was designed. The most prominent findings for RBH were prolonged duration of estrus, delayed LH peak, prolonged lifespan of the preovulatory follicle, and a late postovulatory rise in plasma progesterone. There was also a strong tendency for peri-ovulatory suprabasal progesterone levels in RBH. It is suspected that these deviations cause changes in the microenvironment of the preovulatory follicle, negatively affecting the final maturation of the oocyte. The heterogeneity of the RBH group underlines the multifactorial cause of the repeat-breeder syndrome. The VH formed a homogenous group with data varying within physiological limits. A classification model based on three characteristic variables managed to identify 81% of the VH and 79% of the RBH correctly. Results from this study propose that some heifers have general, consistent problems in synchronizing estrous events, displayed as varying symptoms in the course of consecutive estrous cycles. These subfertile animals could be classified as repeat-breeders.

Risk factors for repeat-breeder syndrome in New South Wales dairy cows

A retrospective case-control study involving 1041 cow lactations from 10 commercial dairy herds in Australia determined relationships between biographic, production, reproductive and disease factors and repeat-breeder syndrome (RBS) (conception to greater than two inseminations). The study population was stratified into primiparous- and multiparous-cow sub-groups and logistic regression was used. Effects of herd were examined by including this variable alternatively as a fixed and a random effect. In the primiparous-cow fixed-effect model, the risk of RBS was increased with post-calving metritis, stillbirth, and with increasing days taken to reach peak milk yield, and reduced following dystocia. An inverted U-shaped relationship with total milk-solids percentage at the time of first service was detected. In the multiparous-cow fixed-effect model, the risk of RBS was increased in cows with chronic metritis, cystic ovarian disease (COD), in cows of parity >5 and in cows that were sub-fertile in the previous lactation. Increasing days to first recorded heat (DFH) reduced risk of RBS and a non-linear relationship with average 120-day milk-protein percentage was found. When herd was fitted as a random effect, stillbirth and 120-day average milk-protein percentage were no longer significant in the primiparous and multiparous models, respectively. The study emphasises the need to control appropriately for the clustering effect of herd and supports the need to minimise periparturient disease and improve nutrient balance to achieve optimal fertility in dairy herds.

Characterisation of the Repeat Breeding Syndrome in Swedish Dairy Cattle

Repeat breeding (RB), defined as cows failure to conceive from 3 or more regularly spaced services in the absence of detectable abnormalities, is a costly problem for the dairy producer. To elucidate the occurrence of RB in Swedish dairy herds and to identify risk factors of the syndrome totally 57,616 dairy cows in 1,541 herds were investigated based on data from the official Swedish production-, AI- and disease- recording schemes. The characteristics of the RB syndrome were studied on both herd and individual cow level. The effects of risk factors on the herd frequency of RB were studied by logistic regression. A generalised linear mixed model with logit link, and accounting for herd-level variation by including a random effect of herd, was used to study the individual animal risk for RB.The total percentage of RB animals was 10.1% and the median proportion of RB animals in the herds studied was 7.5%. The proportion of RB cows in herds increased with decreased herd sizes with decreased average days from calving to first AI, with increased herd incidence of clinical mastitis, with decreased reproductive disorders, and increased other diseases treated by a veterinarian. On animal level, the risk factors were milk yield, lactation number, difficult calving or dystocia, season at first service, days in milk at first service and veterinary treatment for reproductive disorders before the first service. Cows being an RB animal in the previous lactation had a higher risk of becoming an RB animal also in the present lactation. In conclusion our results show that the repeat breeding syndrome is a multifactorial problem involving a number of extrinsic factors as well as intrinsic factors coupled to the individual animal.

Effect of ACTH-challenge on progesterone and cortisol levels in ovariectomised repeat breeder heifers

In order to investigate the potential influence of stress as a component of the repeat breeding syndrome, the adrenocortical capacity for steroid production was evaluated in ovariectomised dairy heifers. In repeat breeder heifers (RBH), marginally elevated plasma progesterone levels during oestrus, so-called suprabasal progesterone levels, have earlier been measured and are believed to impair fertility. The aim was to distinguish if this progesterone could be of extra-gonadal or in this case, adrenal origin. Baseline levels of plasma cortisol and progesterone were determined as well as the corresponding response after induced acute stress in the form of an adrenocorticotropin (ACTH)-challenge. Comparisons were made between strictly selected RBH, n=5 and virgin heifers (VH), n=5 of the Swedish Red and White breed. The heifers were used as their own pre-challenge controls in a 2-day trial. On the control day, saline was injected i.v. and on the treatment day, a synthetic analogue of ACTH (60 μg Synachten®). Via a jugular vein catheter, blood samples were collected every 30 min for 6 h each day of the experiment. Analyses for plasma progesterone and cortisol were made. RBH had a significantly higher ( P<0.01) pretreatment baseline cortisol level (10.1±2.3 nmol l −1) than VH (2.6±0.2 nmol l −1). Moreover, the cortisol response after stimuli was stronger in RBH than VH, especially concerning total hormone production ( P<0.001), but there was also a tendency towards higher peak values ( P=0.06) and longer duration of significantly increased hormone concentrations ( P=0.08). Progesterone concentrations, however, did not differ between the groups. Both baseline levels ( P=0.25) and posttreatment production ( P=0.45) were of the same magnitude in RBH and VH. In conclusion, the study could not confirm that suprabasal progesterone concentrations during oestrus in RBH derive from the adrenal glands. Still, apparent differences were found in adrenocortical activity when ovariectomised heifers, VH and RBH, were subjected to an ACTH-challenge. It is suggested that a sustained adrenal stimulation associated with environmental or social stress could be one factor in the repeat breeding syndrome.

Repeat Breeder Syndrome and its Associated Risk Factors in Québec Dairy Cows

The repeat breeder syndrome has a major impact on herd reproductive performance. In Quebec, reproductive problems are the most important causes of culling in the dairy industry. The objective of this study was to evaluate the occurrence and the risk factors associated with the repeat breeder syndrome (RBS) in Quebec dairy cows and heifers.

Incidence of delayed ovulation in Holstein heifers and its effects on fertility and early luteal function

In the first of 3 experiments 134 first-service and 108 repeat-breeder Holstein heifers were palpated at 12-hour intervals starting 24 hours after insemination to compare the incidence of delayed ovulation in the 2 groups. Delayed ovulation was defined as failure to ovulate within the first 24 hours after insemination. Ovulation occurred within 24 hours post insemination in 92.1% of the animals and was delayed in 7.9% of the cases, with no differences between first-service and repeat-breeder heifers, indicating that the subfertility of the repeat-breeder animals was not due to delayed ovulation. The duration of the delay was at most 12 hours since all the animals had ovulated by 36 hours post insemination. Conception rate of the 19 animals with delayed ovulation (42.1%) was not different (P>0.05) from that of the 223 heifers that ovulated on time (44.8%). In a second experiment, no differences were detected between 15 heifers with delayed ovulation and 15 animals that ovulated on time with respect to their progesterone concentrations during the first 8 days post insemination, indicating that delayed ovulation is not associated with delayed luteinization or subnormal early luteal function. In the third experiment, the conception rate of 126 repeat-breeder heifers that were treated with hCG at the time of insemination was 26.7%; the conception rate of 101 repeat-breeder heifers that were inseminated twice, at 12 and 24 hours after the onset of estrus, was 34.6%; and the conception rate of 105 repeat-breeder heifers which were not treated with hCG and which were inseminated only once was 30.5% (P>0.05) It is concluded that delayed ovulation is not an important cause of infertility and does not constitute an important component of the repeat-breeding syndrome in Holstein heifers.

Epidemiological and economic study of the repeat breeder syndrome in Michigan dairy cattle. I. Epidemiological modeling

Two models of repeat breeder syndrome (RBS) were developed using data obtained from dairy herds participating in the National Animal Health Monitoring System (NAHMS) in Michigan. These models were designed to study the relationship between RBS and six common risk factors: (1) herd characteristics and environment; (2) nutrition during the dry period; (3) diseases which occurred within 72 h of calving; (4) diseases which occurred more than 72 h after calving; (5) reproductive management; (6) milk production. In Model 1, principal components analysis was used to examine the interrelationships among the risk factors. The variable-synthesis approach was used to combine related risk factors into one common risk factor. Herd characteristics and diseases which occurred within 72 h of calving were significant determinants of RBS ( P≤0.01).Milk fever, dystocia and retained placenta occurred as a complex and contributed the most to the cumulative incidence (CI) rate of RBS. In Model 2, a path model was developed to display and to quantify the associations among the significant risk factors that were obtained from Model 1. Dystocia was positively associated with the CI of RBS directly. Milk fever was associated with RBS indirectly through dystocia. Increasing the proportion of corn silage to alfalfa in rations fed to dry cows was associated positively with the CI rate of milk fever and was associated negatively with the CI rate of dystocia. Results of this study suggest that the ration of the dry cow should be balanced in order to prevent dystocia, milk fever and RBS.

Epidemiological and economic study of the repeat breeder syndrome in Michigan dairy cattle. II. Economic modeling

Data from 96 dairy herds randomly selected in the State of Michigan were used to: (1) estimate the economic impact of repeat breeder cow syndrome (RBS) and related risk factors and (2) evaluate the economic effects of changing during the dry period some nutritional risk factors that influence RBS. The economic analyses were based on an epidemiological model which considered both the direct and the indirect effects of the significant risk factors. The mean direct costs of milk fever, dystocia, and repeat breeder syndrome for an 86-cow herd per year were $ 231, $ 529, and $ 994, respectively. Farms that fed 100% dry hay or haylage to dry cows had an increase in the cumulative incidence (CI) rate of milk fever and a reduction in the CI rate of dystocia in comparison with farms that fed a ration containing corn silage. Increasing the annual CI rate of milk fever in a herd by 1% was associated with an increased total (direct and indirect) cost per herd per year of $ 133. Increasing the annual CI rate of dystocia in a herd by 1% was associated with an increased total cost per herd per year of $ 140. These results suggest that proper nutrition during the dry period to prevent milk fever and dystocia is essential for reducing the incidence and cost of repeat breeder syndrome.

Concentrations of Nuclear Progesterone Receptors in Endometrium of Virgin and Repeat Breeder Heifers after Embryo Transfer

The present study aimed to correlate the repeat breeder syndrome in the bovine with an impaired or suboptimal uterine progestational response. Concentrations of nuclear (i.e. transformed) receptors for progesterone (PRn) were determined with a binding and exchange method in endometrial samples from virgin (VH) and repeat breeder (RBH) heifers 15 days post oestrus. The heifers were recipients of Day 7 demi-embryos collected from donors with normal fertility and transferred 8 days prior to tissue sampling. Results were compared with both the type of heifer, the condition of the embryo present within the uterus and the temporal relationship to the hormone plasma levels. The binding data for PRn indicated that a single class of high-affinity, low-capacity sites existed. The amount of PRn in VH endometria holding embryonic structures was significantly greater than in RBH, but no statistical differences were found in their plasma progesterone levels. PRn concentrations were also higher in the uterine horn in which an elongated (greater than 15 mm), morphologically normal embryo was present, when compared to cornua with small (less than 5 mm) embryos, regardless of recipient group. Furthermore, in endometria with an elongated embryo in the lumen, the relative amount of PRn was significantly greater in VH than in RBH. The present results indicate that the RBH recipients of Day 7 demi-embryos by Day 15 have fewer numbers of specific receptors for maternal progesterone, which could explain in part the poorer development of the transferred embryos compared with that in virgin heifers.

Repeated insemination in Michigan Holstein-Friesian cattle: Incidence, descriptive epidemiology and estimated economic impact

Twenty-two Michigan dairy herds participating in a computerized herd-health program were studied to determine the incidence and epidemiologic characteristics of repeat-breeder syndrome. A cow with repeat-breeder syndrome was defined as having been inseminated three or more times within the same lactation. Repeat-breeder syndrome was observed in 24% of 3,309 lactations. Cost components associated with unsuccessful inseminations included costs of delayed conception, extra inseminations, extra veterinary service and losses due to culling. Lactations with repeat-breeder syndrome were associated with a loss of approximately $385. An estimated extra cost of $140 was associated with a second insemination, $279 with three inseminations, $429 with four inseminations and $612 with five inseminations.

The influence of some nutritional factors on the incidence of the repeat breeder syndrome in high producing dairy herds

Data on feeding and the incidence of reproduction disorders in dairy cattle were collected and compared between 2 groups composed of 6 Kibutz dairy herds each. One group contained herds picked at random from dairies with a good overall conception rate (45% and above according to rectal pregnancy examinations) and the other group was randomly selected from those with a low overall conception rate (32% and below). The two groups differed significantly in the incidences of repeat breeder cows (5.48% and 27.35%, respectively), the percentage of problem cows not pregnant 150 days after parturition (14.62% and 38.8%), days to conception (98.5 and 113.7 days), percentage of cows culled due to infertility (5.6% and 15.33%), and in the feeding practices. During the first half of lactation (the high production period) the differences occurred in the amount of digestible protein (11.9% and 9.9% of total dry matter) and in the amount of roughage (33.5% and 20.3% of total dry matter) fed. During the second half of lactation the significant differences between the 2 groups were in the energy level (16.5 F.U. and 13.6 F.U.) and digestible protein fed (10.25% and 8.73% of total dry matter), as well as in the total dry matter fed (17.7 Kg and 15.1 Kg). In the dry period, the only significant difference was in the total dry matter fed (12.7 Kg and 10.5 Kg). It appears that the incidence of repeat breeder cows is influenced by nutritional factors, particularly by the roughage, protein, and energy levels. Proper amounts of these three constituents in the ration during the entire inter-valving period is essential for providing appropriate fertility levels in high producing dairy herds.

Bacterial flora associated with repeat breeding and uterine infections in dairy cows

The study was conducted on 51 uterine biopsy samples collected from 14 normal fertile and 37 repeat breeding cows for bacteriological examinations to find out the prevalence of bacterial flora and their role in repeat breeding syndrome. Presence of bacteria was detected in 23 samples (62.2%) repeat breeding cases in contrast to only 4 (28.6%) bacterial infections from normal fertile cows. About 60% of the microbial isolates were commonly recovered from repeat breeders as well as from normal fertile cows in varying proportions. Of the 37 suffered from repeat breeders, 23 samples (62.2%) yielded 54 bacterial isolates; where Staphylococcus was predominant 14 (37.8%), followed by Bacillus 13 (35.1%), E. coli 11 (29.7%), Pseudomonas 7 (18.9%) while Gram negative minute rod shaped bacteria was 9 (24.3%). The isolates of Pseudomonas and Gram negative minute rod shaped bacteria were obtained only from repeat breeder cows with mucopurulent uterine discharges. There was a positive correlation (r=0.94) between repeat breeders and bacterial infection of uterus. Antibiotic sensitivity in the present study showed that almost all types of bacterial isolates were found moderately and highly sensitive to amoxicillin, oxytetracycline and ciprofloxacin. Key words: Bacteria, repeat breeding, uterine biopsy, histopathology and antibiotic sensitivity DOI = 10.3329/bjvm.v6i1.1342 Bangl. J. Vet. Med. (2008). 6 (1): 79-86