Bovine Dystocia Case Studies

This review focuses on minimizing losses associated with bovine dystocia. Annual financial losses sustained by the United States’ beef and dairy industries are substantial. Studies have shown that thirty-three percent of all of calf death losses in the United States are due to dystocia. Many producers have responded by implementing management practices which have led to a decline in overall occurrences. Current information suggests that additional dystocial births could be circumvented by identifying and removing genetically prone individuals from the herd’s breeding program. Implementation of tests such as genome wide association studies and comparative hormone concentration tests may prove to be useful in this identification process. Despite

preventative efforts, however, dystocial births will inevitably occur in cow-calf operations. Numerous studies have concluded that over half of all death losses in cows and calves due to dystocia could be prevented by identifying cows experiencing obstructed labor and applying timely obstetric assistance. Accurately identifying onset of parturition becomes a paramount factor in reducing delay of assistance to heifers and cows in distress. Detection of changes in body temperature and remote monitoring are potential means of identifying the onset of the birthing process. Implementation of these practices may increase longevity in productive life of the dam and result in higher rates of calf survivability, thus, reducing losses previously experienced by beef and dairy producers.
The economic efficiency of a cow-calf operation depends on the herd’s ability to produce and reproduce. Financial sustainability in such an operation depends heavily on two factors: an operation must a) maintain the productive life of each cow and b) produce and wean a high percentage of calves to be sold or added to the herd. Multiple studies confirm that dystocia is the most common cause of postnatal mortality for calves (Bellows, Patterson, Burfening, & Phelps, 1987; Dargatz, Dewell, & Mortimer, 2004). Financial losses due to dystocia cost the dairy and beef industries hundreds of millions of dollars annually.
A study conducted by Bellows, et al.

(1987) was designed to identify the most common causes of death in new born calves. Over a fifteen year period, researchers collected and performed necropsies on calves whose deaths occurred from birth to weaning and determined cause of death for each. Fifty-one percent of all calf deaths were determined to be due to dystocia. Of the calves which had been assigned a dystocia score, 52.6% were reported as being delivered without assistance. Hence, the authors postulated that as much as 50%, of calf death loss would have been prevented if timely, correct obstetric intervention had been administered. Minimizing the frequency and effects of bovine dystocia becomes a basic element in increasing production and reproduction within the cow-calf operation.
This paper reviews international literature on dystocia. Focus is given to understanding prevalence, cumulative losses associated with pathological conditions which result following complications of dystocia, methods of prevention, and methods identifying parturition onset. The objective is to initiate a basis to compare and select potential methods to prevent dystocia and predict onset of the parturient

process.
A nationwide study was conducted to assess the prevalence of dystocia in current cow-calf beef herds in the United States. Results suggest that approximately 16.7% of heifers and 2.7% of cows required some level of obstetric assistance (Dargatz, et al., 2003). Actual numbers of dystocial occurrences may be significantly higher but went undetected due to extended length of time between observations during the calving season. National estimates for dairy breeds, Holstein-Friesian, suggest that 22.6% of heifers and 13.7% of cows required assistance (Mee, 2007). Estimates may vary among other dairy breeds. Initial financial losses due to mortality of both cows and calves due to dystocia are substantial and easy to asses. Beyond these initial losses lie other significant and unquantifiable deleterious effects.
Calves that have survived a prolonged or difficult birth were observed to be less vigorous, slower to stand, and slower to attempt to nurse. This delay negatively impacted the uptake and absorption of immunoglobulins contained in colostrum and often impaired the calves’ ability to regulate body temperature (Barrier, Ruelle, Haskell, & Dwyer, 2011). Immediate adverse physiological effects often include low levels of blood oxygen, acidic blood pH, and trauma to the cardiopulmonary system. In addition, dystocial calves have proven to be chronically slower growing, lighter at weaning, and show a lifelong propensity to contract respiratory and digestive diseases (Lombard, Garry, Tomlinson, & Garber, 2007).
Similarly, cows which have experienced dystocial deliveries have shown negative correlations in overall health and longevity. A depressed immune system leaves these cows more vulnerable to the contraction of respiratory and digestive diseases throughout their lives. Immediate health is compromised due to increased rates of retained placenta, uterine infection, and mastitis. Excessive inflammation of the utter and reduced milk production negatively impacts cows’ ability to “mother-up” (Mee, 2007).
Long-term reproductive soundness is also adversely impacted. Prolonged or complicated births result in increased calving-to-breeding interval, lower conception rates, and decreased length of productive life. Szabo and Dakay (2008) recorded data and compared the length of productive lives among eutocial heifers and cows and dystocial heifers and cows across beef breeds. Analysis of results indicated that individuals which required little or no assistance maintained average productive lives of 6.2 years. In stark contrast, cows and heifers that suffered from difficult calving had productive lives which were reduced to an average of 2.8 years. This reduction in productive life overwhelmingly results in the culling of these beef females. When all accumulative losses associated with the sequelae of dystocia are taken into consideration, initial treatment proves to be the least costly factor. Projections indicate that subsequent dystocia related losses are four times greater than the initial treatment (Mee, 2007).
There are many factors that contribute to the prevalence or reduction of dystocia in any given herd. Management decisions of the herdsman that may affect the herd’s dystocial rates may include: age at breeding, parity of dam, and nutritional levels during gestation. Similarly, environment and random events such as, seasonal temperature and barometric changes, environmental stressors, malposition, and gender of calf all play a role in affecting these rates. Moreover, it has long been observed that there are genetic components which predispose some individuals to both dystocia and stillbirths (Berger, Cubas, Koehler, & Healey, 1992). For the purposes of this study, distinction is given and focus is largely placed on genetic factors that lead to dystocia. The objective is to better understand how to prevent or predict occurrences of dystocia. Areas of interest include identifying single nucleotide polymorphisms and hormone imbalances.
A genome wide association study (GWAS) conducted by Olsen et al. (2009) sought to find quantitative trait loci (QTL) affecting dystocia in Norwegian Red cattle. Results revealed connections to dystocia on several chromosomes (See Table 1 for a list of 16 markers validated to contribute to dystocia; dir/mat and Stillbirths; dir/mat). Most significant were the findings regarding chromosome six. Olsen et al. found several QTL on BTA6 to have coding which affects both dystocia (DYSdir) and stillbirths (SBdir).
It should be observed that a caveat exists and is stated by Olsen et al. GWAS testing is known to display false positives and is affected by other testing problems. For example, 30% of the single nucleotide polymorphism (SNP) assays were shown to be inaccurate or uninformative. As such, the GWAS is best used as a “rapid initial screening method” to detect chromosome regions which might contain QTL affecting calving ease.
Subsequent combined linkage disequilibrium and linkage tests (LDLA) offered more refined information. Results of these tests supported the findings of the GWAS. The most important correlation between the two tests pointed to marker 285 on BTA6. Previous studies have revealed the functionality of six genes residing at marker 285. Of greatest interest is the cluster’s influence associated with bone and cartilage morphogenesis. This cluster contains genes that code for bone mass and might to contribute to the ultimate size the calf will reach prior to parturition. Information gathered from this study points to the potential benefits of using GWAS to remove genetically predisposed individuals from the breeding program.
Another potential method for predicting herd members predisposed to dystocia relies on a previously established understanding of the hormone cascade that occurs prior to normal parturition. Plasma estrogens are observed to increase significantly in the last week of gestation and effect two critical aspects of the parturient process. First, the elevation in estrogen plasma initiates stromal response and causes softening of the cervix. The continued elevation of estrogen will eventually be responsible for full cervical dilation. Second, this increase is the initial step which activates the hormone cascade which results in the final expulsion of the fetus and the fetal membrane.
Research conducted by Zhang et al. (1999) confirmed the correlation which exists between the occurrence of dystocia and maternal imbalance of estrone sulfate (E1S) and progesterone (P4) concentrations in prepartum cattle. Throughout the gestational period, days 90-270, no significant differences were recorded among eutocial or dystocial cows and heifers. Divergence in comparison was observed at approximately six days prepartum. E1S concentrations rose continually throughout the gestational period and continued an overall increasing trend in eutocial heifers and cows until the day they calved. Conversely, dystocial heifers showed a marked leveling of E1S plasma concentrations from day six to day one prepartum. Multiparas cows also showed a plateau in E1S concentrations, but not until day three prepartum (For a comparison of E1S concentrations among eutocial and dystocial cows and heifers, see Figure 1).
Similarly, no notable differences were observed in maternal Plasma P4 concentrations during gestation days 90-270 in eutocial or dystocial cows and heifers. All showed a downward trend throughout this stage of pregnancy. Divergence was observed at day one in prepartum heifers and even earlier, at day three, in prepartum cows. Eutocial cows and heifers showed a more precipitous decline in P4 levels than did their dystocial contemporaries. (For a comparison of P4 concentrations among eutocial and dystocial cows and heifers, see Figure 2). Zhang et al. postulated that the relationship is causative. The failure to increase plasma estrogen to appropriate levels results in incomplete uterine dilation and a weak response in subsequent hormone levels, thus leading to dystocia.
Monitoring E1S and P4 levels in cattle close to parturition proves to have dual purposes. First, hormone imbalances can be passed to offspring and are often chronic. The chronic nature of imbalances may lead to repeat dystocial birthing events. Individuals that exhibit a deviation from appropriate hormone levels prior to parturition should be considered as candidates to be removed from the breeding program. Second, monitoring hormone levels can be used as a tool to predict both timing of parturition and individuals that are likely to require assistance during calving.
“There is no such thing as an easy calving . . . just varying degrees of difficulty . . . from the dam’s perspective” (Mee, 2007). Despite strides taken toward prevention, dystocial births will always be part of the cow-calf operation. Obstetric intervention is a necessary husbandry practice needed to decrease the overall negative impacts of dystocia. Implementing a means with which to accurately predict the onset of parturition would increase rates of timely intervention when necessary.
Monitoring body temperature in cows prior to calving may prove to be a useful tool in predicting parturition onset. Research conducted by Lammoglia et al. (1997) confirmed previous studies which found diurnal variation in body temperature in both beef and dairy breeds. More importantly, this study showed a decrease in overall body temperature and cessation of the previously observed variation in body temperature at forty-eight to eight hours prior to calving. A subsequent study by Aoki, Kimura, & Suzuki (2005) showed a decrease in vaginal temperatures of greater than or equal to .03°C. The same study reported that approximately 74% of cows gave birth within 36 hours of the decrease in vaginal temperature.
Methods used in both studies prove difficult to repeat in a commercial setting. Lammoglia et al. (1997) measured body temperatures by surgically implanting electronic monitors under the musculature of the left flank. Methods used by Aoki et al. (2005) required the cow to wear a data logging apparatus, worn like a saddle, on their back. Temperature sensors were then inserted at a depth of 25 centimeters into the vagina. Both methods have associated risks of introducing infection and inducing stress during handling. Improving techniques for detection of these body temperature changes will be needed before a system can be widely used.
Ideally, heifers and cows showing signs of imminent parturition would be observed at all times. Constant observation is impractical for most operations, however. Electronic monitoring alarm systems may aid in facilitating the identification of the onset of labor and lead to faster response times when assistance is needed. Palombi et al. (2013) used alarm systems originally designed for use in mares and assessed the system’s effectiveness in cattle. Researchers inserted intravaginal devices and attached them to the labia vulvaris in cows and heifers who showed signs of imminent parturition. The separation of the vulva lips activated an alarm, thus, alerting personnel to the exact moment when the birthing process began.
Control groups which consisted of unmonitored cows and heifers were compared with experimental groups which consisted of alarm monitored cows and heifers. Results showed reductions in many dystocia related death losses and pathologies. Occurrences of stillbirths, defined as calf deaths occurring before, during, or within 48 hours after delivery, in unmonitored cows and heifers were approximately 11.9% compared to 0.85% in monitored groups. Placental retention occurred in 12.93% of control groups compared to 0% in monitored groups. Subsequent postpartum disease evaluation compared the incidence of uterine infections, including metritis and endometritis. Uterine infections were found in 19.28% of control groups and 3.3% of monitored groups. Calving-to-conception intervals showed corresponding results. Unmonitored control groups averaged 147.2 day intervals compared to monitored groups which showed an average of 115 day intervals. Results from this study supported suppositions made by Bellows et al. (1987), Dargatz et al. (2003), and many others who advocate that quick response time leads to reduced losses associated with prolonged and difficult births.
Minimizing losses associated with bovine dystocia is of paramount importance in assuring the financial viability of any beef or dairy operation. The most common cause of postnatal calf mortality is dystocia. Studies suggest that over 50% of these death losses could be prevented if appropriate obstetric intervention was applied. A 2004 nationwide study revealed that 16.7% of heifers and 2.7% of cows on beef cow-calf operations required assistance during parturition.
Because losses due to dystocia are so significant and far reaching, determining methods of prevention is an important topic for discussion.

Research suggests that GWAS testing could be used to predict which dams and sires are likely to have a genetic propendency towards dystocial (DYS/mat and DYS/dir) births. Additionally, monitoring estrogen and progesterone hormone concentrations during the last week of gestation can be useful in predicting which animals will be expected to have dystocia due to a hormone imbalance. Monitoring hormone levels can also provide a method for predicting the time frame in which a cow is likely to

calve.
Many preventative measures have previously been implemented by producers with the objective of reducing dystocial births. Despite these efforts, dysocial events will always be expected, to some extent, in cow-calf operations. The most critical aspect to reduce both initial death loss and the subsequent sequelae of dystocia is timely obstetric intervention when needed. The key to determining time of intervention is the accurate identification of the onset of the birthing process.
Two possible methods of prediction are presented. First, diurnal changes in bovine body temperature ceases and overall body temperature drops at 48 to 8 hours prior to parturition. Detecting this change in body temperature gives an accurate window of time for which the cow can be expected to calve. Second, the use of a remote monitoring alarm system gives a more precise method of detection of the exact moment when the parturient process begins. Implementation of any these practices will improve dam health and breeding efficiency, lead to higher rates of calf survivability, and result in greater overall sustainability of any cow-calf operation.