Dystocia in Cattle: Prospective Analysis in Daily Veterinary Practice (N = 573 Parturitions)

Purpose: The aim of this prospective study was to collect cases of dystocia in 4 rural veterinary practices in Switzerland over 12 months, focusing on calf vitality. Methods: During 12 months, data of 573 assisted parturitions were collected. The age of the cows involved ranged from 2 to 17 years (median 5.2 yr) with a median gestation length of 288 days. Results: Overall, 651 calves were born (61.2% male). 481 were single and 85 were twin births. For 7 calves, no data were available. As to calf vitality: 66.1% of the calves were alive, 25.4% dead, 5.1% weak and 3.4% died during the assisted parturition process. The percentage of dead calves was higher in twins (43.5%) than in singletons (18.9%). The vitality was influenced by gestation length, parity and the time elapsed since the rupture of the amniotic sac. In this study, calf vitality was neither influenced by sex of the calf nor breed of the parents. A uterine torsion was found in 31.8% of the cases with the direction of the rotation an-ti-clockwise in 94%. Twins were twice as often in posterior presentation as single-born calves (31.4% versus 15.6%). Conclusion: Calf vitality was influenced by parity, gestation length and time from amniotic sac rupture to veterinary intervention.

The aim of this study was to collect cases of dystocia in the daily veterinary practice in Switzerland over 12 months and to describe the underlying causes. A special focus was set on calf vitality.

Data collection
Data of 4 rural veterinary practices in the canton of Lucerne, Switzerland, were collected over 12 months (January 2015 -December 2015) and for n = 573 cases. The veterinarians filled out a short questionnaire after each assisted calving.

Cow and pregnancy
Using the individual ear tag number of every cow, the following data were collected via the Swiss animal movement database (http://www.agate.ch/): breed, age, parity, date of last insemination, calving date.

Dystocia
Time elapsed between rupture of the amniotic sac and veterinary intervention was recorded. As herds are small in Switzerland, parturition is generally observed by owners very frequently and the time of the rupture of the amniotic sac is normally recorded. Monitoring systems are used seldom.
The position of the calf, feto-maternal disproportion, uterine inertia, uterine torsion, and applied calving assistance (including number of persons pulling) were registered by the veterinarians, including drugs administered. Additionally, information about the number of fetuses, gender, the estimated birth weight as well as the vitality and malformations of calves were gathered. Calving assistance was done by manual pulling through owners. A calf jack was only used in 3 cases.
The following categories of vitality were used: alive, dead, weak and dying during the assisted parturition process. "Weak" was defined according to Kovacs et al. with calves with low tonicity, needing support for sternal recumbency and head requiring support [10]. Drugs used under parturition were also listed. The cow's condition post partum (p.p.) focusing on injuries resulting from parturition was protocolled.
All data were then transferred to Excel sheets (Microsoft ® Office Excel 2007).

Statistical analysis
Descriptive statistical methods were used. Metric variables were described

Cow and pregnancy
Data from 573 cases were collected of which 15.2% were primipara. Median age of the cows was 5.2 yr, median parity was 3 and median gestation length was 288 days (

Dystocia
From all calvings needing veterinary assistance, 79.8% of the calves were presented in anterior presentation. Twins were twice as often in posterior presentation as single-born calves. The percentage of hip flexion was 16.0% in twins compared to 2.5% in singletons. A feto-maternal disproportion was recorded in 21.8% of the cases. Uterine inertia was found in 179 cows, thereof 45% were classified as primary uterine inertia ( Table 2). The number of cows suffering from uterine inertia increased with increasing parity (10.3% in heifers compared to 75% in 9 th parity). A uterine inertia was diagnosed in 31.6% of singleton dams and 28.2% of twin mothers. A uterine torsion was found in 31.8% of all cases, the direction of the rotation was counter-clockwise in 94% (Table 2). In 52% of the uterine torsions, the degree of the torsion was 270˚.    were slaughtered in an emergency during or immediately after parturition, there from in six cases the calf had been extracted, in one case even alive.
Odds-ratios with 95% Wald confidence limits for the parameter "living calf" versus dead, weak or dying calf for pregnancy dura-

Discussion
According to the practicing veterinarians, the distribution of the dam's breeds in this study reflected the distribution of the breeds in the region. In Brown Swiss cows of this study, uterine torsion was diagnosed in 45% of the cases compared to 31.8% including all breeds. Already Mock (2015) described a higher incidence of uterine torsions in Brown Swiss cows [12]. The rotation of the uterine torsions was anti-clockwise in 94% of the cases which is in agreement with Mock (2015) with 96.2% [12].
In Switzerland, mean pregnancy duration through all breeds was 287 d with longer durations in Brown Swiss (290 d) and shorter duration in Holsteins (282 d) [2]. Different studies describe an increased risk of dystocia with increasing gestation length [3] [4]. It is known that male calves are prolonging the duration of gestation [13]. The higher percentage of male calves (61.2%) in our study might explain a slightly increased median gestation length of 288 d.
The rupture of the amniotic sac is followed by delivery of the calf within 70 min [14]. The timing of intervention during stage 2 of calving clearly influences the risk of stillbirth, with later interventions resulting in a higher risk [15]. This could be demonstrated in this study as in the category > 3 hr between rupture  [18]. Although physiologic, such calves more often need assistance and are less vital [4]. This was confirmed, as posterior presentation was represented with 19.7% of the cases in our study. Additionally, twins were twice as often in posterior presentation as singletons.
Forced extraction with 1 -3 persons are more common in Switzerland than using "calf jacks" (in this study only used in 3 farms). However, it is not recommended that more than 2 persons are pulling, as the risk of injuries is increasing with increased force applied [18]. This could clearly be shown in our study with more than 50% of the cases with 3 persons pulling resulted in injuries compared to 13% with 1 person pulling.
The incidence of caesarean sections (2.4%) was lower than described by Wittwer (1999, 5.2%) [19]. An increasing rate of artificial insemination with sires selected for calving ease might have contributed to a better parturition process and less caesarean sections.
Primipara are suffering more frequently from dystocia than pluripara [2] [3], [16]. However, in our study only 15.2% were primipara, which is less than described by Wittwer (30.8%; 2000) in a former Swiss study on veterinary assistance during parturitions [19]. An explanation might be that in our study, 53% of the sires were beef bulls through AI, most of them selected for calving ease.
Additionally, the median age of the cows in our study as well as the median age of the cow population might be higher than in other regions of the world. Nevertheless, median age of the cows with dead calves or dying calves was lower than median age of cows with living calves (Figure 2).

Conclusion
66% of all calves were born alive with the aid of a veterinarian. Calf vitality was negatively influenced by lower parity, gestation length < 270 d, and an increased period from the rupture of the amniotic sac until the assistance of parturition.
For the farmers, the last point is the only modifiable one: if the parturition process does not advance after the rupture of the amniotic sac, veterinary assistance is needed without delay.