Kirsten Essmeyer:
Possible causes of increased frequency of stillbirth on a large dairy farm in Germany
It was the aim of this study to identify possible causes of stillbirth on a large dairy in Saxony, Germany, and to derive a prophylactic concept for the reduction of the rate of stillbirth on similar dairy facilities.
Four hundred and sixty-three primi- and multiparous cows were observed continuously starting from the time when the animals were moved into the
“reproduction barn” until after completion of parturition. General data such as ear tag number, date of moving, number of lactation, age and date of last insemination were recorded. Furthermore, body condition score (BCS), slope of the pelvis, animal height measured from ground to the Os sacrum, as well as external pelvic-measures (length, width) were determined. After parturition, the internal pelvic area was measured using the pelvic circle according to Bouldoire, Menissier and Vissac.
Upon first signs of the forthcoming labour such as uneasiness of the dam, vaginal discharge and/or abdominal contraction, every action of the dam and the barn staff were documented. The interval from rupture of the allantois/amnion sac until passage of the fetal forehead through the vulva (second stage of labour) and the duration of final expulsion of the fetus (third stage of labour) were recorded.
The birth process was classified in five degrees of difficulty and the positions of the fetus were documented. After birth, the following data were collected from the calves:
vitality, maturity, presence of malformations, sex, weight and various measurements of the fedlock joint and head.
Calves born dead and those that died within the first 24 h after birth, were classified as “stillbirth” and sent to the Institute of Veterinary Pathology, Veterinary Faculty of the University of Leipzig for pathological-anatomical and –histological examination.
Furthermore, a microbiological examination was performed by the Saxonian State Laboratory (LUA).
The following results were obtained:
1. Overall, 9.29 % of all birth were classified as stillbirth. The frequency of stillborn calves was higher in heifers than in cows (18.47 % vs. 4.48 %, P<0.0001). BCS was higher in heifers than in cows. BCS was negatively correlated with the internal pelvic area. Furthermore, there was a trend of a higher frequency of stillbirth in animals with a BCS >3.75 than in cows with a BCS of 3.25 to 3.75.
2. Duration of the second stage of labour influenced the outcome of labour. Dams with stillborn calves had a statistically significantly longer second stage than dams with living offsprings (median: 198.00 min vs. 73.00 min, P< 0.0001). Also, second stage of labour was longer in heifers than in cows (median: 136.00 min vs. 59.00 min, P<0.0001). There were relationships between the duration of second stage of labour and internal pelvic area and degree of pelvic adipose tissue. Internal pelvic area decreased and internal pelvic adipose tissue increased with increasing duration of the second stage.
3. The slope of the pelvis had an influence on frequency of stillbirth. Animals with a declining pelvis had statistically significantly less stillborn calves than animals with a horizontal pelvis (7.14 % vs. 15.69 %, P=0.0082).
4. In living calves, usually the second stage of labour dit not last longer than 2 h.
Therefore, it could be recommended not to intervene into the ongoing birth
process before 2 h after the rupture of the allantois sac. However, this time frame could be reduced when calves were in posterior presentation. Especially in
heifers,statistically significantly more calves were born dead in posterior than in anterior presentation (50,00 % vs. 15,67n %, P= 0.002).
5. The degree of abdominal contractions of the dam also had an influence on the outcome of labour, because it determined the length of the second stage of labour. Time of labour increased as the degree of abdominal contractions decreased.
6. Birth processes that occurred with a working shift were connected with a lower rate of stillbirth than those that started with one shift and ended with another (8.10
% vs. 16.18 %, P=0.034). This could be due to insufficient exchange of
information between shifts. The negative effect of change of shift was especially noticeable when the responsibility was handed over to the milking shift, the staff of which usually has other chores than birth surveillance.
7. Frequency of stillborn calves was lower in spontaneously delivered calves than in those delivered by severe extraction and caesarean section (2.27 % vs. 28.42 % and 41.18 %, respectively, P<0.0001). Also in calves that were delivered by light or medium severe extraction there were less stillbirths than in calves born after severe extractions or caesarean section (4.84 % and 7.41 % vs. 28.42 % and 41.18 %, respectively, P<0,05). Furthermore, vitality was higher in spontaneously born calves than in any type of other assisted calving (median of APGAR-score:
7.22 vs. 6.65, 6.04, 4.28, 4.35, P<0.05). There was also a connection between vitality and duration of second stage of labour. As the latter increased, vitality decreased.
8. Frequency of stillbirth was higher in male than in female calves (12.24 % vs. 7.14
%, P=0.058). However, the weight or skeleton measures were of minor importance for the rate of stillbirth.
9. As the most fequent findings, the pathological examination revealed fetal atelectase (88.37 %), aspiration of amniotic fluid (79.09 %) and bleeding of the thymus (32.56 %), the latter of which could be the result of mechanical lesions due to severe extractions and/or lack of oxygen supply. Further findings were malformations (9.30 %), infections (4.65 % of the calves, 22.72 % of the placenta), fractures (20.93 %), bleedings at various locations (60.47 %) and spotted muscles (4.65 %). After difficult extraction, 100 % of the calves either in anterior or posterior presentation revealed fractures and/or luxation of the ribs.
Also, 100 % and 90 % of those calves, respectively, had bleedings in various organs, and 50 % and 20 % of the calves, respectively, revealed edema of the brain.
10. In conclusion, the severe extraction turned out to be the least favourable of the 5 classes of obstetrical measures. Furthermore, duration of the second stage of labour beyond 2 h was connected with a higher risk of stillbirth. Duration of the second stage of labour was negatively influenced by weak abdominal
contractions and a decreased diameter of the inner pelvic area. In addition, discontinuous control of the birth process with shortcomings of communication had a negative effect on the frequency of stillborn calves.