Camp. Biochem. Physiol. Vol. 83C, No. I, pp. 19-22, 1986 0306-4492/86 $3.00+0.00

Printed in Great Britain c; 1986 Pergamon Press Ltd

PROSTAGLANDIN (PGF,,)-INDUCED PARTURITION IN RED DEER (CEWUS ELAPHUS L.)

ROLF LANGVATN

Directorate for Wildlife and Freshwater Fish, Game Research Division, Tungasletta 2, 7000 Trondheim, Norway. Telephone: (07)91-3020

(Received 14 June 1985)

Abstract-l. Prostaglandin PGF,, seems to act satisfactorily as a birth inducing agent in red deer (Cervus elaphus).

2. The progress of actual delivery and lactation in the experiments of induced parturition corresponds with observations from natural conditions.

3. The pattern of response time to the birth inducing agent agrees with experience from domesticated species, being longest in females with the least developed fetuses.

4. Complications such as those reported from practice with induced parturition in domestic species were not experienced in the three experiments on red deer.

5. Applications of prostaglandin PGF,, prior to approximately 18-20 days preterm probably reduce chances for the offspring to survive. This seemingly being due to ontogenetical immaturity in the fetus, and deficient hormonal development in the mother, necessary for normal lactogenesis.

INTRODUCTION

During the last decade considerable interest has been shown in artificial induction of parturition in domes- tic bovids. For a general introduction and survey see, e.g., Jiichle (1971, 1978), Scherven (1972), Jonsgard (1973), Watner et al. (1974), Thorburn et al. (1977) and First (1979). Numerous papers report in detail tests and comparisons of a variety of chemical agents and treatment regimes in different species (Liggins 1968, 1969; Zerobin et al., 1973; Davies et al., 1979; Welch et al., 1979; Hammond and Matty, 1980; Harman and Slyter, 1980; Johnson and Jackson, 1980). In particular, the importance of prosta- glandins, either alone or in combination with other agents (e.g. corticosteroids), has been demonstrated by extensive tests and management programs to terminate pregnancy preterm (Henricks et al., 1977; Plenderleith, 1978; Day, 1979; Langford, 1979; Welch et al., 1979; Hammond and Matty 1980). However, current experience in artificial induction of par- turition has been restricted to domesticated species, and with few exceptions (e.g. Reynolds and Autenrieth, 1980) no reports concerning wild animals are available.

This paper reports three experiments with induced parturition in Norwegian red deer (Cerous elaphus atlanticus, Lsnnberg). The principal purpose of the experiments was to investigate aspects of cardiac functions in premature calves.

MATERIALS AND METHODS

Three different hinds were used for the experiments which took place in 1980, 1983 and 1984. All hinds were multi- parous, living under near-natural conditions in an enclosure (18 ha) at Songli research station, Orkdal, Norway, together with six to 10 other red deer of different sexes and ages.

The procedure for inducing parturition was the same in all cases, a single intramuscular injection of Dinolyti@ vet., Dinoprost Tromethamin (PGF,,) (Upjohn). The agent is a prostaglandin (tham salt) with a luteolytic effect, causing functional and morphological regression of the corpus luteurn. Further details are given in Table 1.

Although there were significant weight differences between the experimental hinds (Table l), they were all in good physical condition. Differences in live weight were largely due to differences in skeletal size.

Data of conception, or rather copulation, was observed in the case of hind II. For hind I it was known to have taken place between 23 and 30 November. Except for that period hind I was isolated from stags. Hind III showed indications of estrus on November 28 1983, but copulation was not confirmed. After November 29 she refused courtship from the stag, who also seemed to loose interest in hind III.

RESULTS AND DISCUSSION

Hinds I and II were kept under close observation both before and after giving birth. Parturition was in all respects normal and similar to previous deliveries from the same hinds, as well as other hinds in the enclosure and in the wild (Arman, 1974a,b; Arman et al., 1978). The period of labor lasted from 20 to 30min, from first recorded contractions in the ab- dominal wall to delivery. The labor period was shortest in hind II.

Visual assessment suggested a significant size in- crease in the udder during the 3 hr before delivery, and especially so during the first couple of hours after parturition. Lactation appeared to develop normally, and both calves had their first successful suckling- bouts within 45 min of birth. Fetal membranes and placenta were expelled and eaten within 80min in both cases (see Arman 1974a, Arman et al., 1978). Other details are given in Table 2.

19

20 ROLF LANGVATN

In the case of hind III the actual delivery was not witnessed, although introductory symptoms were ob- served from 51 hr after prostdglandin had been ad- ministered. However, the signs of a forthcoming birth were weak, and seemed to cease after 2 hr. The calf was born 54-62 hr after the injection was given, and it was not until the hinds weight was checked and her vulva examined that we learned that birth had taken place. At that time fetal membranes had been expelled.

The udder of hind III did not increase significantly in size either before or after parturition, and there were no signs of lactation. Also, the behavior of hind III seemed to differ from that of other hinds giving birth. Hind III was more social with other red deer and followed the group’s activity rhythm. The calf of hind III was later found dead. Post mortem exam- ination did not reveal whether it was born alive as scavengers already had visited the carcass, and it was difficult to get a precise picture of events. However, fetal souffle was registered at the time prostaglandin was administered to the hind.

Obviously, induction of parturition in hind III worked to the extent that a calf was presented, though little is known about the time aspect. Thus, hormonal activity (primarily gestagens, estrogens, relaxin and oxytocin) was presumably fairly normal and sequentially coordinated during the labor and delivery. On the other hand, the fact that the udder did not enlarge to any recognizable size, and lactation did not occur, indicate deficiency in the hormonal activity which initiates development and growth of udder tissue. It is possible that parturition was in- duced at a time in the gestation period prior to the stage when the complex, sequential set-up of hor- mones necessary for normal lactogenesis was estab- lished.

It should also be mentioned that when primiparous in 1981, hind III gave birth to a male calf on September 26. The calf was born alive, but died a few days later. In that case also no udder growth or lactation took place.

Birth weights differed among the three calves (Table 2), and though female offspring are on average lighter than males (Mitchell, 1971; Staines, 1971; Arman et al., 1978; Guinness et al., 1978a,b; Blaxter and Hamilton, 1980; Clutton-Brock et al., 1981), differences in ontogenetic maturation and growth are the most likely explanations for the observed relationships in the experiments reported here.

Response time from injection of prostaglandin to parturition was longest for the hinds carrying the least developed (lightest) fetuses, an observation in accordance with experience in domesticated species (Welch et al., 1979; Harman and Slyter 1980). It seems unlikely that the small difference in relative dosage given to the hinds could explain the observed differences since there is no consistency between dosage and response time.

It is difficult to know exactly how long prior to normal term the calves were born since gestation length in red deer is known to vary (Guinness et al., 1971; Arman, 1974b). Male calves tend to have a longer gestation length than females (236 f 4.8 vs 234 I5.0 days, Clutton-Brock et al., 1982). Also, hinds receiving supplementary food have a gestation

PGF,,-induced parturition in deer 21

length 5 days shorter than free ranging hinds (231 f 4.4 vs 236 i: 6.6 days, Guinness et al., 1978b). Considering this information, prematurity of the experimental calves cannot be assessed accurately by comparing only actual and normal (average) gestation length. However, a reasonable approach to an estimate for prematurity is to appraise all the information available. This includes birth weights of calves born to each of the experimental hinds in previous years, general knowledge and data on in utero growth rates, skeletal proportions, tooth devel- opment, neonatal cardiophysiological characteristics and general morphological features (Espmark and Langvatn, in press and unpublished data).

Hind I had three calves (all males) prior to the experimental calf, averaging 9.3 kg (range 9.0-9.6 kg) at birth. Assuming female offspring have birth weights approximately 93% that of males (Mitchell, 1971; Staines, 1971; Arman et al., 1978; Guinness er al., 1978a; Blaxter and Hamilton, 1980), and assuming a fetal weight increase of 0.17 kg/day dur- ing the last 2 weeks in pregnancy (unpublished data), it appears that the calf was born approximately 17 days prior to normal term. Daily fetal gains of this magnitude are comparable to relative growth rates reported for other ungulates (Armstrong, 1950; Hudson and Browman, 1959; Grunert and Zaremba, 1979; Robbins and Robbins, 1979).

Similar calculations for hind II (previously three male and four female offspring, range 7.3-9.0 kg) indicate a prematurity of approximately 5 days for the experimental calf. Examination of tooth status in the two calves, and comparison of fetal and neonatal reference collections, support the above appraisals and shows that the calf of hind II was more mature than the calf of hind I. The same applies to a comparison of fur development (hair length and thickness) and body proportions (length of hindleg and hip dimensions).

Additional evidence for the estimates of pre- maturity in Table 2 is provided by electro- cardiographic recordings and observations of freez- ing behavior and bradycardic response to alarm stimuli. Normally this type of reaction ceases 4-7 days post partum (Espmark and Langvatn, 1979; in press), i.e. when body weight is approximately 11-12 kg. At an age of 21 days the calf of hind I weighed 10.4 kg and showed the freezing response. Twenty-eight days after birth and weight was 12.4 kg and the calf showed no freezing or immobility behavior.

The calf of hind II showed bradycardic response and immobility behavior for 7 days, by which time its weight was 12.4 kg. This is 1 day longer than expected on the basis of average figures from calves of com- parable weights. However, it is well within the range of variation to be expected. Details of cardiophysio- logical characteristics in neonatal red deer calves are given by Espmark and Langvatn (in press), see also Langvatn (1984).

Birth weight of the calf of hind III was estimated to have been approximately 5.9 kg, based on skeletal proportions and body size. Considering tooth devel- opment, ossification in the skeleton, cranial sutures and other anatomical criteria, it appeared that it was more premature than the calf of hind I, in spite of

probably being somewhat heavier. For example, pre- molars and incisors were completely covered by the gums in the lower jaws. In addition, the crown edges of first incisors were dorsoventrally oriented and bilaterally parallel to the median plane, a premature position ~approximately 3 weeks preterm compared to reference collections, unpublished data).

It is difficult to give a reliable estimate for pre- maturity in the case of hind III, as no in uiuo information on the calf was available. However, from an overall appraisal of the data and information to hand the indications are that the calf of hind III was born some 20-25 days preterm. Provided hind III conceived at the time signs of estrus was observed (28-29 November 1983), and assuming a gestation length of 236 days without experimental interference, actual gestation length was 214-215 days. This indi- cates a prematurity of 21-22 days. Taking estimated birth weight (5.9 kg) and adding average weight gain over the last 3 weeks of pregnancy (0.15 kg/day, unpublished data) one arrives at an estimate for expected birth weight of approximately 9.1 kg with- out induced parturition.

This is approximately 0.6 kg heavier than average figures for male calves (2 = 8.5 kg, SD = 0.81, N = 11, unpublished data). Three earher offspring of hind III weighed 8.2,9.3 and 8.8 kg for two males and one female, respectively. Thus a male calf weighing 9.1 kg at birth is not unlikely for this big hind. Also, as shown by Blaxter and Hamilton (1980) heavy hinds are more likely to give birth to heavy calves.

During the first week of life the calf of hind II gained weight relatively fast (0.68 kg/day) compared with average figures (0.56 kg/day) (see Espmark and Langvatn, in press). Also later the calf performed quite well as to growth and development.

The calf of hind I was small at birth and after a transient weight gain of 0.2 kg the first day, it lost 0.5 kg over the next 48 hr. Especially during the first three days its mobility was poor and probably re- duced suckling success in spite of a very caring mother. Average weight gain over the first 5 weeks was 0.24 kg/day with a highest rate between days 8 and 21 post partum (0.35 kg/day). The calf never caught up in size with conspecifics of same the sex and age, and it always appeared tender and timid.

Considering the performance of the previous offspring of hind I, it seems likely that growth and development of the experimental calf was influenced primarily by its premature status at birth, even though Hamilton and Blaxter (1980) report lower growth rates in calves born to small hinds compared to large hinds, and that female calves gain weight at lower rate than male calves.

It is not known if, or for how long after birth, the calf of hind III stayed alive. But even if born alive it did not have much chance of surviving since the hind failed to lactate. Also, considering the locomotory ability of the calf of hind I, it is uncertain whether the calf of hind III would have been physically able to move and suckle sufficiently, even if hind III had been lactating. Finally, and probably more important, it is likely that the calf was too premature physiologically to survive EX utero without artificial treatment. This applies perhaps especially to respiration, where deficient production of surfactants at this stage pre-

22 ROLF LANGVATN

term is most likely to influence alveolar shape and function in lung tissue, and thereby gas exchange capacity.

Even though only three hinds were used in these experiments the results suggest that prostaglandin (PGF,,) may be used as a birth inducing agent in red deer. Furthermore, the agent may also be useful in cervid research and treatment such as in experimental situations where the control of parturition is of interest. Prostaglandin (PGF,,) may also aid studies of prematurity and ontogeny, but careful consid- eration and more data are needed on how long prior to normal term birth inducing agents can be applied if the calf is to survive. From general physiological considerations and with some support from these experiments, one could suggest that approximately 18-20 days preterm represents a critical period in these respects.

Complications like retained fetal membrances and dystocia, reported in connection with induced par- turition in domestic species, were not experienced in the experiments on red deer, referred to here, and at least two of the hinds (I and II) reproduced normally after the experiments.

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