Foetal mortality at different stages of gestation in ... - Science Direct

ANIMAL REPRODUCTION SCIENCE ELSEVIER

Animal ReproductionScience40 (1995) 89-97

Foetal mortality at different stages of gestation in alpacas ( Lama pacos) and the associated changes in progesterone concentrations T.W. Knight a,*, M. Ridland a, I. Scott b A.F. Death T.K. Wyeth a

a

A gResearch, Flock House Agricultural Centre, Private Bag 1900, Bulls, New Zealand t~AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand

Accepted 1 June 1995

Abstract From spring 1990 to autumn 1993, 44 spring-mated and 82 autumn-mated alpacas at Flock House Agricultural Centre (FH) had their pregnancies monitored by ultrasound every 10-14 days from day 20 to day 120 of gestation. A further 32 autumn-mated alpacas at Tara Hills High Country Research Station (TH) were monitored in 1992. Trans-rectal probes were used in early gestation and trans-abdominal probes in late gestation. As techniques for pregnancy diagnosis in alpacas improved during the experiment, the stage of gestation at which pregnancies were first confirmed became earlier. From spring 1991 onwards most pregnancies were first diagnosed at 20-30 days of gestation. Progesterone concentrations were determined from individual blood samples collected each time alpacas were brought in for pregnancy diagnosis from spring 1991 onwards. Foetal loss from day 30 onwards was 25.7% with the foetal losses after day 120 of gestation being 9.6-16.7% in different mating groups. There were apparent differences in the pattern of foetal loss between autumn- and spring-mated alpacas at FH with foetal losses before day 81 being 17.3% and 2.8% respectively and no significant difference in foetal loss after day 81 of gestation. The younger New Zealand born alpacas had a similar incidence of foetal loss to the older Chilean born alpacas. There was a suggestion at TH that the stress of transport and relocation of a group of alpacas at 212 _+ 3 days of gestation precipitated a high incidence of foetal loss. The spring-mated alpacas had a longer gestation length (350.1 _+ 2.7 days) than autumn-mated alpacas at FH (340.2 -I- 1.9 days). Keywords: Alpacas; Foetal loss; Progesterone; Reproduction

* Corresponding author: Tel. + 64 6 322 1400; Fax. + 64 6 322 1954; e-mail [email protected]. 0378-4320/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI. 0378-4320(95)0 141 5-2

90

T. W. Knight et al. /Animal Reproduction Science 40 (1995) 89-97

1. Introduction

Low reproductive performance of alpacas is a major problem on the altiplano of South America, with an estimated 50% of females of breeding age failing to produce young each year. A high proportion of this loss is attributed to embryo and foetal mortality which is higher than in other domestic animals (Fernandez-Baca et al., 1970a). Alpacas in New Zealand are generally grazed on abundant green pasture over most of the year and this may result in lower levels of embryonic and foetal mortality than reported in South America. Luteal inadequacy has been shown to be a cause of embryonic loss in sheep (Wilmut et al., 1986). Progesterone supplements post-mating has improved embryonic survival, and increased pregnancy rates and fecundity in sheep (Davis et al., 1986; McMillan, 1987), and pregnancy rates in cattle (Wiltbank et al.,. 1956). Embryonic and foetal losses in alpacas have been associated with luteal inadequacies and low plasma progesterone concentrations (Sumar, 1983). There is evidence that the corpus luteum of pregnant alpacas starts to regress on day 13 after mating and then returns to full activity by day 17, and that a corpus luteum located on the right ovary regresses more rapidly than that on the left ovary (Fernandez-Baca et al., 1970b). The aims of this experiment were to determine the incidence of foetal mortality in alpacas at different stages of gestation, and to determine if foetal mortality was associated with low plasma progesterone concentrations prior to foetal loss.

2. Materials and methods

In February 1990, 50 mixed aged alpacas (47 females, 3 males) arrived at the Flock House Agricultural Centre FH (40°14'S; 175°16'E) from Chile. The alpacas were mated in October and November 1990 and those not conceiving were remated in February, March and April 1991. This pattern of mating in February, March and April (autumn mating) and in October, November and December (spring mating) was maintained. The long gestation of alpacas (341.6 days; San-Martin et al., 1968) means most animals remained in the same mating groups; the exception being where they failed to conceive at one season of mating and were remated the next season of mating. Initially, female alpacas were mated twice daily for 3 days with the same male, but after 1992 the females were only mated once at each oestrus, because repeated mating was found to have no effect on conception rates (Knight et al., 1992). Ten to 14 days after mating, each female alpaca was tested for sexual receptivity with a male. Alpacas not conceiving were remated with the same male. Tests of sexual receptivity continued for 2-3 months in each season. The ultrasonography techniques on alpacas have been described by Ridland et al. (1992). A real-time B mode (Tokyo Keiki) ultrasound fitted with a 3.5 MHz trans-abdominal probe was used for the spring 1990 to autumn 1992 matings and a similar probe for an Aloka SSD-210DX ultrasound was used for the spring 1992 to the autumn 1993 matings. In addition, for the autumn 1991 to autumn 1993 matings the Aloka ultrasound

T.W. Knight et al./Animal Reproduction Science 40 (1995) 89-97

91

with a 5 MHz trans-rectal probe was used. The first diagnoses of pregnancy in spring 1990 and autumn 1991 were at 49-70 days and 51-60 days respectively. Thereafter, the first positive diagnoses of pregnancy were most often at 20-30 days after mating. Once each alpaca was diagnosed pregnant, it was monitored with ultrasound every 10-14 days. The trans-rectal probe was used up to 80 days of gestation, and thereafter the trans-abdominal probe was used until the foetus became too large to readily identify if it was alive. This was usually soon after day 120 (Ridland et al., 1992). Foetal mortality was considered to have occurred if an alpaca had been confirmed pregnant at the previous 10-14 days monitoring with ultrasound, and subsequently no foetus could be found on two successive 10-14 day periods, or if no heart beat could be found in the older foetuses. Foetal mortality after day 120 was presumed to have occurred in those alpacas failing to give birth after-being diagnosed as pregnant at 111-120 days of gestation. In autumn 1992, 32 alpacas at the Tara Hills High Country Research Station (TH) (44°32'S, 169°54'E) were included in the study. Alpacas from Chile had arrived at TH in September 1989 and they were first mated in November 1989. Thereafter, a spring and autumn mating system similar to FH was used. An Aloka SSD-210DX ultrasound fitted with a 5 MHz trans-rectal probe was used in 1992 to monitor pregnancy every 10-18 days, starting 20-30 days after mating. From approximately 90 days post-mating, a Toshiba SAL 32B ultrasound fitted with a 3.5 MHz trans-abdominal probe was used to monitor pregnancy on a monthly basis. Most of the pregnancies monitored were on alpacas born in Chile. At FH, New Zealand born alpacas, 1-2 years old, were present in autumn 1992 (4/25) and 1993 (15/38) and in spring 1992 (3/15). At TH, 11 of the 32 alpacas were born in New Zealand. Daily observations of the alpacas were made throughout parturition, and the day of parturition was recorded for each alpaca. All alpacas were weighed 1 month before mating. In the calculation of the incidence of foetal mortality, only alpacas which were diagnosed as pregnant in the previous 10-18 days were included. The stage of gestation at which death of the foetus occurred was taken as the interval from the last mating to the day of the first negative diagnosis of pregnancy. The incidence of foetal mortality was calculated separately for each 10 day period from day 30 to day 120 of gestation. Foetal deaths after day 120 are presented as one group since at FH only a small proportion of the alpacas were scanned after day 120. The numbers of alpacas included in the calculations varied with each 10 day period because of the different times of gestation that monitoring started (Table 1). Cumulative percentage of foetal losses were calculated by summing the percentage losses over each period. Commencing at the spring 1991 mating at FH and the autumn 1992 mating at TH, all alpacas diagnosed as pregnant were blood-sampled at the time of each ultrasonography up to day 120 of gestation. The blood was collected by jugular venepuncture using 10 ml sodium heparinised vacutainers. Samples were then centrifuged at 1000 × g for 15 rain, and the plasma was removed and stored at - 2 0 ° C until analysed for progesterone by the method described by Ridland et al. (1992). Inter- and intra-assay coefficients of variation were 13.7% and 8.6%, respectively, over the working range of 1.0-20 ng per tube. The assay sensitivity was 0.02 ng ml -r plasma. For comparison of plasma

92


Table 1 Number of alpacas pregnant in the previous 10 day period, and the number and percentage of these alpacas losing foetuses in each 10 day period together with the cumulative percentage of alpacas losing foetuses 10 day periods from mating 31-40 41-50 51-60 61-70 71-80 81-90 91-100 101-110 111-120 >120 Flock House Spring No. pregnant a No. lost b % lost c Cumulative % d

22 0 0 0

27 0 0 0

30 0 0 0

35 1 2.8 2.8

35 0 0 2.8

42 0 0 2.8

42 1 2.4 5.2

41 1 2.4 7.5

40 1 2.5 10.0

39 4 10.3 20.3

Autumn No. pregnant No. lost % lost Cumulative %

41 3 7.3 7.3

61 2 3.2 10.5

66 1 " 1.5 12.0

78 2 2.6 14.6

76 2 2.7 17.3

74 0 0 17.3

74 1 1.4 18.7

73 0 0 18.7

73 0 0 18.7

73 7 9.6 28.3

Total

63 3 4.8 4.8

88 2 2.3 7.1

96 1 1.0 8.1

114 110 116 116 3 2 0 2 2.6 1.8 0 1.7 10.7 12.5 12.5 14.2

114 1 0.9 15.1

113 1 0.9 16.0

112 11 9.8 25.8

24 0 0 0

25 0 0 0

31 0 0 0

30 0 0 6.3

30 0 0 6.3

30 5 16.7 23.0

No. pregnant No. lost % lost Cumulative %

Tara Hills Autumn No. pregnant No. lost % lost Cumulative %

32 1 3.1 3.1

31 0 0 3.1

31 0 0 3.1

31 1 3.2 6.3

a Number of the alpacas pregnant in the previous 10 day period. The values increase as gestation progresses because of the increasing accuracy of pregnancy detection later in gestation, and the values decrease as embryos die. h Number of alpacas losing a foetus. c Percentage of alpacas losing a foetus. d Cumulative percentage of alpacas losing foetuses.

p r o g e s t e r o n e concentration, data f r o m each alpaca w h i c h lost a foetus b e t w e e n days 30 and 120 o f gestation w e r e paired with an alpaca which had not lost a foetus and had m a t e d at the s a m e t i m e (_+ 5 days). O n l y the plasma samples f r o m these alpacas and plasma samples f r o m f i v e alpacas w h o s e pregnancies w e r e questionable w e r e analysed for progesterone. T h e p l a s m a p r o g e s t e r o n e concentrations for alpacas with normal pregnancies was c o n s i d e r e d to be 2 ng m l - 1 or greater (Ridland et al., 1992). 2.1. Statistical analysis Chi square analyses w e r e used to c o m p a r e the i n c i d e n c e o f foetal mortality in N e w Zealand and C h i l e a n born alpacas, and foetal losses occurring after day 81 o f gestation b e t w e e n locations, and b e t w e e n seasons of mating. Statistical analysis o f earlier foetal loss and overall foetal loss c o u l d not be m a d e because the values w e r e calculated f r o m c u m u l a t i v e percentages. The small n u m b e r o f losses in each period o f gestation, e x c e p t after day 120, p r e c l u d e d statistical analysis based on each period of gestation. A n a l y s i s of variance using G L M procedures (Statistical A n a l y s i s Systems Institute Inc., 1987)


93

were used to compare gestation lengths between spring- and autumn-mated alpacas at FH.

3. Results The mean ( ___SEM) liveweights of the autumn- and spring-mated alpacas at FH were 65.1 _+ 2.5 kg and 56.5 + 3.0 kg, and for the autumn-mated alpacas at TH it was 71.2 _+ 1.9 kg. Multiple pregnancies have not been diagnosed by ultrasonography at FH or TH in any of the 158 alpacas diagnosed as pregnant. Five alpacas in which pregnancy status was questionable because no clear images of the foetuses were recorded, were found to have plasma progesterone concentrations of less than 1 ng m1-1. These animals were assumed not to have conceived and were removed from subsequent analyses. Overall, 25.7% of foetuses were lost between day 30 and parturition (Fig. 1) with losses being similar at TH (23.0%) and FH (25.8%). Considering only the FH data, 20.3% of spring-mated alpacas lost foetuses compared with 28.3% of those mated in autumn (Table 1). Before day 81, the spring-mated alpacas at FH lost 2.8% of foetuses compared with 17.3% of foetuses lost in the autumn-mated alpacas. Although these data could not be analysed statistically, the large difference suggests there was a season-ofmating effect at FH on foetal mortality. After day 81, there were no significant differences ( X 2 = 0.37; P > 0.5) in foetal loss at FH between autumn- and spring-mated alpacas. Similarly, the foetal loss after day 81 was not significantly different ( X 2 = 0.74;

14-

- 30

12 ~10

A

-25

o~

-20

u~ o

09

¸

I

o

u//.z

-15

o u_

~///I i///~ i///i ////I ,/111

4-

, m

-10 "~ "5

E

P'//A

~

////~ ,//H

2-

0 o >

I..//'/ i///,

-5

0 I i

0

35

45

55

65

75

85

95

105

115 > 1 2 0

Days of gestation Fig. 1. The histogram shows the incidence of foetal loss in alpacas in each 10-day period of gestation from days 30 to 120, and foetal losses after day 120. The cumulative percentage of foetal losses is shown by the fiequency polygon.


94

P > 0. l) between the autumn-mated alpacas at FH and those at TH. At both locations the percentage of foetuses lost after day 120 of gestation (9.8% and 16.7% for FH and TH, respectively) was high (Table 1). All the foetal losses after day 120 of gestation at TH occurred in a group of 16 alpacas at 212 ___3 days of gestation which were transported for 2 h to a new location. There were two imported Chilean alpacas at FH which repeatedly lost their foetuses and the foetuses lost by these two alpacas accounted for 23% of all foetal loses. They were first mated in autumn 1991 and lost foetuses at 60-80 days of gestation. They were remated in spring 1991 and lost their foetuses after day 90 of gestation. They were again mated in spring 1992 and lost their foetuses after day 120. A third imported Chilean alpaca mated in spring 1990 lost its foetus at 102 days of gestation and never conceived again after five mating periods over 3 years. There was no information on the incidence of repeated foetal loss in alpacas at TH. The foetal loss in the 22 New Zealand born alpacas at FH (18.8%) was not significantly different ( X 2 = 0.032; P > 0.5) from the foetal loss of 23.2% in the 56 Chilean-born alpacas which were first diagnosed pregnant at the same stages of gestation, and in comparable years and seasons as the New Zealand born alpacas. The 11 New Zealand born alpacas at TH had a foetal loss of 18.2% which was not significantly different (X 2 = 0.007; P > 0.5) from the foetal loss of 23.8% for the Chilean-born alpacas at TH. Progesterone concentrations were measured in 12 alpacas which lost foetuses between days 30 and 120 of gestation. Two of these alpacas had low plasma progesterone concentrations 10-20 days before the first ultrasonogram had indicated the foetus had been lost, and despite the foetuses appearing normal. One of these was an alpaca that

e-

,-

5

.9

~

4

u C 0

°

\

3

\

c

\

o

\

~

2

o.

1

\

E -D .

i

0

-45

-35

-25

-15

-5

0

Days before foetus confirmed dead I-Control - - - Foetal loss

Fig. 2. The mean ( +_SEM) progesterone concentrations in the plasma in eight alpacas which lost foetuses, and another eight alpacas which had no foetal loss.


95

subsequently died of cancer. It lost its foetus at day 65 of gestation at which time it had a plasma progesterone concentration of 0.05 ng m1-1. On days 56 and 35 of gestation the plasma progesterone concentrations were 0.9 ng and 1.7 ng ml-l respectively. The second alpaca was first diagnosed pregnant on day 27 of gestation and had a plasma progesterone concentration of 1.0 ng m1-1. The foetus was not present on day 37 of gestation. Another two alpacas had 4.0 and 6.6 ng ml-l progesterone plasma on the day they were first diagnosed as not pregnant, but 10-12 days later the plasma progesterone concentrations had declined to 0-0.4 ng ml-1. The remaining eight alpacas had plasma concentrations of progesterone above 2 ng m1-1 up to the last positive pregnancy diagnosis, but 5-20 days later when the alpacas were first diagnosed as not pregnant, the concentrations had decreased to 0.4 +_ 0.1 ng ml-~ (Fig. 2). The mean duration of gestation for the spring-mated alpacas at FH of 350.1 ___2.7 days was longer ( P < 0.01) than the duration of gestation for the autumn-mated alpacas of 340.2 _ 1.9 days. For the autumn-mated alpacas at TH the mean duration of gestation was 336 _+ 1.6 days.

4. Discussion

Total embryonic and foetal loss from the alpacas in this experiment was likely to be greater than the 25.7% recorded since only a small proportion of the losses from fertilisation to day 30 of gestation would have been identified in this experiment. Fernandez-Baca et al. (1970a) found a 50% loss over the period from fertilisation to day 30 with no foetal loss after day 30 in one trial, and a 44% foetal loss after day 30 in a second trial. The 25.7% foetal loss in the alpacas in the present experiment was much higher than the 2 - 6 % foetal loss after days 30-40 in sheep (Quinlivan et al., 1966; Wilkins et al., 1984) especially considering the alpaca losses does not include losses of foetuses from multiple pregnancies as occurs in sheep. Since the alpacas had access to ample green feed over mating and pregnancy, the high foetal loss cannot be attributed to poor nutrition as it has been in South America (Novoa, 1970). A proportion of the foetal loss at FH could be attributed to several imported Chilean alpacas which repeatedly lost their foetuses. The younger New Zealand born alpacas tended to have a lower foetal loss than the imported Chilean-born alpacas, but the differences were small and not significant. At TH the loss of foetuses after day 120 of gestation could be associated with the stress during transportation and the adaptation to a new environment, since there were no losses of foetuses after day 120 in 16 pregnant alpacas remaining at TH. Foetal losses after day 120 of gestation of 9.8-10.3% were, however, found at FH, despite the alpacas being left undisturbed after day 120 of gestation. The 17.8% foetal loss between days 30 and 81 of gestation in autumn-mated alpacas at FH compared with 2.8% foetal loss in spring-mated alpacas, could reflect a seasonal effect on foetal loss. At TH, however, the autumn-mated alpacas only had a 3.2% foetal loss before day 81 of gestation. This suggests that the differences at FH between autumn- and spring-mated alpacas were not caused by seasonal differences in tempera-

96


ture or photoperiod. Seasonal differences in pasture quality is unlikely to be the cause of the differences, since pastures would be of lower quality in autumn at TH than at FH. In only two of the 12 alpacas was there any suggestion that an inadequacy of progesterone may have caused foetal loss. One of these alpacas died of cancer soon after the foetus was lost. The other alpaca was diagnosed pregnant at 27 days on the basis of a vacuole of pregnancy and a foetus, but no heart beat was observed (Ridland et al., 1992). The foetus may have already died at this first diagnosis and blood sampling. The results suggest that supplementing alpacas with progesterone between 30 and 120 days of gestation is unlikely to reduce foetal loss. Where progesterone supplementation has improved pregnancy rates in other animals it has been given earlier in gestation, before the time the corpus luteum of the oestrous cycle changes to the corpus luteum of pregnancy (Wiltbank et al., 1956; Davis et al., 1986; McMillan, 1987). Foetuses in alpacas are only carried to term in the left uterine horn despite the left and right ovaries ovulating equally (Fernandez-Baca et al., 1970a; Sumar, 1985; Fernandez-Baca, 1993). Embryos resulting from the ovulation of the right ovary must migrate to the left uterine horn, but a proportion remain in the right uterine horn and are lost before parturition. Fernandez-Baca et al. (1970a) found in alpacas slaughtered at different intervals after mating that 13-29% of embryos were in the right uterine horn 28-45 days after mating, but no embryos were present in the right uterine horn at days 87-95 of gestation. It appears the right uterine horn is unfavourable for embryo and fbetal development (Fernandez-Baca, 1993). This may account for the early foetal losses found in this experiment, but not for the losses after day 120 of gestation. The gestation length for the autumn-mated alpacas at FH of 340.2 + 1.9 days was similar to the value of 341.6 ___0.1 days found by San-Martin et al. (1968) for Huacaya alpacas, but longer than the 336.0 _+ 1.6 days for the autumn-mated alpacas at TH. Mean gestation lengths of the alpacas at FH was longer for alpacas mated in spring than in autumn. Similar results have been reported for alpacas at TH (Davis et al:, 1992). She-camels that conceive early in the breeding season have longer gestation lengths than those conceiving later in the breeding season (Elias et al., 1991).

Acknowledgements We would like to thank the farm staff at Flock House Agricultural Centre and Dr G.H. Moore at Tara Hills High Country Research Station for their assistance over the duration of the experiment. We acknowledge funding from the Foundation of Research Science and Technology, and would like to thank the New Zealand Lotteries Board for funding the Aloka SSD-210DX Ultrasound.

References Davis, G., Wulijii:Ti and Pollard, J.C., 1992. Alpaca research in New Zealand. Alpacas Aust., h 14-17. Davis, I.F., Kerton, D.J., Pair, R.A., White, M.B. and Willi'ams,A.H., 1986. Hormone supplementation to increase fertility after uterine artificial insemination in ewes. Proc. Aust. Soc. Anita. Prod., 16: 171-173.


97

Elias, E., Degen, A.A. and Kam, M., 1991. Effect of conception date on length of gestation in the dromedary camel (Camelus dromedarius) in the Negev Desert. Anita. Reprod. Sci., 25: 173-177. Fernandez-Baca, S., 1993. Manipulation of reproductive functions in male and female New World camelids. Anita. Reprod. Sci., 33: 307-323. Fernandez-Baca, S., Hansel, W. and Novoa, C., 1970a. Embryonic mortality in the alpaca. Biol. Reprod., 3: 243-251. Fernandez-Baca, S., Hansel, W. and Novoa, C., 1970b. Corpus luteum function in the alpaca. Biol. Reprod., 3: 252-261. Knight, T.W., Death, A.F., Wyeth, T.K. and Hill, F.I., 1992. Effects of GnRH and of single versus multiple mating on the conception rate in alpacas. Proc. N.Z. Soc. Anita. Prod., 52: 191-193. McMillan, W.H., 1987. Post-mating progesterone supplementation in ewes and hoggets. Proc. N.Z. Soc. Anita. Prod., 47: 151-153. Novoa, C., 1970. Review: Reproduction in Camelidae. J. Reprod. Fertil., 22: 3-20. Quinlivan, T.D., Mm'tin, C.A., Taylor, W.B. and Cairney, I.M., 1966. Estimates of pre- and peri-natal mortality in the New Zealand Romney Marsh ewe I. Pre- and peri-natal mortality in those ewes that conceived to one service. J. Reprod. Fertil., 11: 379-390. Ridland, M., Knight, T.W. and Wyeth, T.K., 1992. Measurement of foetal size by ultrasonography and progesterone concentrations in pregnant alpacas. Proc. N.Z. Soc. Anita. Prod., 52: 191-193. San-Martin, M., Copaira, M., Zuna, R., Rodreguez, R., Bustinza, G. and Acosta, L., 1968. Aspects of reproduction in the alpaca. J. Reprod. Fertil., 16: 395-399. Statistical Analysis Systems Institute Inc., 1987. SAS/STAT TM guide for personal computers, Version 6 edn. SAS Institute Inc., Cary, NC. Suture', J., 1983. Studies on reproductive pathology in alpacas. Masters thesis. Swedish University of Agricultural Science, Uppsala and Universidad Nacional Mayor de San Marcos. Sumar, J., 1985. Reproductive physiology in South American Camelids. In: R.B. Land and D.W. Robinson (Editors), Genetics of Reproduction in Sheep. Butterworths, London, pp. 9, 81-95. Wilkins, J.F., Fowler, P.G., Bindon, B.M., Piper, L.R., Hall, D.G. and Fogarty, N.M., 1984. Measuring foetal loss with real time scanning. Anita. Prod. Aust., 15: 768. Wilmut, I., Sales, D,I. and Ashworth, C.J., 1986. Maternal and embryonic factors associated with prenatal losses in mammals. J. Reprod. Fertil., 76: 851-864. Wiltbank, J.N., Hawk, H.W., Kidder, H.E., Black, W.G., Ulberg, L.C. and Casida, L.E., 1956. Effect of progesterone therapy on embryo survival in cows of lowered fertility. J. Dairy Sci., 39: 456-461.