A Study of Infertility in Scottish Blackface Sheep in Colombia, South America

Br. vet.}. ( 1983). 139, 349

A STUDY OF INFERTILITY IN SCOTTISH BLACKFACE SHEEP IN COLOMBIA, SOUTH AMERICA

Bv H. M. ScoTT,]. A. FERGUSON, R. PASTRANA,* M. 0. K. MADANI,t AND

H.

LL. WILLIAMSt

Ministry of Overseas Development Sheep Project, Colombia, *lnstituto Colombiano Agropecuario, Colombia and fDepartment of Animal Husbandry & Hygiene, The Royal Veterinary College, Boltons Park, Potters Bar, Herts

SUMMARY

The reproductive performance of a flock of226 Scottish Blackface (SB) ewes in Colombia, lat. 5°N, alt. 3200 m, showed that 96·0% were keel marked and 42-4% lambed. Of the 56·7% served once, 66·7% lambed. Of the 43·3% returning to service only 14·9% lambed. More detailed investigations were carried out on a representative sub-group of 19 Blackface ewes and on I 0 ewes of the local Criolla breed. Progesterone profiles indicated that barrenness in SB sub-group ewes was due to relapse into anoestrum following an ineffective service or termination of pregnancy before day 60. INTRODUCTION

The establishment of nucleus breeding flocks to produce rams for crossbreeding purposes is one of the main reasons for exporting sheep from Northern Europe to tropical areas. Its success is largely dependent on the ability of the chosen breed to adapt to and to reproduce in their new environment which may be sub-optimal and may include one or a combination of unfavourable factors such as non-fluctuating photoperiod, high altitude and inadequate nutrition. In a study of the reproductive performance of imported British breeds at Pasto, Colombia (lat. l 0 N), Beaty & Williams (I97Ia and b) and Williams (1975) drew attention to the differing levels of fertility between breeds and to the improvement in performance in successive years. The levels of performance achieved by Scottish Blackface ewes following importation to Colombia in 1976 and 1977 were significantly lower than that recorded in Pas to. Consequently more detailed recording of the main flock was undertaken and a sub-group was formed to provide information on the nature of the infertility.

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BRITISH VETERINARY JOURNAL, 139,4 MATERIALS AND METHODS

Observations were carried out on a flock of246 Scottish Blackface (SB) ewes, imported in january 1977, and 10 Criolla (Cr) ewes at Don Benito, Zipaquira, Colombia (lat. 5°N) at an altitude of 3200 m . The ewes had been maintained on pasture since their previous lambing in March 1978. Harnessed vasectomized rams were run with the ewes from September and entire rams were introduced in mid-November. A sub-group of20 SB ewes were randomly selected for more intensive investigation of reproductive performance; the 10 Cr ewes were also included in this sub-group. Blood samples were collected in heparinized vacutainers from all sub-group ewes twice weekly and transported to the laboratory in chilled insulated containers. The samples were deep frozen prior to transportation in well-insulated containers to the Royal Veterinary College laboratory at Potters Bar for progesterone determinations. Ten SB ewes and four Cr ewes were slaughtered 40 to I 00 days following non-return to service; the genital tracts were examined for presence and number of corpora lutea and foetuses. Crown-rump measurements were taken to establish stage of gestation. Thyroid glands, liver and kidney tissue, cervical vertebrae and radio-ulnar bones of both dams and foetuses were retained for other investigations, to be reported elsewhere .

RESULTS

Performance of main flock A summary of the reproductive performance of the flock of 226 SB ewes is given in Table I. Only nine ewes (4·0%) showed no evidence of keel marks. The majority ( 123 ewes) ofkeel-marked ewes were served only once and 82 (66·7%) of these lambed. Of the ewes keel-marked two or more times (94 ewes) only 14 (14·9%) lambed. Thus a total of96 ewes (42·4%) of the main flock lambed .

TABLE! THE FERTILITY OF A SUB-GROUP AND A FLOCK OF SCOTTISH BLACKFACE EWES

Percentage (no.) Sub-group n = /9 Keel marked One recorded service Pregnant following one service Two or more recorded services Pregnant following two or more services Ewes lambing

100 57·9 72-7* 42·1 37·5* 57·9*

(19) (J l) (8) (8) (3) (I J)

* Based on leve.s of progesterone, post-mortem findings or lambing record . t Based on lambing records.

Flock n = 226 96·0 56·7 66·7t 43 ·3 14·9t 42 ·4t

(217) (123) (82) (94) (14) (96)

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Perfonnance of sub-group ewes One ewe had to be destroyed due to injury a few days after being served and is not included in the data. The performance of the remaining 19 ewes is presented in Table I. All ewes were keel marked; II were marked only once and eight of these lambed. Eight ewes were keel marked two or more times and three lambed. A total of II subgroup ewes (57·9%) lambed. Eight of the I 0 Cr ewes lambed. Six were served once and all lambed, whereas only two of those served two or more times lambed .

Barrenness The data in Table II show the level of barrenness in both main flock and sub-group SB ewes. The nature of the infertility in the sub-group ewes was categorized on the basis of the progesterone profile following service. The first category, described as relapse in to anoestrum, included ewes which showed one or more luteal cycles of< 18 days. This accounted for three of the eight barren ewes. The second category, described as early termination of pregnancy accounted for the remaining five barren ewes. The ewes showed a drop to basal levels of plasma progesterone after a period of > 18 days above basal levels (>0· 75 ng/ml). In these five ewes elevated progesterone levels were maintained for 28, 42, 45, 56 and 59 days respectively. Confirmation of anoestrum was in some cases provided by post-mortem observations. Illustration of the progesterone profiles of these two categories of barrenness and of a normal pregnancy is given in Fig. I.

TABLE II THE INCIDENCE AND TYPE OF BARRENNESS IN BLACKFACE EWES

Percentage {no.) Sub-group n = /9

Category I. Category 2.

Barrenness Relapse into anoestrum Early termination of pregnancy

42·1(8)* 15·8 (3) 26·3 (5)*

Main .flock n= 226 5 7·6 (130)t

• Based on post-mortem examination or drop to basal levels of plasma progesterone. Based on lambing records.

t

l?ecovecY offoestuses Seven foetuses were recovered from six pregnant SB ewes which represented 77·8% ofrhe roraf number of corpora lutea. In the four Cr ewes the six foetuses equalled the number of corpora lutea.

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Fig. I. Progesterone profiles for two ewes (a) completing a pregnancy, (b) relapsing into a noestrum after service (category I) and (c) terminating pregna ncy early (category 2).

DISCUSSION

It is evident from the data presented in Table I that the level of infertility in the Scottish Blackface flock at Don Benito was unacceptably high and markedly higher than that recorded in the Criolla ewes in the sub-group. In another flock of 187 Criolla ewes, 75% lambed. In terms of the behavioural aspects, the level of recorded keel marking in Blackface ewes was high in both the main flock and sub-group. However the percentage of ewes lambing was 42·4 and 57·9 respectively. This disparity between the incidence of keel marking and ewes lambing is the main feature of the reproductive performance of the SB flock. It is also evident from the data of both groups that this differential is considerably greater in ewes returning to service. The combined da ta from the main flock and sub-group show that 32·8% of ewes served once did not lamb compared with 83·3% of those returning to service. Further elucidation of the nature of the infertility through the examination of progesterone profiles was undertaken in the case of sub-group ewes. The analyses indicate that barrenness was due to two categories of malfunction . The first involved a

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relapse into anoestrum with apparent lack of luteal cyclicity following an ineffective service. The second involved early termination of pregnancy characterized by a drop from elevated levels to basal progesterone levels and probably resulting from foetal mortality. Relapse into anoestrum is one of the established manifestations of inadequate photostimulation in a constant photic environment (Williams, 1974 and 1978). Although the Scottish Blackface breed is not as photodependent as other British breeds, the investigation of its reproductive activity in a simulated equatorial light environment has indicated that several facets are adversely affected (Williams & Madani, 1982). It is probable that this aspect ofinfertility is related to an abbreviated and rephased season in their new environment. The evidence in this investigation suggests that failure to cycle following a service denied a proportion of the ewes the opportunity to conceive to a subsequent service. In contrast, some barren ewes of the local Criolla breed showed regular luteal cycles throughout the period of testing. The early termination of apparent pregnancy after 28 to 59 days of elevated progesterone cannot be as readily explained largely due to the dearth of information on a wide range of possible factors which could contribute to this form of infertility. There was no apparent disease factor which could be implicated and the success rate in producing crossbred lambs from SB sires on local ewes suggests that the in(ertility problem was confined to SB ewes. The post-mortem data indicated that there was a disparity between number of corpora lutea and recovered foetuses, and that this was confined to the SB ewes. The investigation of progesterone levels and other aspects in pregnant SB ewes in a simulated equatorial photic environment did not suggest that the light environment per se had an adverse effect on pregnancy (Madani, 1980). Nevertheless a greater number of repeat services and lower ovulation rate was recorded in these ewes. Where other factors such as altitude and/or inadequate nutrition, and possibly their interaction with the photoperiod, lead to the loss of a proportion of foetuses it is obvious that those with a single ovulation will be at considerable risk . The relationships between plane of nutrition, body condition and stage of breeding season, and fecundity are a field ofinvcstigation that has been relatively well researched (Gunn & Doney, 1979). The factors influencing the level of barrenness are less well documented. Apart from the intervention of disease, the literature does not draw attention to a single factor which could possibly account for a level of barrenness greater than 50% in a situation where grassland and animal management endeavour to maximize the level of flock reproductive performance. The future investigation of this problem will involve a detailed assessment of the nutritional adequacy of the herbage at key stages of the production cycle together with more detailed recording of weight and condition changes during the year. ACKNOWLEDGEMENTS

The authors wish to acknowledge the ready co-operation of Mr H. E. Gonzalez and Mrs. A. L. de Galvis, L.I.M .V. Laboratory, Bogota who carried out the post-mortem examinations and Mrs K. Lewis of the Royal Veterinary College who carried out the progesterone assays.

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REFERENCES

BEATY, T. & WILLIAMS, H. LL. (1971a). British Veterina7J•Joumal127, I. BEATY, T. & \>\1 ILLIAMS, H. LL. .(1971b). British Veterinaryjouma/127, 9. GUNN, R. G. & DONEY,j. M. ( 1979). Agricultural Development and Advisory Service Quarterly Review

No. 35, 231. MADANI, M. 0. K. (1980). Ph.D. thesis, University of London. WILLIAMS, H . LL. & MADANI, M. 0. K. ( 1982). Proceedings of the 32nd Meeting European Association

for Animal Production, Zagreb 1981. WILLIAMS, H. Lr.. (1974) . Joumal of Agricultural Scimce, Cambridge 83, 101. WILLIAMS, H. LL. (1975). British Veterinaryjouma/131, 23. WILLIAMS, H. LL. ( t·978). Proceedings of the 28th Meeting European Association for Animal Production,

Brussels, 1977. (Accepted for publication 27 August 1982)