Synchronization of oestrus in cattle, sheep and goats using a prostaglandin analogue.

Abstract

Proc. Aust. Soc. Anim. Prod. (1974) 10; 242 SYNCHRONIZATION OF OESTRUS IN CATTLE, SHEEP AND GOATS USING A PROSTAGLANDIN ANALOGUE H. HEARNSHAW*, B.J. RESTALL*, C.D. NANCARROW+ , and P.E. MATTNER+ Summary The prostaglandin analogue ICI 79939 can induce luteolysis and synchronize oestrus in sheep, goats (effective dose 30 pg s/c) and cattle (effective dose 250 Fertility following mating or insemination in the three species was within acceptable limits. No gross failure of the reproductive system after treatment with the analogue was experienced. 1-19 s/d l I. INTRODUCTION Prostaglandin F~(Y, (PGF2a) causes luteolysis in several species of animals including cattle and sheep. This has led to investigations with PGF2a as an agent for the control of oestrus and ovulation in domestic animals (Inskeep 1973) and to comparison of PGF2a and progestins as practical methods of synchronizing oestrus in cattle (Smith 1973). This paper reports preliminary studies of the use of a synthetic prostaglandin analogue (ICI .79939) in synchronizing oestrus and ovulation in sheep, cattle and goats. II. MATERIALS AND METHODS Trials with sheep and goats were conducted at the NSW Department of Agriculture Research Station, Condobolin during April and May, 1973 and those with cattle at the Agricultural Research Station, Leeton, during May and July, 1973. (a) Sheep (i) Dose Response Four groups of ten mature Merino ewes were injected i.m. with either 125, 62.5, 31.2 or 15.6 ug ICI 79939 in 0.5 ml saline on Day 8 of the oestrous cycle. Thereafter ewes were run continuously with harnessed vasectomised rams (10% of ewe flock) and were examined several times daily for the occurrence of oestrus. Raddled (oestrous) ewes were removed soon after first marking and were returned to the rams on the evening of the same day. Ovarian examinations were carried out 5 days after oestrus on five ewes from each dose group. Raddle colours were changed five days after oestrus and subsequent cycle lengths were recorded. (ii) Fertility One hundred and four Merino ewes at unknown stages of the cycle were injected with 32 pg ICI 79939 (i.m. in 0.5 ml saline). Fourteen rams fitted with marking harnesses were placed with the ewes. On the ninth day after the injection, ewes that had not been marked received a second injection of ICI 79939 at the same dose rate as used previously. The ewes were la&ed under supervision in order to detect any abnormalities or behaviour patterns. (b) Goats Eighteen feral does at unknown stages of the cycle, were injected i .m. wi th A buck, with harness and either 32 pg (9 does) or 16 1-19 (9 does) ICI 79939 * + NSW Dept. of Agriculture, C/- CSIRO, P.O. Box 239, Blacktown, NSW, 2148. CSIRO, Division of Animal Physiology, P-0. Box 239, Blacktown, NSW, 2148. 242 raddle, was then placed with the does and markings recorded several times daily for 3 days. Thereafter returns to service were checked daily. (c) (i) Dose Response ' Prior to the trial,heifers of mixed breed had run continuously with a testosterone-treated steer fitted with a chin ball harness, and Kamar heat mount detectors were used to assist in obtaining records of oestrus. In addition, heifers were observed for oestrus several times a day. Heifers within each of the following bodyweight classes - 220-250 kg (9 heifers); 250-300 kg (10 heifers); 300450 kg (10 heifers) - were randomly allocated to 3 groups that received a dose of either 250, 500 or 1000 pg ICI 79939. The heifers were injected s/c between days 4 and 15 of the oestrous cycle. (ii) Fertility Nineteen parous Hereford cows were injected s/c with 500 1-19 ICI 79939. Rectal palpations of the ovaries of all cows were performed prior to treatment. Any cow showing an induced oestrus or regression of a palpable corpus luteum following treatment was artifically inseminated between 72 and 90 hours after treatment. Jugular blood samples, for progesterone determination,,were collected before and after insemination. Cows were fitted with Kamar heat mount detectors to detect return to service, and pregnancies were confirmed by palpation 15 weeks after insemination. III. RESULTS Cattle (a) Sheep (i) Dose Response All doses of ICI 79939 except 15.6 pg induced oestrus in all animals (Table 1). Induced oestrus was observed 38-48 hours after injection. A fresh ovulation had occurred in all the animals examined and subsequent cycle lengths were within the normal range. Ewes exhibited highly individualistic behaviour, nervousness and excitability and were extremely difficult to move through yards or handle normally. TABLE1 Effect of dose of ICI 79939 on reproductive activity in sheep (ii) Fertility Some 61% of 'the 104 ewes mated on Days 3 and 4 after the first injection of 243 ICI 79939 (Table 2). A further 22.1% mated 3-4 days after the second injection given on Day 9. Thus 83% of ewes mated over the two 2-day periods. A further 8.7% of ewes, considered to have not responded, mated during the 12 day period. Of the ewes that mated after either the first or the second injection, 71% and 52% respectively,lambed. Overall, the lambing figure was 67%. The lambs had an average birth weight of 4.5 kg and there were no obvious abnormalities. TABLE 2 Synchronization of oestrus and fertility in sheep treated with ICI 79939 (b) Coats All 18 does exhibited oestrus within 48 hours of injection of ICI 79939. Three exhibited oestrus within 7 hours of treatment. Ten does (56%) subsequently kidded, The remaining eight does returned to service 19-22 days after the sychronized oestrus. (i) Dose Response .(c) Cattle Table 3 is a summary of the results. Luteolysis occurred in all heifers. All but two animals showed induced oestrus from 46-120 hours after ICI 79939 injection and had a subsequent increase in progesterone concentration, indicating a fresh ovulation. TABLE 3 Effect of dose of ICI 79939 on reproductive activity in cattle (ii) Fertility After treatment of the heifers with ICI 79939, all functional corpora lutea underwent luteolysis as indicated by a decrease in the level of progesterone in peripheral blood. Six of the 19 cows came into oestrus within 65 hours of treatment. These were inseminated at 72 hours and also at 90 hours after treatment. Five other heifers received a single insemination 90 hours after treatment. One of these came into oestrus just prior to that time; the other 4 had either a large 244 follicle, a fresh ovulation or a corpus luteum of reduced size at palpation performed immediately before the insemination. Pregnancy diagnosis (per rectum) carried out 15 weeks later indicated that 7 of the 11 inseminated heifers were pregnant. IV. DISCUSSION The results indicate that ICI 79939 can induce luteolysis and synchronize oestrus in sheep, cattle and goats. In the latter case introduction of the buck may have induced oestrus, particularly in the case of the does exhibiting oestrus behaviour within 7 hours of treatment. Fertility following mating or artificial insemination in the 3 species was within acceptable limits and does not indicate gross malfunction of the reproductive system following-treatment. The interval between treatment and oestrus was more variable in cows than in sheep. In addition, oestrus was not always detected in cows even when luteolysis occurred. Similar variations in time to induced oestrus have been reported by workers administering PGF2a via the uterus (Elsden et al. 1973; Smith 1973). The detection of oestrus in cow herds is difficult and it would be an advantage to inseminate at a predetermined time after injection and still obtain normal fertility. The minimum effective dose of the analogue for cattle has not been determined but it is considerably lower than effective levels of PGF2a given s.c:or i.m. (Lauderdale 1972; Hearnshaw et al. 1973). The reported lack of response at certain stages of the cycle has important managerial implications (Inskeep 1973). Further studies are needed to develop compounds and methods of administration that will result in high fertility following insemination at a set time. V. ACKNOWLEDGEMENTS We wish to thank Mr. R. Kearins (Livestock Officer), N. Ticehurst, N. Grinter, Agricultural Research Station, Condobolin; Dr. I.D. Killeen, A. Kajons, P. Nicoll, S. Phillip, G. Caffery, P. Clements, Agricultural Research Station, Leeton for assistance and management of experimental animals and Mr. P. Connell for progesterone analyses. The prostaglandin analogue 79939 was kindly supplied by Dr. B.D. Hoskins of the Pharmaceuticals Division, ICI Ltd., England. VI. REFERENCES J. Reprod. Fert. ELSDEN, R.P., LEWIS, S., CUMMING, I.A., and LAWSON, R.A.S. (1974). (In press). HEARNSHAW, H., MATTNER, P.E., NANCARROW, C-N., and RESTALL, B.J. (1974). J. Reprod. Fert. (In press). INSKEEP, E.K. (1973). J. Anim. Sci. 36 : 1149. LAUDERDALE, J.W. (1972). J. Anim. Scrr 22 : 246 (Abstract). SMITH, J.F. (1974). J. Reprod. Fert. (In press). 245