Hormonal Augmentation of Fertility in Sheep and Cattle 171 



Treatment of cattle towards the end of the cycle, either with FSH or PMS, 

 has consistently induced multiple o\"ulation (9,10,25,29,31,78), though 

 there is a tendency to reduced response with repeated treatments (77). 

 Though multiple o\'ulations may be readily obtained, it would appear that 

 the actual number is not easily predictable. Sometimes poor recoven.' of ova 

 and apparent failure of fertilization have been reported (25, 29). It has 

 sometimes been the practice to give an intravenous injection at the time, or 

 predicted time, of heat (9, 29, 78), but there does not seem to be any definite 

 indication that this procedure results in a larger number of OMilations or 

 better fertility. 



With a standard dose of PMS, Hammond and Bhattachar>a (43) considered 

 that the OMjlator\- response was less erratic when given 3 days before the 

 time, or presumed time, of heat than when given at the time of corpus 

 luteum removal. Twin OMilations were general under the former conditions. 

 However, similar treatment of animals allowed to calve gave less good results 

 (42), There was, in practice, considerable difficulty in timing the injection so 

 that heat followed 3 days later. 0\iilation counts by rectal palpation of 

 corpora (which were not entirely accurate; on occasion there were more 

 cahes bom than corpora counted) revealed twin ONTilations in a minority.' 

 and occasional animals with 4 or 5 corpora lutea. Contributon." to these 

 results are probably indi%idual variation of cycle length and individual 

 breed and perhaps seasonal differences in sensitivity. 



Recently Gordon (35) has been tr>ing similar treatment on a larger scale, 

 and has had better success both in timing of the injection and in choice of 

 dosage level. Preliminan.' results based on rectal palpation (and which 

 await the tests of panuntion and of funher experience) indicate a considerable 

 discrepancy between number of corpora lutea and number of fetuses. 



In the cow (8) \\ ith good qualit)' insemination the 0N"um is nearly always 

 fertilized but about 30"-\-, fail to stinive, so that there is only about 70'^^ o 

 conception to ser\ice at a given heat period. Gordon's figures suggest that 

 with twin ONulations the conception rate is greater than this, but the chances 

 of both ova surviving are rather poor. This contrasts with Dutt's (27) finding 

 in the sheep of 143°o lambing in sheep with estimated 147''n ONtilation. 



A single FSH injection to sheep, given towards the end of the cycle, has 

 been noted to produce luteinization of unoMilated follicles as well as multiple 

 oNulation (44); but luteinized follicles were detected only in sheep killed 

 se\eral days after ON"ulation. It is thus concei%able that Gordon may have 

 been misled about the number of twin ON^ulations — as opposed to twin corpora 

 — in his animals. 



In sheep, PMS given on the 12th or 13th day of the cycle increases the 

 ONtilation rate, and there is a general parallelism between dose and oMilation 

 rate (2, 62. 76). There is general agreement that the range of response 

 increases with dosase. sinsle 0%'ulations occunins e%en with the hisher dose 



