Effect of time of joining and rate of stocking on the production of corriedale ewes in southern victoria part 5 ovulation rate and embryonic survival

Davis, I.F.; Kenney, P.A.; Cumming, I.A.

Australian Journal of Experimental Agriculture and Animal Husbandry 16(78): 13-18


Accession: 005278867

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Ovulation rate and embryonic survival in a flock of 540 5 yr old Corriedale ewes grazing annual pasture in S Victoria [Australia] were studied. Ewes were stocked at 5, 7 1/2 or 10 ewes/ha, and were joined with rams for 6 wk beginning at either Feb. 8 or April 19, 1971. A comparison with actual lambing data in 1970 was made. Ewes stocked at 5 ewes/ha had a higher ovulation rate and estimated lambing rate (based on embryos surviving to day 28) than those stocked at 7 1/2 or 10 ewes/ha. Ovulation rate was higher for ewes of high liveweight than for ewes of low liveweight among those stocked at 7 1/2 and 10 ewes/ha but not among those stocked at 5 ewes/ha. Ewes joined in April had a higher ovulation rate and estimated lambing rate than ewes joined in Feb. There was no significant interaction between joining time and stocking rate on estimated lambing rate which was in contrast to the previous year 1970, when increased stocking rate reduced the number of lambs born per ewe from the Feb. joining. Embryonic survival was greater among ewes joined in Feb. and stocked at 7 1/2 ewes/ha. There was no difference between stocking rates in embryonic survival among ewes joined in April. There was a trend for fewer twin ova to be lost when shed in April than in Feb.