Can Romney lambs whose scrotums have been shortened by the use of a rubber ring be used as an alternative to vasectomised Perendale rams for inducing early breeding activity in Romney ewe lambs?
OBJECTIVE
To determine if exposure to ram lambs whose scrotums had been shortened by the use of a rubber ring would induce reproductive activity in ewe lambs, and determine if this technique was an effective alternative to vasectomised mature rams.


METHODS
Seven hundred and forty-nine Romney ewe lambs, 7-8 months of age, were randomly assigned to one of three treatment groups. Treatments included exposure for 17 days prior to breeding to either mature vasectomised rams (Vasec), or ram lambs whose scrotums has been shortened via a rubber ring (Ram SS), or not being exposed to either vasectomised or short-scrotum ram lambs (Unteased). Using crayon marks, ewe lambs were identified as having been marked during the first 17 days only, during both 17-day periods, during the second 17 days only, or not marked. Hoggets were weighed on the day of introduction of entire rams. All ewe lambs were diagnosed for pregnancy status using ultrasound.


RESULTS
Unteased ewe lambs and those exposed to ram lambs whose scrotums had been shortened by the use of a rubber ring were less (p<0.05) likely to be marked and pregnant to the first 17 days of breeding than ewe lambs exposed to mature vasectomised rams. Twin-bearing ewe lambs were heavier (p<0.05) than their single-bearing counterparts at introduction of the rams.


CONCLUSIONS
Exposure of ewe lambs to mature vasectomised rams is an effective means of increasing the numbers of ewe lambs bred and pregnant to the first 17 days of breeding. In contrast, a 17-day exposure to ram lambs whose scrotums had been shortened by the use of a rubber ring, at the ratios utilised in the present study, were not a suitable alternative to mature vasectomised rams for inducing early breeding activity in ewe lambs.
Kenyon
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Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand. p.r.kenyon@massey.ac.nz
Morris
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West
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D000818:Animals; D001835:Body Weight / Q000502:physiology; D001947:Breeding / Q000379:methods*; D005260:Female; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D011897:Random Allocation; D012098:Reproduction / Q000502:physiology*; D012611:Scrotum / Q000473:pathology*; D012726:Sexual Behavior, Animal; D012756:Sheep / Q000235:genetics / Q000502:physiology*; D013997:Time Factors; D014659:Vasectomy / Q000379:methods / Q000662:veterinary*