Induction of oestrus and ovulation in Romney ewe hoggets with a progestagen

Abstract

ABSTRAcrNinety-six Romney ewe hoggets from a group of 236 hoggets of known history were treated with intra-vaginal sponges containing 20 mg or 60 mg methyl-acetoxy-progesterone (MAP) for 14 days near the onset of the breeding season. Observations were made for oestrus in all hoggets and for ovulations in a sample of animals from each group. After treatment the amount of MAP "absorbed" from each sponge was chemically determined.The effects of sire, birth rank of hoggets, dose level of MAP, and occurrence of oestrus on the amount of MAP "absorbed" were estimated. The incidence of oestrus within seven days of sponge withdrawal was 62%, and its occurrence was similar for both dose levels of MAP. The numbers of ovulations in treated hoggets were normal.

Successful induction of oestrus, ovulation and pregnancy in adult ewes and ewe lambs out of the breeding season using a GnRH+progesterone oestrus synchronisation protocol

“…The U-synch protocol induced oestrus rates (66.2% and 53.5% in Experiments 3 and 4, respectively) similar to those reported in ewe lambs during the breeding season. These ranged from 48.0% to 97.3% of ewe lambs marked by rams after the use of synchronisation protocols consisting of the standard treatments with a 11-to 12-day progestin device with or without eCG treatment at device removal (Ch'ang et al, 1968;Quirke, 1979;McMillan, 1986;O'Doherty and Crosby, 1990;Kenyon et al, 2012;Mulvaney et al, 2013). Variation in the oestrous response can be attributed to season (deNicolo et al, 2008a), breed (Quirke, 1979), age and length of the period of joining (Mulvaney et al, 2013).…”