Sheep: Breeding season in full swing using a combination of fertility technologies
Published 21/10/2015 | 02:30
Daily grass growth on the sheep block at Lyons reached an unseasonably high level of 60kg of drymatter (DM) per hectare in the first week of October, but it dropped back to 20kg last week.
We are now closing paddocks for spring grazing. We will need an average farm cover for turnout in mid-March of 820kgDM/ha. With moderate spring growth on this site, we are looking at a closing farm cover of approximately 580kgDM/ha.
Yesterday saw one of the busiest days of the year at Lyons with approximately 350 ewes mated using laparoscopic AI. In preparation for this, ewes were sponged on October 5 and sponges were withdrawn in batches on Saturday, October 17.
At sponge withdrawal the ewes received an injection of pregnant mare serum gonadotrophin to increase litter size. Ewes also received a multi-trace bolus in advance of sponging.
The laparoscopic AI technique involves a minor surgery on the animal with the semen deposited directly into the oviduct. Our role as one of the central progeny test flocks for Sheep Ireland is the main reason for using AI. Trans-cervical AI as practiced in cattle has a much lower success rate in sheep so it is not practiced in this scheme. Also we use fixed time AI rather than heat detection, given the major issues with heat detection in sheep.
Interestingly, on a recent trip to a pedigree sheep breeding station in China, I saw that vasectomised rams were being used to detect heat for AI purposes. However, labour supply was much greater on that farm than what is available in Irish circumstances.
Rams will be turned out to these ewes in 12 days time to pick up any repeat cycles from ewes that did not hold on to the AI service. Ewe lambs this year were bred using natural service, but were sponged in preparation. Rams were turned out with the ewe lambs yesterday, 36 hours after sponge withdrawal at a rate of one ram per 11 ewes. This ratio is much different than the normal ram to 40 ewes because all ewe lambs will be on heat within 24 hours.
All our ewes are identified using electronic identification (EID), so all information relating to live-weight, body condition score, and sire used at mating were recorded on the handheld reader. This provides an invaluable source of information and has removed a huge amount of the paperwork involved in our data collection for both research and commercial purposes.