Take good care of ewes in the weeks after mating
Yesterday saw 375 ewes and ewe lambs bred using laproscopic AI at Lyons. Sponges were pulled in two batches on Saturday morning with a three-hour time difference.
Ewes and ewe lambs received 500 units of Pregnant Mare Serum Gonadotrophin (PMSG) to increase ovulation rate, at sponge removal. As not all ewe lambs are being AI'ed, rams went in with the remainder 36 hours after sponge withdrawal. Rams will be turned out to pick up repeats 14 days after the initial mating.
We are targeting a scanned litter size of 1.9-2.0 with the mature ewe flock, even though we have fallen about 0.15 lambs short of this for the last year or two, partly due to an increase in the number of barren ewes.
The mature ewes had an average weight of 74kg at mating and the ewe lambs averaged 50kg. This puts the ewe lambs at approximately 68pc of their mature live weight. It's important to have ewe lambs at a minimum of 60pc of their mature weight at mating.
Recent research from Britain shows that if you feed lambs for catch-up growth after mating you risk these ewe lambs producing lambs of low birth weight, with reduced vigour, reduced reserves of brown fat (the main energy reserve in the newborn lamb) and consequently increased risk of mortality.
The ewes and ewe lambs will remain on a stable plane of nutrition during the first month after mating. After mating, it takes approximately three weeks for the embryo to implant.
During this time the embryo is extremely susceptible to loss, especially if there is stress on the ewe. Therefore, handling of the flock should be minimised during this period. Also, overfeeding during this period is to be avoided, as this too can increase the risk of embryo loss through increased clearance of progesterone (the hormone responsible for the establishment of pregnancy) from the system.