BY: KEN GEENTY
After weaning is often considered the time to sit back and watch the new season’s lambs grow as you celebrate good or lament mediocre results. But don’t underestimate that between now and next mating. Ewe and ram preparation is essential to ensure at least as good, if not a better, lambing percentage in spring. Improving the lamb weaning percentage (lambs weaned/ewes mated x 100) by 5-10% each year is a worthy goal.
The key steps are planning and implementation. Detailed or strategic plans should already be set in readiness for tactical day-to-day implementation. It’s likely many farmers underestimate the power of well-thought-through plans, which should include optimistic but achievable goals. Ensure these are SMART goals – specific, measurable, achievable, relevant and time-bound.
Revisional inputs from rural professionals and farming mates are always invaluable, particularly as the season progresses and new challenges unfold.
Don’t work ewes too hard
Lambing performance will be penalised if ewes are ‘screwed down’ or worked hard to maintain summer pasture quality to the extent they lose weight. Other options for pasture control such as use of cattle or other dry stock are preferable so ewes can be preferentially fed to achieve and maintain body condition score (BCS) of 2.5 to 3.
Ovulation rate at mating is the main determinant so target liveweight gains should be 5 to 6kg for each condition score increase required. If ewes are light at lamb weaning the absolute priority is to achieve target BCS of 3 or better leading into mating. The pathway can vary but gradual building or maintenance at a good weight can yield similar lambing results. Steady maintenance is the most feed-efficient as each kg lost will take 17 megajoules of metabolisable energy (MJ ME) or about 1.7kg of pasture drymatter to regain. This is equivalent to just under two days of maintenance feeding.
With an average BCS of 3 or better an ovulation rate of 1.9 can be expected, leading to a lamb tailing rate of about 160% if lamb survival is up to scratch. The amount of pasture required to maintain ewe BCS over the lamb weaning to mating period is shown in Table 1.
Extra feed for liveweight gain, assuming average pasture quality of 10 MJ ME per kg of drymatter, is:
- 50g/day gain: add about 30% to maintenance requirement
- 100g/day gain: add about 60% to maintenance requirement
- 150g/day gain: add about 100% to maintenance requirement
A good strategy, particularly if pasture is limited, is to draft off ewes with BCS of 2 or less and preferentially feed them so the ewe flock average is about the BCS 3 target at mating.
Weighing of ewes at lamb weaning time is a good benchmark from which to assess feeding requirements over the period to next mating. Whereas more frequent BCS checks can be used for tactical decisions to achieve the above targets. This avoids more time-consuming yarding and weighing and can be done in the corner of a paddock or when ewes are yarded for some other job. About 10% of the ewes in each mob should be checked to gauge average overall BCS.
It is extremely important for a good conception rate that ewes are ‘on the rise’ during the weeks leading up to ram joining rather than losing weight.
Ram preparation
Preparation of your ram breeding team is crucial for good lambing results. Expecting them to perform when underdone is like throwing a half-fit rugby player into the All Blacks. A summary checklist for a top ram breeding team is:
- With veterinary help, check all rams for testicular abnormalities before ram buying time.
- Commence good feeding and exercise 8 to 10 weeks before mating.
- Buy rams from brucellosis accredited ram breeders.
- Ensure your ram breeder has similar breeding objectives as you and good genetic trends.
- Use lower ewe:ram ratios with younger ewes and/or rams.
- Consider use of infertile vasectomised rams to get ewes cycling and compress lambing.
- Spend time with your ram breeding team and ensure top nutrition.
As much interaction with your ram team as possible during the couple of months leading up to ram joining will pay dividends. Include constant checks for physical or health defects. Ensure good nutrition so your rams are in similar or better body condition than your ewes. Remember they will be working hard and may need that spare gas tank of body fat reserves to call on, particularly at high ram:ewe ratios approaching 1:100.
A vet check early on is very worthwhile. Included will be such things as testicle size and integrity, scrotal temperature, scrotal mange etc. In studs a semen quality test may be added along with serving capacity.
Use of vasectomised rams is an option to induce ewe cycling and to compress the lambing period. When harnessed, the onset of breeding activity can be monitored, and later with entire rams the spread of lambing indicated. Vasectomised rams can be introduced in low numbers a month before mating is due to start. If done well at least 65% of your ewes should mate in the first 17-day breeding cycle, meaning the bulk of your lambing will be during two cycles or just over a month.
It’s important to remember that both ewe and ram preparation are equally important for a good lambing percentage.
Lamb wastage
Lamb wastage is larger than most farmers most realise. Farm surveys measuring ovulation rates of ewes in good condition at mating time have shown up to 12% embryonic loss by pregnancy. That’s scanning 2-3 months into pregnancy. Another 18-25% of potential lambs are lost around lambing. This means for each 100 ewes mated some 30-40 of the 190 potential lambs in the example above are lost by lamb tailing. Little can be done to avoid the embryonic losses but minimising BCS losses during mid-late pregnancy and careful lambing management can reduce deaths between scanning and tailing.
- Ken Geenty is a primary industries consultant.
