Often, the most efficient farms can also boast a low carbon footprint. Achieving or exceeding benchmarks is not only good for the farm business, but can also reduce greenhouse gas emissions per kg of meat produced.
There are a number of considerations after lambing that can help to maximise lamb survival within the flock and so improve farm efficiencies.
Lamb vigour
Using rams that were themselves vigorous at birth, helps improve lamb survival. A smaller, vigorous lamb is more likely to survive than a larger lamb which needs continual assistance to suck. Lambs getting onto their feet within 10 minutes and sucking by 20 minutes is a good target because:
- Lambs lose heat 4 times faster to the ground than the air.
- Rapid intake of colostrum can make up for deficiencies such as a light birth-weight, bare coat or poor weather conditions.
- Quick colostrum intake aids the absorption of gamma globulins which protect against disease.
- Mothers pay more attention to vigorous lambs and lick and dry them quicker.
Vigorous lambs are less at risk of predation and have the ability to seek shelter.
Lamb growth rates
Target lamb growth rates at grass from birth to weaning (at 100 days) should be 280g/day for twins and 380 g/day for singles. As a rule of thumb, singles should have gained “1 pound per day of age”.
Lamb mortality
To identify the reasons for lamb mortality, keep a daily tally of the lambs disposed of by keeping separate bags for lambs that have been spray marked (or not).
After lambing, it is possible to review the deaths and ascertain the causes, for example:
- A large number of lambs in bags at the start of lambing (unmarked) could indicate sub-clinical toxoplasmosis or a similar type of infection.
- A large number of marked lambs in bags could point to exhaustion and/or hypothermia due to bad weather.
Increasing deaths toward the end of lambing could indicate an increase in disease such as watery mouth
Mismothering
Mismothering is often the cause of death in newborn lambs. Avoid overstocking fields (if lambing outside) and aim to lamb 5-7 ewes/acre if expecting twins. Singles can be set stocked at higher rates at 10 ewes/acre. On upland farms, 3-4 ewes with twins/acre. Group size should be no more than 120-150 ewes.
Avoid trough or snacker feeding post lambing; use buckets or blocks to supplement ewes and graze on pastures with adequate cover. Twin and single bearing ewes do not need concentrates once grass length is 4-6cm.
Lamb stealing ewes can cause problems both in the shed or when lambing outdoors. These ewes should be segregated. Providing salt licks may reduce lamb stealing.
Finishing lambs from grass
In large flocks, graze singles separately from twins. Twin lambs get 25% less milk than singles, making up the difference from grass. This exposes them to a 50% higher parasite load, leading to different dosing requirements.
Where all lambs are grazed together getting some singles away by weaning, even at lighter weights will reduce the overall grass requirements for the flock and may allow sward height to rise. Sell as soon as lambs are at target weight or in condition. A 1 cm sward height rise in July can increase weaned lamb daily gain by around 100 g/day.
On intensively stocked farms, creep feeding of lambs can result in earlier sales, freeing up grass for ewes. It can also alleviate trace element problems and reduce finishing risks due to variable weather. Response of lambs at grass at 5 kilos of fresh feed to one of liveweight gain prior to weaning is possible. When concentrates are fed after weaning conversion rates are worse at eight to one. Supplementation improves killing out percentage by around 2%. Inclusion of 50% whole cereals in creep feed reduces finishing costs. However if lambs are kept too long on concentrates or miss premium prices earlier in the season it may not be economic.
Many farmers set stock ewes and lambs and hope for a good match in pasture supply and growth, however with more variable weather patterns perhaps its time to rethink this strategy. Rotational grazing will not control parasites but can increase the percentage of grass which has been grown that is utilised and thus give higher output/ha. Overgrazed paddocks at under 2 cm grow 40% less grass. For rotationally grazed paddocks the sward height target is going in at 6-8 cm and coming out at 4-6 cm for maximum lamb growth.
Bringing in cattle to control grass works well but goes against clean grazing policies.
Many farms do not rotationally graze due to poor water supplies and awkward field access. However making better access to fields using grazed raceways and putting in troughs and electric fencing is worthwhile.
Reducing the worm burden
Worm larvae tend to be found in the bottom 2cm of pasture so try to keep swards in the 4-6 cm range if set stocked. Preferably on grass not grazed in the previous year by lambs.
If lambs are stocked at less than 8 lambs/ha, worms are rarely a clinical problem and little dosing is required.
