Since my last article on the drought, many farms across the Midlands and East Anglia have seen very little, if any, meaningful rain, writes Nerys Wright.
Grass covers are tight, feed stocks are under pressure and some sheep are being asked to do a lot on very little. Rather than dwell on that, let us think positively and plan for what happens when the rain finally arrives.
This summer, many flocks have had relatively low worm burdens. Dry, hot conditions are not ideal for the development and movement of infective larvae on pasture, so faecal egg counts have generally been lower than we might expect at this time of year. However, that will not be true for everyone. Where sheep have been grazing lower into the sward, or where lambs and ewes have been under nutritional stress, immunity and resilience may be compromised.
Performance
Thinner ewes, smaller lambs and groups already affected by other disease challenges may therefore still have seen higher counts or poorer performance. The important point is that rain will change the risk picture. Worm eggs passed out in dung develop through larval stages before reaching the infective third-stage larvae.
In dry weather, development and movement onto grass can be slowed or limited, and larvae are more likely to remain protected within dung pats or close to the soil surface. When moisture returns, dung pats soften, larvae can migrate onto the herbage and sheep are more likely to pick them up while grazing.
That brings a double-edged sword: much-needed grass growth, but also a possible flush of parasite challenge. Fit, well-fed adult ewes should usually cope with a moderate worm burden, but thin ewes, ewes recovering from disease or those in poorer condition following the drought may justify checking with a faecal egg count.
Lambs need even closer attention. Their immunity to worms is still developing and they can be hit harder by a sudden intake of larvae. Remember, there can be a delay of up to three weeks between lambs eating infective larvae and eggs appearing in the dung.
Performance can slip before a faecal egg count rises, so do not rely on FECs alone. Watch daily liveweight gain and overall thrift. If lambs look checked after the rain, take fresh samples, speak to your vet or adviser and treat only when the evidence supports it. The rain will be welcome when it comes. The key is to be ready for the grass and the worms that may follow it.
Nerys Wright is an independent sheep consultant. Call 07891 187643 or visit sheepconsultancy.co.uk.