This year’s fine weather at lambing time, followed by warm dry conditions meant lambs got off to a good early start and good quality, early grass also ensured that ewes had plenty of milk, allowing rapid lamb growth rates. 

For the first 10 weeks of life the majority of a lamb’s feed requirements come from milk. After 10 weeks a lamb’s grass intake will be about 1kg dry matter per day, increasing by about 100g per week as their diet starts to shift away from milk. 

However, once lambs start eating grass they may become exposed to parasitic infections, such as coccidiosis and nematodirus worm infections. 
Twins and triplets have a higher parasite challenge. Coccidiosis and nematodirus worms are typically are seen at about six to eight weeks of age, but this year the SAC Veterinary labs were diagnosing nematodirus infection as late as the first week in July. 

Nematodirus worms were typically an issue for lambs in late spring, but more recently this infection has also been seen in summer and autumn. There have been a few reports of nematodirus resistance to benzimidazole (white drench) wormers, but in general these products are suitable for nematodirus infections. Two treatments about 10 days apart is usually sufficient, but a post-dosing check on faeces samples seven to 10 days after treatment may be carried out.

Late nematodirus infections may have concurrent teladorsagia worm infection. Teladorsagia resistance to white drenches is widespread, so it would be advisable to consider using an alternative wormer in this situation.

After weaning it is also important to monitor lamb growth rate. Common causes of poor growth rates at this time include inadequate grass quality and quantity, parasitic gastroenteritis due to teladorsagia worms and trace element deficiencies, such as cobalt and selenium.

Faecal worm egg counts are a useful guide to identifying parasitic worm infections, but worm egg counts alone do not permit full identification of worm species. This is more easily carried out by a post-mortem examination. 

Individual faecal samples (preferably 10) should be collected for a bulk faecal worm egg count. This is to allow the lab select an equal amount for testing from each sample, so that the result is representative of all the animals sampled. 

Undiagnosed wormer resistance can reduce weight gain by 50g per day in the absence of clinical signs of parasitic gastroenteritis, such as scouring or ill thrifty lambs. In order to investigate possible wormer resistance, a post drenching efficacy check on the same animals included in the individual or pooled samples of faeces is recommended. 

As for the faecal egg count examination individual samples should be collected and the pooling undertaken by the lab. Post drench samples should be collected after seven days for levamisole (yellow wormers) and after 14 days for other wormers.

Several regions in Scotland are low in soil cobalt and selenium and consequently there is poor plant uptake of these trace elements. Trace element deficiencies are more significant after weaning, as nutrition is predominately from grass. 

In order to investigate deficiencies blood samples from rapidly growing lambs may be analysed in the lab for vitamin B12 (cobalt dependant) and glutathione peroxidase (a selenium dependant enzyme).

Copper deficiency may be an issue in areas of Scotland, where there is high soil molybdenum. Care must be taken in supplementing some sheep breeds, as these are prone to copper toxicity. 

Trace element supplementation is most conveniently supplied to weaned lambs in the form of intra-ruminal boluses.