Young cattle on crops

It is common practice to winter young growing beef cattle on brassica crops. Brassica crops are a great source of dry matter over a period when dry matter is at a premium. Good crops may yield 6-7 tonnes of DM/ha, and, in wet areas, condensing stock onto a good crop enables valuable winter pasture to be saved while at the same time ensuring pasture renewal programmes are instigated.

Why then do some cattle not thrive while on or coming off winter brassica crops? Trace element status is a huge factor in young cattle growing well. Checking young cattle’s trace element status coming off winter crops is important for the following reasons:

• Copper is an important element for bone and tissue growth as well as good immune function in young stock. Copper levels can vary markedly in crops and this can be exasperated by other factors. Cattle grazing crops are usually break-fed, and this can lead to a large ingestion of soil. Ingesting iron, sulphur and/or molybdenum from soil can antagonise copper uptake such that cattle may be quite deficient at the end of crop feeding.
• Up to 30 % of New Zealand is considered selenium deficient. There is a good correlation between soil and plant selenium, with the Se concentration in plants often too low to meet the needs of grazing ruminants. Symptoms of selenium deficiency in young stock are poor growth rates and general ill thrift.
• Brassica crops can contain anti-iodine agents, goitrogenic properties. Goitrogens are compounds that produce goitre. While clinical iodine deficiency may be manifested as goitre, subclinical iodine deficiency may manifest with poor growth rates or ill thriftiness in young growing stock.

So the take home message is, how well do you know how your stock is doing post winter off crops? Are they not growing to their potential despite being fed well? Blood testing for some of the key trace elements is a simple means of ensuring that young cattle have their growth potential maximised and that their feed utilisation is maximised over spring and summer. Call your Vetlife vet to discuss this further.