Experts at Scotland’s Rural College have revised their advice to farmers encountering Long Bone Deformity in their calves.
The problem, caused by shortening of the long bones such as those in the leg, has been an issue in the north of the UK for some twenty years. It appears to be linked to an unusual form of Manganese deficiency. Now specialists with SAC Consulting, part of SRUC are doubling their recommended dose of Manganese.
The scientific name for Long Bone Deformity is chondrodystrophy. The calves are born small due to the shortening of their bones, giving them a characteristically short, often bow legged appearance. In addition they may have dished faces and domed heads. In some cases deformities can be so bad that the calves cannot stand to suckle and have to be put down.
According to Dr Basil Lowman of SAC Consulting, where Long Bone Deformity occurs, it is not only a welfare issue but has a major financial cost and, just as importantly, it is seriously depressing for farmers to deal with at calving time.
Long Bone Deformity is seen where winter rations for pregnant cows consist almost entirely of silage. The fourth to fifth months of pregnancy, when a calves bones and joints are developing rapidly, appears to be the most critical. It is generally associated with high quality pit silage but can occur with big bale silage and can be particularly prevalent in cows fed red clover silage, hence it can become an increasing problem for organic producers.
Based on experience a common recommendation is to restrict silage to no more than 75% of the cows’ total dry matter intake. For dry, pregnant beef cows needing a relatively low energy intake it is usual to use straw to balance the silage ration. This can be a problem on the west side of the country, where many stock farms don’t grow grain. Straw can be expensive to buy so other options are required.
The potential links with manganese deficiency followed work in Canada where scientist had noted an identical pattern of abnormalities linked to cow rations severely deficient in the mineral. They decided to measure the manganese levels in both the blood of dry, pregnant beef cows and the feed given to them.
Groups of cattle were fed one of 3 different forages diets on demand (ad-lib). The diets they investigated were grass silage and hay, both made from the same grass, with red clover silage being the third.
Although the manganese level of the hay ration was lowest the cows fed on it had the highest blood level of manganese and produced no deformed calves. The grass silage, made from the same grass, had more manganese but the blood levels were lower than the hay group with 28% of the calves born suffering from Long Bone Deformity. The red clover silage contained the most manganese, but gave the lowest blood level with 38% of the calves born deformed.
This experiment suggested that some kind of compound produced during the silage fermentation process could be binding with the manganese, making it unavailable for the cow to digest. As a result, and aware of the increasing incidence of Long Bone Deformity, SAC Consulting have decided to double their recommended manganese requirements for dry spring calving beef cows overwintered mainly on grass silage rations.
Dr Basil Lowman of SAC Consulting says:
“Although there is no hard scientific evidence that manganese is causing the problems, we are happy to increase the recommendations. The target is a total intake of 1000mg of manganese per cow per day. Where there is a perceived problem I would suggest farmers use a mineral supplement containing around 7,000 mg per kilogramme. It is well within the allowances and is relatively inexpensive. With this amendment we aim to ensure that calves are born normal, healthy and full of vigour next spring.”