14 March 1996

Maize may lack iodine leading to infertility

INFERTILITY in dairy cows on maize diets may be due to iodine deficiency, warns mineral supplier Mill Feed Anglia.

It claims that reports of iodine deficiency are increasing in all geographical areas, even when maize is only one-third of the diet.

Iodine can be responsible for poor fertility and a high incidence of retained placentas, and is often overlooked in mineral supplementation of maize-based diets, it adds.

Independent vet consultant Tony Andrews, warns that poorly balanced maize diets can lead to many mineral deficiencies, so when feeding maize for the first time take extra care to ensure correct mineral supplementation.

"But there are many causes of infertility, so dont jump to conclusions," he says. "Get a vet to perform a full investigation for deficiencies, for these are often multi-factorial." Retained placentas can also be caused by a lack of attendance or poor hygiene at calving, he adds.

"Iodine deficiency also causes abortion, stillbirths and dopey, weak calves with enlarged thyroid glands," says Dr Andrews.

But he warns producers to avoid making a diagnosis based on thyroxin levels in cows blood. The thyroxin hormone levels are affected by oestrogen levels before calving and when cows are bulling. Consistently low thyroxin levels in a large number of the herd are needed to indicate iodine deficiency, he adds.