Animal Health Problems: Non Life-Threatening Illnesses

Table of Contents

1. Infertility due to Phyto-oestrogens
   • Causes
   • Prevention
2. Molybdenum Poisoning
   • Symptoms
   • Causes
3. Other Animal Health Problem Recommendations
   • Life Threatening Illnesses
   • Photosensitivity
   • Problems Caused by Specific Forages
4. Related Links

Infertility due to Phyto-oestrogens

Causes

Phyto-oestrogens are plant compounds found in legumes that can cause temporary to permanent infertility in animals. They can reduce not only the number of successful matings but also the number of multiple births and cause an increase in uterine prolapses. Phyto-oestrogens activity varies with the legume species, the plant strain and with growing conditions.

In Ontario, red clover is the legume usually associated with causing temporary infertility problems. Red clover contains a class of fertility depressant compounds called isoflavones. The leaves of red clover are very high in isoflavone content, while the stems and petioles have lower levels. Isoflavones can cause infertility in sheep, but appear to have little activity in cattle.

Prevention

If the feed contains more than 30% red cover, keep ewes off pasture or not fed silage for at least a month prior to flushing and mating. If more than 80% of the forage is red clover, problems with return to service and barrenness may occur. Varieties of red clover with reduced levels of isoflavones are not, at present, adapted for use in Ontario - a predominantly red clover-based feed is not recommended for the breeding flock.

Alfalfa, white clover and birdsfoot trefoil do not contain isoflavones. However, with severe insect or disease damage, these legumes can produce compounds called coumestans, which are also highly oestrogenic. Planting legume varieties with good resistance to insects and diseases, proper grazing and fertility management, and growing legumes in mixtures with grasses helps to remove coumestan fertility problems associated with sheep.

Molybdenum Poisoning

Causes

Molybdenum is an essential mineral for both plants and animals. However, accumulations of molybdenum in toxic levels can occur in plants growing on soils rich in molybdenum or low in copper. In certain parts of eastern Ontario, particularly in Dundas and Carleton counties, there are high quantities of molybdenum in the soil. Clovers are excellent accumulators of molybdenum and this form of poisoning usually takes place on fields with a high clover content. Cattle are more vulnerable than sheep to the adverse effects of high molybdenum levels.

Symptoms

The symptoms of poisoning in cattle are acute scouring, depressed milk production, weight loss, and rough, faded, black to red coats.

Sheep can also be affected and will show symptoms of copper deficiency, as molybdenum is an antagonist to copper.

Horses are tolerant to high molybdenum levels.

Related Links

... on forages and pastures, visit Forages and Pastures (OMAFRA)
... on weed control, order Publication 75 Guide to Weed Control: Forage Crops
... on agronomy for field crops, order Pub. 811 Agronomy Guide for Field Crops: Chapter 3 Forages
... on field crop protection, order Publication 812, Field Crop Protection Guide
... on livestock, visit Livestock (OMAFRA)