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Cultural Practices
There are six main dairy breeds; the most popular being Holstein-Friesian and Brown Swiss. The others include Jersey, Guernsey, Ayrshire, and Milking Shorthorn. Regardless of the breed of animals, over the last 40 years many producers have opted to register individual cows or entire herds as a means of improving production and increasing herd value. The registration process, wherein a strict record of breeding and animal health is kept, has been greatly facilitated by the artificial insemination process. Whether registered or not, for cattle beyond their useful productive life (12-15 years), heifers are often raised by the very operation in need of replacements. Offspring born from cows or heifers will be bred at the age of two or three years, and produce a calf, before beginning to produce milk for the herd.
In the Midwest, dairy herds may be kept in barns, loafing sheds, or confined lots during cold weather, but most cows are still grazed on pastures during the summer. Most housing barns are heated only by animal body heat in the winter but have windows and ventilation fans to regulate temperature in the spring and summer. Some barns have walls made from plastic shades that may be automatically rolled up or unrolled, similar to green house systems, for temperature control. Younger calves may be housed in indoor pens or single calf hutches in any season.
Insect Pests
The most common pests for cattle are flies, lice, and internal parasites. Depending on the season and location, cattle grubs, mange, and ticks can be problems. Other insects, such as gnats and mosquitoes, can be quite numerous and a severe nuisance, but do not generally cause serious problems with dairy cattle. In addition to their direct effects on cattle, flies are a great nuisance to dairy workers. Sites with heavy fly infestations produce irritable animals, maggots (fly larvae) in feeds and manure, sticky fly excrement covering milking equipment and building surfaces, and an increase in spiders and their webs. Dust and animal hair adhering to fly excrement and spider webs can find their way into lungs and the milking lines.
Horn flies and face flies are most commonly found in pastures, usually coming into buildings only when on the cows' backs. These flies sit on the face, neck, shoulders, and back of the animal and feed on either their blood or secretions from the nose, mouth, and eyes. Although healthy cows may be able to withstand as many as 200 horn flies without reductions in weight gain, their presence is certainly annoying and can be troublesome to dairy operators. There are other types of flies that are associated with buildings; stable flies and house flies are the most common of these. House flies are more of a nuisance and general sanitation problem than as a direct pest on cattle. Stable flies, along with deer flies and horse flies, feed on blood from the back and legs. Stable flies have a long, bayonet-like proboscis that causes a painful sting, and as few as five stable flies on the legs of cattle has been shown to reduce performance in weight gain. Gnats and mosquitoes are mainly a nuisance and can be kept from buildings by screens and ventilation fans. In addition, flies can spread diseases such as pinkeye. In northern Illinois, Indiana, Ohio and Iowa and across through to Nebraska and north, the fly season lasts from June to early September. In southern Illinois, Indiana, Ohio and through Missouri and Kansas the fly season lasts from early May to mid-October.
Cattle grubs, also known as heel flies, gadflies, or warble flies, are often found at muddy stream crossings. In scattered areas, they can be a serious pest but are not extremely. The adults bite and lay their eggs in the hair of the hocks and legs. When the eggs hatch, the larvae burrow through the skin and, while maturing, migrate through the tissues of the cow. The larvae eventually exit through the skin of the back. Meat quality can be reduced and the hide is scarred by the exit holes.
Mange mites are microscopic insects that live on the skin. Some live on oily secretions while others live on skin cell contents. The irritation from the mites causes animals to rub themselves excessively to relieve the discomfort, often rubbing hair off. One uncommon type of mange, cattle scabies, can produce large, spreading sores and requires quarantine.
Lice are tiny, biting insects that feed on blood. Rather large populations may live on adult cows without major health problems. In severe infestations, the cows may scratch hair off in order to relieve the itchy feeling or develop respiratory infections due to reduced thriftiness. These insects spread easily between animals, especially during winter when animals are housed together for long periods of time. Young calves are most affected and large lice populations may cause death. Calves are stunted in their growth, and become susceptible to secondary infections such as pneumonia.
Internal parasites rob animals of the nutrient value from their digested feed. Roundworms and flukes often attack the organs of both calves and cows. Their eggs pass through the manure and hatch in pastures or weeds alongside of feed lots. Cows become infected when they eat grass that has larvae growing on it. Internal parasites can cause dehydration, coccidiosis, pneumonia, malnutrition, and other secondary diseases of the liver, heart, lungs, stomach, and intestines in cows and calves. If left untreated, the cows show reduced milk production and calves are stunted in growth and may appear gaunt due to weight loss.
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