Author: ksubci

Cattle producers recognize that summer is the season to battle flies on cattle. Several types of flies cause irritation and pain, reduce weight-gain, and transmit disease-causing germs, but each of the fly species have unique characteristics that should be considered before the battle begins. As in many contests, knowing your opponent is critical to increase chances for success. Four of the most common fly pests for cattle in North America are horn flies, face flies, stable flies, and horse flies. 

Horn flies are a biting insect that takes more than 30 blood meals a day and spend almost all their time on the backs, sides, and poll of cattle. When horn fly numbers become very large, cattle spend a lot of time and energy fighting them rather than grazing – therefore weight gain and milk production are reduced. In addition, these flies have been implicated in the spread of mastitis in beef herds. These flies seem to prefer adult cattle more than suckling calves, but when populations get very high, calves will be affected also. Female horn flies deposit eggs in fresh manure and the larvae survive much better in the manure of grass-fed cattle compared to the manure of cattle consuming grain rations. Eggs hatch from the manure pat within a week and then live as a pupae in the soil under the manure pat. The entire life-cycle takes about 10 to 20 days depending on the weather and because each female horn fly will lay as many as 400-500 eggs in her lifetime, the population can become very large in a very short period of time. Horn fly numbers usually peak in early summer and then decline as heat and dryness decrease the suitability of manure pats for the immature larvae and pupae. Late in the summer or in early fall, the conditions may improve for the immature horn flies and the population can increase again. 

Because horn flies spend almost all their lives on cattle, applying chemical pesticides to cattle can be an effective method to expose the flies to lethal doses. Several different types of pesticides that are safe to use on cattle are effective against horn flies, but some horn fly populations are resistant to the pyrethroid class of chemicals. If you used a pyrethroid insecticide last year and you were not satisfied with the level of horn fly control you achieved, then it may be wise to switch to a different chemical class for your pesticide this year. Backrubbers and dust bags can be a very economical method to apply pesticides if the cattle are forced to use them daily to get to water or mineral feeders. Proper placement and frequent re-filling are necessary for this control method to work well. Insecticide ear tags can be an effective method to deliver pesticide to your cattle on a daily basis, but resistance to pyrethroid tags can be a problem unless several general rules are followed: delay tagging until fly populations reach about 200 flies per animal, tag all cattle in the herd by following the instructions on the label, rotate the insecticide class so that cattle aren’t exposed to the same chemical class year-after-year, and remove the tags at the end of the fly-season. Sprays and pour-on products that are re-applied every 7 to 21 days can also be effective and these products have the advantage that timing of re-application can be adjusted based on the fly population with the obvious disadvantage of needing multiple applications. Larvicide (larvae-killing) products that are included in mineral or feed will pass through to kill fly larvae and pupae in the manure pat. To be effective, cattle must consume these oral products daily so that all fresh manure has an effective dose before the female horn fly lays her eggs. Because newly hatched horn flies will migrate to find cattle, control is most effective if all the fresh manure within several miles of your herd is effectively treated. Non-chemical control of horn flies focuses on decreasing the contact between cattle and new flies emerging from manure pats by dragging pastures to speed drying and exposure of larvae and pupae to dry heat. 

Face flies don’t actually bite cattle, but the female has sharp mouth parts similar to a rasp that she uses to damage the skin so that she can suck up liquids such as eye secretions, discharge from the nose, or blood from wounds. The face fly is different from the horn fly in that this species spends very little time on cattle and spends most of itslife resting on fence posts, plants, or other vegetation. Because they spend so little time on cattle, treating cattle with pesticides is less likely to result in the flies receiving a lethal dose. It does appear that daily application of pyrethroid insecticides directly on the face of cattle does reduce the time that face flies will spend on cattle. Backrubbers and dustbags that effectively apply insecticide to the face as well as ear tags are methods that can provide daily insecticide exposure. Because pour-ons and sprays are not applied daily, these methods of chemical application are not likely to reduce face fly problems. Like the horn fly, face fly females also lay eggs in fresh, grass-fed manure pats and the immature stages live in the manure pat and in the nearby soil. Because face flies can fly long distances, dragging pastures to break up manure pats and using oral insecticides in the mineral or feed may not be as effective as for horn flies which migrate less. 

Stable flies are blood-suckers that mainly feed on the front legs of cattle. These flies have a very painful bite, and even a small population can cause a great deal of discomfort and cattle will try to avoid them by stamping their legs, bunching together, or standing in water. Stable fly eggs are deposited in rotting plant matter mixed with moist manure or soil such as around hay feeding sites, the edges of feeding aprons, and around hay stacks. Because the fly eggs aren’t laid in fresh manure, the oral larvicides do not provide effective control. Applying insecticides with a spray or mist at weekly intervals is the only chemical control that is effective for pasture cattle. Sanitation and clean-up of wasted feed around hay rings, feedbunks, and fence rows is an important non-chemical method of stable fly control. For cattle confined to a feedlot, fly predators (also called parasitic wasps) can be used because they effectively kill immature flies. But because these types of non-stinging wasps are not strong fliers, they are not effective in pasture situations. Parasitic wasps must be purchased and released in areas likely to have fly eggs about once a month during the entire fly season. 

Horse flies are very large and have a painful bite. After a blood meal, female horse flies will lay their eggs on plants near ponds or streams. Because horse flies are large and hardy, chemical pesticides seem to have little effect, and because they do not lay their eggs in manure or decaying plant matter, sanitation is not effective as a control method. 

Complete elimination of all flies is not possible, but by knowing about different fly pests that will confront your cattle, effective control strategies can be planned. Because fly populations will vary from one year to the next based on factors such as rainfall, grazing density, and previous exposure to chemical insecticides, fly control strategies have to be flexible and may need to be changed.

Bulls play a tremendously important role on cattle ranches. They require a significant monetary investment associated with purchase price, housing costs, feed, and veterinary care. They also serve as a source of risk to the ranch, with poor reproductive performance having a great impact on percentage of the cows that become pregnant and the average calf age at weaning. In addition, poor performance of progeny due to poor genetic contribution to the herd impacts calf value and desirability of heifer offspring as replacement females. Careful attention to selection based on predictions of genetic contribution to desirable traits, management to protect health, breeding soundness examination to remove bulls with questionable breeding ability, and appropriate bull-to-cow breeding ratios are required to optimize the investment ranchers make in their bulls. 

The cost of bulls to a ranch can be calculated in several ways: the total bull cost per year, bull cost per cow exposed, or bull cost per calf weaned. I think the most informative measure is cost per calf weaned. This calculation includes the initial purchase price, the salvage value, and costs for feed, housing depreciation, and veterinary expenses. In addition, it considers the number of years the bulls are used, the number of cows exposed per bull (the cow-to-bull breeding ratio), and the percentage of cows exposed that wean a calf. Because many factors other than purchase price impact the cost of bulls per calf weaned, the actual cost of bulls per calf weaned can vary greatly between herds. 

The primary way that bulls improve herd income is to be highly fertile so that nearly all the cows become pregnant and they become pregnant early in the breeding season so that there is a front-end loaded age distribution at the time calves are weaned. Of secondary importance is the genetic value of the progeny for growth and carcass characteristics for feeder calves, and for longevity and fertility on the available forages for replacement females. 

Selection tools such as EPDs are used to identify new herd bulls that add value due to their genetic contribution to progeny performance, while breeding soundness examinations and appropriate husbandry are the tools to measure and assure fertility. 

A breeding soundness examination of bulls (BSE) is a thorough examination of the bull to estimate his ability to get a high percentage of exposed cows pregnant in a short period of time. The need for BSEs is based on the fact that many prospective breeding bulls are infertile, subfertile, or unable to mount and breed successfully, and examination prior to the breeding season reduces the risk of breeding failure due to bull problems. The overall effect of BSE is to eliminate many infertile bulls and to improve the genetic base for fertility within the herd and breed. Although individual situations vary, national reports indicate that 10% to 20% of bulls will fail a thorough BSE (and another 10% that pass a BSE will perform poorly in the breeding pasture). 

An important reason to carefully examine all bulls for breeding soundness prior to every breeding season is to be able to safely expose as many cows as possible to each bull. A high cow to bull ratio increases the number of offspring from superior sires and decreases total bull costs per calf weaned. Limited research indicates that mature bulls with high reproductive capacity can be exposed to as many as 50 cycling cows in single-bull pastures but fewer cows per bull in breeding pastures with multiple bulls, with the national average of about 30 cows per bull. Young bulls should be exposed to fewer cows than mature bulls. For bulls less than three years of age, a commonly used rule of thumb is that a bull can successfully breed as many cows as his age in months (e.g. a 15 month old bull should be exposed to no more than 15 cows). Although a high ratio of cows to bulls helps to reduce bull costs, it also exposes the herd to poor reproductive performance risk if the bulls fail to maintain good semen quality and quantity, or if bulls have reduced desire or ability to mate cows in heat due to injury, illness, or low libido. 

Regardless of how many cows are allotted to each bull, it is important to carefully monitor bulls during the breeding season. Bulls should be evaluated frequently to detect any early signs of injury, excessive weight loss, or illness; and if problems are detected, affected bulls should be replaced by fertile bulls. While many matings occur at times that are not convenient for observation, witnessing successful matings ensures that a bull is able to mount and breed cows successfully.  

During the breeding season and for the rest of the year, basic husbandry and feeding skills are important for bull care. Bulls need appropriate housing to provide protection during severely cold or hot weather – both of which can lead to temporary fertility problems. In addition, bulls should be maintained in good body condition throughout the year. 

Because bulls are so important for the genetic progress and reproductive efficiency of cattle herds; and because bulls account for a significant expense, excellent bull selection and care are critically important for optimum herd management. Bulls should be selected based on their ability to get a lot of cows pregnant early in the breeding season that will result in the birth of calves that will be high-value when they are sold. Once bulls are selected for the herd, they need to be fed to maintain good body condition and housed to protect them from injury risk. In addition, bull fertility and mating ability should be evaluated prior to each breeding season and monitored throughout breeding.