Category: Herd Management

Bull Management

Posted on by
Bob Larson, DVM, PhD
Reproductive physiologist and Epidemiologist
Beef Cattle Institute
Kansas State University
RLarson@vet.k-state.edu

It is pretty obvious to state that bulls play a tremendously important role on cattle ranches. In the first place, obtaining a high percentage of cows pregnant in a controlled breeding season requires bulls that are fertile and have the ability and desire to mate cows and heifers that are in heat. It is also clear that the genetic makeup of a cowherd has a tremendous impact on profitability. In order to ensure that a bull is adding considerable value to the herd, he must fit within the herd’s genetic goals for low production costs and high demand for the offspring. The importance of the bull battery to the genetic profile of the herd is apparent when one remembers that this year’s bulls control 50% of the genes in the marketable product and that in commercial herds, greater than 90% of the genetic progress of a herd is via bull selection. 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.

According to a USDA survey, the two most common reasons that bulls are culled from commercial herds is because of infertility and physical unsoundness or injury. In order to address these risks, bulls should be thoroughly evaluated before each breeding season so that only bulls that are likely to be able to get a high percentage of exposed cows pregnant in a short period of time are turned out into the breeding pasture. The need for a thorough breeding soundness examination (BSE) 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 BSEs is to eliminate many subfertile 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).

Because some bulls that have good quality semen and pass a physical examination still fail to successfully breed cows, it is necessary that bulls be observed closely during the breeding season. Because bulls that are not successfully mating have a tremendous negative impact on herd reproductive efficiency, every day (or nearly every day), producers should get bulls up and watch them walk and observe their underlines for indication of penis or prepuce problems in order identify lameness or injury that will prevent successful mating.

By using a thorough BSE to exclude questionable breeders before the breeding season starts and frequent observation during the breeding season to ensure successful mating ability, a relatively high cow to bull ratio can be used with the result that the number of offspring from superior sires is increased and the total bull-cost per calf weaned is decreased. The limited research that is available indicates that mature bulls with high reproductive capacity can be exposed to as many as 50 to 60 cycling cows in single-bull pastures (but fewer cows per bull in breeding pastures with multiple bulls). 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). The number of bulls required to adequately cover the breeding females is related to many factors. Environmental factors include: terrain, carrying capacity of the pasture, and pasture size. Bull factors include: age, condition, fertility, and social status. Social dominance of bulls is important to consider in multiple-sire breeding pastures. Several studies have shown that the most dominant one or two bulls in multi-sire pastures end up breeding a majority of the 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 due to injury, illness, or low libido. Close observation of bulls during the breeding season is required in order to be assured that the bulls are getting cows bred. Injuries to bulls during the breeding season are relatively common. When a bull does become lame or incapable of breeding because of an injury to his reproductive tract, he needs to be removed from the breeding pasture and replaced by another bull.

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, becoming neither excessively thin nor fat. When developing bulls from weaning until they are turned out for their first breeding season, their diet should allow them to express full growth potential without becoming overly heavy. Restricting energy, protein, vitamins or minerals at any time between birth and maturity can delay the onset of puberty of young bulls and possibly reduce lifetime daily sperm output because of reduced testicular development early in life. Research has shown that bulls fed medium-energy diets from weaning to two years of age had greater reserves of sperm cells and higher quality semen than bulls developed on high-energy diets. In addition, young bulls grown at a rapid rate have a higher risk of bone and joint problems in their legs. This syndrome in bulls has also been described as leg weakness, degenerative joint disease, osteoarthritis, osteoarthrosis, and polyarthritis.

The two to three months leading up to the breeding season is an important period of time to ensure that bulls are in good shape to be “breeding athletes”. Exercise is important during the pre-breeding season period because during the breeding season the bull may travel several miles per day and maintain long periods of physical activity. If given ample area, bulls will usually exercise themselves. In designing bull facilities, it is a good idea to locate feeding and water areas as far apart as possible to encourage exercise. Bulls should have adequate body condition at the start of the breeding season so that weight loss during this period of high physical activity does not cause physiologic stress. At the same time, bulls should not be over-conditioned. If bulls are too fat, physical activity is reduced and excessive weight loss during the breeding season can occur. If bulls are in good body condition (BCS 5.0 to 5.5) then a forage-based diet with supplemental concentrate will be adequate to build the desired energy reserves. If the bulls are thin, then they may need substantially more concentrate feed.

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.

Role of your veterinarian in your business

Posted on by
Bob Larson, DVM, PhD
Reproductive physiologist and Epidemiologist
Beef Cattle Institute
Kansas State University
RLarson@vet.k-state.edu

There are many people that impact the success of your ranching business, including your customers, your lenders, and your suppliers. One of the important suppliers for cow-calf producers is the local veterinarian. Veterinarians can provide important advice and service to improve ranch income, decrease costs, provide protection from losses due to disease, and offer options for marketing high-health cattle.

Ranch income is primarily derived from the sale of calves either at weaning for commercial operations or as breeding bulls or heifers for seedstock producers. Commercial ranchers can increase their income by increasing the pounds of calves at weaning and seedstock operations the number of marketable breeding animals from the same land and cow resources by increasing the reproductive efficiency of the herd. Veterinarians can provide advice and services to monitor and evaluate heifers, cows, and bulls so that a high percentage of the herd is able to successfully mate at the start of each breeding season.

Nutrition has an important impact on whether or not growing bulls and heifers reach puberty at an appropriate age and your veterinarian may be able to provide you with appropriate diets to meet targeted weight gain goals. Genetics also strongly influences whether developing bulls and heifers reach puberty by target ages, and your veterinarian is a valuable resource when considering selection and culling decisions. By doing breeding soundness examinations of bulls and heifers near yearling age, your veterinarian can help you identify the individuals that reach puberty at the time and with the amount of feed resources that you have identified to meet your ranch goals.

Doing breeding soundness examinations of mature bulls prior to the start of each breeding season allows your veterinarian to remove bulls that may fail during the breeding season due to foot or leg problems, other health problems, or reproductive tract problems. Although the reproductive tracts of mature cows are not routinely evaluated before the start of each breeding season, managing and monitoring the cows to confirm that a high percentage of the cows calve early enough in the calving season and in good enough body condition to resume fertile cycles by the start of the breeding season helps to ensure that herd reproductive efficiency will be high.

Monitoring body condition scores of the cow herd and rainfall amounts as predictors of future forage production potential allows your veterinarian to provide advice on a changing year-by-year basis to alter stocking density, timing of weaning, and supplementation strategies to ensure that cows enter the calving and breeding seasons in good body condition. The land base and herd size dictate much of the cost-side of cow-calf production and making sure that a high percentage of the cow herd becomes pregnant early in the breeding season allows those costs to be spread over a large number of marketable calves. By using body condition scores collected at several key points in the production cycle, your veterinarian can help you fine-tune the management of your herd based on the ranch forage-base, and the availability of cost-effective supplements or grazing alternatives, and the optimum cow size and milking ability for your herd. 

While every production year is expected to generate income from the sale of calves and to incur expenses associated with pasture and supplementation costs as well as cow depreciation and bull costs, significant losses due to disease is expected to be a rare event for cattle operations. Losses that are expected to occur rarely if at all but that could have a devastating impact on the financial status of a ranch if they did occur must be managed with cost-effective risk management strategies. Because disease losses do not occur every year, providing no defense may appear to be a sufficient and very low-cost management strategy in the short-run. However, over a longer time-frame, it would be very unusual for a herd with minimal disease protection to avoid devastating financial losses due to disease at some point in the future. Your veterinarian can provide valuable information about the likelihood that your herd could suffer losses from various diseases and the expected magnitude of those losses should your herd be exposed. By considering the likelihood of a disease, the magnitude of losses associated with that disease, and the effectiveness of available control strategies, your veterinarian can work with you to optimize the disease risk management of your ranching business.

Marketing of cattle, whether feeder calves or breeding animals, increasingly includes information about health status. When considering the optimum herd health program from a marketing standpoint, the risks that down-stream buyers face and their willingness to purchase from suppliers who can reduce that risk must be considered. For example, your herd may have very low risk for a disease and incurring expenses through diagnostic testing or herd certification may not reduce your herd’s already minimal risk; but the costs could easily be offset by customers willing to pay for that low disease risk. Increasingly, you must think of your down-stream customers as you work with your veterinarian to plan a health program that not only meets the needs of your herd but also provides a cost-effective marketing advantage.

A successful cattle business requires a combination of cattle and business expertise. Many successful ranchers count on a trusted team of advisors and suppliers to help them improve the profitability and sustainability of their ranching business. Finding and working with a local veterinarian who can provide assistance to increase income, control costs, and manage risks should be a goal of every cattle producer.