Some bulls were gaining four or more pounds per day, which can be detrimental to future fertility and soundness. John P. Gaelic, DVD, PhD, cattle reproductive health, University of Calgary has done many studies on nutrition in bulls.
There is good evidence to show that if you feed bulls high-energy diets after weaning, you get very rapid weight gain, but you also create a lot of problems with excessive fat in the scrotum, reduction in semen quality, more risk for laminates/founder, liver abscesses, amenities, etc. These bulls can end up with liver abscesses, damaged claws and feet, and in some cases permanent reduction in number of sperm produced and often poor semen quality.
According to Duane Michelsen, DVD, a cattle breeder near Pullman, Washington (retired from the faculty at Washington State University, where he did fertility studies in beef cattle for many years, and thousands of breeding soundness exams on bulls) says most purebred breeders are going away from this type of overfeeding because they now realize the permanent damage that can be done. Feed and management of these young bulls is very important, however, to ensure that they can stay sound and fertile.
Mark and Della Else raise purebred Herefords and Angus near Townsend, Montana. Then through winter they are fed at a neighbor’s feedlot, who raises registered Red Angus.
“Together we’ve come up with a target goal of having them gain about three pounds a day, and we don’t get too aggressive. “We’ve had good luck with this program in terms of bulls maintaining soundness,” he says.
They are fed a ration that contains chopped hay and straw, along with a bull developer pellet. “When growing bulls, it’s important that the ration is geared toward longevity and soundness as well as growth and gain.
“In our program, we want to give young bulls every chance to exhibit their performance, but at the same time keep them sound and not too fat. “Our bulls are on a 130 to 140-day gain test on this feed, then the 70 days before they go into our sale we feed more hay and just coast them, so they can make a transition to grass and not melt.” This also enables lumen microbes to change from the more concentrated ration to grass (cellulose) more easily than from a higher starch diet.
“What we’ve used for many years that really helps these young bulls is flax based lick supplements. We put tubs out for them, and found that this supplement helps with scrotal development and semen quality,” he says.
Feeding young bulls is always a balancing act, walking a fine line between over-feeding and providing nutrition for optimum growth. We’ve done some fine-tuning over the years, to minimize bloat issues or digestive problems, and have backed our gains off just a little,” he says.
The bulls are weighed a couple of times while on test, to see how they are doing as a group, and as individuals, to know if feed should be adjusted to have them gaining a little more or a little less. Feeding a moderate ration and not pushing them too much helps avoid foot problems and fat in the scrotum (which interferes with fertility).
He feels that breeders need to give bulls a chance to perform but not cross the line and feed too much. Choosing from the array of feed stuffs available for feeding and developing bulls can be challenging for many beef cattle producers.
The feed industry, popular press and other cattlemen often offer conflicting advice about feed stuffs or their ingredients. Fiber-based energy-supplying coproducts are also acceptable feed choices (soybean hulls, citrus pulp, wheat middling).
Cattle have been reported to over consume soybean hulls in self-feeding scenarios, potentially leading to bloat problems and possible death. Self-feeding of any feed stuff without proper management practices in place or knowledge of feed -intake patterns should be avoided.
Similarly, the need for roughage in the diet may necessitate the use of medium- to good-quality forages to support the desired growth level. The selection of any particular roughage option will depend upon the age, body weight and growth requirements of the bull.
The selection of hay should be based on the performance goals for the bull with the objective of meeting the nutrient requirements. Silage from either corn or sorghum is also a great roughage source for feeding bulls.
When pasture is utilized, a number of issues need to be considered, including adequate forage availability, intake and quality to meet the feeding goals. An often overlooked consideration in allocating pasture for bulls is the difference in forage intake compared to cows.
Winter pasture is generally high in both crude protein and TEN, which can go a long way toward meeting the nutrient requirements for growing and maintenance bulls. An acceptable recommendation is that bulls be moved off of WCS at least 90 days prior to the initiation of the breeding season, which allows an opportunity for the sperm present in the testes to be turned over.
The general answer is yes; both organic and inorganic supplements may be utilized effectively as mineral sources for bull development. Regardless of the choice to include organic sources, the use of a well-balanced mineral-and-vitamin supplement to meet the bull’s requirements is the main management consideration.
The uses of organic minerals that may result in the greatest benefit include zinc, selenium and copper. The authors did indicate that the recommended level of 30 parts per million (ppm) in the diet (NRC, 1996) was likely too low to be of benefit.
What is important is to provide the bulls the same mineral supplementation program that any productive member of the beef herd should have. Bulls need the appropriate supply of energy, protein, vitamins and minerals to meet the production goals sought by the producer.
Adequate quantity and acceptable quality forage will go a long way to meet the nutritional requirements of herd bulls. Yearling bulls should be in condition score 6 (1 = thin and emaciated; 9 = obese) before the start of the breeding season.
After removal from the cow herd after the breeding season, yearlings should be kept separate from the older bulls if possible at least through their second winter. Yearlings need to be fed or grazed on a good quality forage or pasture.
Their supplemental feeding regime can be equated to the program for bred- yearling heifers. These bulls are growing rapidly, in addition to replacing the condition they lost during the breeding pasture.
Extra care and feed of yearling bulls after the breeding season should increase their longevity. Get two-year-old bulls in condition or their working clothes well before the start of the breeding season.
Two-year-old bulls should have more of their mature size by breeding season as compared to yearling bulls. After this age of bull finishes the breeding season, good quality grass pasture should be adequate.
In many areas, producers follow a late winter/early spring calving program (February to May in the USA), depending on the available feed, growth of early pasture, and prevailing climate. Spring-born calves commonly are weaned at 6–7 mo, and their dams bred back while on pasture.
Heifers may be bred to calve first as 2-yr-olds (22–25 mo) if good winter feeding is practiced to ensure adequate development. Heifers should weigh 55%–60% of mature body wt at breeding time and should be fed well thereafter to allow for continued growth, good milk production, and prompt rebreeding.
Mature cows have greater body reserves and lower nutrient requirements than heifers; therefore, they can be wintered on rations of poorer quality. Young bulls should not be fed large amounts of starch, with gains of 2.5–3.5 lb (1.1–1.6 kg) per day being very adequate.
Yearling bulls grown on extremely high energy diets are more likely to have disease issues and reduced longevity in the breeding herd. In highly fitted show bulls, a gradual reduction in the ration and much exercise are needed before they will be in suitable shape and condition for pasture breeding.
14% Bull Power is formulated with high quality palatable protein sources. Rapidly growing calves utilize dietary energy best when a nutritionally balanced ration is fed.
Energy supplied by 14% Bull Power is in the form of highly digestible fiber. 14% Bull Power and medium quality roughage make a total diet containing the nutrients needed to promote economical, efficient growth and development of weaned calves and yearling cattle.
14% Bull Power promotes lean tissue (muscle) growth without excessive fattening. Pelleting reduces sorting and separation and promotes even consumption of nutrients and feed additives.
High quality ingredients are used in 14% Bull Power to ensure palatability and promote consistent feed intake. Feeding 14% Bull Power two or more times daily promotes consistent, even consumption, freshness and overall good bunk management.
Proper management and nutrition of bulls is essential to ensure cow/calf producers maximize reproductive efficiency and genetic improvement of the calf crop. In addition, the herd bull influences overall herd fertility more than any other single animal, and loss of fertility by a bull can cause substantial loss to a potential calf crop.
Therefore, bull selection can be the most powerful method of genetic improvement in the herd, but bulls with low fertility, structural problems and low libido reduce the percent calf crop weaned. The number of cows bred during the breeding season plays the largest role in percent calf crop weaned, and percent calf crop weaned is the single most important factor influencing profitability in beef operations.
Since greater than 90% of the beef cows in the United States are bred by natural service, it is important that bulls be managed to optimize breeding performance. Second, physical characteristics, such as scrotal circumference, mating ability, and semen quality play a role in a bull's fertility.
Third, libido and social dominance influence a bull's ability and desire to service cows. High levels of energy can increase weight, height, and scrotal circumference without effecting age at puberty or first mating, showing nutritional effects on bull development without affecting sexual development.
Highly fitted or excessive conditioned bulls may fatigue rapidly, contributing to fewer cows serviced. This weight loss should come from energy stored as fat (condition) rather than muscle tissue.
Furthermore, extremely low energy can delay puberty and potentially impair sperm production. The age and weight at which puberty occurs also varies greatly among breeds and level of nutrition during development; however, research with various breeds suggests that a practical indication of eminent puberty is when scrotal circumference is between 27 and 29 cm (Unstrap et al., 1978).
Sperm quality and quantity continues to increase for several months after the initiation of semen production. Only about 35%, 60%, and 95% of 12, 14, and 16-month-old bulls, respectively, are reproductively mature and produce good quality semen (Barth, 2000).
Nutrition Seed stock producers are the primary individuals managing the development program of bulls being sold. Bulls are often managed as one group even though there may be large differences in age, size, and body condition.
Many seed stock producers have established specific feeding programs to fit the desired animal performance where bulls show their genetic potential and are cost-efficient. The key to a well-developed feeding program is that nutrient requirements are meet and animals are not under-or over-fed.
Excess external fat cover is not only found on the back of the bull, but also in the scrotum. Being overly fat also increases stress on the bull and limits his ability to travel, so he can search out and service cows that are in estrus.
Post-weaning nutrition: During the time period from weaning to first breeding season is when producers are determining rations. Nutrient requirements for growing bulls can be found in NRC (2000) or through the extension service.
There are many possible rations that could be used to develop bulls at the desired animal performance prior to the first breeding season. The best ration depends heavily on the availability and cost of feed ingredients.
The key is developing the ration to meet the desired animal performance without over- or under-developing the bull. Under-nutrition results in delayed puberty and over-nutrition can reduce semen production and quality.
Thin bulls should be put on a ration with a higher level of energy to increase rate of gain. If bulls purchased or previously in your ownership are in good condition you will need to ensure that they are adapted to high-forage rations prior to turn out.
If bull(s) get extremely thin during the breeding season you may want to replace him because his ability to service the cows will probably be reduced. Nutritional management post-breeding is influenced by both age of bulls and amount of weight loss during the course of the breeding season.
Mature bulls in fairly good condition after the breeding season can be managed on pasture or an all-roughage diet without supplements during the winter. Hay quality should be 8 to 10% crude protein and fed at 2% of body weight.
Rations should be modified based on available feed ingredients and to manage the bulls to maintain moderate body condition. Young bulls are still growing, so the ration should be formulated to gain 1½ to 2 pounds per day depending on the magnitude of weight loss during breeding.
The need to supplement young bulls on summer/fall pasture will depend on the quality and quantity of forage available. The best method for developing a diet for bulls is to test potential feeds and formulate a ration based on age, size and desired performance.
For example, during the winter feeding program, feeding roughage at 2% of body weight plus 3 to 6 pounds of grain so total diet protein content is 10 to 11% will often provide the targeted rate of gain in young bulls. As you develop a ration for your bulls remember to include a quality mineral and vitamin program.
Two Breeding Seasons per Year: Some producers have both spring and fall calving herds, hence double-using bulls. This puts additional management onto these producers to ensure that bulls will be prepared to serve cows at each breeding season.
Young bulls may need to gain 2 to 2 ½ pounds per day to recover from weight loss. Even with the best nutrition program some bulls have low fertility or other reproduction problems which will limit their servicing capacity.
It may include pens/pastures, fences, water/watered, forage supplies, corrals, working areas and natural barriers. The key is having facilities that can safely handle fighting bulls and ensures the safety of those working with the cattle.
Pens and pastures should be large enough to ensure bulls adequate exercise to prepare them for the breeding season. To encourage bulls to get exercise, locate feeding areas away from water.
This ranking may affect the number of cows a given bull will service in a multiple-sire herd. Livestock managers must be aware of these relationships to ensure normal breeding rates.
This allows them to determine the social ranking prior to turning them into the cow herd. In addition, when cows are synchronized and bred by natural service, greater pressure is placed on the herd bull.
The best method for developing a health protocol is by working with your local veterinarian. You should determine the vaccinations to be given, parasite control, and other specific procedures most suited to your location.
Those conditions can influence the bull's ability to service the female or depress the semen quality. All of these conditions impact the profitability through reduced number of calves born.
A BSE includes a physical examination, measurement of scrotal circumference, and evaluation of semen quality. To successfully complete a breeding soundness evaluation, a bull must have at least 30% sperm motility, 70% normal sperm morphology, and a minimum scrotal circumference based on age (Table 1; Chenoweth et al., 1992).
Bulls should be tested approximately six weeks to one month prior to the breeding season by a veterinarian. Mating ability can be described as the physical capabilities needed to successfully breed a cow.
A bull must be able to see, smell, eat, and move normally to successfully breed cows. The physical examination closely scrutinizes a bull's eyes, teeth, feet, legs, and nutritional level (evaluated by body condition score).
Any disease or injury that affects joints, muscles, nerves, bones, or tendons may cause a bull to be structurally unsound. In addition to structural unsoundness, diseases or injuries to the penis or prepuce can result in an inability to breed via natural service.
These abnormalities will only be detected by careful examination or observing an attempted mating of a cow. A bull that has high quality semen but is unable to physically breed cows is unsatisfactory for natural service.
Furthermore, a negative genetic correlation exists between a sire's scrotal circumference and age of puberty in his daughters. It is important to remember that substandard nutrition, extreme environmental temperatures, and disease can reduce semen quality, and that the quality of semen from a single bull may change over time.
Sperm motility is calculated by evaluating the percentage of spermatozoa in a sample ejaculate that have progressive (headfirst) movement under a microscope. Therefore, both primary and secondary abnormalities are equally important when evaluating sperm quality.
Therefore, selection of bulls with greater than 80% normal sperm can increase overall pregnancy rates in a herd. Out of 34 young bulls (< 2 years) that failed their first BSE, 26 of these bulls successfully passed a second BSE and were classified as satisfactory potential breeders in a study conducted at the University of Missouri (Elmore et al., 1975).
Furthermore, it has been shown that semen quality in young bulls can improve for up to 16 weeks following puberty. Injury, disease, fever, and extreme environmental conditions are four of the main factors that can decrease sperm production.
In light of these facts, it is important to realize that the results of a single BSE are not valid for the life of a bull, and testing a bull annually, usually a month prior to breeding season is recommended. It is important to remember that scrotal circumference, semen quality, and mating ability (evaluated in a BSE) are not related to libido.
Libido has positive effects on pregnancy rate and, as such, can influence the success of an entire breeding season. For this reason, it is important to evaluate a bull's desire to mate prior to the start of breeding season.
A bull's eagerness can range from no sexual interest to successfully mating with the female. Libido can be more practically evaluated by closely watching a bull after introducing him to a cow herd.
Conclusion Proper nutrition is needed to ensure that the bull's reproductive development and performance is maximized. Since reproductive traits are not highly heritable, greater selection intensity is required to achieve genetic improvement.
Structurally sound bulls with a large scrotal circumference and high semen quality should be selected as herd sires. Paternity tests in multisided beef herds by blood grouping.
Effect of energy intake on reproductive performance of dairy bulls. Pregnancy rate in cows and heifers bred to bulls selected for semen quality.