HEALTHY, FERTILE BULLS ESSENTIAL FOR A PRODUCTIVE HERD

by: Lee Jones
DVM, MS

Part 2 of 2

Healthy, fertile bulls are essential for a productive herd. A fertile, healthy, mature bull can breed 30 or more cows in a 75 to 90 day breeding season. Bulls have to be managed in the off season to maintain health and fertility. Prior to each season bulls need to be evaluated for their ability to breed cows. It is important to evaluate their feet and legs, their overall health and their fertility.

Having a thorough breeding soundness exam (BSE) performed at least 30 days prior to the breeding season is important to find out if he has the ability to breed cows. (A BSE does not measure a bull's libido or sex drive.) Bulls use a lot of energy finding and breeding cows in heat during the breeding season. It is important that bulls be in peak body condition prior to breeding season for optimum performance especially in extensive pastures. It is common for bulls to lose body weight during the breeding season due to increased activity and decreased intake. It is essential they have adequate body reserves to get through the season.

It is important also to have adequate bull power. A good rule of thumb for a bull-to-cow ratio is 1:15-20 for a bull two years old or less and 1:25-30 for older bulls. Thin bulls are often infertile or sub-fertile and do not have the endurance required to cover all cows during a controlled breeding season.

A BSE has two components: a semen evaluation to determine sperm quality and a physical examination which includes his reproductive organs and overall anatomy. A simple semen check may miss some critical anatomic conditions that prohibit him from getting cows bred. When buying a bull it is wise to ask if the bull has had a thorough BSE by a trained veterinarian. If not, ask for one or have the bull checked out. Not doing so is like buying a truck without checking to see if it runs first.

Also, used bulls can carry reproductive diseases like vibriosis or trichmoniasis. While it is best to avoid buying and introducing used bulls into your herd, all used bulls should be tested and cleared before using on cows. (In one study five percent of open cows purchased through a sale barn tested positive for trichmoniasis.)

A bull's enthusiasm for his job, referred to as libido, can only be measured by watching him at work. If he is a lazy breeders or seems to show no interest in breeding cows he may not feel well and a physical exam is in order to see if his condition can be treated.

During the off season many bulls are kept in an available pasture and more or less out of sight and out of mind. While bulls should be low maintenance during the off season it is easy to neglect their basic nutritional needs. Bulls need to maintain good body condition and be in good condition for the breeding season BCS five or six is optimal. However, a bull can be in good condition and still fail his BSE because of mineral and vitamin deficiencies. Therefore, a complete nutrition plan for the bull pen including adequate vitamins and minerals is essential.

Many folks put out a trace mineral block and call it good. However, trace mineral is exactly that a trace amount. For a 1,500 to 1,800-pound breeding machine trace just isn't good enough. Just like cows, bulls require adequate minerals like Cu, Zn and Se. It takes almost 60 days from start to finish for sperm development. If a bull fails a BSE exam due to a deficiency it may take six to eight weeks before his exam is acceptable.

In the cow herd it is important to provide the highest quality mineral during late gestation through lactation and breeding. In bulls, it is ideal to provide high quality mineral products two months prior to breeding cows and through the breeding season. Like cows, bulls need to have consistent access to free choice, high quality mineral. Skimping on providing mineral could mean the herd skimping on making calves.

Copper is often associated with fertility and it is essential for fertile bulls. Several research studies showed improvement in bull fertility from supplementing with high quality organic minerals. Some studies have shown benefits of changing inorganic sources which improved bioavailability in Cu and Zn. Selenium is critical for sperm production, motility and head formation which is critical to fertilization. Se and Vitamin E may play a role in hot environments to help reduce the effects of heat stress on bull fertility. While most reports focus on the benefits of mineral supplements to improve the motility and morphology of sperm, adequate micromineral supplementation is just as important to maintain the entire male reproductive tract, accessory sex glands and hormone production as well as sperm production.

Providing organic minerals year-round is probably not beneficial and is an expensive management practice, however, feeding organic minerals prior to breeding and the calving season has been shown to improve fertility, conception rates and overall calf health. A good quality mineral supplementation program is still recommended during the off season as well. Many areas in the southeast are deficient in Se and some areas are also deficient in Zn. Last month's article described some of the antagonisms that reduce mineral absorption and cause deficiency. It is important to periodically test forages and water sources for elements that could have a negative impact on your mineral program.

Good mineral supplements are well worth the money and there are ways to keep supplement costs down. A little management goes a long way in achieving an effective, efficient mineral program and a healthy, fertile cow herd.







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