Bull sales are prevalent this time of year, and current sale averages are setting records. Taking care of that bull investment from the time of purchase until he is turned in on pasture for the breeding season is critical. Forage plays an important role in this transition period.
Bulls from weaning to yearling age are often managed to measure their genetic growth potential. The type of feed ration they are developed on during this time can contain a high percentage of concentrates and a low percentage of forage to maximize growth rate. At the end of this feeding period, some bulls may be “overconditioned,” which can affect their fertility and ability to settle cows.
Bulls that are overconditioned will have a body condition score (BCS) of 7 or higher on a scale of 1-9. Young bulls should be at a BCS of 6-6.5 at the start of the breeding season to compensate for weight loss during the breeding season. Bulls that are actively breeding can lose up to 200 pounds during the breeding period. Bulls at a BCS of 7 or higher can have fat deposits in the scrotum that interfere with temperature regulation, which can affect semen quality.
Evaluation of overconditioned bulls at the University of Georgia found that only 41% passed a breeding soundness examination compared to an 81% passage rate of bulls in adequate condition. Bulls that are overconditioned may also lack the stamina required to work through an entire breeding season.
There are several management strategies that can ease the transition of bulls from being overconditioned to breeding-season condition. When new bulls are brought into your operation, consider biosecurity. Ideally, bulls should be quarantined for 30 days or at least two weeks before being introduced to other animals. This reduces the risks of introducing disease into your herd.
• Provide an area where bulls can exercise, with fresh water available.
• Give bulls time. A 90-day transition period is the best. This gives the bull time to adjust to different feeds, surroundings and routines. Another benefit of a 90-day transition period is that it fits the spermatogenesis cycle, which lasts approximately 60 days. If there are any problems with the bull’s semen quality, 90 days is enough time for a new cycle to complete and resolve any problems.
• Know what the feed ration was that the bull was developed on prior to purchase. Initially, after purchase, if he can continue to be fed a similar ration to what he has been used to, this will reduce stress and help to keep him healthy.
• Avoid rapid and dramatic changes in diet. If bulls have been developed on high-concentrate diets, the change to a forage-based diet should be gradual. Replace concentrate with forage at a rate of 10% a week over several weeks. While we don’t want young bulls to put on excessive condition, we still want them to grow.
A daily weight gain of 1.5-2 lbs. per day should be the target. To do this, bulls will need access to a good supply of quality forage. Forage quality should be 10% crude protein and 60-70% total digestible nutrients. Good grass hay or a grass legume blend will work well to stimulate rumen microbial development. Avoid feeding pure alfalfa hay that might cause bloat or other digestive issues. Aim to have the bull transitioned to a forage-based diet 2-3 weeks before the start of the breeding season. The goal is for him to be ready to consume and digest pasture and range forages.
Once bulls are out on pasture, they should be monitored for excessive weight loss or physical problems that can prevent them from breeding. If possible, provide bulls with supplementation to keep them growing and in good breeding condition.
If you buy bulls that are overconditioned and turn them straight out into pasture for breeding, you may not recognize them at the end of the breeding season. Time spent getting bulls into breeding-season shape is time well spent, just like an athlete training for a sporting event. — North Dakota State University Extension
