Breeding bulls, purchased or home-raised, are a large capital investment that needs to guarantee a return on the investment, say Matt Hersom and Todd Thrift, Assistant Professors, UF/IFAS, Department of Animal Sciences, Gainesville, FL. This publication is part of the University of Florida IFAS, 2008 Beef Cattle Short Course Proceedings.

However, the bull is often the nutritionally forgotten or most marginalized component of the beef cattle enterprise. This is unfortunate because proper bull management, particularly nutrition, is vital to ensure the long-term viability of the beef cattle enterprise. The bull contributes one-half of the genetics to each calf crop, without a functional bull, that contribution and an adequate calf crop is not realized. Therefore, proper and adequate nutritional management of the herd bulls is paramount to the breeding season success and economic viability of the beef enterprise.

There are a number of well defined nutritional periods during a bull’s life.

  • Pre-puberal – pre-weaning.
  • Pre-puberal – post-weaning to 30-60 days pre-breeding.
  • Conditioning prior to the breeding season.
  • Management during the breeding season.
  • Management after the breeding season

Pre-weaning

During this period the bull is at the dam’s side and nutrition during this period is likely adequate to ensure normal growth and development. Exceptions would be indicated when the dam’s nutritional environment limits milk production. Creep feeding of potential herd sire bulls is utilized in some instances. Currently, there is little or no data that have evaluated the long-term effects of creep feeding on bull performance.

Post-weaning

This period of nutritional development should allow the bull to grow at nearly the bull’s genetic potential. The nutritional design of many growing programs or bull test station diets is a concentratebased, low-roughage, high-energy diet. The goal of this period is to grow the bulls rapidly, but avoid excessive fat development. The nutritional program should also be designed to avoid digestive upsets or affect soundness. The high-energy, high-plane of nutrition also stimulates the onset of puberty particularly in later maturing breeds. Adequate research indicates that either under- or over-nutrition during this period can have detrimental effects on bull development, attainment of puberty, and semen quality. Welldesigned bull test diets or purebred bull breeders with sound development programs should allow bulls to express their growth potential without any deleterious effects on future performance.

Conditioning prior to the breeding season

This period is the most important next to the development phase, but that could be debated. Not only do growing bulls need this conditioning period, but mature bulls need to be conditioned before entering service during the breeding season. Growing bulls generally have just gone through the development phase which consisted of high-energy concentrate based diet. As such these bulls need to be cycled down from that high plane of nutrition. That means there needs to be a transition from the test diet or development diet to a conditioning or maintenance diet that is often foragebased. The transition to a forage-based diet often occurs when the bulls are losing their teeth, compounding the stress of the diet transition. The conditioning period should be around 60 days. This time frame should allow adequate time for the bulls to adjust to a new diet. For well conditioned bulls this time frame will allow bulls to moderate their fat cover and “harden up,” likewise thin bulls will have adequate time to increase their body condition if required. Additionally, the 60-day time frame provides adequate time for the sperm population to turnover and quality sperm to develop prior to the bull entering breeding service. The bull should enter the breeding season in a body condition score of 5.5 to 6.5 (9 point scale). This body condition score provides the bull adequate body reserves to draw upon during the defined breeding season.

Nutrition during the breeding season

The nutritional environment during this period is almost always the same as the cow herd. Therefore special nutritional attention for bulls is nearly impossible. As a result, the conditioning period prior to initiation of the breeding season becomes all the more important. Bulls during the breeding season can lose from 100- 400 lbs of bodyweight which equates to a loss of 1 to 4 units of body condition score. The amount of bodyweight and body condition loss will be influenced by the age of the bull, prior body condition, length of the breeding season, level of activity experienced by the bull, and breed type of the bull. Young bulls and terminal sire type bulls in the Florida environment will likely lose more body weight and condition during the breeding season compared to older or maternal type bulls in the Florida environment.

Nutrition after the breeding season

The bulls after the breeding season likely will need some attention to restore their bodyweight and body condition. The amount of bodyweight and body condition that needs to be replaced after the breeding season can be considerable depending upon how much bodyweight and body condition the bull mobilized. A 2,000 lb bull that loses 200 lbs could require up to 1,200 lb of 65% TDN feed to fully regain all of the bodyweight that was mobilized. As mentioned previously young bulls and terminal sire type bulls likely will lose more bodyweight. Greater the bodyweight loss by the bull will result in greater amounts of nutritional inputs that will be required to regain bull bodyweight. The length of the breeding season and length of the resulting recovery period will dictate the intensity of feeding to recover the lost bodyweight. Maternal sire type bulls are likely to be expected to regain bodyweight on pasture alone or with minimal supplemental feed. Terminal sire type bulls may require supplemental feeds to regain lost bodyweight because pasture quality may not support the needed performance. Likewise the use of young bulls that still have growth requirements will likely result in greater feed input requirements after the breeding season.

Feedstuff Considerations

“What are good feeds to feed, develop, and manage bulls?”

Feedstuff selection for feeding bulls should be based upon the necessity of meeting the nutrient requirements of the growing bull and the unit/price of the important nutrients (energy, protein, minerals). For growing bulls energy is most likely the nutrient that limits growth, thus feedstuffs that contain adequate energy concentrations to support the desired level of growth should be consider. In most cases energy-dense feedstuffs will be some type of cereal grain or coproducts (corn, oats, corn gluten feed, dried distillers grains). Fiber based energy supplying co-products are also acceptable feed choices (soybean hulls, citrus pulp). Cattle have been reported to over consume soybean hulls in self-feeding scenarios with cattle incurring bloat problems and possible death. Selffeeding of any feedstuff without proper management practices in place and knowledge of feed intake patterns should be avoided.

Protein feeds can consist of any of the oilseed meals or selected co-products (soybean, cottonseed or dried distillers grains, corn gluten feed). The utilization of urea in formulated diets or pre-formulated protein supplements may be an economical source of nitrogen if the diet contains adequate energy. 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 digestible protein in good quality forages can help offset the need for very high inclusion levels of protein concentrates.

A variety of roughage sources are fully acceptable as ingredients for bull rations. The selection of any particular roughage option will depend upon the age, bodyweight, and growth requirements of the bull. Common roughage sources include bermudagrass and bahiagrass hay. The selection of hay should be based upon 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. Silage is particularly useful during the development phase and can have application during the transition phase. Obviously, pasture is a primary choice for roughage in a bull diet. When pasture is utilized a number of issues need to be considered including adequate pasture forage availability, adequate forage intake, and acceptable forage quality to meet the feeding goals. An often overlooked consideration in allocating pasture for bulls is the difference in forage intake compared to cows. Bulls, in some cases can be 1.5-2.0 times as large as cows. Additionally, developing or reconditioning of bulls need higher quality pasture, and thus the opportunity to select higher quality pasture. Thus bulls may need to be stocked at 1.5 to 3.0 times the land area of a cow. Winter pasture would be a particularly good choice as a forage source in bull rations. Winter pasture is generally high in both crude protein and total digestible nutrients (TDN) which can go a long way to meeting the nutrient requirements for growing and maintenance bulls.

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