Livestock: March 2002 Other Livestock Articles

The welcomed signs of spring are finally becoming apparent. The grass is greening up, trees are blooming and calves are being born. With newborn calves showing up in many producers' pastures, the success of last year's management begins to become more apparent. Percent calf crop may be the simplest to measure and the most important indicator of a sound management system that cow-calf producers have available.

With the results of last year's breeding season fresh in producers' minds, it is time to address the breeding season for this year. One of the first decisions to be made is when to start the breeding season. Table 1 gives an example of a gestation table to help plan calving dates and the calving season. This table is based on a 285-day gestation length. Remember that the length of gestation can vary by 10 days or more.

Some of you out there may be thinking, "The bulls have been out all year, why would I be concerned with turning them out?" The concept of utilizing a controlled breeding season is a sound decision to implement in your production system. The commonly recognized advantages of a controlled calving season are numerous and include accurately matching the nutritional requirements of the cow herd, concentration of management effort, more uniform calf crop, elimination of less fertile females from the cow herd and defined annual check points for your production and management system.

Another advantage of a controlled breeding season is the reduction in the number of feedlot heifers calving while on feed. This is a significant problem in the feeding industry. By having all calves born and consequently weaned at a set time, the chance of a heifer being bred while still with the cow herd will be all but eliminated completely. The National Research Council reports that a pregnant heifer has a 35 percent higher nutritional requirement than does an open heifer. Therefore, it stands to reason that bred heifers in a pen of feeder heifers would gain at a lower rate and at a decreased efficiency of gain.

There are two common reasons for not having a controlled breeding season. The first is the concern of what to do with the bulls during the nine to ten months of the year that they are not breeding cows. Producers also fear that they will miss some calves and ultimately some income, if they hold a cow open to fit her into a controlled breeding season. The concern for bull housing is easily overcome by the incorporation of a small bull trap into the pasture system. This trap can be easily constructed of a two or three wire electric fence that will serve the purpose quite well. If a majority of the females are bred anyway, the bull should be fairly easy to contain. The issue of reduced number of calves to sell is very real. However, several studies have shown that the cow that calves out of sequence will rarely produce a calf that is heavy enough to cover the cost of owning that cow.

The move to a controlled breeding season need not be a drastic one year decision where a large number of out-of-synch cows are sold. The change can be made gradually over a two to three year period by gradually shortening the breeding season by two or three weeks a year.

Another concern this time of year is the reproductive capacity of your bulls.

All bulls should be subjected to a Breeding Soundness Evaluation (BSE) within 30 days of bull turnout. It is estimated that 10-20 percent of all breeding bulls will be removed from the bull battery every year. Therefore, evaluate the bulls you are planning on using early enough to replace bulls that do not have an adequate BSE. Be sure to have young bulls subjected to the same examination prior to purchase and do not overwork yearling bulls the first breeding season. The rule of thumb is one cow for each month of age a bull is until he turns three years old. See table 2 for the recommended cow to bull ratio.

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