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Serving Your Sire!

Last month, the Saskatchewan Ministry of Agriculture hosted a series of workshops on bull selection and evaluation. These timely seminars covered topics that all Canadian cow-calf operators should have an understanding of when making herd replacement and management decisions. The topic of expected progeny differences (EPDs) was addressed by Sean McGrath, a beef producer and genetic consultant from Vermilion, Alberta while Lee Sinclair from Merial covered genetic testing. Both talked about emerging genetic tools for sire and replacement heifer selection. Garner Deobald, a beef producer and bull judge for Agribition, demonstrated the physical characteristics of a good bull, while local veterinarians covered the basics of fertility evaluation. I had the challenge of addressing the nutritional management of the bull battery and would like to share some of the key issues arising from this presentation.

Many of you who calve in March and April will be turning bulls out toward the end of May, while those calving later in the spring will look at a mid-to late-July turnout. Ideally you are practicing a short, concise breeding season of 45 to 65 days. Success in these programs depends on high fertility in your cows and the bull battery. Yearling bulls purchased from test stations or purebred breeders likely need to be adjusted from relatively high energy growing programs to forage-based rations.

Diet change should be gradual so you do not throw them off feed. Yearlings should have reached puberty two to four months prior to the date you expect to breed them and should be conditioned to your operation for a minimum of 60 days. Both steps help ensure these young bulls will be producing high-quality semen when turned out to the breeding pasture. During the conditioning period, keep in mind that yearlings are still growing. Target breeding weights should be a minimum of 55 per cent of mature weight. To meet this goal, your feeding program during conditioning will need to target two to 2.5 pounds a day gain, depending on the bull’s condition. For a 1,300-pound bull this will require supplementing good-quality grass hay with up to 10 pounds of barley or its equivalent. A protein supplement may or may not be required, depending on the quality of the forage.

Two-year old and mature bulls also require conditioning prior to the breeding season. In the case of two-year olds, the target breeding weight should be 80 to 85 per cent of mature weight. As with yearlings, these bulls are still growing and should be gaining at a rate of one to two pounds per day through turn out, depending on condition. Mature bulls should be turned out with a body condition score of 3 to 3.5 (5 point scale). The conditioning period can be used to put on a bit of extra weight if required. If you were looking to increase body condition score from 3 to 3.5 over a 60-day period (a weight gain of approximately 90 pounds), you would target 1.5 pounds a day weight gain. In all cases, we want to avoid bulls that are over-conditioned or carrying too much fat. These bulls can be poor breeders due to fertility issues (i. e. poor semen quality) or because they are just plain lazy! The conditioning period should also provide for exercise to harden up your bulls and if necessary to get them acquainted with each other.

Minerals are just as important for your bulls as they are for the cows. In particular, trace minerals such as zinc, copper and manganese play a critical role in reproduction. Zinc is involved with sperm production and deficiencies can lead to poor fertility. Copper deficiency can lead to problems with structural soundness, poor conception rates and over all poor energy status. Inorganic sources of minerals (i. e. copper sulphate) form the basis of most mineral programs. These include trace mineral salt formulations as well as many of our commercial minerals (i. e. 2:1 or 1:1 minerals).

If you have not been feeding a mineral to your bulls or if you suspect there is potential for them to be deficient in one or more minerals, one solution is too feed a chelated mineral mix during the conditioning period. Chelated minerals are also known as organic minerals. These are specialty formulated such that they are complexed to a protein or amino acid. These minerals are absorbed more efficiently than typical inorganic mineral sources and can alleviate a deficiency in a shorter time frame than inorganic minerals. Chelated minerals are expensive, however. For the commercial cattleman, my recommendation would be to go to a chelated mineral program only if you suspect fertility issues due to a specific trace mineral deficiency and if your time frame for correcting that deficiency is short. As I have written previously in this column, the best mineral program is one that ensures year round mineral consumption by all breeding animals in the herd.

Finally, as this year’s breeding season approaches, don’t forget to have your bulls evaluated for fertility by your veterinarian. Too many cow-calf producers have learned the hard way that turning out sub-fertile bulls can be an expensive mistake.

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JohnMcKinnon isabeefcattle nutritionistat theUniversityof Saskatchewan

About the author


John McKinnon

John McKinnon is a Professor Emeritus at the University of Saskatchewan and a consulting nutritionist who can be reached at [email protected].



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