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Bulls need to rebuild after breeding season

A proper feed and mineral program prepares them for next year

By midsummer, most producers pull their bulls from the spring cow herd, mainly to maintain a desirable 60-day breeding season and to avoid any temporary sterility caused by heat stress. As a beef nutritionist, I advocate that bulls be treated with lots of attention during the post-breeding season. They should be put on a good plane of nutrition for the rest of the summer until late fall, after which they should be properly overwintered. This helps them maintain or obtain good body condition and health, leading to the good fertility necessary for next year’s breeding season.

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Post-breeding bulls should be segregated into different feeding groups — growing yearlings, two-year-olds and mature bulls. Each group has special nutritional needs. For example, yearling bulls are still growing (they need to achieve 75 per cent of their mature bodyweight) and may also need to recover a couple of hundred pounds of lost body condition. Therefore, they require a post-breeding diet, which supplies 60-65 per cent TDN dietary energy and 14 per cent protein, so they can gain 1.0-1.5 lbs per day until the next breeding season. This compares to mature bulls, which might recover some bodyweight, but often need to maintain body condition, thus requiring a lower 55-60 per cent TDN and 11 per cent protein diet.

Such nutrient requirements necessary to recover/maintain optimum body condition score (BCS) are really the underlying objective of most successful post-breeding bull feed and management programs. Beef bulls are the most sexually active and fertile (highest sperm count and viability) when they have a body condition score of 5.5 to 6.0 (re: on a scale of 1= emaciated to 9 = obese) at the start of the breeding season. In contrast, skinny bulls with a BCS lower than 5.0 often have lower libido and sperm production.

Putting both young and mature bulls on good quality mixed legume-grass pastures is the best practical post-breeding feed choice until winter. Ideally, it would be tame, well-fertilized fields with timely rains. However, it’s most likely native prairie pasture that takes spotty thunderstorms. And, if one isn’t prepared to supplement a great deal of hay or purchased protein-feeds on this loose pasture, bulls must graze comparably more acres.

A program that works

Case-in-point: A friend runs about 300 black-Angus cows with about 15 breeding bulls. He grazes both his young and mature bulls on the same 200 acres of pasture that was once an alfalfa field but hasn’t been broken up for years and thus has been largely been replaced by wild grass species. He supplements a few 20 per cent low-moisture molasses cattle lick tubs placed near an available waterer, as well as provides loose cattle mineral in three-compartment mineral feeders which are mounted on old truck tires.

His commercial “breeder” mineral is fed at 70-100 g (three to four oz.) per head, daily. It contains good levels of calcium, phosphorus and magnesium that compliments his native pastures for bulls. Furthermore, it contains highly bioavailable chelates of copper and zinc, both known to be essential for superior bull fertility. Selenium is also be provided at three mg/hd/d as well as recommended levels of vitamins A, D, and high vitamin E (1000 iu/hd/d). Salt blocks are put out to round out the nutrition of these pastures.

In addition to good pasture nutrition, my friend is aware that a good source of water is important for grazing bulls, especially during times of summer heat stress. He makes sure pasture waterers are in good working order and can easily supply 40-50 litres of water per head per day in comfortable weather and replenish 100 litres-plus of water per bull during hot weather conditions.

Aside from providing plenty of water, my friend alleviates other stresses in his bulls such as controlling fly populations that parallel hot summer weather. He uses three main methods of fly control — ear insecticide tags, back rubbers and a pour-on insecticide for 30-60 day control. As a side note, my friend has successfully for years used essential garlic oil added to his breeder cattle mineral to control face flies and bulldog horse flies.

It’s a good program that helps breeding bulls recover from this year’s successful breeding season, yet at the same time helps prepare them to return to the cow herd next year with optimum fertility.

About the author

Columnist

Peter Vitti is an independent livestock nutritionist and consultant based in Winnipeg. To reach him call 204-254-7497 or by email at [email protected]

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