Answer to the Question Why Are Cow-calf Beef Feeding Programs Based on the Use of Roughages
Professional Version
In many areas, producers follow a late winter/early spring calving program (February to May in the USA), depending on the available feed, growth of early pasture, and prevailing climate. Fall calving has become more prevalent, particularly in the south. Wintering the lactating cow presents a much greater nutritional problem than does wintering the pregnant, nonlactating cow. Spring-born calves commonly are weaned at 6–7 mo, and their dams bred back while on pasture. Heifers may be bred to calve first as 2-yr-olds (22–25 mo) if good winter feeding is practiced to ensure adequate development. Heifers should weigh 55%–60% of mature body wt at breeding time and should be fed well thereafter to allow for continued growth, good milk production, and prompt rebreeding.
Mature cows have greater body reserves and lower nutrient requirements than heifers; therefore, they can be wintered on rations of poorer quality. Their ration should provide a minimum of 8% total or crude protein in the dry matter; if it does not, then 1–2 lb (0.5–1 kg) of a 20%–30% protein supplement or its equivalent should be fed daily. A mineral mix and salt should be provided. Cows should calve in body condition score 5.5–6 (0–9 scale).
Under profitable systems of management, a mature beef cow should maintain her weight from fall to fall. Lactation requires more nutrients than gestation. However, feeding beef cows more than is necessary for satisfactory production, such as is frequently done in purebred herds and show herds, is also undesirable. Large accumulations of body fat may lead to lowered conception rates, difficult calving, a lower calf crop, and a shorter life span for the cow.
A system of "creep feeding" can be practiced in which suckling calves are allowed access to a grain mixture in a self-feeder in an enclosure or to high-quality forage in an adjacent pasture where only calves have access. A creep-feed mixture of high-fiber co-product feeds such as corn gluten, dry distiller's grains, and soyhulls can be combined with a salt-vitamin-mineral mix to provide a palatable ration for the calves. The mixture should be rather large particles to prevent dustiness. A commercial 14%–16% protein creep feed may be used as an alternative.
Growing bull calves should also receive a balanced ration. Young bulls should not be fed large amounts of starch, with gains of 2.5–3.5 lb (1.1–1.6 kg) per day being very adequate. Yearling bulls grown on extremely high energy diets are more likely to have disease issues and reduced longevity in the breeding herd. Mature bulls commonly are wintered in the same manner as the cow herd, with a greater feed allowance during the late winter. In highly fitted show bulls, a gradual reduction in the ration and much exercise are needed before they will be in suitable shape and condition for pasture breeding. Breeding stock should have adequate nutrients in their ration and be gaining weight before and during the breeding season. Deficiency of several nutrients, especially carotene, phosphorus, energy, and protein, reduces fertility. These nutrients should be present in adequate amounts in the ration at least 6–8 wk before breeding.
It is common practice to feed calves and yearlings to make moderate gains in winter, with faster and less expensive gains on summer pasture. Such cattle may be sold as feeders in the spring or finished out in dry lot the following fall. The cost of winter gain on harvested feeds invariably is higher than summer gain on pasture; hence, it is advisable to winter cattle so as to make the greatest possible gains on pasture. To maintain good health, weanling calves should gain >1 lb (0.5 kg)/day. Two pounds (1 kg) of grain plus 1–2 lb (0.5–1 kg) of protein supplement are recommended in addition to nonlegume roughage. If legume roughage is fed, no protein supplement is needed. Older cattle, particularly if they enter the winter in fleshy condition, may just maintain their weight. A free-choice mineral mixture with trace mineralized salt should be supplied. Limited amounts of grain fed to yearling cattle on pasture during the late summer may increase their market value.
This phase of beef production consists of full feeding of grain with limited amounts of roughage until market weight and finish are reached. Older cattle may reach finish weight on pasture alone (or with only a few pounds of grain/day) or after 60–90 days in the feedlot on high-grain rations to improve market grade and to remove any yellow tinges from their body fat (due to stored carotene from pasture forage). Weanling calves can be shipped directly to the feedlot and fed finishing rations for 150–250 days, whereas yearlings require ~150 days. Grain consumption of cattle on full-feed is ~2–2.5 lb/100 lb (1 kg/45 kg) body wt. Roughage consumption usually is limited to approximately one-fourth to one-third of the total concentrate consumption after cattle are on full-feed. Cattle consume ~3% of their body wt/day when self-fed mixed rations. For calves, ~1.5–2 lb (<1 kg) of a 33% protein supplement is required daily for best gains and market grades when nonlegume roughage is fed.
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Source: https://www.msdvetmanual.com/management-and-nutrition/nutrition-beef-cattle/feeding-and-nutritional-management-of-beef-cattle
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