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Understanding nutrient needs of two-year-old cow

Understanding nutrient needs of two-year-old cow

PROBABLY the most pivotal time for a beef cow to maintain a position in the beef herd is the first three months after her first calf is born, according to Karla Jenkins, range management specialist at the University of Nebraska-Lincoln.

As a two-year-old, cows have not completely matured, and they still have nutrient requirements for growth. Jenkins explained that nutrient needs for the fetus increase steadily during the last trimester of pregnancy, and then once the calf is born, feeding it means the nutrient requirements increase even more for lactation. Peak lactation will not occur until about eight to nine weeks after the calf is born, Jenkins said.

If the cow is expected to remain on a 365-day calving interval, Jenkins pointed out that she must rebreed by 80-85 days after calving, which is shortly after peak lactation.

"It is important to remember that if a cow cannot meet all these demands, resumption of the estrous cycle will be the first to be compromised," Jenkins said.

University of Nebraska-Lincoln beef specialist Dr. Rick Rasby summarized research that determined that thin (body condition score of less than five on a nine-point scale), young cows had a 36-66% pregnancy rate, while young cows maintained in good body condition had a 91% pregnancy rate.

"Cow body condition at calving is the most important factor in determining how quickly a cow will breed back after calving," Rasby explained.

According to Rasby, some producers feel that if cows are thin at calving, then "flushing" — feeding a high level of energy — the cow after calving will compensate for poor condition and result in acceptable breed-back.

Although he said this management practice works in limited situations, in most cases, extra energy after calving will stimulate milk production and will not result in replenishment of energy reserves that seems to be necessary to signal the reproductive axis to "gear up" and ensure acceptable reproductive performance.

Rasby said because young cows have a small rumen compared to mature cows, the quality of the diet needs to be high to meet her nutritional requirements. Feeding medium-quality hays without supplementation is not an option. Young, lactating females managed on these diets will lose weight and body condition. Young females that lose weight and body condition before the start of their second breeding season will have reduced rebreeding performance.

Jenkins said many producers have integrated crop and livestock operations, and by the time the intense activity of calving is over, they are busy preparing for spring planting. When so many other pressing issues are at hand, it is easy to overlook the body condition of the young cow. By the time the drop in condition is noticed, it may not be possible for the cow to gain enough condition to rebreed in a timely manner, she explained.

Jenkins stressed the importance of monitoring body condition and body condition score changes in the young cow before calving and up until breeding.

The National Research Council's 1996 "Nutrient Requirements for Beef Cows" publication estimates that the young cow needs a diet with around 68% total digestible nutrients (TDN) and a crude protein content of around 12.5% to be in a positive energy and metabolizable protein balance when her needs are greatest.

Feeding 20 lb. of hay that contains 60% TDN and 3 lb. of dried distillers grains on a dry matter (DM) basis to a 1,000 lb. cow could meet this demand, as could feeding 15 lb. of wheat straw and 8 lb. of wet distillers (DM basis).

The TDN content of most pastures in April, May and June can also supply this need if the quantity of growth is enough to support the forage intake of the number of head grazing. If producers have pastures containing predominately cool-season grass species, Jenkins said it is important to note that these experience peak growth in June. Even producers with predominately warm-season pastures may see a decrease in forage quality if rainfall is limited in July and August.

Therefore, if young cows are to be bred in July and August, Jenkins said producers need to be aware that the TDN levels of these pastures may be around 50% and crude protein may be below 7%. In this situation, cow condition must be monitored carefully, and a protein and energy supplement likely will be needed. Feeds such as distillers grains, field peas, range cubes or other regionally available, high-energy byproducts may be warranted.


Ergot poisoning

Along with many other problems that livestock producers have to deal with as a result of the ever-changing climate, ergot poisoning can routinely be a concern.

According to an Iowa State University Extension report, ergot is a fungus that grows on the seed head of cereal grains and grasses. Environmental conditions such as a cool, wet spring followed by hot early-summer temperatures are ideal for the ergot fungus to grow. Delayed harvesting of grass hay because of rain means that late-cut hay may also be at risk of ergot development.

Historically, rye was commonly affected by the ergot fungus, but wheat, barley, oats, brome, fescue, bluegrass, timothy and other grasses can also be infected. All animals are susceptible to ergot, but cattle are often most affected.

"This fungus produces a group of chemicals called alkaloids, and the alkaloids cause vasoconstriction (constriction of blood vessels) with many different clinical signs, depending on effects of consuming contaminated grain or forages," said Steve Ensley with the Iowa State Veterinary Diagnostic Lab. "In summer, this can mean heat intolerance, and in cold weather, poor circulation can lead to loss of the tips of ears and tails and reduced ability to withstand cold temperatures."

According to the report, the type and quantity of toxic alkaloids vary depending on the specific fungus infecting the plant, the type of plant and the environmental conditions. Therefore, the risk of poisoning and the specific clinical signs may vary depending on climatic conditions and the species of fungus present.

To determine if pastures or hay are affected, Iowa State Extension recommends that producers inspect the seed heads for dark-brown, purple or black bodies within the seed head. The fungus produces a mass called the sclerotia that completely replaces the ovary tissue of the plant and is often larger than a typical seed. These sclerotia will eventually fall to the ground and overwinter.

There is no practical way to eliminate the ergot-producing fungi from pastures. The incidence and severity of future outbreaks will vary with climatic conditions. Its presence and severity can be determined each year by careful field inspection. Fescue grass may be at additional risk since the toxins produced by endophyte-infected fescue are very similar to ergot toxins.

Clinical signs of ergot poisoning in cattle include a "summer slump" during the hot summer. Cattle will commonly develop a rough hair coat, lose weight and spend extended periods of time standing in water or shade, if available.

Gangrenous ergotism (synonymous with fescue foot) is a result of vasoconstriction in the legs and tail. Gangrenous ergotism is often associated with cold temperatures but can be seen in the summer also. Initially, cattle will be lame, usually in the hind limbs first. Swelling at the coronary band develops, and the animal will eventually slough its hoof if not removed from the ergot alkaloid in time.

As with fescue toxicosis, agalactia (decreased or no milk production) can occur. Finally, nervous ergotism is sometimes reported. Nervous signs may be associated with vasoconstriction in the brain or other alkaloids that specifically cause hyperexcitability and tremors, especially with forced movement.

The report says treatment of ergotism is primarily focused on removing the animal from the source of the ergot toxins because there is no antidote. Animals can recover if they are removed early enough before severe clinical signs are present. However, once gangrene has begun, there is little that can be done.


Feedlot software

The Iowa Beef Center is releasing a newly revised version of its feedlot monitoring software this month. The Iowa State "Feedlot & Cost Monitoring Software" was initially created in 1982 and has been used by cattle feeders to track costs, profits and performance.

The software continues to reflect the philosophy that feeders need to objectively measure, monitor and react to changes based on existing and past livestock and financial performance.

"This software provides an affordable means to compile cattle feeding financial and performance information and to assist in the interpretation of what is occurring," said Dr. Garland Dahlke, who created the program.

The updated version allows for the same feed-to-beef focus as previous versions, including feeding period summaries, projections, closeouts, itemized account records and custom feeding invoice statements.

A major change in the revised version is to allow for individual animal monitoring and projections as necessary for heifer and bull development. Along with this feature, animal health issues have a greater focus, with the new release providing an opportunity to track drug inventories and to import processing and treatment protocols.

Cost and income channels are more flexible in terms of defining and recording the production inputs and outputs being tracked. Environmental documentation dealing with nutrient excretion, weather and manure logistics are incorporated to meet current reporting requirements.

Finally, the renewed interest in benchmarking has been addressed with the ease of compiling and reporting closeout data via the internet.

The new feedlot monitoring software may be accessed by contacting the Iowa Beef Center at (515) 294-2333. The cost is $600 for new users and $200 for existing users to upgrade.

Volume:86 Issue:07

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