Many areas of the U.S., but particularly the West, have experienced drought the past few years. Unfortunately, it appears summer 2001 will be no different for many of these afflicted areas. In drought conditions, nutrition, grazing and parasite factors present three major areas of concern.
In a drought, the initial stress to the animal is nutritional. As the forage dries out, the nutrients in the feed are declining while the nutrient requirements of the calf are increasing. In the cow, the stress of lactation plus a growing fetus, in addition to her own maintenance requirements, magnifies the effects of poor nutrition. This may lead to lower weaning weights and delayed breeding.
In addition, the cow will have to be fed more later to achieve the proper body condition score (BCS) before calving next year. Consider these factors:
A cow in thin condition may require 10-15% more energy in her diet during cold weather than a cow in good condition. The cow provides nearly 70% of her calf's nutrition. The cow's ability to provide ample milk depends on her overall condition and the quality of her own nutrition.
A cow in good nutritional condition is nearly 50% more likely to cycle within 90 days of calving than a thin cow.
The calf obtains 30% of its nutrition from sources other than the cow — grazing or supplemental feed. Supplemental feed needs to be high quality to benefit the calf, as it has a limited stomach capacity and may not digest feed as well as older animals.
Management-wise, early weaning of calves or creep feeding may be options. If possible, cull old or dry cows and separate cattle according to body condition. Save the best feed or the largest quantity of feed for the younger animals.
One pitfall to avoid is spending too much on supplemental feed. Look for sources of inexpensive feed or by-product feeds in your area (see “2001 Feed Composition Guide,” February BEEF, page 10, or check out www.beef-mag.com  for the feed values of almost 300 feedstuffs). Otherwise, moving or selling the cattle may be the only options.
In nutrition-stressed cattle, the number of parasites needed to impact productivity reduces dramatically. Particular attention may be needed this year for both flies and internal parasites.
Drought conditions reduce the amount of forage available, and overgrazing is often unavoidable. As a general rule, hot dry conditions reduce parasite larvae numbers. Due to the short grazing, however, the number of larvae ingested may be higher because most of them are located at ground level.
If supplemental feed is given, the cows will congregate more in one area. Thus, the concentration of larvae may be increased.
One of the most costly internal parasites of cattle is Ostertagia ostertagi (brown stomach worm). If the environmental conditions are particularly hostile to the parasite — extreme heat or cold — the organism will inhibit in the larval stage and remain dormant inside the cattle. When conditions improve, the worms resume development and move outside the animal's body, which may lead to large increases in parasite numbers later in the year.
David Wieland is a nutrition consultant specializing in cow/calf, feedlot and horses. Based in Shepherd, MT, he also publishes a subscription newsletter. For more information, contact him at 406/373-5512 or e-mail at [email protected] .