By: Tim Steffens, Marty Rhoades, Eric Bailey and David Lust
Drought is part of life for range livestock operations. We have no control over how much or when rain falls. However, we can either mitigate or intensify drought damage through our management.
When palatable plants are grazed more severely and frequently than less desirable plants around them, they need time to recover leaf mass between defoliations if they are to compete effectively. This recovery time must be longer in drought because the growth rate is slower. In addition, rainfall infiltration decreases and the evaporation rate increases on soils with poor plant cover. When grazing removes too much vegetation and there is not enough time for plants to recover, degradation is more severe. To avoid this damage you should begin managing for drought long before the next dry period. Timely planning and decisive, correct action will determine whether the next drought creates a temporary setback or an ongoing crisis.
Historical rainfall patterns can help you predict drought and make more timely adjustments to livestock numbers and recovery periods, and thereby maintain rangeland and financial health. However, average rainfall information is only valuable if you understand how the variability of rainfall around the average is likely to affect rangeland productivity. Important questions to answer include: What is the range in rainfall for the area? How likely is rainfall to be above or below the average and by how much? Which months are wettest or most reliable?
When the values are arranged from lowest to highest, the one with the same number of values above as below is referred to as the median. Below-average rainfall is more likely than above average rainfall in every month (Table 1, Figure 1). Also, median totals for April through June and for July through October are less than average (Table 1) because of a few unusually heavy rainfall events (Figure 1). Though very heavy rainfall events bring up the average, they are less effective for plant growth than their volume would imply. Intense rains can runoff excessively, which decreases infiltration into the soil. Likewise, high evaporation rates, common in semi-arid environments, make low-volume rainfall less effective in promoting plant growth. When rainfall effectiveness is considered, below-average rainfall is normal.
Since most of the moisture in the High Plains comes when temperatures are relatively high, warm-season grasses usually dominate native plant communities. Exceptions include swales, intermittent watercourses and areas next to perennial streams, where cool season grasses like western wheatgrass, squirreltail, needle-andthread and forbs can be more common. Managing for these plants, particularly during and after drought is important because they can extend availability and increase overall forage nutrient density for grazing animals early and late in the season.
Data from the Sandy Loam Ecological Site Description for Major Land Resource Area 77C, a common site in the Panhandle region, (last column in Table 1) shows that over half of the annual forage production occurs in April to June, though only about 33 percent of the annual rainfall occurs during this period. Forty six percent of the rain for the year falls from July to October but promotes only one third of the total production because of higher temperatures and advanced grass maturity later in the season. For the same reason, only about half as much forage is produced in July as in June, and only about half as much is produced in August as in July, even with similar rainfall in those months.
You can think of available forage like hay in a barn—on a given amount, you can carry a few head for a long time or many head for a short time. Therefore, it is critical to assess forage availability when forage growth normally slows significantly or stops. Prompt reductions in animal numbers in response to shortfalls at these times will prevent more drastic reductions later in the season. The question you must answer is, “How long can I graze the animals I have before the next expected precipitation and forage growth?” If forage is marginal, it is also important to monitor rainfall until the next critical date and, if necessary, make additional adjustments.
The first critical time to asses forage availability and growth is in mid to late June. At this time of year, forage plants are beginning to mature and evaporation rates are high. At this stage, plants will grow less per unit of precipitation even if subsequent rainfall is above average, making the prospects for adequate forage later extremely low, even if soil moisture improves. More importantly, below average rainfall is more likely for the rest of the summer.
The second critical point in the production year to assess forage availability is near the end of the growing season, generally in late September. You need enough forage, at this point, to feed the livestock until significant new growth becomes likely in May. At this time, you can also make some predictions about the following growing season.
Buds that develop into new grass stems are produced in the fall, so late summer and fall rain and growth are critical for plant vigor for the following year. How many buds survive the winter to make new stems is determined by the weather from fall until the spring green up. If soil moisture in the fall is low and/or the winter is dry, the potential for adequate perennial grasses the following year decreases. If a wet spring follows, most of the buds that survived should make a viable stem, but because there may be fewer stems, there will likely be a higher proportion of stem to leaf than normal, making for poor quality forage.
So how should managers deal with drought?
Many ranchers have gone bankrupt by thinking their herd has irreplaceable genetics and trying to feed all their cows through a drought. Under this approach, they feed all the cows until, or even after, they have no equity and the rangeland is seriously damaged.
So how can livestock producers avoid this trap and still keep livestock numbers high enough for gross margin to cover overhead costs? Conservation reserve program (CRP) grazing may provide short-term relief, but forage quality is likely to be lower than normal due to a low proportion of green leaf to weathered residue. To help ensure adequate performance, livestock must be able to select a high proportion of leaf and leave most of the stem and old growth. This means that more of the total plant material (standing residue or litter) should remain in the pasture at the end of the grazing period, if cows are to stay in good condition and rebreed.
When evaluating whether to sell or feed, you have to consider tax ramifications and market conditions. You also must consider possible losses in cow productivity due to poor nutrition, loss of equity from increased feed costs (to include additional pasture), and possible loss of future forage production due to overgrazing.
The cost to develop or purchase replacements has to be recovered with a very limited number of calves, and the expense of carrying an unproductive cow for a year must be covered by net income from the remaining calves that cow produces. These expenses will likely be higher in a drought year. Many people overestimate a cow’s productive life. Therefore, land managers should evaluate how many calves the average cow produces in her life and decide, realistically, if they can recoup the additional expenses of keeping her through the drought. Tables 2 and 3 show the average number of calves weaned per cow at different levels of reproductive performance. These tables assume open or dry cows are culled, but no reductions for any other reasons. Since breeding for the second calf often has a lower pregnancy rate and removes more cows from the herd earlier than shown, these tables may be optimistic. Given that most people keep a heifer calf as a replacement, the average number marketed would be about one less than the figures shown. As such, the cost of additional forage during drought may be difficult to recoup.
If forage supplies are short in June, it is not likely there will be enough rainfall to support normal livestock demand for the remainder of the growing season without pasture damage (Table 1). Given the economic realities of cow longevity, reducing the herd will often be more prudent than buying additional feed.
One option is to wean calves early. Research findings estimate that for every 2.5 days that a 250 to 350 pound calf is weaned, another day of forage is available for the cow. That is a 40 percent reduction in daily forage demand while the calf would have been nursing. This may be a conservative estimate considering the increased forage intake of the calf as it gained weight through the lactation period and the higher requirements of a lactating compared to a dry cow.
When you need to reduce forage demand even more, culling cows may be necessary. Drought can be an excellent opportunity to upgrade the quality of the herd by eliminating poorly performing mothers, bad skeletal structure or udders, and bad dispositions, etc.
To reduce forage demand, some people choose to sell cows based on age. There are two basic approaches. The first is to keep younger cattle because they have the greatest current market value and their longer remaining life expectancy makes them more likely to recoup financial losses. However, heifers and first-calf cows also have the greatest demand for forage quality, which may be lacking in a drought and, therefore, reduce pregnancy rates.
Producing cows generally lose little value and may even gain value until about their second calf. After the second calf they will depreciate slightly but maintain that value fairly well until they are between 5 and 6 years old. At that point, they drop substantially in value. The change in value of different age classes can be used to minimize financial risk over the course of a drought, and should be considered. One way to do so is to sell the younger cattle because they will bring the most money. Under this approach, you keep middle-aged to older cows, since they do not have the growth requirements of the younger classes. As well, the older cows are usually well adapted and, therefore, a reliable genetic base from which to restock when the drought ends. If the drought lasts longer than anticipated, older cows, having already fully depreciated, can then be sold to further reduce forage demand without as great of a financial loss. The AgriLife publication Matching the Cattle Production Cycle to Rainfall Patterns on the High Plains (ERM-013) provides a discussion of some other considerations and options to help match forage demand and supply in drought-prone areas.
The time to formulate a drought strategy is while it is raining. Growing conditions in the fall largely determine the rangeland production potential for the following spring. Spring precipitation largely determines how much of that potential is achieved. Without adequate growth by late June or early July, forage resources will likely be limited at least until the following spring. That limited forage can carry a few animals longer or more animals for a shorter time.
Whatever strategy you choose to cope with drought, it is important to have a plan in place before drought becomes serious so that decisions are not made under stress. Having a plan for which, how many, when, and in what order to sell livestock is crucial. You can make better decisions ahead of time than at the chute gate. If conditions call for culling, do not delay. Once you have used the best information available to formulate a plan, that plan must be put into action for it to do any good.
Bear in mind that sometimes success can mean losing less than you would have otherwise. No strategy is foolproof, but avoiding deep losses is the better plan more often than not. A common story involves one rancher liquidating his herd and another rancher holding on a day longer, just in time for the drought to break. This scenario begs two questions. 1) Would they both have been better off to have reduced livestock numbers earlier; and 2) what is the probability of the drought breaking just in time again. Historical rainfall information indicates reducing the herd early to match forage availability is the better bet.
Download a printer-friendly version of this publication: Using Historical Rainfall Patterns to Plan for Drought in the High Plains
Do you have a question -or- need to contact an expert?