Roger Gates: Ways to salvage forage during times of drought
August 20, 2012
There have been a few thunderstorms locally, which reminds me that rain is still possible.
As it has been for most of 2012, rainfall has been "scattered" at best. Grassland managers in the Tri-State area have several reasons to be thankful:
1. We've enjoyed about three prior years of precipitation.
2. Most pastures came into the spring with carry-over old growth.
3. Conditions are not as severe as to the those south and west.
Summaries of long-term research at the SDSU Range and Livestock Experiment Station near Cottonwood; and the USDA-ARS Fort Keogh Livestock and Range Research Laboratory near Miles City, MT; indicate that two climatic factors are most influential in determining the quantity of vegetation that accumulates during the growing season in pastures dominated by cool-season grasses, as is typical in our region.
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The first factor is the date of the last killing freeze in the spring. That was certainly not a factor this year, as the spring was unusually early and warm.
The second factor is spring precipitation. When April-June precipitation is less than normal, there is a good chance that pasture growth will also be below normal for the entire growing season. Below average precipitation began in April and was compounded by the absence of snow cover and higher temperatures that accelerated evaporation.
In early July, a reliable projection of pasture feed supply for the growing season can be made. Drought response plans should take advantage of this "early warning information" to make management decisions early in the season rather than later. In the best case, contingency plans that were already in place can be implemented. The earlier adjustments are made, the less severe they need to be.
For example, consider a grazing plan that calls for 5 months of grazing from May 1 through the end of September. If growing conditions reduce pasture feed supply by 10 percent, a stocking reduction of 15 percent made on June 15 will allow a balance between feed supply and animal demand to be maintained. If the decision is delayed until Aug. 1, a 25 percent reduction in animal numbers will be necessary to avoid overgrazing.
Adjustments involve balancing the supply of available feed with the demand for animal consumption. Several alternatives are available:
• Destocking – reduce the number of animals through culling and marketing
• Modifying herd composition – increasing the percentage of lighter weight animals
• Early weaning
• Improve grazing efficiency
• Plant, then graze annual forages
• Graze crop salvage or aftermath
• Supply purchased feed (hay and/or grain)
A stocking plan which included a fraction of the total herd as "liquid" animals makes destocking decisions more straightforward. Sale of yearlings carried over or purchased for grass reduces the animal demand immediately. Sale runs are high across the country in response to widespread pasture shortages. Fortunately, prices for breeding females appear to have remained stable. Returns from the sale of lighter weight animals appear to have softened. Prior identification of less-productive females also facilitates destocking decisions.
Early weaning provides demand relief in two ways. Removing the calf eliminates its own grazing demand and additionally, eliminates the lactation requirement for the cow. Many research studies have confirmed that calves weaned as early as 45 days can perform well after weaning. Widespread research has also demonstrated the benefit to cow performance. Body condition scores increase and rebreeding can be enhanced in comparison to cows supporting a calf to normal weaning age.
Fewer studies have examined the impact on pasture forage. A cooperative study conducted on mixed-grass rangeland near Dickinson, ND by scientists from NDSU, SDSU and the University of Wyoming examined disappearance of pasture vegetation when grazed by cows weaned in mid-August compared with normal weaning in early November.
Herbage disappearance in pastures grazed by dry cows was 40 percent less than in pastures grazed by pairs during the mid-August to early November period. Early weaning requires planning to handle and market calves, but clearly can provide relief to pastures impacted by poor growing conditions.
Pasture subdivision, most likely with temporary fencing, and combining herds to raise stock density, can increase the fraction of available herbage which is consumed by livestock. Grazing efficiency for season-long stocking can be expected to average 25 percent (one-fourth of available forage is consumed by livestock) in well-managed pasture. More intensive management (higher stock density, shorter pasture occupation, increased pasture rest) can increase grazing efficiency to 35 percent or more. That may not sound like much, but it represents a 40 percent increase in forage harvested by livestock!
Initiating more intensive stocking in response to drought, however, may not be the best idea. More intensive management skills in any arena are best learned gradually. The consequences of errors in judgment (insufficient water supply) are magnified as stock density increases.
Planting annuals for grazing may be an alternative for some operations. Care needs to be taken with the risks of nitrate accumulation in plants that grow in limited moisture conditions. Greg Lardy described the risks very well in his consideration of salvaging drought-stressed crops in last week's column.
Crop aftermath is generally low in nutrient availability, but may be sufficient for animals with low requirements such as cows in early pregnancy that have been weaned early. Volunteer growth in stubble fields may enhance nutrient availability, but diet quality will decline rapidly as stocking rate increases and animal opportunity for selection is limited.
Purchasing feed is an option, but prices for hay and grain are increasing rapidly this year. Decisions about purchases should be based on cost per unit of nutrient rather than simply cost per pound. F