Capitalizing on surplus forage growth
August 17, 2008
After several growing seasons with substantially less than normal rainfall, many areas in the Tri-State area are enjoying an exceptional year for growth of pasture and hayland plants. Many areas have received normal or better precipitation and temperatures have generally been below normal. Traveling the countryside in mid-August, the pervasiveness of green vegetation is striking! Two patterns are peculiar after so many consecutive years of severely limiting growing conditions. First, the overall quantity of growth in many pastures reflects both the excellent growing conditions and the conservative approach many ranchers used in establishing stocking rates. Secondly, the regrowth of alfalfa in mixed grass-alfalfa hayfields is conspicuous. Regrowth is evident even in cereal grain fields cut and baled for hay.
Favorable growing conditions this year have provided the opportunity for forage plants to begin recovery from extended drought. Accumulated growth may also provide an opportunity to enhance production of reduced feed costs as well. A number of strategies might be employed by producers who are willing to develop a flexible approach to capitalize on surplus growth.
Unlike the beginning of the growing season, when the quantity of feed available for grazing must be estimated and future growing conditions are unknown, pasture growth has been nearly completed by late summer and the quantity available can be determined rather accurately. Fall stocking decisions can be made by matching available feed supply and animal demand within little uncertainty. While overgrazing should always be avoided, excessive use in the fall will delay and reduce growth in the springtime.
After allowing adequate plant growth to promote recovery and determining what quantity of herbage is truly excess, options for utilizing this growth might include: 1) stockpiling growth for winter grazing by cows, reducing the hay feeding requirement; 2) grazing calves after weaning rather than selling them immediately; 3) offering fall or winter custom grazing for sale; 4) retaining more females, either cows or replacement heifers, anticipating improved future growing conditions and increasing overall herd size; 5) retaining cull cows after weaning, expecting recovery of weight and condition and increasing potential revenue from salvage; 6) extend the period of grazing for yearlings beyond what was planned, utilizing additional growth.
Utilization of rangeland or tame pasture during the fall requires no particular management attention other than recognizing that nutrient quality declines rapidly as vegetation growth slows and plants mature. Wetter and cooler conditions this year may have maintained higher nutrient concentrations than most years. However, energy and protein content of autumn pasture will generally be insufficient to support optimum performance of animals with potential for rapid growth, such as recently weaned calves. Supplemental protein, if it can be supplied cost-effectively, will likely improve performance. For dry cows, fall pasture is likely to supply adequate nutrients.
The opportunity to graze alfalfa regrowth presents greater risk/reward alternatives and requires a careful and deliberate management plan. Alfalfa grazing should be managed to harvest as much of the high quality nutrients as possible, without sacrificing future productivity of the stand.
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If sufficient regrowth has occurred in hayfields to provide fall grazing, fencing and water must be adequate. The quantity and quality of feed available might justify temporary fencing and hauling water to unfenced hayfields.
Standard recommendations for cutting alfalfa suggest cutting alfalfa no later than about six weeks before frost, to allow stands to recover, limiting winter injury and promoting initial spring growth. Research in the north central U.S. indicates that careful grazing may not interfere with alfalfa’s “winterization” process. Grazing lightly, so that 6-8 inches of growth remains on alfalfa plants, is the key.
In addition to stand damage, bloat is the other potential risk introduced by grazing alfalfa. Bloat occurs when gases resulting from digestion are trapped in the animal’s rumen in stable foam, interfering with the normal belching process. Alfalfa is nutritionally valuable because of rapid digestion. Compounds characterized by high digestion rates are normal constituents of the alfalfa plant, but also contribute to stable foam.
Several precautions can reduce the risk of bloat. Mixed grass/alfalfa stands generally dilute the alfalfa component of the diet consumed, thereby reducing the offending compounds. However, dismissing the risk when grazing alfalfa regrowth on mixed grass/alfalfa hayfields could be premature. Summer growing conditions has promoted much greater growth of alfalfa than the accompanying cool-season grasses. What is actually available to the grazing animal may be almost entirely alfalfa. Bloat risk declines as alfalfa plants mature and as animals consume a greater proportion of stem.
Standard practices to reduce bloat incidence include providing a supplement containing poloxalene, or administering it in drinking water; never turning hungry animals into alfalfa; providing access to grass hay; and careful and frequent observation, particularly when animals are first introduced to alfalfa.
A final consideration is the impact of freezing temperatures on bloat risk. Plant tissue rupture resulting from a freeze tends to further accelerate digestion rates and elevates the risk of bloat. This condition extends for three to five days following the freeze. Therefore, if alfalfa is being grazed as frost dates approach, alert observation is essential. Moving animals onto alfalfa immediately after a frost should certainly be avoided.
Alternatively, a week or so after a killing freeze, when alfalfa has gone dormant, the risk of bloat is small and potential damage to the stand is limited as long a some residue is allowed to remain.
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