Managing Summer Slump

Managing the Summer Slump Matt Booher, Virginia Tech - NRCS adapted from Livestock Notes by Dr. Mark McCann

As beneficial as recent spring moisture has been for much of Virginia, we know heat and dry conditions may soon be upon us. The expected seasonal decline in pasture and livestock performance from June- August is usually called “summer slump”. Toxic tall fescue gets much of the blame and is definitely a major contributor, but there are other factors that come into play as well. Most Virginia pastures are based on cool season perennials such as tall fescue, orchard grass, and bluegrass. These grasses are most productive when temperatures are in the 60's and 70's, and growth will decline above 80ºF, even when moisture is adequate. This depression gets worse if accompanied by drought. As the growth of these grasses slows or stops, sugar content and digestibility drop as well. Protein, particularly in tall fescue, may drop some or remain relatively stable. Legumes such as ladino clover, red clover, and alfalfa are somewhat tolerant of warm temperatures and can complement the forage on offer if they are present going into the summer slump. When the pasture is comprised of 20% legume or higher, the high protein and digestibility of these forages can help buffer declines in animal performance caused by toxic fescue and declining forage quality of grasses. The presence of legumes and non-toxic grasses such as orchardgrass, Kentucky bluegrass, and crabgrass in pastures can be impacted by the management of the spring flush of grass growth. Tall standing forage can shade out clovers and other contributing plants. Tall fescue is more prone to do this due to its combination of height and density. Managing this spring flush through grazing management and/or harvesting excess growth as hay is important to maintain clover stands and allow other summer grasses to contribute to the forage mix. While summer stockpiling tall fescue pasture is a good, low-cost method for storing spring growth for later, you should consider the potential impact of this practice on other forages in the mixture. If you will be grazing livestock with high nutrient requirements, you may choose to clip the summer stockpile around late-May to open the canopy and allow a more diverse mixture of forage species to stockpile, or you may choose to make hay and forgo summer stockpiling. Keep in mind that the 2 month old calf receiving 20 lbs of milk/d probably weighed 150 lbs at the time, while the calf receiving a far smaller amount of milk at 6-7 months of age should weigh 400-500 lbs. Therefore the performance of the 6-7 month old calf is much more of a reflection of the forage quality and quantity on offer than their limited milk intake. Unfortunately, for spring born calves, this corresponds to July and August summer slump in forage growth and nutrient content. The negative impact of endophyte infected tall fescue compounds and intensifies the previously discussed forage growth and cow lactation issues. The toxic Ergot alkaloids are highly concentrated in the seed, though they are present in the leaf and stem tissue as well. The effects of the toxins are most visible during the summer months. Grazing activity and forage intake are depressed on endophyte infected pastures during the summer months which lead to reduced cattle performance. What are management suggestions for toxic tall fescue? 1) The age old suggestion for diluting infected tall fescue still works. The dilution can be other grasses, legumes or even supplemental feed, anything that takes the place of infected tall fescue. 2) Managing pastures through clipping or grazing management to reduce seed heads and stems which contain higher toxin levels. These management practices will produce a more open forage canopy which will prevent shading of diluting forages such as clovers and warm season grasses. 3) Given this year’s combination of relatively affordable feed costs and high calf prices, creep feeding is probably an economical decision to add profitable weight.