Feed supplement options for summertime toxic fescue grazing

Published on Thu, 04/05/2018 - 9:25am

Feed supplement options for summertime toxic fescue grazing

 By Michael Cox for American Cattlemen

With summertime high temperatures fast approaching, toxic fescue issues will soon reach peak over the coming weeks. The losses associated with toxicosis have been well documented and researched; some $1 billion in lost beef performance occurs across the industry annually. However, there is potential to reduce the rate of lost performance through targeted feed supplementation during this challenging period of toxicity.

Feed Supplements
Toxins occur in endophyte infected grasses such as Kentucky 31 in the form of an ergovaline – a toxic alkaloid. The endophyte fungus which grows between the plant cells is responsible for releasing this harmful chemical. The chemical restricts blood-flow to the body extremities, resulting in heat stress, fescue foot, abortions, poor conception rate and low performance. Ideally, toxic fescue pastures should be regrassed with novel endophyte free varieties, but sometimes this isn’t a practical or timely solution As the losses associated with fescue toxicity can be significant and costly, producers should aim to reduce the toxicity threat during summer.

Mineral supplementation plays an important role in all profitable beef production, and summertime -toxic fescue grazing is no different. Reduced total forage intake levels from toxic fescue-induced heat-stress will automatically lower mineral intake levels in cows. Free-access minerals can help to overcome this shortfall and alleviate some of the fescue’s toxicity. Selenium, zinc, copper and magnesium are the most important trace elements required when grazing toxic fescue. These trace elements are necessary for maintaining immune function, which becomes compromised in cattle grazing toxic fescue. Zinc and copper have been shown to have a binding effect on the harmful toxins. Copper supplementation must also be considered as endophyte-infected fescue contains lower copper levels than novel endophyte tall fescue. Copper deficiency symptoms such as rough coats, increased open rates and hoof problems can be exacerbated by toxic fescue as the endophyte also decreases the bioavailability of copper for the animal. Mineral blocks or bagged minerals can be a labor friendly way of providing correct mineral supplementation to livestock. Producers should check with their suppliers regarding salt levels in minerals, as intakes will vary depending on salt quantities.

The dilution effect in the diet by supplementing corn, corn byproducts, soyahulls etc. will improve animal performance on herds grazing Kentucky 31. Research from University of Missouri Extension indicates that ‘feeding corn at a rate of 1% of bodyweight to livestock groups can be effective,’ however such high feeding levels may reduce grass fiber digestion. A ‘sweet-spot’ of .7% of bodyweight supplementation will allow for reduced toxicity effects while maintaining healthy forage digestion. As intakes are reduced in cattle grazing toxic fescue, it is necessary to provide adequate levels of supplementation to overcome low intakes. Kentucky based research has shown that feeding 5lbs soyahulls/steer/day ‘substantially increased steer daily weight gain and winter coat shedding.’ The study also noted a 4-fold increase in blood serum prolactin levels. Low prolactin levels in the blood is an indicator of fescue induced toxicity.
While producers have many feed supplementation ingredient options, it is important to consider the utilization rate of your feeding system. Feed utilization can vary dramatically from 75% to 90% if supplement is allocated directly onto pasture vs in feed bunkers. If feeding in bunkers, adequate head-space must be provided so that all stock can eat at the same time.

Home-grown supplements
Incorporating home-grown summer annual forages are another option for beef ranchers to dilute fescue toxins. Summer annuals such as sorghum-sudan or pearl millet will offer forage diversity and non-toxic, high quality nutrition during the traditional ‘summer slump’ period. University of Oklahoma Extension research suggest that feeding summer forages on a ‘interval limit-grazing’ system can lower labor workload and provide adequate protein and energy supplementation. The ‘interval limit-grazing’ simply involves offering cows a large grazing allocation (approximately 5 hours of grazing) of summer annual crops several times per week, as opposed to a smaller daily allocation. Between these large grazing bouts of summer annuals, cows can be grazed on lower quality fescue forage. No-till seeding of legumes such as red clover or ladino clover will also provide greater forage quality while diluting the effects of fescue. Clovers will also boost dry matter intake levels. Pastures should contain 25% to 40% clover content, as these levels will provide adequate availability, while minimizing bloat risk. Introducing perennial grasses into toxic fescue pastures is generally to be avoided, as cattle will overgraze the more palatable grasses. This will allow toxic fescue to outcompete the introduced non-toxic grasses.

Grazing Management
Grazing management of toxic fescue will also play a significant role in the requirement for supplements. Previously, it had been understood that the seed head of fescue contained the highest levels of toxic alkaloid ergots, however latest research coming out of University of Missouri shows that the bottom two inches of the plant is actually the most toxic part of endophyte infected fescue. Many ranchers carry out summer clipping of seed heads to reduce toxicity, and while this will be of benefit, it is also important to leave a 3-inch stubble after grazings.
In conclusion, there are many methods of limiting the toxicity effects of endophyte infected pastures through various forms of supplementation. Producers should identify the threats of their individual  pastures and take steps to mitigate these risks before herd performance is negatively affected this summer.