Author
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AIKEN, GLEN |
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Submitted to: Cow Country News
Publication Type: Popular Publication Publication Acceptance Date: 2/6/2017 Publication Date: 3/1/2017 Citation: Aiken, G.E. 2017. From the Lab Bench: Is forage quality that complicated?. Cow Country News. Pgs. 52-53. Interpretive Summary: The true definition of forage quality is based on performance of the cattle when the forage serves as the major source of nutrients. A high-quality forage is expected to maintain cows in good body condition and facilitate high milk yields and weaning weights. Post-weaned calves have average daily gains above 2 pounds per day and much higher for those with the genetic potential. Depending on the physiological status of the cattle (3rd trimester of pregnancy, lactation, etc.), feeding a moderate quality forage may require supplementation with concentrates or co-product feeds. A low-quality forage is generally regarded as reliable in meeting the maintenance requirements of dry cows. An estimate of forage quality is needed before the forage is fed or grazed; otherwise, how do you know if, when, or how much nutrient supplementation is required to meet a production goal. Digestible energy (total digestible nutrients or digestible dry or organic matter) and crude protein are typically used as estimates of forage quality. These are the critical nutrients, but it is not just the density of these nutrients in a given forage that predicts forage quality. Rather, it is the amount of intake of the required nutrients that matters. How can you know the dry matter intake before a forage is fed or grazed? Most service laboratories that analyze forage nutrients will provide a Relative Feed Value and/or Forage Quality Index. Both account for intake, but neither can be used directly in formulating rations. Including these indices with a nutrient analysis, however, is extremely useful because the index can provide an estimate of forage quality and the nutrient analysis can be used for ration formulation. This information can be of use to cattlemen in correctly formulating feed rations that are fed to pastured cattle. Technical Abstract: An article was written to discuss the definition of forage quality. The true definition of forage quality is based on performance of the cattle when the forage serves as the major source of nutrients. However, an estimate of forage quality will be needed before the forage is fed or grazed. Digestible energy (total digestible nutrients or digestible dry or organic matter) and crude protein are typically used as estimates of forage quality. These are the critical nutrients, but it is not just the density of these nutrients in a given forage that predicts forage quality; rather, it is the amount of intake of the required nutrients that matters. Most service laboratories that analyze forage nutrients will provide a Relative Feed Value and/or Forage Quality Index. Both account for intake, but neither can be used directly in formulating rations. Including these indices with a nutrient analysis, however, is extremely useful because the index can provide an estimate of forage quality and the nutrient analysis can be used for ration formulation. Forage Quality Index is calculated from total digestible nutrients and a predicted dry matter intake. |
