Milk per Acre Spreadsheet for Combining Yield and Quality into a Single Term

Improvements in forage quality have historically been difficult to quantify or determine cost/benefits. A spreadsheet (Milk90) was developed that combines yield and quality into a single term using the concept of milk produced per acre of forage. Forage yield and quality, animal production, and inputs costs can be varied. The spreadsheet assumes maximum forage use and approximates a balanced ration given the forage quality, with corn (Zea mays L.) and soybean (Glycine max L.) meal used as the energy and protein sources, respectively. Milk from forage is determined as the percentage of total ration energy coming from forage times total milk production less animal maintenance requirement. Milk per acre is calculated as milk per ton of forage times forage yield. The spreadsheet allows comparison of changes in yield, forage quality, and production costs. Milk90 is intended for extension and teaching purposes to allow ranking of benefits resulting from changes in management practices. The spreadsheet operates in Lotus 1231 version 2.0 or higher and is available on request. Research Question The value of improvement in forage yield is easily documented but, while importance of forage quality is generally accepted, quantifying the economic value of quality has been difficult. This is particularly true when tradeoffs with other factors, such as yield or persistence, are concerned. This paper reports on the development of a spreadsheet which combines forage yield and quality into a single term using the concept of milk produced per acre from forage. Literature Summary Traditional methods of valuing forage quality have calculated total digestible nutrients per acre—which does not consider energy density, or have calculated improved forage quality without regard to yield (e.g., relative feed value). More sophisticated models are available to combine yield and quality but these are not readily usable by extension and teaching personnel. Study Description A spreadsheet (Milk90) was developed that combines yield and quality into a single term (milk per acre) assuming maximum forage use and approximating a balanced ration using National Research Council equations. Applied Question How can changes in forage yield and quality be compared? Milk90 is a Lotus 123 combining forage yield and quality into a single term. Forage yield and quality, animal production, and input costs can be varied. An example of a portion of the output is shown in Fig. . The spreadsheet approximates a balanced ration assuming maximum forage use and calculates the percentage of ration energy coming from the forage. Milk from forage is assumed equal to the percentage of energy coming from forage less the animal maintenance requirement. Milk90 allows comparison of changes in yield, forage quality, and production costs. It is intended for extension and teaching purposes to allow ranking of benefits resulting from changes in management practices. Output of Milk90 image