Considering a separate total mixed ration for low producers or when to cull an open cow? The University of Wisconsin's CULL.xls spreadsheet can help you make those tough calls.
Output values from CULL.xls are dollar contributions to fixed costs/cow/day. Daily returns are reported in a table based on level of production and somatic cell count (SCC) level.
Given today's prices, for example, a cow milking 60 lb./day with a 325,000 SCC returns only 30¢/day over the major variable costs. At $12/cwt. milk, that same cow would contribute $1.50/day, and at $15/cwt. milk she would contribute $3.30/day.
CULL.xls requires only a few inputs to access your specific farm situation. You'll need your herd's average milk production/day, average butterfat, protein and SCC tests along with your latest base price for milk and value of components. The spreadsheet asks for dollar values per point of fat and protein, while the market quotes values per pound of product, so just move the decimal point one place to the left.
Your nutritionist can help with the average feed amounts and cost/cow/day. Use the standard values in the spreadsheet or your own labor costs/cwt./day and the value of miscellaneous supplies (all other variable costs) per cwt. Finally, enter your current feed levels and values and you're ready to roll!