intake multiplier was set at 100 percent. All DIP values were then set at 80 percent, and diet CP was adjusted until DIP requirements were close to being balanced. Predicted DMI varies with daily milk production and forage quality. The CP required to meet diet DIP required for microbial growth is constant for a given diet but increased as diet TDN increased because microbial growth is a constant proportion of TDN. However, the UIP balance changes with milk and pregnancy requirements.

Diet A (50 percent TDN) met energy and UIP requirements in months 7 to 10 (cows just dry), became deficient in energy in month 11, and deficient in both energy and UIP in month 12. Diet B (60 percent TDN) is adequate in energy in all months and UIP in all but month 2 of lactation. Diet C (70 percent TDN) exceeded energy and UIP requirements in all months.

The energy reserves flux (Mcal/mo) is given for each month of the reproductive cycle for each diet evaluated. Appendix Table 13 can be used to estimate days for a CS change by dividing the Appendix Table 13 value by the predicted daily energy balance. To reduce a negative energy balance, 1 Mcal diet NE_m will substitute for 1 Mcal negative energy balance. To utilize energy reserves, 1 Mcal diet NE_m can be replaced by 0.8 Mcal tissue energy.

Appendix Table 13 gives Mcal mobilized in moving to the next lower CS, or required to move from the next lower CS to the one being considered, for cows with different mature weights. For example, a 500-kg cow at CS 5 will mobilize 207 Mcal in declining to a CS 4. If NE_m intake is deficient 3 Mcal/day, this cow will lose 1 CS in (207 * 0.8)/3=55 days. If consuming 3 Mcal NE_m above