Beef Cow Annual Energy Balance
Central Ohio · 1,350 lb moderate-frame beef cow · 90-day wean · Dynamic BCS buffer · Milk pullback under nutritional stress · Rebreeding ~80 days post-calving
Color key:
Good surplus
Slight surplus
Minor deficit (within BCS buffer)
Moderate deficit (BCS draws down)
Supplement needed
Scenario Comparison Summary
| Calving Month | Rating | Annual Supp (Mcal) | Min BCS | End BCS | vs. March | Rebreed ~ | Late Gest ~ | Key Note |
|---|---|---|---|---|---|---|---|---|
| October | ★ Optimal | None required | 5.03 | 5.25 | −100% | ~Jan | ~Aug | Zero supplement required. BCS draws down through early gestation, recovers on spring/fall flush. Rebreed ~January. |
| June | 2nd Best | 104 Mcal | 5 | 5.52 | −50% | ~Sep | ~Apr | Late gestation aligns with spring flush. Peak lactation during summer slump is the challenge. Rebreed ~September. |
| March | Traditional | 208 Mcal | 5 | 5.6 | baseline | ~Jun | ~Jan | Most common — late gestation hits Jan/Feb on winter hay at highest demand. Rebreed ~June. |
| December | Worst | 116 Mcal | 5 | 5.2 | −44% | ~Mar | ~Oct | Peak lactation in coldest months drains BCS fastest. Late gestation Oct/Nov is the one advantage. Rebreed ~March. |
Calve: October★ OptimalAnnual supplement: None requiredMin BCS: 5.03End BCS: 5.25Rebreed: ~Jan | Late gest: ~Aug
Zero supplement required. BCS draws down through early gestation, recovers on spring/fall flush. Rebreed ~January.
| Month | Phase | Cow NEm (Mcal/d) |
Forage (Mcal/d) |
Balance (Mcal/d) |
BCS Start |
BCS End |
Milk NE (Mcal/d) |
Milk Reduced |
Supp (Mcal/d) |
Monthly Supp (Mcal) |
|---|---|---|---|---|---|---|---|---|---|---|
| Jan | Early Gestation | 16.9 | 13.4 | -3.6 | 5.5 | ▼ 5.25 | — | — | — | — |
| Feb | Early Gestation | 16.9 | 13.6 | -3.3 | 5.25 | ▼ 5.03 | — | — | — | — |
| Mar | Early Gestation | 16.9 | 17.8 | +0.8 | 5.03 | ▲ 5.08 | — | — | — | — |
| Apr | Early Gestation | 16.9 | 28.2 | +11.2 | 5.08 | ▲ 5.28 | — | — | — | — |
| May | Mid Gestation | 17.8 | 28.6 | +10.8 | 5.28 | ▲ 5.48 | — | — | — | — |
| Jun | Mid Gestation | 17.8 | 20.1 | +2.3 | 5.48 | ▲ 5.64 | — | — | — | — |
| Jul | Mid Gestation | 17.8 | 15.5 | -2.3 | 5.64 | ▼ 5.49 | — | — | — | — |
| Aug | Late Gestation | 18.7 | 17.1 | -1.5 | 5.49 | ▼ 5.38 | — | — | — | — |
| Sep | Late Gestation | 19.2 | 22.3 | +3.1 | 5.38 | ▲ 5.58 | — | — | — | — |
| Oct ★ | Peak Lactation | 22.8 | 26.8 | +4 | 5.58 | ▲ 5.78 | 6.5 | — | — | — |
| Nov | Mid Lactation | 21.8 | 20.1 | -1.7 | 5.78 | ▼ 5.66 | 5.5 | — | — | — |
| Dec | Late Lactation | 20.5 | 14.5 | -6 | 5.66 | ▼ 5.25 | 4.2 | — | — | — |
| TOTALS / SUMMARY | Start: 5.50 | End: 5.25 | None | |||||||
Energy balance — solid: cow requirement | dashed: forage available | shaded red: deficit zone
BCS tracking — bold: this scenario | faint dashed: other scenarios | dashed line: 5.0 floor
Calve: June2nd BestAnnual supplement: 104 McalMin BCS: 5End BCS: 5.52Rebreed: ~Sep | Late gest: ~Apr
Late gestation aligns with spring flush. Peak lactation during summer slump is the challenge. Rebreed ~September.
| Month | Phase | Cow NEm (Mcal/d) |
Forage (Mcal/d) |
Balance (Mcal/d) |
BCS Start |
BCS End |
Milk NE (Mcal/d) |
Milk Reduced |
Supp (Mcal/d) |
Monthly Supp (Mcal) |
|---|---|---|---|---|---|---|---|---|---|---|
| Jan | Mid Gestation | 17.8 | 12.7 | -5.1 | 5.5 | ▼ 5.15 | — | — | — | — |
| Feb | Mid Gestation | 17.8 | 12.9 | -4.8 | 5.15 | ▼ 5 | — | — | 2.7 | 81 |
| Mar | Mid Gestation | 17.8 | 17 | -0.8 | 5 | — 5 | — | — | 0.8 | 23 |
| Apr | Late Gestation | 18.7 | 26.3 | +7.7 | 5 | ▲ 5.2 | — | — | — | — |
| May | Late Gestation | 19.2 | 27.7 | +8.5 | 5.2 | ▲ 5.4 | — | — | — | — |
| Jun ★ | Peak Lactation | 22.8 | 25.5 | +2.7 | 5.4 | ▲ 5.59 | 6.5 | — | — | — |
| Jul | Mid Lactation | 21.8 | 19 | -2.8 | 5.59 | ▼ 5.39 | 5.5 | — | — | — |
| Aug | Late Lactation | 20.5 | 20.1 | -0.4 | 5.39 | ▼ 5.37 | 4.2 | — | — | — |
| Sep | Early Gestation | 16.9 | 24 | +7 | 5.37 | ▲ 5.57 | — | — | — | — |
| Oct | Early Gestation | 16.9 | 21.9 | +5 | 5.57 | ▲ 5.77 | — | — | — | — |
| Nov | Early Gestation | 16.9 | 17.1 | +0.2 | 5.77 | ▲ 5.78 | — | — | — | — |
| Dec | Early Gestation | 16.9 | 13.1 | -3.8 | 5.78 | ▼ 5.52 | — | — | — | — |
| TOTALS / SUMMARY | Start: 5.50 | End: 5.52 | 104 Mcal | |||||||
Energy balance — solid: cow requirement | dashed: forage available | shaded red: deficit zone
BCS tracking — bold: this scenario | faint dashed: other scenarios | dashed line: 5.0 floor
Calve: MarchTraditionalAnnual supplement: 208 McalMin BCS: 5End BCS: 5.6Rebreed: ~Jun | Late gest: ~Jan
Most common — late gestation hits Jan/Feb on winter hay at highest demand. Rebreed ~June.
| Month | Phase | Cow NEm (Mcal/d) |
Forage (Mcal/d) |
Balance (Mcal/d) |
BCS Start |
BCS End |
Milk NE (Mcal/d) |
Milk Reduced |
Supp (Mcal/d) |
Monthly Supp (Mcal) |
|---|---|---|---|---|---|---|---|---|---|---|
| Jan | Late Gestation | 18.7 | 12 | -6.7 | 5.5 | ▼ 5.04 | — | — | — | — |
| Feb | Late Gestation | 19.2 | 12.2 | -7 | 5.04 | ▼ 5 | — | — | 6.4 | 196 |
| Mar ★ | Peak Lactation | 22.8 | 22.4 | -0.4 | 5 | — 5 | 6.5 | — | 0.4 | 12 |
| Apr | Mid Lactation | 21.8 | 31.8 | +10 | 5 | ▲ 5.2 | 5.5 | — | — | — |
| May | Late Lactation | 20.5 | 31.3 | +10.8 | 5.2 | ▲ 5.4 | 4.2 | — | — | — |
| Jun | Early Gestation | 16.9 | 20.8 | +3.9 | 5.4 | ▲ 5.6 | — | — | — | — |
| Jul | Early Gestation | 16.9 | 16.2 | -0.7 | 5.6 | ▼ 5.55 | — | — | — | — |
| Aug | Early Gestation | 16.9 | 18.6 | +1.7 | 5.55 | ▲ 5.67 | — | — | — | — |
| Sep | Early Gestation | 16.9 | 24 | +7 | 5.67 | ▲ 5.87 | — | — | — | — |
| Oct | Mid Gestation | 17.8 | 21.1 | +3.4 | 5.87 | ▲ 6.07 | — | — | — | — |
| Nov | Mid Gestation | 17.8 | 16.4 | -1.4 | 6.07 | ▼ 5.97 | — | — | — | — |
| Dec | Mid Gestation | 17.8 | 12.4 | -5.3 | 5.97 | ▼ 5.6 | — | — | — | — |
| TOTALS / SUMMARY | Start: 5.50 | End: 5.6 | 208 Mcal | |||||||
Energy balance — solid: cow requirement | dashed: forage available | shaded red: deficit zone
BCS tracking — bold: this scenario | faint dashed: other scenarios | dashed line: 5.0 floor
Calve: DecemberWorstAnnual supplement: 116 McalMin BCS: 5End BCS: 5.2Rebreed: ~Mar | Late gest: ~Oct
Peak lactation in coldest months drains BCS fastest. Late gestation Oct/Nov is the one advantage. Rebreed ~March.
| Month | Phase | Cow NEm (Mcal/d) |
Forage (Mcal/d) |
Balance (Mcal/d) |
BCS Start |
BCS End |
Milk NE (Mcal/d) |
Milk Reduced |
Supp (Mcal/d) |
Monthly Supp (Mcal) |
|---|---|---|---|---|---|---|---|---|---|---|
| Jan | Mid Lactation | 21.8 | 16.2 | -5.6 | 5.5 | ▼ 5.11 | 5.5 | — | — | — |
| Feb | Late Lactation | 20.5 | 15.1 | -5.4 | 5.11 | ▼ 5 | 4.2 | — | 3.8 | 116 |
| Mar | Early Gestation | 16.9 | 17.8 | +0.8 | 5 | ▲ 5.06 | — | — | — | — |
| Apr | Early Gestation | 16.9 | 28.2 | +11.2 | 5.06 | ▲ 5.26 | — | — | — | — |
| May | Early Gestation | 16.9 | 29.5 | +12.6 | 5.26 | ▲ 5.46 | — | — | — | — |
| Jun | Early Gestation | 16.9 | 20.8 | +3.9 | 5.46 | ▲ 5.66 | — | — | — | — |
| Jul | Mid Gestation | 17.8 | 15.5 | -2.3 | 5.66 | ▼ 5.5 | — | — | — | — |
| Aug | Mid Gestation | 17.8 | 17.9 | +0.1 | 5.5 | ▲ 5.51 | — | — | — | — |
| Sep | Mid Gestation | 17.8 | 23.1 | +5.4 | 5.51 | ▲ 5.71 | — | — | — | — |
| Oct | Late Gestation | 18.7 | 20.3 | +1.6 | 5.71 | ▲ 5.82 | — | — | — | — |
| Nov | Late Gestation | 19.2 | 15.6 | -3.5 | 5.82 | ▼ 5.58 | — | — | — | — |
| Dec ★ | Peak Lactation | 22.8 | 17.3 | -5.5 | 5.58 | ▼ 5.2 | 6.5 | — | — | — |
| TOTALS / SUMMARY | Start: 5.50 | End: 5.2 | 116 Mcal | |||||||
Energy balance — solid: cow requirement | dashed: forage available | shaded red: deficit zone
BCS tracking — bold: this scenario | faint dashed: other scenarios | dashed line: 5.0 floor
Model basis: NRC Beef Cattle 2016 adjusted 5% for forage-efficient moderate-frame beef cow (NEm base = 0.077 × BW0.75 × 0.95 = 16.29 Mcal/day for 1,350 lb cow). Forage calibrated so October calving requires zero supplementation with BCS cycling naturally 5.0–5.8. Spring forage 0.67–0.68, summer 0.52–0.57, fall 0.60–0.61, winter hay 0.51–0.53 Mcal/lb DM. BCS floor 5.0 = supplement trigger (rebreeding rates decline below this). 1 BCS unit = 440 Mcal stored energy. Milk pullback activates below BCS 5.0 reducing cow demand at calf's expense. BCS gain capped at 0.20 units/month. Conception at day 80 post-calving (2.5–3 month rebreeding window). Gestation = 283 days. First-pass model — heat stress penalty, breed variation, and direct calf nutrition cost not yet included.