TABLE 3.
Lactation performance, body measurements and energy partitioning of primiparous and multiparous cows fed high‐starch (29.2% ± 0.70; means ± SD) vs. low‐starch (22.3% ± 0.52; means ± SD) diets
| Primiparous | Multiparous | p Value 1 | ||||||
|---|---|---|---|---|---|---|---|---|
| Item | High starch | Low starch | High starch | Low starch | SEM | Parity | Starch | Parity × starch |
| Yield, kg/day | ||||||||
| Milk | 40.4 | 41.5 | 53.2 | 48.7 | 1.76 | <0.01 | 0.31 | 0.11 |
| 3.5% FCM 2 | 36.6 | 38.4 | 48.6 | 46.0 | 1.58 | <0.01 | 0.82 | 0.18 |
| Fat | 1.15 | 1.24 | 1.51 | 1.48 | 0.05 | <0.01 | 0.62 | 0.35 |
| Protein | 1.22 | 1.18 | 1.58 | 1.41 | 0.05 | <0.01 | 0.04 | 0.19 |
| Lactose | 1.98 | 1.91 | 2.54 | 2.28 | 0.07 | <0.01 | 0.04 | 0.18 |
| Composition, % | ||||||||
| Fat | 2.84 | 3.03 | 2.94 | 3.10 | 0.12 | 0.48 | 0.15 | 0.91 |
| Protein | 2.96 | 2.90 | 2.93 | 2.92 | 0.02 | 0.97 | 0.08 | 0.23 |
| Lactose | 4.80 | 4.68 | 4.74 | 4.73 | 0.04 | 0.88 | 0.17 | 0.24 |
| SNF 3 | 7.44 | 7.32 | 7.38 | 7.40 | 0.04 | 0.93 | 0.13 | 0.18 |
| Fat: protein | 0.95 | 1.04 | 0.99 | 1.06 | 0.03 | 0.61 | 0.05 | 0.91 |
| Milk urea nitrogen, mg/dl | 11.7 | 12.4 | 11.7 | 13.0 | 0.44 | 0.56 | 0.02 | 0.49 |
| β‐hydroxybutyrate, mmol/L | 0.05 | 0.07 | 0.05 | 0.07 | <0.01 | 0.29 | <0.01 | 0.90 |
| MY/DMI | 1.75 | 1.89 | 1.87 | 1.82 | 0.05 | 0.61 | 0.40 | 0.08 |
| 3.5% FCM/DMI | 1.56a | 1.75b | 1.68 | 1.71 | 0.04 | 0.37 | <0.01 | 0.04 |
| Body measurements | ||||||||
| BW, kg4 | 549 | 544 | 658 | 638 | 16.4 | <0.01 | 0.44 | 0.63 |
| BCS 5 | 2.86 | 2.79 | 2.85 | 2.79 | 0.48 | 0.19 | 0.62 | 0.16 |
| BFT, mm | 26.8 | 25.9 | 25.5 | 25.9 | 0.06 | 0.66 | 0.54 | 0.14 |
| BW change, kg/day | 0.11 | .0.01 | 0.20 | 0.05 | 0.11 | 0.60 | 0.28 | 0.86 |
| BCS change | 0 | –0.07 | –0.06 | 0.03 | 0.06 | 0.75 | 0.87 | 0.21 |
| BFT change, mm6 | 0.90 a | –0.90 b | –1.20 b | –0.70 a | 0.59 | 0.12 | 0.28 | 0.05 |
| Energy partitioning, % of intake | ||||||||
| Maintenance | 25.9 | 26.5 | 23.1 | 25.1 | 0.84 | 0.01 | 0.13 | 0.42 |
| Milk | 71.9 | 73.4 | 73.7 | 74.5 | 1.62 | 0.38 | 0.48 | 0.82 |
| Body tissue gain | 2.21 | 0.06 | 3.11 | 0.40 | 2.08 | 0.76 | 0.25 | 0.89 |
a,
bWithin parity, means of starch levels with different superscripts differ (p ≤ 0.05).
1
Contrasts for parity (Par), starch level (St) and interaction (Par × St).
2
FCM yield = 0.432 × milk yield + 16.23 × fat yield (Council, 2001).
3
SNF = solid non‐fat.
4
BW = over a 7‐week period from week 1 of adaptation to week 6 of sampling.
5
BCS = body condition score was determined using a five‐scale method where 1 = emaciated and 5 = obese (Ferguson et al., 1994).
6
BFT = backfat thickness was measured using the ultrasonographic method (Schröder & Staufenbiel, 2006).