Table 1.
Effect of 3-nitrooxypropanol (3NOP) on feed dry matter intake, lactation performance, and body weight change of Holstein dairy cows
| Treatment* | P value† | |||||||
| Item | Control | Low3NOP | Medium3NOP | High3NOP | SEM‡ | C vs. Trt. | L | Q |
| Dry matter intake, kg/d | 28.0 | 28.0 | 27.7 | 27.5 | 0.45 | 0.58 | 0.38 | 0.69 |
| Milk yield, kg/d | 46.1 | 46.4 | 45.9 | 43.6 | 1.21 | 0.59 | 0.21 | 0.19 |
| ECM yield, kg/d§ | 44.9 | 45.2 | 46.2 | 43.9 | 1.59 | 0.91 | 0.84 | 0.44 |
| Feed efficiency kg/kg¶ | 1.64 | 1.65 | 1.67 | 1.62 | 0.033 | 0.94 | 0.80 | 0.41 |
| Milk fat, % | 4.08 | 3.98 | 4.02 | 4.25 | 0.123 | 0.98 | 0.43 | 0.15 |
| Milk fat yield, kg/d | 1.85 | 1.81 | 1.87 | 1.85 | 0.086 | 0.98 | 0.90 | 0.85 |
| Milk true protein, % | 3.06 | 3.14 | 3.12 | 3.13 | 0.033 | 0.07 | 0.14 | 0.31 |
| Milk true protein yield, kg/d | 1.37 | 1.46 | 1.45 | 1.33 | 0.042 | 0.42 | 0.75 | 0.02 |
| Milk lactose, % | 4.78 | 4.79 | 4.81 | 4.77 | 0.026 | 0.69 | 0.95 | 0.32 |
| Milk lactose yield, kg/d | 2.16 | 2.22 | 2.25 | 2.04 | 0.069 | 0.90 | 0.43 | 0.05 |
| Body weight, kg | 664 | 672 | 672 | 664 | 5.0 | 0.38 | 0.83 | 0.13 |
| Body weight change, g/d# | 210 | 353 | 451 | 330 | 71.2 | 0.05 | 0.09 | 0.16 |
Control = 0 mg/kg of 3NOP, Low3NOP = 40 mg/kg of 3NOP, Medium3NOP = 60 mg/kg 3NOP, and High3NOP = 80 mg/kg 3NOP (dietary dry matter basis). Data, except body weight change, are presented as covariate-adjusted means.
Contrasts: C vs. Trt., Control vs. all 3NOP treatments; L, linear effect of 3NOP; Q, quadratic effect of 3NOP. Treatment × experimental week interactions for dry matter intake, milk yield, feed efficiency, and body weight: P = 0.05, 0.97, < 0.001, and 0.93, respectively; milk composition and ECM yield data, P ≥ 0.17.
Largest SEM published in table. Production data were averaged per experimental week and the average values were used in the statistical analysis. Dry matter intake, milk yield, feed efficiency, and body weight data, n = 460, 480, 460, and 474, respectively; body weight change, n = 48; milk composition and ECM yield data, n = 140 (n represents number of observations used in the statistical analysis).
Energy-corrected milk (kg/d) = kg of milk × ((38.3 × % fat x 10 + 24.2 × % true protein x 10 + 16.54 × % lactose × 10 + 20.7) ÷ 3,140) (48). Based on milk yield during the weeks of milk sampling (i.e., experimental weeks 6, 9, and 12).
Feed efficiency = milk production ÷ feed dry matter intake.
Body weight change = (average body weight, final week of experiment – average body weight, second week of covariate period) ÷ days on experiment.