Table 6.
Effects of different evaporative cooling regimens and the use or absence of PE on milk yield and milk composition of lactating Holstein cows (n = 8).
| Variables | CT | PE | p Value | |||||
|---|---|---|---|---|---|---|---|---|
| R5 | R10 | R5 | R10 | SEM | Adit | Cool | Adit × Cool | |
| Dry matter intake | 25.4 | 24.5 | 25.0 | 24.6 | 0.21 | 0.6642 | 0.0205 | 0.4222 |
| Milk yield, kg/d | ||||||||
| Actual | 39.3 a | 35.5 b | 36.1 b | 36.3 b | 0.50 | 0.0014 | <0.0001 | <0.0001 |
| 4% FCM 1 | 36.7 | 32.2 | 34.0 | 33.7 | 0.77 | 0.5898 | 0.0359 | 0.0627 |
| ECM 2 | 36.8 a | 32.4 b | 33.9 a,b | 33.8 a,b | 0.70 | 0.4251 | 0.0180 | 0.0239 |
| Milk fat | ||||||||
| % | 3.67 | 3.81 | 3.97 | 3.45 | 0.11 | 0.8914 | 0.3753 | 0.1389 |
| kg/d | 1.40 | 1.23 | 1.33 | 1.25 | 0.04 | 0.7003 | 0.0896 | 0.6038 |
| Milk protein | ||||||||
| % | 3.45 b | 3.54 a | 3.54 a | 3.48 b | 0.03 | 0.4643 | 0.7059 | 0.0028 |
| kg/d | 1.34 a | 1.20 b | 1.21 b | 1.22 b | 0.02 | 0.0176 | 0.0022 | 0.0011 |
| Milk lactose | ||||||||
| % | 4.52 | 4.50 | 4.49 | 4.55 | 0.02 | 0.7836 | 0.3753 | 0.0917 |
| kg/d | 1.76 a | 1.53 b | 1.57 b | 1.61 b | 0.04 | 0.0501 | 0.0022 | <0.0001 |
| Milk efficiency | ||||||||
| Actual/DM intake | 1.55 a | 1.46 b | 1.47 b | 1.49 b | 0.50 | 0.1794 | 0.0525 | 0.0056 |
| FCM/DM intake | 1.47 | 1.32 | 1.43 | 1.36 | 0.03 | 0.9923 | 0.0447 | 0.4690 |
| ECM/DM intake | 1.47 | 1.33 | 1.43 | 1.36 | 0.03 | 0.9054 | 0.0323 | 0.4217 |
| CCS × 103 | 2.42 | 2.48 | 2.41 | 3.06 | 0.25 | 0.4545 | 0.3656 | 0.4364 |
CT = control treatment; PE = pepper extract; R5 = sprinkler cycles of 30 s on and 4.5 min off; R10 = sprinkler cycles of 30 s on and 9.5 min off (R10); SEM = standard error of mean; Adit = use of PE as additive; Cool = evaporative cooling regimens; Adit × Clim = interaction between cooling regimens and PE. a,b Means followed by different letters in the line are different at the 5% level. 1 FCM was calculated as milk yield (kg/d) × [milk fat (%) × 0.15 + 0.4]. 2 ECM was calculated as milk yield (kg/d) × {[0.3887 × milk fat (%)] + [0.2356 × milk protein (%)] + [0.1653 × milk lactose (%)]}/3.1338 [26].