| Popis: |
Forty-eight mid-lactation Holstein cows were assigned to one of four treatments and kept within an open freestall barn from June 13 to September 15, 1996. Treatments were 1) sprinklers in the feed alley plus misters over the freestalls; 2) sprinklers in the feed alley; 3) misters over the freestalls; 4) no water cooling. Fans over feed alleys and free stalls were on continuously when temperature exceeded 23.8°C. Sprinklers operated for four 3-min cycles/h and mist was on continually above 27.8°C. Cows were group-fed the same diet. Half the stalls were bedded with mortar sand and half with rubber-filled mattresses. Least squares means for the four treatments, respectively, were area PM temperature: 25.8 b , 28.7 a , 26.1 b , 29.3 a °C; area PM humidity: 89.6 a , 72.1 b , 87.2 a , 68.3 b %; respiration rate (per minute): 51 c , 53 c , 58 b , 70 a ; rectal temperature: 38.7 b , 38.7 b , 38.7 b , 39.1 a °C; DMI: 24.3 a , 23.5 a , 22.0 b , 22.5 b kg/d; milk production: 23.6 a , 22.1 b , 22.0 b , 21.2 c kg/d; milk fat: 3.6, 3.6, 3.5, 3.6%; milk protein: 3.2 a , 3.3 a , 3.1 b , 3.2 a %; body weight gain: 0.38, 0.41, 0.31, 0.20 kg/d; and cooling water use: 3749, 3633, 428, 0 L/d. Water accumulation was not observed in the free stalls. Cows remained in free stalls more for the treatment with mist over the free stalls. Indicators of mastitis (SCC and bacterial culture) did not differ among treatments. Although cooling either area was advantageous, cows with mist in the free stalls and sprinklers at the feedbunk areas produced more milk than cows with either system alone. |
