Behavior of 3 breeds of heifers exposed to sun and to shade at vicosa minas gerais brazil 1. rectal temperature and respiratory rhythm

Oliveira, J.S.E.; Garcia, J.A.; Da-Silva, J.F.C.; Milagres, J.C.

Revista da Sociedade Brasileira de Zootecnia 9(1): 46-71


Accession: 004814631

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The experiment was conducted at the Universidade Federal de Vicosa (Minas Gerais, Brazil) to study the behavior of Holstein (H), 1/2 Holstein-Zebu (1/2 Hz) and 3/4 Holstein-Zebu (3/4 HZ) heifers under shaded and nonshaded environments. Six heifers of each of the 3 groups were equally distributed to the 2 environments. During the experiment, the average air temperatures in the three 28 day periods were, and C, respectively. The relative humidities were 73.0, 74.0 and 72.6% in the 3 periods. Rectal temperature (RT) and respiratory rate (RR) were taken twice a week in the morning and in the afternoon. The 2 variables were lower in the morning and in the shaded environment in all 3 crossbred groups of heifers. There was a decrease in the variables from the 1st to the 3rd period but no difference was found between the 3/4 HZ and 1/2 HZ groups from period 2 to period 3. The RT was lower in the 3/4 HZ heifers than the other groups but the RR was lower in the 1/2 HZ heifers and higher in the purebreds. The response of the 3 groups of heifers in RT and RR were not uniform for all the environments, periods and turns (morning and afternoon). The interactions were statistically significant mainly for RR. In the nonshaded environment the purebred showed the highest RT and RR. The high RT in the 1/2 HZ groups of heifers could be due to the black coat color. The low RR in the same group suggests that that group of heifers was not in physiological discomfort.