Abstract
This study is aimed to evaluate the physiological responses and the production of milk cows of the Holstein breed, pure, in the dry and rainy seasons. During the period from March to October rectal temperature (TR), respiratory rate (FR) and milk production (PL) were taken at 7 am and at 3 pm twice a week, in eleven cows. At the same time, in these cows there were also recorded temperatures of air and black globe, humidity and it was calculated the Globe and Humidity Temperature Index (ITGU). Statistical analyzes were performed by the method of least squares and this revealed significant effects of the animal, also the year of the period and month collection period within the year on the variables recorded, with higher TR and FR during the rainy season, when the PL was higher. There was a significant time interaction and animals just for the PL and the interaction time of collection and time for PL and TR. The effects of ITGU in the shade and the sun were different only concerning the FR. Milk production was extremely low in all periods of the year and in the dry season, in the afternoon, there was a higher body heat, and in the rainy season the use of the mechanisms of respiratory evaporative heat loss was intensified.
Highlights
O ambiente térmico é um dos fatores de restrição no desempenho de vacas de leite criadas em sistemas de produção intensivos ou extensivos
This study aimed to evaluate the physiological responses and the production of milk cows of the Holstein breed, pure, in the dry and rainy seasons
Statistical analyzes were performed by the method of least squares and this revealed significant effects of the animal, the year of the period and month collection period within the year on the variables recorded, with higher temperatura retal (TR) and frequência respiratória (FR) during the rainy season, when the produção de leite (PL) was higher
Summary
O trabalho foi conduzido no setor de Bovinocultura da Universidade Federal Rural do Semi-Árido (UFERSA), localizado em Mossoró, região oeste do Rio Grande do Norte. As coletas de dados foram realizadas duas vezes por semana, das 7 h e às 15 h, antes das ordenhas, durante o período chuvoso (março a junho) e o período seco (julho a outubro). Foram utilizadas todas as vacas que se encontravam sendo ordenhadas em cada dia de coleta, perfazendo uma média 11 vacas da raça Holandesa em diferentes estágios de lactação durante todo o período experimental. Também foram registradas, às 7 h e as 15 h, as temperaturas dos termômetros de bulbo seco e de bulbo úmido, bem como a umidade relativa do ar, por meio de um termohigrômetro. As temperaturas dos dois globos-termômetros foram também registradas nos mesmos dias e horários das coletas. A análise estatística foi realizada pelo método dos quadrados mínimos, consistindo em análises de variância e testes de comparação de médias, além de estudos de correlação
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