Rectal temperatures, respiratory rates, production, and reproduction performances of crossbred Girolando cows under heat stress in northeastern Brazil

Abstract

This study compared the two breed groups of Girolando (½ Holstein ½ Gyr vs. ¾ Holstein ¼ Gyr) through analysis of the percentages (stressed or non-stressed cows) of rectal temperature (RT), respiratory rate (RR) and pregnancy rate (PR), and means of production and reproduction parameters to determine the group best suited to rearing in semiarid tropical climate. The experiment was conducted at the farm, in the municipality of Umirim, State of Ceará, Brazil. Two hundred and forty cows were used in a 2 × 2 factorial study; 120 of each group were kept under an intensive system during wet and dry seasons. The environmental parameters obtained were relative humidity (RH), air temperature (AT), and the temperature and humidity index (THI). Pregnancy diagnosis (PD) was determined by ultrasonography 30 days after artificial insemination (AI). The milk production of each cow was recorded with automated milkings in the farm. The variables were expressed as mean and standard error, evaluated by ANOVA at 5% probability using the GLM procedure of SAS. Chi-square test at 5% probability was applied to data of RT, RR, pregnancy rate (PR), and the number of AIs to obtain pregnancy. The majority of ½ Holstein cows showed mean values of RT and RR within the normal range in both periods and shifts. Most animals of the ¾ Holstein group exhibited the RR means above normal during the afternoon in the rainy and dry periods and RT means above normal during the afternoon in the dry period. After analyses, ½ Holstein crossbred cows are more capable of thermoregulating than ¾ Holstein cows under conditions of thermal stress, and the dry period was more impacting for bovine physiology with significant changes in physiological parameters, even for the first breed group. Knowledge of breed groups adapted to climatic conditions of northeastern Brazil can directly assist cattle farmers in selecting animals best adapted for forming herds.

Effect of temperature humidity index on the onset of post- partum ovarian activity and reproductive behavior in Bos indicus cows

“…These observations are similar to those reported in other studies indicating that the state of Tabasco has a climate where high temperature and humidity levels predominate throughout the year (Angulo-Córdova et al, 2004). Thus, a THI above the limit of comfort (> 74) can affect the reproductive ability of the animals (Amundson et al, 2006) causing a decrease in the normal development of cattle (da Costa et al, 2015). Moreover, a high THI can affect feed intake in animals (Renaudeau et al, 2012) which would explain the poor body condition at the start of the experiment (3.8 ± 1.33) and reflected in back fat loss during the last trimester of gestation.…”

What is the best temperature-humidity index equation to indicate heat stress in crossbred dairy calves in a tropical environment?

“…The RR of the calves in the afternoon exceeded the limit considered physiologically appropriate for the species, which varies from 20 to 40 movements per minute (SILANIKOVE, 2000). The RT in dairy cattle ranges from 38°C to 39.3°C (COSTA et al, 2015) and can reach up to 39.5°C in younger animals (FEITOSA, 2008). The mean RT in the afternoon did not exceed the reference range for the species.…”

Thermal Stress Indices in Young Nellore Bulls Raised in Tropical Environments

“…Os bovinos neste estudo estavam em equilíbrio térmico uma vez que, mantiveram a temperatura média retal dentro da faixa de normalidade [17,23], já o valor máximo esteve acima. Se a temperatura retal se mantém no padrão fisiológico, isso significa que os mecanismos de termorregulação são capazes de eliminar o excesso de calor, ou seja a termólise foi equivalente a termogênese [9].…”