Dairy cattle raised under harsh conditions have to adapt and prevent heat stress. The aim of this study was to evaluate physical characteristics and their association with heat tolerance in different ...genetic groups of dairy cattle. Thickness of the skin and coat, length and number of hairs, body measurements, as well as physiological parameters and body temperatures by infrared thermography were determined in 19 Holstein and 19 Girolando (½ and ¾ Holstein) cows. The Holstein cattle were less tolerant to heat stress than Girolando (GH50 and GH75 Holstein), because of the difficulty in dissipating heat due to the larger body size, as well as thicker and longer hairs. The correlations between physical characteristics, physiological parameters, and thermographic measurements prove to be inconsistent among genetic groups and therefore are not predictive of heat tolerance, while the regressions of morphometric characteristics on physiological and thermographic measures were not significant. Thus, the physical characteristics were not good predictors of physiological indices and thermographic temperature and so should not be used.
ABSTRACT The objective of this study was to investigate changes in physiological parameters of dairy cows and understand which physiological parameters show greater reliability for verification of ...heat stress. Blood samples were collected for analysis and included hematocrit (Ht), erythrocyte count (ERY), and hemoglobin count (HEMO). In addition, physiological variables, including rectal temperature (RT), heart rate (HR), respiratory rate (RR), and panting score (PS) were recorded in 38 lactating cows. These varied according to genetic group (1/2, 3/4, and pure bred Holstein (HO)). Analysis of variance considering the effects of genetic group, days, and their interaction as well as linear and quadratic effect of the black globe humidity index (BGHI) was performed, as well as broken-line regression. These values were higher in pure HO than in 3/4 and 1/2 groups. The average BGHI during the morning was 74, when 70, 43, and 13% of pure HO, 3/4, and 1/2, respectively, presented RR above reference value. The RR was the best indicator of heat stress and its critical value was 116 breaths/min for 1/2, 140 for 3/4, and 168 breaths/min for pure HO cows. In the HO group, physiological variables increased linearly with BGHI, without presenting inflection in the regression. The inflection point occurred at a higher BGHI for the 1/2 group compared with the other groups. Hematocrit and HEMO were different among genetic groups and did not vary with BGHI, showing that stress was not sufficient to alter these hematological parameters. The 1/2 HO group was capable of maintaining normal physiological parameters for at least 3 BGHI units above that of HO and 1 to 3 units higher than 3/4 HO for RR and RT, respectively. Respiratory rate is the physiological parameter that best predicts heat stress in dairy cattle, and the 1/2 Holstein group is the best adapted to heat stress.
This study was realized to analyze the combinations of climatic, physical, and socio-economic variables on distribution of breeding values for performance characteristics and scrotal circumference of ...Brangus cattle. Records of 84,703 Brangus animals, born from 2000 to 2010 distributed in 65 farms in Brazil were used. The characteristics analyzed were average daily gain from birth to weaning and from weaning to yearling (WW and YW), visual scores of conformations (WC and YC), muscle score (WM and YM), precocity score (WP and YS), and size score (WS and YS) at weaning and yearling and scrotal circumference (SC) at yearling. Components of (co)variance estimated through the animal model employing methodology to AIREML. Mean estimates of direct heritability obtained for visual scores at weaning (WC 0.16, WM 0.16, WP 0.19, and WS 0.22) were lower than those obtained at yearling (YC 0.28, YM 0.26, YP 0.24, and YS 0.40). WW had heritability greater than YW (0.27 and 0.12) and a heritability of 0.36 obtained for SC. Canonical, discriminant, and cluster analyses were performed in the SAS® 9.4 program. Three clusters of genetic values averages per farm were formed according to climatic, physical, and socio-economic variables. Brangus animals are from states of RS, PR, SP, MG, GO, MG, and MS. The highest breeding values were strongly related to thermal amplitude and municipality area. Spatial distribution of the breeding value of Brangus animals can help in the development of environmental indices, genetic evaluations, and the choice of animals for certain environments.
ABSTRACT The objective of this study was to determine whether infrared thermography is a useful tool for the recognition of dairy cows in a state of thermal heat stress, as well as to identify the ...best region of the animal to be evaluated for this recognition. Physiological variables, including rectal temperature, respiratory frequency, cardiac frequency, and panting score were recorded in 38 lactating cows. For the assessment of environmental parameters, a digital black globe thermometer (TGD-200 model) was used. Thermographic photographs of different regions of the body of cows were taken using an infrared camera (FLIR® System T300) and indicated respective superficial temperature. Physiological variables and superficial body temperature in different regions varied between genetic groups (Girolando: ½ Holstein × ½ Gir and ¾ Holstein × ¼ Gir; purebred Holstein). The environmental temperature ranged from 20.7 to 37.9 °C with a relative humidity reaching 95%. The mean rectal temperature (40.84 °C), respiratory frequency (111.36 breaths/min), and cardiac frequency (99.22 beats/min) were higher for pure Holstein than for Girolando cows. Positive correlations were found between the physiological parameters and thermographic measures. The highest positive correlation (0.74) was found between the temperature in the lateral region of the udder and rectal temperature. Thermography is a good indicator of thermal comfort. The best region to identify heat stress in cows using thermography is the lateral region of the udder.
O objetivo deste trabalho foi determinar as características físicas preditoras do efeito do calor sobre os diferentes grupos genéticos de bovinos leiteiros. Foram utilizados trinta e oito animais, ...entre eles 19 da raça Holandesa, 08 Girolando ½ Holandês e 11 Girolando ¾ Holandês. Foram realizadas mensurações para as características físicas, como: espessura da pele e pelame, contagem e comprimento de pelos e medidas corporais, sendo essa realizada uma única vez por animal. Os parâmetros fisiológicos coletados foram: temperatura retal (TR), frequência respiratória (FR), frequência cardíaca (FC), escore de ofegação (EO). As imagens termográficas foram obtidas por uma câmera infravermelha (FLIR® System T300), onde se coletaram as temperaturas das regiões do lado direito (Ladod), lado esquerdo (Ladoe), olho direito (Olho), visão lateral do úbere direito (Uberelat), visão posterior do úbere (Uberetras) e pata dianteira direita na visão posterior (Pata). Os bovinos da raça Holandesa foram mais sensíveis ao estresse térmico por calor em relação aos Girolando (1/2 e 3/4 Holandês). A análise discriminante identificou o perímetro torácico como a característica física que tem influência na tolerância ao calor dos animais. A análise canônica separou os animais da raça Holandesa dos animais da raça Girolando ½ e ¾ Hoandês. A porcentagem de variação nos fatores principais foram maiores durante a tarde do que na manhã, porém foram baixos. As regressões e correlações não foram significativas, assim as características físicas não foram boas em predizer os indices fisiológicos e as temperaturas termográficas, portanto não devem ser utilizadas.
The objective of this study was to determine the physical characteristics predictive of the effect of heat on different genetic groups of dairy cattle. Thirty eight animals, including 19 Holstein, 08 Gir ½ Holstein and 11 Gir ¾ Holstein were used. Measurements to the physical characteristics were carried out: skin and coat thickness, number and length of hair and body measurements, performed once per animal. The physiological parameters collected included: rectal temperature (RT), respiratory rate (RR), heart rate (HR) and panting score (SP). Thermographic images were obtained by an infrared camera (FLIR T300 ® System), which collected the temperatures of the regions on the right and left side, eye, lateral view of the right udder, posterior view of the udder and right front leg in posterior. The Holstein cattle were less tolerant to heat stress than Girolando (1/2 and 3/4 Holstein) because these animals had difficulties in dissipating heat due to the larger body size, as well as thicker and longer coats. The correlations between physical characteristics, physiological parameters and thermographic measures were inconsistent between genetic groups are therefore not predictive of heat tolerance, while the regressions of morphometric characteristics on physiological and thermographic were not significant. Thus physical characteristics were not good at predicting the physiological indices or thermographic temperatures and therefore should not be used as measures of heat tolerance in dairy cattle.
Dois estudos foram realizados com o objetivo de analisar a distribuição espacial de diferentes raças bovinas e dos valores genéticos de animais Brangus no Brasil, relacionando sua ocorrência com ...variáveis climáticas, físicas e socioeconômicas. O objetivo do primeiro estudo foi analisar a relação das variáveis climáticas, físicas e socioeconômicas com a distribuição de raças bovinas. Neste estudo utilizou-se as informações município e estado das raças Aberdeen Angus, Ayrshire, Braford, Brangus, Charolês, Devon, Flamenga, Hereford, Pinzgauer, Shorthorn e Simental. As raças foram classificadas conforme sua finalidade: carne, dupla aptidão e leite e posteriormente espacializadas no programa ArcGis 10.2. As raças leiteiras estudadas estavam localizadas nos estados do Rio Grande do Sul e Santa Catarina, as raças de duplo propósito em Minas Gerais e no Rio Grande do Sul e as raças de carne estão concentradas na região sul do país. As regressões logísticas demonstraram que as raças de corte e dupla aptidão tendem a ser criadas em regiões com menor temperatura máxima e média, menor amplitude térmica e ITU, porém em municípios com alta umidade e altitude, menor produto interno bruto, pouca orientação técnica, baixo controle de doenças e parasitas e pouca rotação de pastagens A análise de variância mostrou que as raças de carne, leite e dupla aptidão não variaram para as características climáticas, físicas e socioeconômicas. No segundo estudo objetivou-se analisar a associação das variáveis climáticas, físicas e socioeconômicas com a distribuição dos valores genéticos para características de crescimento e perímetro escrotal de animais da raça Brangus. Foram utilizados registros de 84.703 animais da raça Brangus, nascidos entre 2000 e 2010 distribuídos em 65 fazendas do Brasil. Os animais localizaram-se nos estados RS, PR, SP, MG, GO, MG e MS. Á desmama, as maiores médias dos valores genéticos por fazenda estão agrupadas no cluster 1 e ao sobreano agruparam-se no cluster 2. Os maiores valores genéticos ficaram fortemente relacionadas com amplitude térmica e área municipal. Ter conhecimento da distribuição espacial de raças bovinas e dos valores genéticos de animais Brangus pode auxiliar no desenvolvimento de índices ambientais, avaliações genéticas e escolha de animais para determinados ambientes.
Two studies were conducted in order to analyze the spatial distribution of different breeds and breeding values of Brangus animals in Brazil, relating their occurrence to climatic, physical and socioeconomic variables. The aim of the first study was to analyze the relationship of climatic, physical and socioeconomic variables with the distribution of bovine breeds. In this study we used the municipality and state information of the Aberdeen Angus, Ayrshire, Braford, Brangus, Charolais, Devon, Flemish, Hereford, Pinzgauer, Shorthorn and Simmental breeds. Breeds were classified according to their purpose: beef, dual purpose and milk and spatialized using ArcGis 10.2. The dairy breeds studied were located in the states of Rio Grande do Sul and Santa Catarina, the dual purpose breeds in Minas Gerais and Rio Grande do Sul and the beef breeds are concentrated in the southern region of the country. Logistic regression showed that both beef and dual purpose cattle are more likely to be raised in municipalities with lower maximum and average temperatures, lower thermic amplitude and THI, although, with high humidity and altitude, with lower gross domestic product, where technical guidance, rotation of pastures and control of diseases and parasites were low Analysis of variance showed that beef, dairy and dual purpose breeds did not ranged for climatic, physical and socio-economic characteristics. The second study aimed to analyze the association of climate, physical and socio-economic characteristics with the distribution of breeding values of growths traits and scrotal perimeter of Brangus animals. Records of 84.703 Brangus animals, born between 2000 and 2010 distributed in 65 farms in Brazil were used. Cluster analysis formed three clusters of average breeding values per farm. Animals were located in the Brazilian states of RS, PR, SP, MG, GO, MG and MS. At weaning, the highest averages of breeding values per farm were grouped in cluster 1 and to yearling in cluster 2. The highest breeding values were strongly related to thermal amplitude and municipal area. knowledge the spatial distribution of cattle breeds and breeding values of Brangus animals can help in the development of environmental indices, genetic evaluations and in the choice of animals for certain environments.
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