Alex Sandro Campos Maia

Características do pelame de vacas Holandesas em ambiente tropical: um estudo genético e adaptativo

ABSTRACT - The traits of the haircoat (haircoat thickness, average hair lenght with respect skin surface, number of hair per unitarea, hair mass density, hair angle and average hair diameter) were estimated in 973 Holstein cattle in the period between November 2000and April of 2001. These traits were measured in an area 20cm below the dorsal line in the center of the thorax, for the black as for thewhite haircoat. Hair samplings were performed with adapted pliers. The method of Restricted Maximum Likelihood (REML) was usedto estimate the variance and covariance components under the Animal model, the program used being the MTDFREML. The resultsshowed that traits of black haircoat were different from that of the white haircoat, when the animals are breed in a tropical environment.Black haircoat was less dense, with shorter and ticker hair fibres in order to ease the heat dissipation, while the white haircoat was denserwith longer hairs, which favored protection against direct solar radiation. The selection of predominantly black cows would be a goodchoice under the strong solar radiation in tropical environment, because the pigmented skin under this type coat. Such a selection couldbe easily performed considering the high heritability (hThe traits of the haircoat (haircoat thickness, average hair lenght with respect skin surface, number of hair per unit area, hair mass density, hair angle and average hair diameter) were estimated in 973 Holstein cattle in the period between November 2000 and April of 2001. These traits were measured in an area 20cm below the dorsal line in the center of the thorax, for the black as for the white haircoat. Hair samplings were performed with adapted pliers. The method of Restricted Maximum Likelihood (REML) was used to estimate the variance and covariance components under the Animal model, the program used being the MTDFREML. The results showed that traits of black haircoat were different from that of the white haircoat, when the animals are breed in a tropical environment. Black haircoat was less dense, with shorter and ticker hair fibres in order to ease the heat dissipation, while the white haircoat was denser with longer hairs, which favored protection against direct solar radiation. The selection of predominantly black cows would be a good choice under the strong solar radiation in tropical environment, because the pigmented skin under this type coat. Such a selection could be easily performed considering the high heritability (h2=0.75) of the proportion of black coat, and must consider a less dense haircoat with short and tick hairs to help the dissipation sensible and latent heat.

Variação estacional dos hormônios tireoideanos e do cortisol em ovinos em ambiente tropical

The variation of cortisol and thyroid hormones in Corriedale sheep bred in a tropical environment was evaluated. Fourteen males and seven females were observed in a climatic chamber at 45oC for nine days, eight hours per day. Rectal temperature (TR), respiratory rate (FR), air temperature (TA) and air humidity (PV) were recorded. The animals were ranked according to their responses for TR and FR and then the five highest (A group) and five lowest (NA group) ranked animals were selected. These ten animals were moved to a pen where they were observed along one year for TR and FR two times a day, and blood-sampled once a week. The results showed differences for T3, T4, and cortisol concentrations, which were attributed to variations in TA and PV. Cortisol concentrations were higher and T3 and T4 ones were lower under increased TA and PV. Correlations of TA and PV with cortisol values were r = .224 and r = .395 respectively. The negative correlations of TA with T3 (r = -.151) and T4 (r = -.156) showed that increase in TA may be followed by decrease in the metabolic rate. No significant difference for all variables investigated was found between the two groups, thus it is not recommended the use of TR and FR as the only criteria to evaluate sheep performance in tropical environments.

Principles of Animal Biometeorology

Contents -- 1. The Environment -- 2. Basic Physical Mechanisms -- 3. Thermal Balance and Thermoregulation -- 4. Heat Exchange Between Animals and Environment: Mammals and Birds -- 5. Heat Exchange Between Animals and Environment: Aquatic Mammals -- 6. Shade and Shelter -- 7. Thermal Stress Indexes -- 8. Special Methods -- Index.

Variação anual de hormônios tireoideanos e características termorreguladoras de vacas leiteiras em ambiente quente

This work was carried out with the objective to study the annual behavior of thermo regulators traits in dairy cows. Two hundred cows were used during two consecutive years and the respiratory rate (RR), rectal temperature (RT), as well as a blood sample was collected for triiodothyronin (T3) and thyroxin (T4) dosages, were recorded. Air temperature and humidity were also recorded and the black globe humidity index (BGHI) and radiant heat load (RHL) were calculated in the same days of data collection. There was no significative effect of the year for the majority of studied variables, however, the effects of month of collection and herd were significative for all variables. All values of RT were inside of the amplitude of normality, indicating homoeothermic condition. The RR was altered in every seasons of the year and herds, showing a constant necessity of thermolisys. In herds with higher RT and RR, there was a reduction T3 and T4 liberation. In seasons of higher BGHI and RHL, there was increase in the RT, followed for higher RR and lower T3 and T4 plasmatic concentrations.

Mean surface temperature prediction models for broiler chickens—a study of sensible heat flow

Body surface temperature can be used to evaluate thermal equilibrium in animals. The bodies of broiler chickens, like those of all birds, are partially covered by feathers. Thus, the heat flow at the boundary layer between broilers’ bodies and the environment differs between feathered and featherless areas. The aim of this investigation was to use linear regression models incorporating environmental parameters and age to predict the surface temperatures of the feathered and featherless areas of broiler chickens. The trial was conducted in a climate chamber, and 576 broilers were distributed in two groups. In the first trial, 288 broilers were monitored after exposure to comfortable or stressful conditions during a 6-week rearing period. Another 288 broilers were measured under the same conditions to test the predictive power of the models. Sensible heat flow was calculated, and for the regions covered by feathers, sensible heat flow was predicted based on the estimated surface temperatures. The surface temperatures of the feathered and featherless areas can be predicted based on air, black globe or operative temperatures. According to the sensible heat flow model, the broilers’ ability to maintain thermal equilibrium by convection and radiation decreased during the rearing period. Sensible heat flow estimated based on estimated surface temperatures can be used to predict animal responses to comfortable and stressful conditions.

Evaporative cooling and cutaneous surface temperature of Holstein cows in tropical conditions

Foram estudados os efeitos da temperatura cutânea (Ts) sobre a taxa de termolise por evaporacao cutânea (Es) de vacas Holandesas cronicamente expostas ao sol, considerando a pigmentacao do pelame. Dezesseis vacas puras de origem foram medidas quanto a evaporacao e a temperatura cutâneas as 13 h, apos 6 horas de exposicao ao sol, no mesmo local (flanco, pescoco e gluteo) e considerando separadamente as malhas negras e as brancas. A evaporacao cutânea foi medida por meio de capsula ventilada. Nas areas negras a taxa de sudacao (138,9 ± 8,5 g.m-2.h-1), a taxa de termolise por evaporacao cutânea (93,3 ± 5,7 W.m-2) e a temperatura da superficie cutânea (33,1 ± 0,2°C) foram maiores que nas areas brancas (109,5 ± 9,7 g.m-2.h-1, 73,6 ± 6,5 W.m-2 e 32,6 ± 0,2°C, respectivamente). Ha uma relacao exponencial entre evaporacao e temperatura cutâneas, que pode ser representada pela equacao Es = 31,5+3,67 exp{(Ts-27,9)/2,19115}, com coeficiente de determinacao r2=0,68. A taxa de termolise por evaporacao cutânea permanece quase constante (cerca de 48 W.m-2) ate que a temperatura cutânea atinge aproximadamente 31°C.

Estimativas de parâmetros genéticos e fenotípicos de características do pelame e de desempenho reprodutivo de vacas holandesas em clima tropical

The present study aimed to evaluate the effects of hair coat on age at first calving (IPP) and calving interval (IEP) of Holstein cows managed under free stall with fans and sprinklers and to estimate genetic and phenotypic parameters for these traits. Data were analyzed by the least-squares method using a model that included the effects of year; season; origin of sire; sire within origin; number of inseminations; age (only for calving interval); percentage of black meshes; hair coat thickness; hair length; number of hair per unit area; hair diameter; effective transmissivity and reflectivity. Covariance components were estimated by REML using an Animal Model. Heritability estimates for IPP, IEP, percentage of black meshes, number of hair per unit area, hair coat thickness, hair length and hair diameter were 0.23±0.08, 0.19±0.10, 0.75±0.08, 0.05±0.04, 0.04±0.05, 0.36±0.09, and 0.63±0.08, respectively. Genetic correlation between hair diameter and IPP (IEP) was equal to -0.37±0.17 (-0.49±0.27). However, genetic correlations between IPP and hair thickness (-0.56±0.46), number of hair (-0.66±0.43) and black meshes (0.04±0.16) were unfavorable for jointly selection for sexual precocity and fitness to tropical environment. High values of heritability estimates and genetic correlations between diameter, IPP and IEP indicate that is possible to select for thickness of hair diameter and improve reproductive efficiency.

Perda de calor por evaporação cutânea associada às características morfológicas do pelame de cabras leiteiras criadas em ambiente tropical

A perda de calor por evaporacao cutânea e as caracteristicas morfologicas do pelame (espessura da capa, comprimento medio dos pelos, numero de pelos por unidade de area e diâmetro medio dos pelos) foram avaliadas em 254 cabras das racas Saanen, Alpina e mesticas ½ Boer ½ Saanen. Utilizou-se uma capsula ventilada para medir a evaporacao cutânea, determinada em tres regioes do corpo (proximo ao pescoco, meio do flanco e quarto traseiro), enquanto as caracteristicas morfologicas do pelame foram avaliadas a partir de amostras de pelos, tomadas 18 cm abaixo da coluna vertebral, exceto a espessura da capa, que foi medida in situ. Os resultados indicaram que os animais apresentam pelame pouco denso, formado por pelos finos e compridos. Animais mesticos (½ Boer ½ Saanen) apresentaram taxas de evaporacao cutânea mais elevadas que os puros das racas Saanen e Alpina.

Stocking densities and feeding strategies in shrimp and tilapia polyculture in tanks

The objective of this work was to evaluate the performance of Pacific marine shrimp (Litopenaeus vannamei) and tilapia (Oreochromis niloticus), in a polyculture in tanks subjected to different stocking densities and feeding strategies, in comparison with monoculture. Two experiments were performed, at the same time, in a completely randomized design with three treatments and four replicates each. Treatments for experiment I were: monoculture with 10 shrimp per m2 (10S:0T); polyculture with 10 shrimp and 0.5 tilapia per m2 (10S:0.5T); and polyculture with 10 shrimp and 1 tilapia per m2 (10S:1T). Shrimp was the main crop, and feed was provided based on shrimp biomass. Treatments for experiment II were: monoculture with 2 tilapia per m2 (2T:0S); polyculture with 2 tilapia and 2.5 shrimp per m2 (2T:2.5S); and polyculture with 2 tilapia and 5 shrimp per m2 (2T:5S). Tilapia was the main crop, and feed was provided based on fish requirements. In the experiment I, tilapia introduction to shrimp culture resulted in lower shrimp growth and poor feed conversion rate. In experiment II, shrimp introduction to tilapia culture did not interfere with fish performance. Polyculture is more efficient with the combination of 2 tilapia and 2.5 or 5 shrimp per m2 and feed based on fish requirements.

Thermal equilibrium of goats.

The effects of air temperature and relative humidity on thermal equilibrium of goats in a tropical region was evaluated. Nine non-pregnant Anglo Nubian nanny goats were used in the study. An indirect calorimeter was designed and developed to measure oxygen consumption, carbon dioxide production, methane production and water vapour pressure of the air exhaled from goats. Physiological parameters: rectal temperature, skin temperature, hair-coat temperature, expired air temperature and respiratory rate and volume as well as environmental parameters: air temperature, relative humidity and mean radiant temperature were measured. The results show that respiratory and volume rates and latent heat loss did not change significantly for air temperature between 22 and 26°C. In this temperature range, metabolic heat was lost mainly by convection and long-wave radiation. For temperature greater than 30°C, the goats maintained thermal equilibrium mainly by evaporative heat loss. At the higher air temperature, the respiratory and ventilation rates as well as body temperatures were significantly elevated. It can be concluded that for Anglo Nubian goats, the upper limit of air temperature for comfort is around 26°C when the goats are protected from direct solar radiation.