Dados de estação meteorológica oficial subestimam o estresse por calor em bovinos leiteiros criados em ambiente tropical / Official meteorological station data underestimate the heat stress on dairy cattle in a tropical environment

Determinaram-se os valores de temperatura do ar, umidade relativa e índice de temperatura e umidade (ITU) de uma propriedade rural de produção de leite a pasto e da estação meteorológica oficial mais próxima, confrontando-os. Na fazenda, as leituras dos dados foram registradas por uma estação meteorológica automática, a cada cinco minutos, de fevereiro de 2015 a setembro de 2016. Depois, calcularam-se a média por hora e o ITU horário. Selecionaram-se os valores diários mínimo, médio e máximo. O mesmo foi feito com os dados da estação meteorológica oficial, que foram horários. As temperaturas mínima e média na estação meteorológica foram maiores que na fazenda durante todo o período experimental e em 16 meses, respectivamente. A temperatura máxima da propriedade rural foi maior que a da estação em seis meses. Já a umidade relativa mínima, a média e a máxima da estação meteorológica foram inferiores às da fazenda. O ITU mínimo foi maior na estação oficial e o ITU máximo superior na fazenda em todos os meses. Por fim, o número de dias com um ITU máximo igual ou superior ao ITU crítico foi maior na fazenda. Assim, dados da estação meteorológica oficial subestimam o estresse por calor.(AU)

The values of air temperature, relative humidity and Temperature Humidity Index (THI) of one pasture-based milk production farm and from the nearest official weather station were confronted. At the farm, data readings were recorded by an automatic weather station, every five minutes, from February 2015 to September 2016. Then, the hourly average and hourly THI were calculated. The minimum, average, and maximum daily values were selected. The same was done with data from the official hourly weather station data. The minimum and mean temperature in the meteorological station were higher than on the farm throughout the experimental period and in 16 months, respectively. The maximum temperature of the rural property was greater than that of the station in six months. Meanwhile, the minimum, average, and maximum relative humidity of the meteorological station were lower than those of the farm. The minimum THI was higher at the official station and the maximum THI was higher at the farm in every month. Finally, the number of days with a maximum THI equal to or greater than the critical THI was greater on the farm. Thus, official weather station data underestimate the heat stress.(AU)

Ocorrência do SNP c.767G>T no gene DNM1responsável pelo colapso induzido pelo exercício em cães da raça Labrador Retriever no estado de São Paulo / Occurrence of DNM1 SNP c.767G>T responsible for exercise-induced collapse in Labrador Retriever in the Sao Paulo state

O colapso induzido pelo exercício (EIC) é considerado uma síndrome autossômica recessiva que afeta principalmente cães da raça Labrador Retriever. A doença é caracterizada por fraqueza muscular e colapso após exercício intenso. Usualmente, ocorre recuperação clínica após o episódio, mas alguns animais podem vir a óbito. Os sinais clínicos são decorrentes do polimorfismo de base única (SNP) c.767G>T no gene Dynamin 1 (DNM1). O objetivo deste trabalho foi determinar a ocorrência deste SNP em 321 cães da raça Labrador Retriever do Estado de São Paulo. Primers específicos para a amplificação de todo o exon 6 do gene DNM1 foram usados nas PCRs utilizando DNA a partir de amostras de sangue ou swab bucal, a avaliação final foi realizada com sequenciamento direto dos produtos da PCR. Dentre os 321 animais estudados, 3,4 % (11/321) eram homozigotos para o SNP c.767G>T no gene DNM1 e 24,6% (79/321) eram heterozigotos. Somente um dos 11 animais homozigotos apresentavam sinais clínicos compatíveis com a EIC. Este é o primeiro estudo sobre a ocorrência deste SNP no Brasil e considerando que quase 25% dos animais estudados eram heterozigotos, a genotipagem dos animais para este SNP pode ser importante antes dos acasalamentos para cães desta raça. A EIC deve ser considerada nos diagnósticos diferenciais de enfermidades neuromusculares em cães da raça Labrador Retriever.

The exercise-induced collapse (EIC) is considered an autosomal recessive syndrome that mainly affects Labrador Retriever dogs. The disease is characterized by muscle weakness and collapse after intense exercise. Recovery usually occurs after exercise but some animals may die. The clinical signs occurs due to the single-nucleotide polymorphism (SNP) c.767G>T in Dynamin 1 (DNM1) gene. The aim of this study was to evaluate the occurrence of this SNP in 321 Labrador Retriever dogs from São Paulo state. Specific primers for amplification of the entire exon 6 of the DNM1 gene were used in a PCR performed with DNA from blood or buccal swab samples, direct sequencing was performed for the final evaluation. Among 321 animals studied, 3.4% (11/321) of animals were homozygous for the DNM1 SNP (c.767G>T) and 24.6% (79/321) were heterozygous. Only one of the 11 homozygous animals in this study had previous clinical signs compatible with this disease. This is the first study that evaluated the occurrence of DNM1 SNP (c.767G>T) gene in Brazil and considering that almost 25% of the studied animals were heterozygous, the routinely evaluation of this SNP may be important before this breed mating The EIC should be include in the differential diagnosis of neuromuscular diseases in Labrador Retriever dogs.

Optimization of the Divergent method for genotyping single nucleotide variations using SYBR Green-based single-tube real-time PCR.

A novel technique, called Divergent, for single-tube real-time PCR genotyping of point mutations without the use of fluorescently labeled probes has recently been reported. This novel PCR technique utilizes a set of four primers and a particular denaturation temperature for simultaneously amplifying two different amplicons which extend in opposite directions from the point mutation. The two amplicons can readily be detected using the melt curve analysis downstream to a closed-tube real-time PCR. In the present study, some critical aspects of the original method were specifically addressed to further implement the technique for genotyping the DNM1 c.G767T mutation responsible for exercise-induced collapse in Labrador retriever dogs. The improved Divergent assay was easily set up using a standard two-step real-time PCR protocol. The melting temperature difference between the mutated and the wild-type amplicons was approximately 5°C which could be promptly detected by all the thermal cyclers. The upgraded assay yielded accurate results with 157pg of genomic DNA per reaction. This optimized technique represents a flexible and inexpensive alternative to the minor grove binder fluorescently labeled method and to high resolution melt analysis for high-throughput, robust and cheap genotyping of single nucleotide variations.

Fatty and hemorrhagic liver and kidney syndrome in breeding hens caused by aflatoxin B1 and heat stress in the Sudan.

Fatty liver in animals is commonly associated with toxic or nutritional disease. In tropical Africa, fatty liver in poultry is of considerable economic importance. However, it's occurrence and association with renal damage have not yet been reported. We now report the effects of hemorrhagic and fatty hepatorenal syndrome in Hybro breeding hens naturally exposed to heat stress and fed low level of aflatoxin B1.

Use of ammonium chloride and sodium bicarbonate in acute heat exposure of broilers.

Ammonium chloride (NH4Cl) and sodium bicarbonate (NaHCO3) were added separately to the drinking water of 42- to 52-day-old broilers. Birds were given access to the water ad libitum for a total of 42.5 hr consisting of 18.5 hr prior to an 8-hr interval of severe heat exposure and a further 16 hr-post exposure. Water and feed intake during the treatment period were unaffected by either NH4Cl at 6.25 g/liter (.63%) of distilled water (DW) or NaHCO3 at 3.15 g/liter (.32%) DW. Water intake was increased by approximately 20% in birds given water containing 6.25 g of NaHCO3/liter (.63%) DW, while both feed and water intake were severely limited by NH4Cl at 31 g/liter (3.1%) DW. Blood pH of birds was substantially lowered by consumption of NH4Cl, while consumption of NaHCO3 did not significantly affect blood pH. Blood pH of all treatments increased during the heat exposure period and declined afterward; however, blood pH change appeared to be more pronounced for birds receiving the NH4CL. A correlation coefficient (r = -.31) existed between blood pH and mortality, while a correlation (r = -.72) was demonstrated between water consumption and mortality.

Milk production of Friesian cows subjected to high daytime temperatures when allowed food either ad lib or at night-time only.

Four lactating Friesian cows housed in climate chambers were exposed to the following sequential treatments: I, a four-week period when they were allowed constant access to an ad lib supply of a complete diet and water in a thermoneutral environment (ambient temperature (Ta) 14 to 20 degrees C and relative humidity (r.h.) 50 to 75%); II, a five-week period during which they were exposed to Ta 38.5 degrees C/r.h. 85% for 61/2 h during daytime and Ta 14 to 20 degrees C/r.h. 50 to 75% for the remainder of each day with constant access to ad lib complete diet and water; III, a four-week period under the same environment as treatment II but with access to food restricted to between 19.00 and 07.00; IV; a four-week period under the environment and feeding regime described for treatment II. The voluntary food intake (VFI) of cows subjected to II was not depressed as a result of high daytime temperature despite the fact that they exhibited daytime clinical features indicative of heat stress; this was because of a 27.8% compensatory increase in night-time feeding. Nevertheless there was an accompanying significant increase in the rate of lactation decline of 8.7% per month greater than that normally expected under the thermoneutral conditions (I). Subsequent restriction of food access to night-time (III) resulted in a significant reduction in mean VFI of 7.5%; however, the rate of lactation decline was drastically reduced to a value not dissimilar to the natural decline of 3.97% per month observed under thermoneutral conditions (I).

Plasma fibronectin concentrations in dogs with disseminated intravascular coagulation.

Plasma fibronectin concentrations were significantly (P less than 0.001) below the reference range in dogs with disseminated intravascular coagulation (DIC) secondary to nonlymphomatous neoplasia, acute necrotizing pancreatitis, sepsis, chronic active hepatitis, and heat stroke. There was no statistical evidence of a group effect. Decrease in fibronectin concentration was associated with severe DIC, although no attempt was made to correlate fibronectin concentration with prognosis. These findings parallel those reported for severely ill human beings with diseases associated with DIC. They exemplify the potential of spontaneous diseases in animals as models for the study of human disease.

Response of broilers to hyperthermic stress following treatment with a new cyclo-oxygenase inhibitor.

Two trials were conducted using broiler chickens to test the efficacy of pretreatment with Banamine, an inhibitor of prostaglandin synthesis, on various heat stress indices. Significant differences were found in peripheral prostaglandin F (PGF) levels between immature male and female broilers with pullets having a higher concentration. Females also had less mortality during the hyperthermic challenge, which was independent of medication treatment. Confinement and transport of male broilers resulted in elevated levels of PGF, which were markedly lowered near the time of heat stress death. All levels of Banamine appeared to give some measure of protection against heat stress in male broilers as evidenced by higher survival rates and longer survival times.

Effect of dietary thyroid hormone on survival time during heat stress.

Broilers were fed corn-soybean meal diets supplemented with either 3, 5, 3'-triiodothyronine (T3) or thyroxine (T4) for various time periods ranging from 8 to 26 days. Survival times during heat stress were determined for females and males fed the control, T3, and T4 diets. Serum hormone concentration for serums collected prior to heat stress was determined by radioimmunoassay. The combined results of both trials show significantly shortened survival times for T3 and T4 and that T3 had a much greater effect than T4. Male broilers had shorter survival times than females and there was no interaction of hormone and sex. Serum T3 and T4 concentrations were greater in serum T4 concentration, but dietary T4 had no effect on serum T3 concentration.

Mortality from heat stress in broiler chickens influenced by anticoccidial drugs.

The relationship of anticoccidial drug to heat stress mortality in broilers was studied in a replicated floor-pen experiment during a period of hot weather in Georgia. Overall mortality during the 8-week study averaged 6% in unmedicated and monensin-medicated birds or lasalocid-medicated birds, 10% in arprinocid-medicated birds, and 36% in nicarbazin-medicated birds. Most of the death losses were attributed to heat stress. Maximum death losses coincided with three periods of hot weather, when the birds were 22, 33, or 49 days old. Of 114 dead birds in the nicarbazin treatment, 68 were male and 46 were female.