Pasa assay for diagnosing insecticide resistance in the horn fly population in Rondonia.

Knockdown (kdr) resistance is caused by a reduction in the sensitivity of the insectnnervous system to pyrethroids. Kdr resistance in field populations of horn flies can severely limit pyrethroid usefulness in fly control programs. Early detection and characterization of kdr resistance are critical to the development of resistance management strategies. Studies at the Embrapa Rondonia experimental farm, Porto Velho, RO and at Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA/ARS, Kerrville, TX were conducted to verify the genotypes of the Embrapa Rondonia horn fly population. First, the population was assessed using cypermethrin-impregnated filter papers produced at the Embrapa Rondonia Animal Health Laboratory. Horn flies from an untreated cattle herd were caught with a sweep net and used for bioassays. Flies were exposed for two hours to filter papers treated with technical grade cypermethrin in acetone, using cypermethrin concentrations from 0.01 ?g to 3,200 ?g/cm2. Control flies were exposed to filter papers treated only with acetone. Three groups of ten flies were exposed at each concentration. All flies exposed to cypermethrin concentrations between 800-3,200 ?g/cm2 died. Genomic DNA was isolated from individual adult flies that survived bioassay concentrations of 200-400 ?g/cm2 and 30 flies tested by PASA (PCR amplification of specific alleles) assay for the presence of a specific nucleotide substitution in the sodium channel gene sequence that has been associated with kdr resistance in horn flies. PASA was performed using two parallel PCRs, with each PCR containing three sets of primers, and genomic DNA to detect pyrethroid resistance-associated nucleotide differences in individual flies. Two primers, FG 234 and FG 243, provided a positive control PCR product while the products of primer FG 138 with primer FG 130 (reaction 1) or with primer FG 134 (reaction 2) produced diagnostic products for genotyping the kdr allele. Reaction products were visualized after 4% agarose gel electrophoresis followed by UV illumination after staining with Syber Green. The kdr allele was not detected in flies from the Embrapa Rondonia population, which was considered a pyrethroid susceptible homozygous (SS) population. This result was expected for this horn fly population as there is no report of treatment with pyrethroids in the last six years

Efficiency of low versus high airline pressure in stunning cattle with a pneumatically powered penetrating captive bolt gun

The efficiency of stunning cattle was assessed in 443 animals (304 pure Zebu and 139 crossbred cattle), being mainly mature bulls and cows. Cattle were stunned using a Jarvis pneumatically powered penetrating captive bolt gun operating with low (160–175 psi, N = 82) and high (190 psi, N = 363) airline pressure, which was within the manufactures specifications. Signs of brain function and the position of the shots on the heads were recorded after stunning. Velocity of the captive bolt and its physical parameters were calculated. Cattle shot with low pressures showed more rhythmic respiration (27 vs. 8%, P < 0.001), less tongue protrusion (4 vs. 12%, P = 0.03) and less masseter relaxation (22 vs. 48%, P < 0.001). There was an increased frequency of shots in the ideal position when cattle were shot with the low compared to high airline pressures (15.3 vs. 3.1%). Bolt velocity and its physical parameters were significantly (P < 0.01) higher when using high pressure. Airline pressures below 190 psi are inappropriate when shooting adult Zebu beef cattle with pneumatically powered penetrating captive bolt guns

Redistribuição da água e capacidade de campo em latossolo amarelo distrocoeso, em Cruz das Almas, Bahia.

A água é um dos principais componentes do sistema solo, sendo essencial para a vida vegetal e animal, ocupando, juntamente com o ar, todo o espaço poroso existente. Diante disso, o objetivo deste trabalho foi avaliar a redistribuição da água e a capacidade de campo in situ e em laboratório em diferentes horizontes de um Latossolo Amarelo Distrocoeso em Cruz das Almas, BA. No campo, medidas de potencial matricial foram feitas com tensiômetros de mercúrio em um experimento de perfil instantâneo. Os tensiômetros foram instalados nas profundidades de 0,285 m, 0,525 m, 0,810 m, 1,12 m, e 1,30 m. A capacidade de campo foi também determinada em laboratório, utilizando tubos de plástico preenchidos com solo peneirado. Amostras de solo foram coletadas no meio de cada horizonte, até a profundidade de 1,40 m, em duas repetições, com estrutura indeformada e deformadas, para as determinações físicas do solo. A redução do potencial matricial foi mais lenta nos horizontes coesos AB e BA, e estes não atingiram a capacidade de campo mesmo decorridos 50 dias de medição. Nos horizontes Bw1, Bw2 e Bw3 o potencial de -6kPa foi atingido, respectivamente, após 41, 10 e 1 dias. Foram encontrados potenciais matriciais variando entre -6 kPa e -36 kPa para os horizontes BA, Bw1, Bw2 e Bw3 para determinação da capacidade de campo em colunas de solo, e de -94 kPa e -69 kPa para os horizontes Ap e AB, respectivamente