Genome wide scan for quantitative trait loci affecting tick resistance in cattle (Bos taurus x Bos indicus).

BACKGROUND: In tropical countries, losses caused by bovine tick Rhipicephalus (Boophilus) microplus infestation have a tremendous economic impact on cattle production systems. Genetic variation between Bos taurus and Bos indicus to tick resistance and molecular biology tools might allow for the identification of molecular markers linked to resistance traits that could be used as an auxiliary tool in selection programs. The objective of this work was to identify QTL associated with tick resistance/susceptibility in a bovine F2 population derived from the Gyr (Bos indicus) x Holstein (Bos taurus) cross. RESULTS: Through a whole genome scan with microsatellite markers, we were able to map six genomic regions associated with bovine tick resistance. For most QTL, we have found that depending on the tick evaluation season (dry and rainy) different sets of genes could be involved in the resistance mechanism. We identified dry season specific QTL on BTA 2 and 10, rainy season specific QTL on BTA 5, 11 and 27. We also found a highly significant genome wide QTL for both dry and rainy seasons in the central region of BTA 23. CONCLUSIONS: The experimental F2 population derived from Gyr x Holstein cross successfully allowed the identification of six highly significant QTL associated with tick resistance in cattle. QTL located on BTA 23 might be related with the bovine histocompatibility complex. Further investigation of these QTL will help to isolate candidate genes involved with tick resistance in cattle.

Predição do peso vivo a partir de medidas corporais em animais mestiços Holandês/Gir / Prediction of live weight based on body measurements in crossbred animals Holstein/Gir

O objetivo deste estudo foi investigar as relações entre o peso corporal e as medidas corporais altura de garupa (ag), comprimento de garupa (cg), comprimento corporal (cc) e perímetro torácico (pt), em bovinos oriundos principalmente do cruzamento das raças Holandês e Gir. Foram utilizados dados de 483 vacas, 469 novilhas e 62 machos, de três rebanhos distintos, analisados separadamente para cada categoria a fim de estabelecer equações polinomiais dos pesos em relação às medidas corporais. As correlações simples do peso corporal com pt, cc, cg e ag foram respectivamente 0,807; 0,440; 0,187 e 0,504 para vacas; 0,928; 0,735; 0,819 e 0,880 machos, e 0,942; 0,748; 0,902 e 0,573 para novilhas. Embora as regressões de peso corporal em relação ao cc e cg tenham sido significativas (P<0,05), o aumento da porcentagem de explicação das variações do peso corporal obtido com a inclusão destas medidas, em adição ao pt, não parece justificar o custo das medições. As equações de predição do peso corporal em função do pt foram as seguintes: para vacas, peso = 12.174 - 187,410 pt + 0,97196960 pt² - 0,00162382 pt³, para novilhas, peso= 1.717-35,167 pt + 0,238978 pt² - 0,00046260 pt³ e, para machos, peso = -3.862+76,014 pt-0,488837 pt²+ 0,00109755 pt³.

The objective of this study was to investigate the relationship between hip height (ag), rump length (cg), body length (cc) and heart girth (pt) with live body weight of crossbred animals, mainly from the cross between Holstein and Gir breeds. Data on 483 cows, 469 heifers and 62 males in three herds were analyzed for each category using polynomial regression equations of body weight on measurements. The correlations between body weight and pt, cc, cg and ag were, respectively 0.807, 0.440, 0.187 and 0.504 for cows, 0.928, 0.735, 0.819 and 0.880 for males and 0.942, 0.748, 0.902 and 0.573 for heifers. Although the regressions of body weights on cc and cg were significant (P<0.05), the additional goodness of fit of a model that includes these two traits in addition to heart girth does not justify the extra cost for recording these traits. The prediction equations were: for cows, body weight = 12174-187.410 pt+0.97196960 pt²-0.00162382 pt³, for heifers, body weight = 1717-35.167pt+0.238978pt²-0.00046260pt³ and for males, body weight = -3862+76.014pt-0.488837pt²+0.00109755pt³.

[Epidemiological aspects of American tegumentary leishmaniasis in Varzelândia, Minas Gerais, Brazil]. / Aspectos epidemiológicos da leishmaniose tegumentar americana em Varzelândia, Minas Gerais, Brasil.

To characterize an area of endemic leishmaniasis, aiming to test a candidate leishmania vaccine, a prospective epidemiological survey was implemented in 1999 in a rural area of Varzelândia, Minas Gerais, Brazil. From a total of 1,253 persons in 246 households, 1,170 were included, of whom 593 (50.6%) were males and 662 (56.5%) were under 21 years of age. A Montenegro intradermal test performed in 1,120 individuals and evaluated in 1,020 was reactive in 282 (27.6%). Serological testing through indirect immunofluorescence and ELISA was performed in 970 individuals (82.9%). Antibodies to Leishmania sp. were detected in 117 (13.1%) and 170 (17.5%), respectively, by the two tests. Cutaneous scars similar to those seen in American tegumentary leishmaniasis were found in 297 individuals (25.4%), 282 of whom were submitted to the intradermal test, while only 168 (59.6) were reactive. Initial leishmaniasis prevalence of 5.8% was recorded, and an annual leishmaniasis incidence rate of 4.6% was observed after one year of follow-up. The epidemiological characteristics observed in this location are suggestive of an endemic area with old colonization.

Aspectos epidemiológicos da leishmaniose tegumentar americana em Varzelândia, Minas Gerais, Brasil / Epidemiological aspects of American tegumentary leishmaniasis in Varzelândia, Minas Gerais, Brazil

Para caracterizar uma área endêmica de leishmaniose tegumentar americana susceptível de intervenção com candidato à vacina anti-leishmania, foi iniciado em 1999 estudo longitudinal em área rural do Município de Varzelândia, Minas Gerais, Brasil. Inicialmente, foram cadastrados 1.253 indivíduos distribuídos em 246 domicílios, dos quais, 1.170 concordaram em participar do trabalho. Desses, 593 (50,6 por cento) eram masculinos e 662 (56,5 por cento), menores de 21 anos. A intradermorreação de Montenegro foi realizada em 1.120 indivíduos, lida em 1.020 dos casos, e observada reatividade em 282 (27,6 por cento) deles. Anticorpos anti-leishmania foram testados mediante imunofluorescência indireta e teste ELISA em 970 (82,9 por cento) indivíduos, obtendo-se positividade, respectivamente, em 127 (13,1 por cento) e 170 (17,5 por cento) para os dois testes. Na avaliação inicial, foram observados 297 (25,4 por cento) indivíduos com cicatrizes cutâneas semelhantes às deixadas pela doença. Desses, 282 realizaram a intradermorreação que foi positiva em168 (59,61 por cento). A prevalência de casos de leishmaniose tegumentar no início do estudo foi de 5,8 por cento e, depois do primeiro ano, observou-se incidência anual de 4,6 por cento de casos. As características epidemiológicas observadas nesse local sugerem tratar-se de uma área endêmica de colonização antiga.

Association of the bovine major histocompatibility complex (BoLA) BoLA-DRB3 gene with fat and protein production and somatic cell score in Brazilian Gyr dairy cattle (Bos indicus)

The effect of the bovine major histocompatibility complex (BoLA) locus on animal health may be due to a direct action of its alleles on immune functions, whereas its indirect effect on production traits might be explained by the better general health conditions of more productive animals. In the present study, the BoLA-DRB3 gene was investigated in 1058 cows belonging to seven Brazilian Gyr Dairy herds (Bos indicus, Zebu cattle). A total of 37 alleles were identified, 15 of them described for the first time in a Zebu breed. A highly significant association (p < 0.02) was observed between allele *54 and a decrease (-26.1 kg) in milk protein yield and there was a significant association (p < 0.05) between this allele and lower (-26.07 kg) milk fat yield. There was also a significant association (p < 0.05) between allele *6 and decreased (-12.47 kg) milk protein and allele *7 and increased (12.72 kg) milk protein. There were also indications of association (p < 0.10) between somatic cell score (SCS) and alleles *3 (SCS increased by 0.54 units) and *31 (SCS increased by 0.46 units). The highly significant association of allele *54 with lower protein yield suggests the possible use of this allele in marker-assisted selection programs.

Genetic and phenotypic parameters of productivity traits on the first three lactations in Gyr cattle herds

Records of Gyr cows selected for milk production were obtained from the National Gyr Dairy Cattle Breeding Program (Embrapa/CNPGL) and analyzed, in order to estimate genetic parameters for the first three lactations and to verify the effects of some environmental factors on milk production from 1979 to 1994. Genetic parameters were estimated by REML with an animal model and a group of fixed effects that included classes of herd, year, season and age at calving. Milk production means and standard deviations were 2,183 kg, 707 kg; 2,682 kg, 762 kg and 2,638 kg, 851 kg, for first, second, and third lactations, respectively. Heritability estimates were 0.20, 0.12, and 0.19 for first, second, and third lactations, respectively, and repeatability was 0.44. Genetic correlation estimates were: 0.68 between first and second lactations, 0.84 between first and third lactations and 1.0 between second and third lactations. Results confirm other research for specialized dairy breeds and firmly suggest that even in breeds of Indian origin the best time to make selection decisions is during the first lactation.

Variações sazonais no comportamento de vacas holandesas estabuladas em sistema free stall / Seasonal variation in the behavior of holstein cows housed in a free stall barn

O efeito da estação (verão e inverno) sobre o comportamento alimentar e postural de 19 vacas holandesas em lactação, confinadas em free stall, foi avaliado durante 11 dias nos meses de verão (janeiro, fevereiro e março), e 14 dias, nos meses de inverno (junho, julho e agosto), nos anos de 1993 a 1995. A temperatura ambiente (TA) e a umidade relativa do ar (UR), foram monitoradas diariamente, durante o período citado. As atividades referentes a alimentação, ruminação e ócio, bem como a posição dos animais (em pé ou deitada) foram anotadas a cada 10 minutos durante 24h. A estação do ano influenciou todas as variáveis relacionadas ao comportamento. No verão, as vacas diminuíram o tempo de alimentação e de ruminação e ficaram mais tempo em pé, enquanto no inverno, permaneceram mais tempo no ócio e na posição deitada. A produção de leite afetou o tempo de ruminação e a postura corporal dos animais mostrando que vacas no estágio inicial da lactação e de maior produção reduzem o tempo de ruminação e ficam mais tempo de pé. A mudança de comportamento entre as estações reflete a tentativa dos animais de evitar o estresse calórico [AU]