ABSTRACT The purpose of this study was to access and characterize single nucleotide polymorphisms (SNP) located within the HSF1 and HSPA6 candidate genes for adaptability in Angus breed raised in subtropical climate. Samples of DNA from 20 animals representing extreme phenotypes for adaptability traits were obtained. Sequence variations in the candidate genes were described by sequencing target regions. We identified 12 SNP located in the HSF1 gene. Moreover, four of the six SNP found in the HSPA6 gene cause amino acid substitutions in protein-coding regions. We also identified a representative SNP (called tag SNP) in a region of the HSF1 gene with high linkage disequilibrium (r2 = 0.87) that may represent 11 SNP located in this gene. Minor allele frequency observed for the SNP ranged from 0.10 to 0.50 and 0.02 to 0.21 for the HSF1 and the HSPA6 genes, respectively. Overall, almost all SNP analyzed showed significant deviation from the Hardy-Weinberg Equilibrium and half of the loci had heterozygosity greater than 0.50. The data suggest that there is sequence variability in these genes that could be exploited by breeding programs. There is genetic variation in HSF1 and HSPA6 genes in this populations of Angus breed, which is fundamental to obtain response to selection.

Canchim, a synthetic breed of cattle derived from the Charolais and Zebu group has been used in the beef-cattle industry in Brazil as an alternative for intensifying production. One of the main concerns with this breed is its poor fat deposition and consequently, there is an effort to increase the performance for this trait. The thyroglobulin gene is located in a QTL region for fat deposition, and reports describe the influence of a polymorphism in the 5´ leader sequence of that gene on marbling and subcutaneous fat thickness. This study analyzed the association of this polymorphism in the thyroglobulin gene, as well as of two flanking microsatellite markers, CSSM066 and ILSTS011, with backfat thickness in 987 Canchim beef cattle. The CSSM066 and ILSTS011 microsatellite markers have a effect on fat thickness in the studied populations. However, this trait did not have association with the polymorphism of the thyroglobulin gene, which suggests that other genes of bovine chromosome 14 may be responsible for the variation in this trait.

The aim of this work was to study the genetic variability among the wild boars, crossbred animals and pigs using microsatellite markers. Five genetic groups were studied. The fragments of three microsatellites developed for Sus scrofa domestica - IGF1, ACTG2 and TNFB - were amplified through PCR technique to evaluate the expected intra populacion variability (He) and observed (Ho) heterozygosity, and endogamy coefficient (F IS ) within each population and inter population variability F IS , testing relationship among five genetic groups to establish the genetic distance among them. The high level of observed heterozygosity values varied between 0.537 and 0.7871. Generally, F IS was low, suggesting that the endogamy did not exist between the tested animals.

Avaliou-se o grau de infestação natural por ectoparasitas em fêmeas bovinas de corte de três grupos genéticos. Foram realizadas contagens, de julho de 2003 a dezembro de 2004, de carrapatos (Rhipicephalus (Boophilus) microplus), moscas-dos-chifres (Haematobia irritans) e bernes (larvas de Dermatobia hominis) em fêmeas dos grupos genéticos Nelore (NE), Angus x Nelore (AN), Canchim x Nelore (CN) e Simental xNelore (SN) infestadas naturalmente. Foram feitas de 6 a 10 contagens em cada animal, totalizando 5.384 observações em fêmeas de sete estádios fisiológicos (bezerras, novilhas vazias, novilhas prenhes, vacas primíparas, com ou sem bezerro, e vacas pluríparas, com ou sem bezerro). Os dados, transformados por log10 (n + 1), foram analisados pelo método dos quadrados mínimos, com um modelo estatístico que incluiu os efeitos de grupo genético da fêmea, de animal dentro de grupo genético (erro a), de ano-época da contagem, de estádio fisiológico e da interação grupo genético x ano-época da contagem. A diferença entre os grupos genéticos dependeu do ano-época da contagem, contudo, em geral, as fêmeas nelores foram as menos infestadas pelo carrapato e as Angus x Nelore, as mais infestadas pela mosca-dos-chifres e pelo berne. Houve efeito de estádio fisiológico da fêmea em todas as três características estudadas, e as diferenças variaram com a característica. Apesar da interação grupo genéitco x ano-época de contagem, existem diferenças entre os grupos genéticos Nelore, Canchim x Nelore, Angus x Nelore e Simental x Nelore quanto ao grau de infestação natural por carrapatos, por moscas-dos-chifres e por bernes.

It was evaluated in this work, the degree of natural infestation by external parasites in beef cattle females from three genetic groups. Countings of cattle tick (Rhipicephalus (Boophilus) microplus), horn fly (Haematobia irritans) and beef-worm (Dermatobia hominis) were performed from July 2003 to December 2004 in females from the genetic groups Nellore (NE), Angus x Nellore (AN), Canchim x Nellore (CN), and Simmental x Nellore (SN) naturally infested. It was realized from 6 to 10 countings in each animal, totalizing 5,384 observations in females at seven physiological stages (calf; empty heifers, pregnant heifers, primiparous cows with or without calf; and pluriparous cows, with or without calf). Data, which were transformed by log10 (n + 1), were analyzed by the least square method with a statistical model that included effects of the female genetic group, of the animal within a genetic group (error a), year-season counting, physiological state, and year-season x genetic group interaction. Differences among genetic groups depended on year-season counting; however, in general, Nellore females were the least infected by ticks, and Angus x Nellore females were the most infected by horn flies and by beef-worms. There was a physiological stage effect of the female in all the three studied characteristics and the differences changed accordingly to the trait. Despite of the counting year-season x genetic group, there are differences among Nellore, Canchim x Nelore, Angus x Nellore and Simmental x Nelore genetic groups regarded to the degree of natural infestation by cattle tick, horn fly and beef-worm.

Os objetivos neste trabalho foram estudar os efeitos de ambiente sobre a espessura de gordura subcutânea (EGS), a área de olho-de-lombo (AOL) e o peso aos 19 meses de idade e estimar parâmetros genéticos para essas características. Utilizaram-se informações obtidas de 987 bovinos da raça Canchim (5/8 Charolês + 3/8 Zebu) e do grupo genético animal MA (filhos de touros charoleses e vacas 1/2 Canchim + 1/2 Zebu) nascidos em 2003, 2004 e 2005. Os componentes de covariância foram estimados pelo método da máxima verossimilhança restrita utilizando-se um modelo animal com efeitos fixos (ano de nascimento, grupo genético, rebanho e sexo) e os efeitos aleatórios genético aditivo direto e residual. As médias de área de olho-de-lombo e peso foram mais altas nos machos que nas fêmeas. No grupo genético MA, as médias para todas as características foram mais altas que na raça Canchim e houve ainda efeitos de rebanho e de ano de nascimento. As estimativas de herdabilidade para AOL (0,33 ± 0,09), EGS (0,24 ± 0,09) e peso (0,23 ± 0,09) foram moderadas, enquanto que a estimativa de correlação genética (0,21 ± 0,24) entre EGS e AOL foi baixa, o que sugere que essas características são controladas por diferentes conjuntos de genes de ação aditiva. As correlações genéticas para peso estimadas com EGS (0,57 ± 0,23) e com AOL (0,62 ± 0,16) foram moderadas. Conclui-se que as características ao sobreano devem responder à seleção nos rebanhos estudados e que a seleção para aumento de peso também eleva EGS e AOL e vice-versa.

The objective in this work was to study the effects of environmental factors on subcutaneous fat thickness (BFT), loin eye area (REA) and body weight (BW) measured at 19 months of age and to estimate genetic parametersfor these traits. It was used information obtained from 987 Canchim (5/8 Charolais + 3/8 Zebu) and MA genetic group (offspring of Charolais bulls and 1/2 Canchim + 1/2 Zebu cows) bulls and heifers, born in 2003, 2004, and 2005. Covariance components were estimate by restricted likelihood method using animal model with fixed effects (year of birth, genetic group, herd, and sex) and residual and direct additive genetic random effects. Means of loin eye area and weight were higher for males than for females. In the MA genetic group, the means, for all traits, were higher than in the Canchim group, and there were still the effects of herd and year of birth. The heritability estimates of REA (0.33 ± 0.09), BFT (0.24 ± 0.09) and BW (0.23 ± 0.09) were moderate, while genetic correlation estimate (0.21 ± 0.24) between BFT and REA was low, suggesting that traits are controlled by different sets of genes with additive action. Genetic correlations of BW with BFT (0.57 ± 0.23) and REA (0.62 ± 0.16) are moderate. It is possible to conclude that those traits can respond for selection and they indicate that selection for BW will increase also enhance BFT and REA and vice versa.

O uso de marcadores genéticos pode favorecer a identificação de animais geneticamente superiores em bovino de corte. O gene PIT1 codifica para o fator de transcrição Pit-1, crítico para ativar a expressão dos genes da prolactina, hormônio de crescimento e PIT1. Esta pesquisa investiga o efeito do polimorfismo HinfI-PIT1 sobre características de crescimento em 509 animais da raça Canchim, pertencentes à duas linhagens, GG1 e GG2. Os genótipos do gene PIT1 foram identificados pela técnica PCR-RFLP. Os efeitos dos genótipos sobre valores fenotípicos para pesos ao nascimento (PN), pesos padronizados à desmama (P240) e ao ano (P365), ganhos médios diários de peso do nascimento à desmama (GMND), e da desmama aos 12 meses de idade (GMD12) foram analisados pelo método dos quadrados mínimos. Foram observados efeitos de interação entre grupo genético do animal e genótipo de PIT1 sobre P240, GMND e GMD12 (P < 0.05). Diferenças entre médias dos genótipos HinfI (-/-), HinfI (+/+) e HinfI (+/-) para P240 e GMND foram observadas em GG2 (P < 0,05), revelando superioridade do genótipo HinfI (-/-). As médias dos genótipos (+/+) e (+/-) para P240 e GMND, não diferiram, sugerindo efeito de dominância do alelo HinfI (+). O alelo HinfI (-) mostrou-se favorável sobre P240 e GMND em GG2, quando em homozigose. A diferença de comportamento de PIT1 observada nos dois grupos genéticos pode sugerir a ação de loco de característica quantitativa ligado ao gene PIT1, segregando apenas em GG2.

Use of genetic markers can aid on the identification of animals with highest breeding values in beef cattle. The PIT1 gene codes for the Pit-1 transcription factor is essential for the activation of prolactin, growth hormone and PIT1 genes. This research is an investigation of the effect of PIT1-HinfI polymorphism on growth traits of 509 Canchim animals, from two lineages, GG1 and GG2. PIT1 genotypes were identified through PCR-RFLP. Genotype effect on phenotypic values for birth weight (BW), standardized weaning weight (W240), weight at 12 months of age (W365), and the average daily weight gain from birth to weaning (AGBW), and from weaning to 12 months of age (AGW12) were analyzed by the least squares method. Effects of the interaction between the animal's genetic group and PIT1 genotype for W240, AGBW and AGW12 were observed (P < 0.05). Differences between means of HinfI (-/-), HinfI (+/+) and HinfI (+/-) genotypes for W240 and AGBW were observed in GG2 (P < 0.05), revealing superiority of (-/-) genotype for those traits. Means for genotypes (+/+) and (+/-) for W240 and AGBW, did not differ from one another, suggesting a dominance effect of the HinfI (+) allele. The HinfI (-) allele had a favorable effect on W240 and AGBW in GG2, when present in homozygosis. The difference between PIT1 behavior observed in the two genetic groups may suggest the action of a quantitative trait locus linked to PIT1, segregating only in GG2 population.

Quantitative trait loci (QTL) mapping in livestock allows the identification of genes that determine the genetic variation affecting traits of economic interest. We analyzed the birth weight and weight at 60 days QTL segregating on bovine chromosome BTA14 in a F2 resource population using genotypes produced from seven microsatellite markers. Phenotypes were derived from 346 F2 progeny produced from crossing Bos indicus Gyr x Holstein Bos taurus F1 parents. Interval analysis to detect QTL for birth weight revealed the presence of a QTL (p < 0.05) at 1 centimorgan (cM) from the centromere with an additive effect of 1.210 ± 0.438 kg. Interval analysis for weight at 60 days revealed the presence of a QTL (p < 0.05) at 0 cM from the centromere with an additive effect of 2.122 ± 0.735 kg. The region to which the QTL were assigned is described in the literature as responsible for some growth traits, milk yield, milk composition, fat deposition and has also been related to reproductive traits such as daughter pregnancy rate and ovulation rate. The effects of the QTL described on other traits were not investigated.

Resistance of beef cattle heifers to the cattle tick Boophilus microplus was evaluated by artificial infestation of 66 beef cattle heifers of the following genetic groups: 16 Nelore (NE), 18 Canchim x Nelore (CN), 16 Angus x Nelore (AN) and 16 Simmental x Nelore (SN). The animals, with a mean age of 16.5 months, were maintained with no chemical tick control in a Brachiaria decumbens pasture. Four artificial infestations with 20,000 B. microplus larvae were carried out 14 days apart and from day 18 to day 22 of each infestation the number of engorged female ticks (> 4.5 mm) was counted on the left side of each heifer. Data were analyzed as the percentage of return (PR = percentage of ticks counted relative to the number infested), transformed to (PR)¼, and as log10 (Cij + 1), in which Cij is the number of ticks in each infestation, using the least squares method with a model that included the effects of genetic group (GG), animal within GG (error a), infestation number (I), GG x I and the residual (error b). Results indicated a significant GG x I interaction, because AN and SN heifers had a higher percentage of return than CN and NE heifers, while CN heifers showed a higher percentage of return than the NE heifers only in infestations 3 and 4. Transformed percentages of return were NE = 0.35 ± 0.06, AN = 0.89 ± 0.06, CN = 0.54 ± 0.05 and SN = 0.85 ± 0.06.

Segregation between a genetic marker and a locus influencing a quantitative trait in a well delineated population is the basis for success in mapping quantitative trait loci (QTL). To detect bovine chromosome 5 (BTA5) birth weight QTL we genotyped 294 F2 Gyr (Bos indicus) x Holstein (Bos taurus) crossbreed cattle for five microsatellite markers. A linkage map was constructed for the markers and an interval analysis for the presence of QTL was performed. The linkage map indicated differences in the order of two markers relative to the reference map (<A HREF="http://www.marc.usda.gov/">http://www.marc.usda.gov</A>). Interval analysis detected a QTL controlling birth weight (p < 0.01) at 69 centimorgans (cM) from the most centromeric marker with an effect of 0.32 phenotypic standard-error. These results support other studies with crossbred Bos taurus x Bos indicus populations.

The Canchim beef cattle (5/8 Charolais + 3/8 Zebu) has been selected for meat production in Brazil since late 1950. In the present work the effects of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) polymorphisms were investigated in 688 animals born between 1998 and 2000. These animals belonged to two genetic groups, i.e., traditional and new lineages. Genotype effects on expected breeding values for birth weight (BW), weaning weight (WW) and yearling weight (YW) were investigated by the least square method. Significant effects were found for GH genotype on YW (p < 0.05), with positive effects associated with the LV (leucine/valine) genotype. For IGF-1 genotypes, significant effects were found on BW (p < 0.01) and YW (p < 0.01). Average substitution effects for IGF-1 alleles estimated by regression analysis suggested a positive effect of the IGF-1 225 bp allele on BW and of the 229 bp allele on YW.

Several studies have investigated the relationship between heterozygosity, genetic distance and production traits. The objective of the present study was to evaluate the influence of the degree of heterozygosity and genetic distance on growth, carcass and reproductive related features in F1 bovine crosses. We tested 10 polymorphic markers in 330 purebred cattle (Nelore, Canchim, Aberdeen Angus and Simental) and 256 crossbred cattle belonging to four crossbred groups. Individual heterozygosities (Hi) and multilocus genetic similarity (Dm) were estimated and used in correlation analysis against individual phenotypic measurements. Significant (p < 0.05) Hi effects occurred for birth weight, 15 to 18 month weight, hot carcass weight and longissimus rib eye area. The extent to which increased heterozygosity (deltaH) in F1 crosses can be predicted from the genetic distance of parental breeds was also investigated using Nei's standard genetic distance (Ds) and standard heterozygosity (Hs). High correlations were found between deltaHi, deltaHs and the Ds of the parental breeds. Our results suggest that heterozygosity of the ten molecular markers used in this study may affect live weight during at least one growth phase. Parental genetic distance was a suitable predictor of the degree of progeny heterozygosity.

Aberdeen Angus beef cattle from the Brazilian herd were studied genetically using restriction fragment length polymorphism (RFLP) of the kappa-casein - HinfI (CSN3 - HinfI), beta-lactoglobulin - HaeIII (LGB - HaeIII) and growth hormone AluI (GH- AluI) genes, as well as four microsatellites (TEXAN15, CSFM50, BM1224 and BM7160). The RFLP genotypes were determined using the polymerase chain reaction (PCR) followed by digestion with restriction endonucleases and electrophoresis in agarose gels. With the exception of the microsatellite BM7160, which was analyzed in an automatic sequencer, the PCR products were genotyped by silver staining. The allele and genotype frequencies, heterozygosities and gene diversity were estimated. The values for these parameters of variability were comparable to other cattle breeds. The genetic relationship of the Aberdeen Angus to other breeds (Caracu, Canchim, Charolais, Guzerath, Gyr, Nelore, Santa Gertrudis and Simmental) was investigated using Nei's genetic distance. Cluster analysis placed the Aberdeen Angus in an isolated group in the Bos taurus breeds branch. This fact is in agreement with the geographic origin of this breed.

No presente trabalho, 180 fêmeas da raça Nelore, provenientes de oito rebanhos, foram analisadas quanto aos marcadores microssatélites TEXAN15, BM1224 e CSFM50 e aos polimorfismos de comprimento de fragmentos de restrição (RFLP) nos locos k-caseína, beta-lactoglobulina e hormônio de crescimento (GH). Com exceção de GH, todos os marcadores foram polimórficos na amostra estudada. Os valores de heterozigosidade, diversidade gênica, conteúdo de informação polimórfica (PIC) e probabilidade de exclusão de paternidade (PE) foram estimados. Os maiores valores de PIC (0,685) e PE (0,521) foram obtidos para o marcador BM1224.

In the present work, 180 Nellore females from eight herds were analyzed for TEXAN15, BM1224 and CSFM50 microsatellites and for the restriction fragments polymorphism (RFLP) at the locos k-casein, beta-lactoglobulin and growth hormone (GH). Excepted for GH, all markers were polymorphic in the studied sample. The values of heterozigozity, gene diversity, polymorphic information content (PIC) and paternity exclusion probability (PE) were estimated. The highest PIC (0.685) and PE (0.521) values were obtained for microsatellite BM1224.

Os genótipos de <FONT FACE="Symbol">k</FONT>-caseína (<FONT FACE="Symbol">k</FONT>-CN), <FONT FACE="Symbol">b</FONT>-lactoglobulina (<FONT FACE="Symbol">b</FONT>-LG) e hormônio de crescimento foram determinados por reação em cadeia de polimerase (PCR) e digestão com enzima de restrição em sete raças de bovinos (Nelore, Gir, Guzerá, Caracu, Charolesa, Canchim and Santa Gertrudis). A <FONT FACE="Symbol">k</FONT>-caseína apresentou dois alelos e as freqüências mais elevadas para o alelo A foram observadas em Bos indicus (0,93, 0,92 e 0,91% para as raças Gir, Guzerá e Nelore, respectivamente). A <FONT FACE="Symbol">b</FONT>-lactoglobulina apresentou dois alelos em todas as raças estudadas, sendo a freqüência do alelo A mais elevada nas raças européias. O loco de hormônio de crescimento apresentou dois alelos em Bos taurus e foi monomórfico (alelo L) em todas as raças zebuínas. A maior freqüência para o alelo V foi observado na raça Charolesa. Os marcadores investigados revelaram alta similaridade entre as raças, com a formação de dois grupos principais: um composto de raças zebuínas e a raça Santa Gertrudis e outro composto das raças européias e a raça Canchim.

The genotypes for k-casein (<FONT FACE="Symbol">k</FONT>-CN), <FONT FACE="Symbol">b</FONT>-lactoglobulin (<FONT FACE="Symbol">b</FONT>-LG) and growth hormone (GH) were determined by polymerase chain reaction (PCR) and restriction enzyme digestion in seven breeds of cattle (Nelore, Gyr, Guzerá, Caracu, Charolais, Canchim and Santa Gertrudis). <FONT FACE="Symbol">k</FONT>-Casein had two alleles with the A allele occurring at a higher frequency in Bos indicus breeds (0.93, 0.92 and 0.91% for Gyr, Guzerá and Nelore, respectively). The <FONT FACE="Symbol">b</FONT>-lactoglobulin locus had two alleles in all of the breeds. European breeds had a higher frequency of the <FONT FACE="Symbol">b</FONT>-LG A allele than Zebu breeds. The GH locus had two alleles (L and V) in Bos taurus and was monomorphic (L allele only) in all of the Bos indicus breeds evaluated. The highest frequency for the V allele was observed in Charolais cattle. The markers used revealed a considerable similarity among breeds, with two main groups being discernible. One group consisted of Zebu and Santa Gertrudis breeds and the other consisted of European and Canchim breeds.