Polymorphisms in the Prion Protein Gene of cattle breeds from Brazil / Polimorfismos no gene da proteína priônica em bovinos no Brasil

One of the alterations that occur in the PRNP gene in bovines is the insertion/deletion (indel) of base sequences in specific regions, such as indels of 12-base pairs (bp) in intron 1 and of 23- bp in the promoter region. The deletion allele of 23 bp is associated with susceptibility to bovine spongiform encephalopathy (BSE) as well as the presence of the deletion allele of 12 bp. In the present study, the variability of nucleotides in the promoter region and intron 1 of the PRNP gene was genotyped for the Angus, Canchim, Nellore and Simmental bovine breeds to identify the genotype profiles of resistance and/or susceptibility to BSE in each animal. Genomic DNA was extracted for amplification of the target regions of the PRNP gene using polymerase chain reaction (PCR) and specific primers. The PCR products were submitted to electrophoresis in agarose gel 3% and sequencing for genotyping. With the exception of the Angus breed, most breeds exhibited a higher frequency of deletion alleles for 12 bp and 23 bp in comparison to their respective insertion alleles for both regions. These results represent an important contribution to understanding the formation process of the Brazilian herd in relation to bovine PRNP gene polymorphisms.(AU)

Uma das mudanças que ocorrem no gene PRNP em bovinos é a inserção e/ou deleção (indels) de sequências de bases, em determinadas regiões como, por exemplo, as indels de 12 pares de bases (pb) no íntron 1 e 23pb na região promotora. O alelo de deleção de 23pb está relacionado com a suscetibilidade à Encefalopatia Espongiforme Bovina (EEB), assim como a presença do alelo de deleção de 12pb. Neste estudo foi genotipada a variabilidade de nucleotídeos da região promotora e íntron 1 do gene PRNP em bovinos das raças Angus, Canchim, Nelore e Simental, para identificar os perfis genotípicos de resistência e/ou suscetibilidade à EEB de cada animal. Foi realizada a extração de DNA genômico para amplificação das regiões alvo do gene PRNP, por meio da reação em cadeia de polimerase (PCR) utilizando-se primers específicos. Os produtos da PCR foram submetidos à eletroforese em gel de agarose a 3%, e sequenciamento para a realização da genotipagem. Com exceção da raça Angus, a maioria das raças apresentaram maiores frequências do alelo de deleção tanto para 12pb como 23pb, em comparação com seus respectivos alelos de inserção, para as duas regiões. Esses resultados abrem caminhos para o conhecimento de como o rebanho brasileiro está sendo formado com relação aos polimorfismos do gene PRNP bovino.(AU)

Genomic structure and marker-derived gene networks for growth and meat quality traits of Brazilian Nelore beef cattle.

BACKGROUND: Nelore is the major beef cattle breed in Brazil with more than 130 million heads. Genome-wide association studies (GWAS) are often used to associate markers and genomic regions to growth and meat quality traits that can be used to assist selection programs. An alternative methodology to traditional GWAS that involves the construction of gene network interactions, derived from results of several GWAS is the AWM (Association Weight Matrices)/PCIT (Partial Correlation and Information Theory). With the aim of evaluating the genetic architecture of Brazilian Nelore cattle, we used high-density SNP genotyping data (~770,000 SNP) from 780 Nelore animals comprising 34 half-sibling families derived from highly disseminated and unrelated sires from across Brazil. The AWM/PCIT methodology was employed to evaluate the genes that participate in a series of eight phenotypes related to growth and meat quality obtained from this Nelore sample. RESULTS: Our results indicate a lack of structuring between the individuals studied since principal component analyses were not able to differentiate families by its sires or by its ancestral lineages. The application of the AWM/PCIT methodology revealed a trio of transcription factors (comprising VDR, LHX9 and ZEB1) which in combination connected 66 genes through 359 edges and whose biological functions were inspected, some revealing to participate in biological growth processes in literature searches. CONCLUSIONS: The diversity of the Nelore sample studied is not high enough to differentiate among families neither by sires nor by using the available ancestral lineage information. The gene networks constructed from the AWM/PCIT methodology were a useful alternative in characterizing genes and gene networks that were allegedly influential in growth and meat quality traits in Nelore cattle.

Identification of KCNJ11 as a functional candidate gene for bovine meat tenderness.

The potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) gene was investigated as a candidate for meat tenderness based on the effects reported on muscle for KCNJ11 gene knockout in rat models and its position in a quantitative trait locus (QTL) for meat tenderness in the bovine genome. Sequence variations in the KCNJ11 gene were described by sequencing six amplified fragments, covering almost the entire gene. We identified single nucleotide polymorphisms (SNP) and validated them by different approaches, taking advantage of simultaneous projects that are being developed with the same Nelore population. By sequencing the KCNJ11 in Nelore steers representing extreme phenotypes for Warner-Bratzler shear force (WBSF), it was possible to identify 22 SNPs. We validated two of the identified markers by genotyping the whole population (n = 460). Analysis of association between genotypes and WBSF values revealed a significant additive effect of a SNP at different meat aging times (P ≤ 0.05). In addition, an association between the expression levels of KCNJ11 and WBSF was found, with lower expression levels of KCNJ11 associated with more tender meat (P ≤ 0.05). The results showed that the KCNJ11 gene is a candidate mapped to a QTL for meat tenderness previously identified on BTA15 and may be useful to identify animals with genetic potential to produce tender meat. The effect of KCNJ11 observed on muscle is potentially due to changes in activity of KATP channels, which in turn influence the flow of potassium in the intracellular space, allowing establishment of the membrane potential necessary for muscle contraction.

[Grazing systems, rotenone and parasites control in crossbred calves: effect on live weight gain and on parasites burdens]. / Sistema de pastejo, rotenona e controle de parasitas em bovinos cruzados: efeito no ganho de peso e no parasitismo.

Practices for endo and ectoparasite control in beef cattle were evaluated in two independent experiments. First, the effects of rotenone on Rhipicephalus (Boophilus) microplus ticks were evaluated in vitro and in experimentally infected calves. In the second trial, the effects of grazing systems associated with endo and ectoparasite treatments on parasite burden and weight gain of naturally parasited animals were evaluated. Rotenone showed acaricide action on larvae and engorged ticks during in vitro tests and on larvae in experimentally infected calves. Three treatments with endectocide decreased (P < .05) the number of EPG and ticks and increased (P < .05) the weight gain in the dry season. Animals treated with only one application of levamisole showed EPG intermediate and different (P < .05) from the groups treated with endectocide (lower) and control (higher) in the dry season, but the weight gain obtained with this treatment did not differ from the control group. During the raining season the animals treated with fipronil were significantly less parasited by horn fly, tick and larvae of Dermatobia hominis and the group treated with rotenone were significantly less parasited by horn fly in relation to control. Animals under rotational grazing showed significantly higher EPG than those under continuous grazing. Three treatments with endectocide in the dry season plus three acaricide treatments with fipronil in the raining season reduced EPG, tick, and screw worm larva counts, and provided a significant increase (23 kg) of live weight gain in relation to untreated animals.

Sistema de pastejo, rotenona e controle de parasitas em bovinos cruzados: efeito no ganho de peso e no parasitismo / Grazing systems, rotenone and parasites control in crossbred calves: effect on live weight gain and on parasites burdens

Foram realizados dois experimentos para avaliar o controle de endo e ectoparasitos de bovinos. No primeiro avaliou-se in vitro e, em animais experimentalmente infestados, o efeito da rotenona no carrapato Rhipicephalus(Boophilus) microplus e, no segundo, avaliou-se o efeito do pastejo rotacionado e de tratamentos contra endo e ectoparasitos na carga parasitária e no desenvolvimento de animais naturalmente parasitados. In vitro a rotenona mostrou ação acaricida nas larvas e nas teleóginas, e nas larvas nos animais estabulados. Três tratamentos com endectocida, no período seco, diminuiram significativamente a contagem de ovos por grama de fezes (OPG) e o número de teleóginas, e, aumentou significativamente o ganho médio de peso. Os animais tratados com uma aplicação de levamisol estavam nesse período com médias de OPG intermediárias e significativamente diferentes dos grupos controle e tratados com endectocida. O ganho de peso, entretanto, não diferiu significativamente do grupo controle. No período das águas, os animais tratados com fipronil estavam significativamente menos parasitados por teleóginas, mosca-dos-chifres e por larvas de Dermatobia hominis; e os tratados com rotenona. menos parasitados por mosca-dos-chifres que os animais controle. Diferentemente do esperado, os animais sob pastejo rotacionado estavam no período seco com OPG significativamente maior que os em sistema contínuo. Três tratamentos com endectocida, no período seco, e três tratamentos acaricida com fipronil, na estação chuvosa, diminuíram significativamente o OPG, o número de teleóginas e o de larvas de berne, e proporcionou um aumento significativo de 23 kg de peso vivo em relação aos animais não tratados.

Practices for endo and ectoparasite control in beef cattle were evaluated in two independent experiments. First, the effects of rotenone® on Rhipicephalus (Boophilus) microplus ticks were evaluated in vitro and in experimentally infected calves. In the second trial, the effects of grazing systems associated with endo and ectoparasite treatments on parasite burden and weight gain of naturally parasited animals were evaluated. Rotenone showed acaricide action on larvae and engorged ticks during in vitro tests and on larvae in experimentally infected calves. Three treatments with endectocide decreased (P < .05) the number of EPG and ticks and increased (P < .05) the weight gain in the dry season. Animals treated with only one application of levamisole showed EPG intermediate and different (P < .05) from the groups treated with endectocide (lower) and control (higher) in the dry season, but the weight gain obtained with this treatment did not differ from the control group. During the raining season the animals treated with fipronil were significantly less parasited by horn fly, tick and larvae of Dermatobia hominis and the group treated with rotenone were significantly less parasited by horn fly in relation to control. Animals under rotational grazing showed significantly higher EPG than those under continuous grazing. Three treatments with endectocide in the dry season plus three acaricide treatments with fipronil in the raining season reduced EPG, tick, and screw worm larva counts, and provided a significant increase (23 kg) of live weight gain in relation to untreated animals.