Summary The present study investigated four restriction fragment length polymorphisms (RFLPs) in the leptin gene and five short tandem repeats (STRs) in its vicinity in 160 females from a synthetic beef cattle breed (5/8 Aberdeen Angus and 3/8 Nelore), and evaluated possible associations between these markers and reproductive performance. A high level of genetic diversity was observed, STRs being more variable than RFLPs. Heterozygosities ranged from 0.67 to 0.87 in STRs and from 0.12 to 0.49 in RFLPs, suggesting that the selective process applied to the Brangus‐Ibage cattle had not affected the total genetic diversity expected for crossbreeds. Two alleles (IDVGA51*181 and LEPSau3A1*+) seem to increase calving interval (CI) by about 79 and 81 days, respectively. Therefore, selection against carriers of these mutations could improve CI by at least 2 months, despite the seasonality of the mating period employed here. LEPSau3AI system seems to influence weight at first calving (WFC). Heterozygotes (LEPSau3AI*+/LEPSau3AI*−) had higher WFC than LEPSau3AI*−/LEPSau3AI*− homozygote. Selection for animals with this genotype could result in some advantages for post‐calving recovery. CI and WFC are indirect measurements of reproduction reflecting also animal body conditions, and therefore it is difficult to determine whether or not IDVGA51*181 and LEPSau3A1*+ alleles directly affect the reproductive system. Although further analysis of other herds should be performed to confirm these data, the association of genetic markers with better reproductive performance is a very interesting finding and could be used in marker‐assisted selection to improve reproduction in beef cattle.

A cadeia da carne de frango no Brasil é um importante setor do agronegócio, ocupando a terceira maior produção mundial e o primeiro lugar nas exportações. Para atender a demanda, é fundamental minimizar os problemas de manejo, que causam o aparecimento de problemas fisiológicos. A seleção genética intensiva, que é usada na obtenção de taxas de crescimento mais rápidas para frangos de corte, contribuiu para que as linhagens melhoradas atuais sejam muito susceptíveis ao estresse térmico. Quando a temperatura ambiente se eleva acima da zona de termoneutralidade, a ave é submetida a uma condição de estresse, podendo gerar hipertermia aguda, alcalose respiratória, desequilíbrio eletrolítico, redução no consumo de alimento, menor taxa de crescimento, aumento na mortalidade e/ou até mesmo efeitos negativos na qualidade da carne, pela incidência de carnes pálidas e, em outros casos, escuras, interferindo nas propriedades como rendimento industrial, capacidade de retenção de água, cor e maciez. Os resultados de avaliação dos parâmentros de qualidade observados na literatura evidenciam que o estresse térmico, crônico ou agudo sofrido por frangos de corte geram consequências negativas sobre as propriedades funcionais da carne. São necessários mais estudos sobre essa questão, principalmente em relação ao Brasil, por ser um país tropical, com elevadas temperaturas, especialmente, no verão, para compreender, prevenir e contornar a extensão ou intensidade do estresse, evitando problemas e prejuízos para a cadeia da carne.

The aim of the present study was to verify associations between reproductive efficiency and four microsatellite markers located in synteny with genes involved in the regulation of reproductive mechanisms. A sample of 107 females from a Brangus Ibagé population (5/8 Aberdeen Angus x 3/8 Nelore) was characterized for ETH225 (D9S1) and MM12E6 (D9S20) microsatellites, mapped on chromosome 9, and HEL5 (D21S15) and AFZ1 (D21S37) on chromosome 21. Associations between the genetic markers and reproductive efficiency were determined by one-way analysis of variance using calving interval (CI), live weight at calving (LWC), live weight at first calving (LW1C) and live weight at second calving (LW2C) as dependent variables. The genotypes were classified according to allele size into homozygous for long alleles, homozygous for short alleles and heterozygous. A longer CI was observed for individuals homozygous for long alleles at the HEL5 locus compared with the others (p = 0.022). For the AFZ1 locus, an inverse correlation between allele size and calving interval was observed (p = 0.022), suggesting that homozygosity for long alleles at this microsatellite could be advantageous. Analysis of the combined effect of favorable genotypes at HEL5 and AFZ1 indicated that animals with unfavorable genotypes (homozygous for long alleles at HEL5 and homozygous for short alleles at AFZ1) presented a significantly longer CI (p = 0.003) when compared to the other genotypes. The ETH225 and MM12E6 systems did not present any association with CI. None of the systems studied showed any significant association with LWC, LW1C or LW2C.

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Three short tandem repeats (STRs),

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ABSTRACT

Brazilian poultry industry has reached a high level of development in both meat and egg production as a result of constant technological modernization. Further improvements can be achieved through genomics, but before this can be accomplished, a better understanding of gene expression profiles and nucleotide polymorphisms is necessary. Since animal physiology is directly or indirectly controlled by the pituitary and hypothalamus, the aim of the present work was to identify and analyze genes expressed in these tissues in chicken lines with different growth potential. Two pituitary and hypothalamus cDNA libraries from 21 day broiler (TT) and layer (CC) chickens lines were constructed and allowed identification of 3,074 unique sequences and 77 single nucleotide polymorphisms (SNPs). The collection of expressed sequence tags (ESTs) and SNPs identified in this study represents an important resource for future studies aimed at identifying genes responsible for growth in chicken.