BackgroundGenetic improvement in livestock populations can be achieved without significantly affecting genetic diversity if mating systems and selection decisions take genetic relationships among individuals into consideration. The objective of this study was to examine the genetic diversity of two commercial breeds of pigs. Genotypes from 1168 Landrace (LA) and 1094 Large White (LW) animals from a commercial breeding program in Brazil were obtained using the Illumina PorcineSNP60 Beadchip. Inbreeding estimates based on pedigree (Fx) and genomic information using runs of homozygosity (FROH) and the single nucleotide polymorphisms (SNP) by SNP inbreeding coefficient (FSNP) were obtained. Linkage disequilibrium (LD), correlation of linkage phase (r) and effective population size (Ne) were also estimated.ResultsEstimates of inbreeding obtained with pedigree information were lower than those obtained with genomic data in both breeds. We observed that the extent of LD was slightly larger at shorter distances between SNPs in the LW population than in the LA population, which indicates that the LW population was derived from a smaller Ne. Estimates of Ne based on genomic data were equal to 53 and 40 for the current populations of LA and LW, respectively. The correlation of linkage phase between the two breeds was equal to 0.77 at distances up to 50 kb, which suggests that genome-wide association and selection should be performed within breed. Although selection intensities have been stronger in the LA breed than in the LW breed, levels of genomic and pedigree inbreeding were lower for the LA than for the LW breed.ConclusionsThe use of genomic data to evaluate population diversity in livestock animals can provide new and more precise insights about the effects of intense selection for production traits. Resulting information and knowledge can be used to effectively increase response to selection by appropriately managing the rate of inbreeding, minimizing negative effects of inbreeding depression and therefore maintaining desirable levels of genetic diversity.
Caseins comprise make up about 80% of the total protein content of milk and present polymorphism with changes in the amino acid sequence. Within this abundance of proteins, kappa-casein is noteworthy, since it has been associated with differences in milk yield, composition and processing. The objective of this study was to observe the existence of polymorphism in the kappa-casein gene in female buffaloes. For this purpose, blood samples from 115 female buffaloes, collected with vacutainer by needle punctionure of the jugular vein, were used. for genomic DNA extraction was done from blood samples. The PCR-RFLP and SSCP techniques demonstrated that the studied animals were monomorphic for the kappa-casein gene. Only allele B was observed in these animals, which was present in homozygosis. Therefore, it was not possible to quantify the gene action on milk yield and its constituents. The monomorphism observed in the population studied would allow the development of a method to identify mixtures of cow and buffalo milk in mozzarella cheese production, especially because, in cattle, the kappa-casein gene is polymorphic.
Mozzarella cheese is traditionally prepared from bubaline (Bubalus bubalis) milk, but product adulteration occurs mainly by addition of or full substitution by bovine milk. The aim of this study was to show the usefulnes of molecular markers to identify the admixture of bovine milk to bubaline milk during the manufacturing process of mozzarella cheese. Samples of mozzarella cheese were produced by adding seven different concentrations of bovine milk: 0%, 1%, 2%, 5%, 8%, 12% and 100%. DNA extracted from somatic cells found in cheese were submitted to PCR-RFLP analysis of casein genes: α-s1-CN -CSN1S1 that encompasses 954 bp from exon VII to intron IX (Alu I and Hinf I), β-CN -CSN2 including 495 bp of exon VII (Hae III and Hinf I), and κ-CN -CSN3, encompassing 373 bp of exon IV (Alu I and Hind III). Our results indicate that Hae III-RFLP of CSN2 exon VII can be used as a molecular marker to detect the presence of bovine milk in "mozzarella" cheese. Mozzarella cheese has its origin in Italy where it is traditionally manufactured from bubaline (Bubalus bubalis) milk. The most commonly employed production process of mozzarella cheese is a traditional technique where bacterial fermentation of milk induces pH reduction and curd precipitation (Chapman et al., 1981). Nowadays, many countries that have a considerable number of buffalo cows widely use the milk of these animals for mozzarella cheese production.Some dairy products can be adulterated by milk admixture from different species in order to maximize profit. Certification is, thus, a way to guarantee cheese quality and to protect consumers against fraudulent producers. Bubaline breeders demand high precision technology to validate milk origin to assure that only bubaline milk is present in the composition of the manufactured product. The most common type of adulteration in the manufacture of mozzarella cheese is the addition or full replacement of bubaline milk by bovine milk. Consequently, several methods have been developed to detect milk mixture in these products.Methods based on electrophoresis and chromatography include isoelectric focusing (Moio et al., 1989), high-performance liquid chromatography (Visser et al., 1991;Veloso et al., 2002;Enne et al., 2005), nuclear magnetic resonance spectroscopy (Andriotti et al., 2000), and also hydrophobic interaction chromatography (Bramanti et al., 2003). However, these methods present limitations due to time intensive protocols and/or high costs.An alternative way to detect milk mixtures is the use of molecular markers to identify the DNA of different species (Bardin et al. 1994;Branciari et al., 2000;Rea et al., 2001;Bottero et al., 2002; Leoparelli et al., 2007). Here we describe a relatively rapid and simple method to identify admixtures of bovine milk to bubaline milk, by extracting DNA directly from Mozzarella cheese and analyzing a β-casein gene polymorphism.Samples of "pasta filata" mozzarella cheese were produced using 7 L of milk according to the methodology developed by Kuo et al. (2001). The samples ...
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