Global warming has been affecting animal husbandry and farming production worldwide via changes in organisms and their habitats. In the tropics, these conditions are adverse for agriculture and animal production in some areas, due to high temperatures and relative humidity, affecting competitiveness related to economic activities. These environments have deteriorated livestock production, due to periods of drought, reduction in forage quality and heat stress, eliciting negative effects on reproduction, weight gain, and reduced meat and milk production. However, the use of animals adapted to tropics such as breeds derived from subspecies Bos primigenius indicus and native breeds from tropical countries or their crossings, is an alternative to improve production under high-temperature conditions. Therefore, physiological adaptation including gene expression induced by heat stress have been studied to understand the response of animals and to improve cross-breeding between cattle breeds to maintain high productivity in adverse weather conditions. Heat stress has been associated with lower reproductive performance in cows, due to the impact on blastocyst production, decreased implantation and increased embryonic death. Thus, for decades, in vitro fertilization and embryo transfer techniques have focused on studying the optimal conditions for production of high-quality embryos to transfer. The aim of this review is to discuss the effects of heat stress in bovine embryos, and their physiological and genetic modulation, focusing on the genes that are related with major adaptability to heat stress conditions and their relationship with different embryonic stages.

Salmonellosis is a common infectious disease in humans caused by Salmonella spp., which in recent years has shown an increase in its incidence, with products of avian origin being a common source of transmission. To present a successful infective cycle, there are molecular mechanisms such as virulence factors that provide characteristics that facilitate survival, colonization, and damage to the host. According to this, the study aims to characterize the virulence factors of Salmonella spp. strains isolated from broilers (n = 39) and humans (n = 10). The presence of 24 virulence genes was evaluated using end‐point PCR. All the strains of Salmonella spp. isolated from broiler chickens revealed presence of 7/24 (29, 16%) virulence genes (lpfA, csgA, sitC, sipB, sopB, sopE, and sivH). Regarding the strains isolated from cases of gastroenteritis in humans, all strains contained (14/24, 58, 33%) virulence genes (lpfA, csgA, pagC, msgA, spiA, sitC, iroN, sipB, orgA, hilA, sopB, sifA, avrA, and sivH). In summary, the presence of virulence genes in different strains of Salmonella isolated from broilers and humans could be described as bacteria with potential pathogenicity due to the type and number of virulence genes detected. These findings are beneficial for the pathogenic monitoring of Salmonella in Colombia.

Real-time PCR is widely used to study the relative abundance of mRNA due to its specificity, sensitivity, and repeatability quantification. However, relative quantification requires a reference gene, which should be stable in its expression, showing lower variation by experimental conditions or tissues. The aim of this study was to evaluate the stability of the expression of five commonly used reference genes (actb, ywhaz, b2m, sdha, and 18s rRNA) at different physiological stages (alert and emergency) in three different cattle breeds. In this study, five genes (actb, ywhaz, b2m, sdha, and 18s rRNA) were selected as candidate reference genes for expression studies in the whole blood from three cattle breeds (Romosinuano, Gyr, and Brahman) under heat stress conditions. The transcription stability of the candidate reference genes was evaluated using geNorm and NormFinder. The results showed that actb, 18SrRNA, and b2m expression were the most stable reference genes for whole blood of Gyr and Brahman breeds under two states of livestock weather safety (alert and emergency). Meanwhile, actb, b2m, and ywhaz were the most stable reference genes for the Romosinuano breed.

Salmonella spp. is one of the leading causes of foodborne bacterial infections, with major impacts on public health and healthcare system. Salmonella is commonly transmitted via the fecal‐to‐oral route, and food contaminated with the bacteria (e.g., poultry products) is considered a common source of infection, being a potential risk for public health. The study aims to characterize the antimicrobial resistance‐ and virulence‐associated genes in Salmonella isolates recovered from chicken marketed carcasses (n = 20). The presence of 14 antimicrobial and 23 virulence genes was evaluated using end‐point PCR. The antimicrobial genes were detected in the following proportion among the isolates: bla_TEM 100%, dfrA1 and bla_CMY2 90% (n = 18), aadA1 75% (n = 15), sul1 and sul2 50% (n = 10), floR 45% (n = 9), qnrD 20% (n = 4), and aadA2 15% (n = 3). catA, sul3, qnrS, and aac(6′)-Ib genes were absent in all isolates. Regarding virulence‐associated genes, all Salmonella strains contain invA, fimA, avrA, msgA, sopB, and sopE. The cdtB gene was present in 95% (n = 19) of isolates, whereas spvC and spvB were present in 55% (n = 11). Other virulence genes such as spiC, lpfC, lpfA, and csgA were present in 90% (n = 18) of strains. The presence of antimicrobial and virulence genes in several Salmonella strains in chicken meat suggests the potential pathogenicity of the strains, which is relevant given the possibility of cross‐contamination which represents a significant threat to public health.

Aim: The aim of this study was the genotypic characterization of the strains of Salmonella spp. isolated from broiler chickens and humans with gastroenteritis from two regions of Colombia, by BOXA1R-polymerase chain reaction (PCR) and random amplification of polymorphic DNA (RAPD)-PCR methods. Materials and Methods: Forty-nine strains of Salmonella were assessed, 15 from poultry farms in Santander region, and 34 from Tolima region isolated from poultry farms (n=24) and the stool samples of people with gastroenteritis (n=10). BOXA1R primers were selected for repetitive element-based PCR (REP-PCR) and five arbitrary primers, namely, GTG 5, OPB 15, OPP 16, OPS 11, and P 1254 were used for RAPD-PCR to generate DNA fingerprints from the isolates. Fingerprint data from each typing method were under composite analysis and the diversity of the data was analyzed by grouping (clustering). The dendrogram was generated by the unweighted group method with analysis of the arithmetic mean based on the Dice similarity coefficient. In addition, Simpson's index was evaluated to discriminate the power of the methods. Results: OPP 16 primer and composite analysis proved to be superior compared to other REP-PCR typing methods. The best discriminatory index was observed when GTG 5 (0.92) and OPP 16 (0.85) primers were used alone or combined with RAPD-PCR and BOX-PCR (0.99). Conclusion: This study indicated that OPP 16 and GTG 5 primers provide suitable molecular typing results for the discrimination of the genetic relationship among Salmonella spp. isolates and may be useful for epidemiological studies.