A genome-wide linkage analysis for reproductive traits in F2 Large White × Meishan cross gilts

Female reproductive performance traits in pigs have low heritabilities thus limiting improvement through traditional selective breeding programmes. However, there is substantial genetic variation found between pig breeds with the Chinese Meishan being one of the most prolific pig breeds known. In this study, three cohorts of Large White × Meishan F(2) cross-bred pigs were analysed to identify quantitative trait loci (QTL) with effects on reproductive traits, including ovulation rate, teat number, litter size, total born alive and prenatal survival. A total of 307 individuals were genotyped for 174 genetic markers across the genome. The genome-wide analysis of the trait-recorded F(2) gilts in their first parity/litter revealed one QTL for teat number significant at the genome level and a total of 12 QTL, which are significant at the chromosome-wide level, for: litter size (three QTL), total born alive (two QTL), ovulation rate (four QTL), prenatal survival (one QTL) and teat number (two QTL). Further support for eight of these QTL is provided by results from other studies. Four of these 12 QTL were mapped for the first time in this study: on SSC15 for ovulation rate and on SSC18 for teat number, ovulation rate and litter size

Managing the litter from hyperprolific sows

The practice of breeding from hyperprolific sows producing very large litters is becoming a normal occurrence in commercial pig production. However, the relationship between large litter size and piglet mortality is well established. In order to minimise the health and welfare challenges associated with large litters and maximise the economic potential of increased numbers born, various genetic, nutritional and management interventions are required. This chapter outlines the different challenges associated with hyperprolificacy before focusing on management strategies adopted over the farrowing and lactation period to tackle those challenges. These include early interventions to assist vulnerable piglets, such as those suffering from intrauterine growth retardation, as well as strategies involving whole litter interventions (e.g. use of nurse sows, artificial rearing) to help rear supernumerary piglets

Differential expression of genes in follicular cells of swines

The main purpose of the present study was to identify for candidate genes related to ovulation in swines. To do so, it was investigated in ovarian follicular cells through quantitative real-time PCR the differential expression of the following genes: steroidogenic acute regulator (STAR), GATA-binding protein 4 (GATA), prostaglandin F2α (PGF2α), progesterone receptor (P4R), follicle-stimulating hormone receptor (FSHR), and cytochrome P450 aromatase (CYP19). These genes encode hormone receptors (FSHR and P4R), hormone (PGF2α), steroidogenic proteins (STAR and CYP19) and transcription factor (GATA). Folicular cells were collected from sows with high and low number of piglets/litters during the follicular phase of the estrus cycle. There was difference in transcript abundance among low and high prolific sows for the STAR, GATA, PGF2α, P4R and CYP19 genes. For the FSHR gene, the fold change was not considered to be significantly different. Because in the present study only the transcript level of the above mentioned genes was analyzed, no inference can be made regarded to protein translation or activity. Therefore, gene sequence trials and other functional studies will be necessary to complement the present results, allowing a better understanding on biological complexity of these genes and their use as markers for prolificity in swines.O objetivo neste trabalho foi identificar genes candidatos relacionados à ovulação em suínos. Para tanto, investigou-se a expressão diferencial dos genes STAR (steroidogenic acute regulator), GATA (GATA-binding protein 4), PGF2α (prostaglandin F2α), P4R (progesterone receptor), FSHR (follicle-stimulating hormone receptor) e CYP19 (cytochrome P450 aromatase) em células foliculares ovarianas por meio de reação em cadeia da polimerase em tempo real (qRT-PCR) quantitativo em tempo real. Esses genes codificam para receptores hormonais (FSHR e P4R) hormônio (PGF2α), proteínas esteroidogênicas (STAR e CYP19) e fator de transcrição (GATA). As células foliculares foram coletadas durante a fase folicular do ciclo estral de porcas com alto e baixo número de leitões/leitegada. Houve diferença na abundância de transcritos entre porcas com alta e baixa prolificidade para os genes STAR, GATA, PGF2α, P4R and CYP19. Para o gene do FSHR, a alteração na abundância dos transcritos não foi significativamente diferente. Considerando que foi analisado somente o nível de transcrição desses genes mencionados, não se pode fazer inferências com relação à tradução ou atividade proteica. Portanto, ensaios de sequenciamento gênico e outras análises funcionais serão necessários para complementar esses achados e possibilitar melhor entendimento da complexidade biológica desses genes e seu uso como marcadores para prolificidade em suínos