High prolificacy of sows and increased fetal survival lead to greater incidence of intrauterine crowding (IUC), which may then affect pre- and postnatal development of the progeny. The aim of the study was to assess the impact of IUC, using unilaterally hysterectomized-ovariectomized gilts (UHO), on organ and muscle development of their progeny at birth. In the study, 7 UHO and 7 intact control (Con) Swiss Large White gilts were used. At farrowing, if available, 3 male and 3 female progeny with a low (>0.8 and <1.2 kg), medium (>1.2 and <1.4 kg), and high (>1.6 kg) birth weight (BtW) were killed. Internal organs and brain were weighed, and semitendinosus (STN), psoas major (PM), and rhomboideus (RH) muscles were collected. Histological analyses were performed in PM, RH, and STN (dark and light portion) using myofibrillar ATPase staining after preincubation at pH 10.3. Myosin heavy chain (MyHC) polymorphism was determined in the PM using SDS-PAGE gel electrophoresis. Despite that only one-half of the uterine space was available, litter size was smaller (P < 0.01) only by 35% in UHO compared with Con gilts. However, UHO progeny tended (P = 0.06) to be lighter than Con progeny. The average BtW of the selected piglets did not differ (P = 0.17) between the 2 sow groups, whereas PM and kidneys tended to be lighter (P < 0.07) in UHO than in Con progeny. Compared with Con progeny, the PM and the STN(dark) of UHO progeny had fewer (P ≤ 0.05) secondary and total myofibers as well as fewer (P = 0.10) primary myofibers in the PM. In the RH, the secondary-to-primary myofiber ratio was smaller (P < 0.01) in UHO than in Con progeny, whereas the total number of myofibers did not (P = 0.96) differ. The relative abundance of fetal MyHC was less (P = 0.02) and that of type I MyHC tended (P = 0.09) to be greater in UHO than in Con offspring. With increasing BtW, organ and brain weights increased (P < 0.01). Muscle cross-sectional area and total number of myofibers in the light portion of the STN were greater (P < 0.05) in high and medium than in low piglets. In conclusion, IUC reduced hyperplasia of secondary and total myofibers in the STN(dark) and PM. These effects were independent of the BtW and sex.

There are indications that intrauterine crowding may cause intrauterine growth retardation with the possibility of an impaired myofiber hyperplasia. The aim of the study was to confirm this by generating large differences in uterine space using sows that were unilaterally hysterectomized-ovariectomized (HO; crowded) or unilaterally oviduct ligated (OL; non-crowded). In the study, seven HO and seven OL Swiss Large White third parity sows were used. At farrowing, litter size and litter birth weight were determined. Subsequently, within each litter two male and two female progenies each with the respectively lowest (L) and highest (H) birth weight were sacrificed. Internal organs and brain were weighed, and longissimus (LM) and semitendinosus muscle (SM) samples were collected. Histological analyses were performed in both muscles using mATPase staining after preincubation at pH 4.3 and 10.2. Myosin heavy chain (MyHC) polymorphism was determined in the LM by means of SDS-PAGE. The number of piglets born alive was similar in both sow groups, but litter size expressed per uterine horn was lower (P , 0.05) in OL than HO sows. Consequently, OL progeny were markedly heavier (P , 0.01). Regardless of gender, the organs, the brain and the SM were heavier (P , 0.001) in OL and H compared with HO and L offspring, respectively. Compared with HO pigs, the SM of OL offspring tended (P , 0.1) to have more myofibers, which were of larger (P , 0.05) size. However, myofiber density appeared to be lower (P , 0.1) in the SM of OL than HO pigs. The impact of birth weight on myofiber characteristics was limited to the lower (P , 0.05) myofiber density in the SM and the larger (P , 0.01) myofiber size in the light portion of the SM of H than L offspring, whereas myofiber hyperplasia did not differ between birth weight categories. The SM, but not the LM, of male offspring had a greater (P , 0.05) myofiber density. This did not affect total SM myofiber number. The relative abundance of fetal and type I MyHC in the LM was lower (P , 0.05) and that of type II MyHC was greater (P , 0.001) in OL than HO pigs. The current data suggest that regardless of birth weight and gender, in the LM and SM of individuals born from a crowded environment, not only hyperplasia but also hypertrophy of myofibers is impaired and their maturity seems delayed.

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Offspring born from normal litter size (10 to 15 piglets) but classified as having lower than average birth weight (average of the sow herd used: 1.46 6 0.2 kg; mean 6 s.d.) carry at birth negative phenotypic traits normally associated with intrauterine growth restriction, such as brain-sparing and impaired myofiber hyperplasia. The objective of the study was to assess long-term effects of intrauterine crowding by comparing postnatal performance, carcass characteristics and pork quality of offspring born from litters with higher (.1.7 kg) or lower (,1.3 kg) than average litter birth weight. From a population of multiparous Swiss Large White sows (parity 2 to 6), 16 litters with high (H 5 1.75 kg) or low (L 5 1.26 kg) average litter birth weight were selected. At farrowing, two female pigs and two castrated pigs were chosen from each litter: from the H-litters those with the intermediate (H I 5 1.79 kg) and lowest (H L 5 1.40 kg) birth weight, and from L-litters those with the highest (L H 5 1.49 kg) and intermediate (L I 5 1.26 kg) birth weight. Average birth weight of the selected H I and L I piglets differed ( P , 0.05), whereas birth weight of the H L -and L H -piglets were similar ( P . 0.05). These pigs were fattened in group pen and slaughtered at 165 days of age. Pre-weaning performance of the litters and growth performance, carcass and meat quality traits of the selected pigs were assessed. Number of stillborn and pig mortality were greater ( P , 0.05) in L-than in H-litters. Consequently, fewer ( P , 0.05) piglets were weaned and average litter weaning weight decreased by 38% ( P , 0.05). The selected pigs of the L-litters displayed catch-up growth during the starter and grower-finisher periods, leading to similar ( P . 0.05) slaughter weight at 165 days of age. However, H L -gilts were more feed efficient and had leaner carcasses than H I -, L H -and L I -pigs (birth weight class 3 gender interaction P , 0.05). Meat quality traits were mostly similar between groups. The marked between-litter birth weight variation observed in normal size litters had therefore no evident negative impact on growth potential and quality of pigs from the lower birth weight group.

BackgroundIntra-uterine crowding (IUC) observed in hyperprolific sows impairs myofiber hyperplasia and overall fetal growth. Arginine supplementation (ARG) in gestation diets has been shown to positively affect litter and muscle development. The study objective was to assess whether the effect of ARG on offspring characteristics, with special emphasis on myofiber hyperplasia, differs under IUC conditions from these responses, because in that situation growth retardation is particularly prevalent due to reduced fetal nutrient supply. Unilateral oviduct ligation (OL) was used as a model for an uncrowded and hyperprolificacy (IN) as a model for a crowded intra-uterine environment.MethodsFive OL and five IN sows were fed a diet supplemented daily with either 43 g l-alanine (Ctrl) or 25 g l-arginine from d 14 to 28 of gestation in a cross-over design (two periods: 5th and 6th parity). At farrowing, two male and two female offspring, respectively, with a low and intermediate birth weight (BtW) were selected. After euthanization, the Semitendinosus muscle (STM) was removed and weighed, and the light and dark portions (STMd and STMl) were prepared for myofiber histochemistry using ATPase staining and the entire STM for gene expression analysis of myogenesis-related genes using RT-qPCR. In addition, various organs were removed and weighed. Data were analyzed using the MIXED model in SYSTAT.ResultsNo effect of either IUC or dietary treatment was found in litter characteristics. Offspring of ARG sows displayed a greater muscle area in STM (P < 0.01) as a result of the greater myofiber hyperplasia (P < 0.01). The increase was more distinct in the STMl (P < 0.05) than in the STMd (P = 0.131). Offspring of OL sows were heavier at birth (P < 0.01), had a heavier STM (P < 0.05), liver (P < 0.01) and kidney (P < 0.05), but when expressed relative to birth weight, these differences were absent. In addition, IUC had an effect (P < 0.05) on the expression of one of the myogenesis-related genes investigated.ConclusionsIndependent from the extent of IUC, ARG improved BtW, muscle and organ weights and myofiber hyperplasia in offspring.

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El artículo aborda tres cuestiones fundamentales que intentan dar cuenta de los complejos e intrincados caminos por los que transcurre el desarrollo de aprendizaje. Para ello, en primer momento buscará establecer las relaciones epistemológicas entre formación y experiencia, que ofrezcan claves para repensar la manera en que estos procesos atraviesan el curso de la existencia. Seguidamente, encontrará ofrecer algunos significados del viaje como posibilidad de transformación personal y como condición indispensable para confrontar y profundizar los contenidos privados de la experiencia. Finalmente, ve en este proceso un recurso educativo imprescindible para intentar dibujar los vínculos entre culturas.