Cambios nutrimentales en el lechón y desarrollo morfofisiológico de su aparato digestivo / Nutritional changes in piglets and morphophysiologic development of their digestive tract

This review shows the development of the pig gastrointestinal tract (GIT) since intrauterine life. Immediately after birth, the GIT begins another important stage in its ontogenesis, which ensures for the piglets to have access to the protective substances in colostrum and milk nutrients. Another important stage in the development of the GIT begins after weaning. In general, life changes in the days around weaning leading to a decrease in feed intake, which, in turn, leads to nutritional stress that results in the atrophy of intestinal villi, diminishing the piglets ability to digest and absorb nutrients necessary for growth. The small intestine loses weight due to a net loss of intestinal mucosa. The decrease in voluntary feed intake also produces a reduction in both pancreatic enzyme activity, due to lack of substrate, and brush border enzyme activity, due to physical loss of enterocytes in the small intestine and to lack of substrate. Once the animals begin to eat solid food the organism goes through an adaptation process to all the adverse factors previously mentioned and GIT growth and digestive function are restored. During this process, the amount of feed provided to the newly weaned piglet and the ingredients used play an important role in GIT maturation.

En esta revisión se muestra el desarrollo que tiene el tracto gastrointestinal (TGI) desde la vida intrauterina. Inmediatamente después del nacimiento el TGI inicia otra fase importante de su ontogénesis, la cual garantiza el acceso de los lechones a sustancias protectoras del calostro y a los nutrimentos de la leche. Otra etapa de importancia en el desarrollo del TGI se da después del destete, en general, en los días alrededor del mismo se presentan cambios en la vida del lechón los cuales conducen a una disminución en el consumo de alimento por la confluencia de una serie de factores que llevan a un estrés nutricional, y tiene como consecuencia la atrofia en las vellosidades intestinales, disminuyendo la capacidad del lechón para digerir y absorber los nutrimentos necesarios para su buen crecimiento. El peso del intestino delgado se ve afectado debido a una pérdida neta de mucosa intestinal. La disminución en el consumo voluntario también produce una reducción en la actividad de las enzimas pancreáticas, por la falta del sustrato necesario para su acción, y de las enzimas de borde en cepillo, en primer lugar por una pérdida física de enterocitos a nivel del intestino delgado y, en segundo lugar, por una ausencia de sustrato. Una vez que los animales empiezan a consumir alimento sólido, el organismo pasa por un proceso de adaptación a todos los factores adversos antes mencionados y los animales comienzan a recuperar el crecimiento del TGI y con ello sus funciones digestivas. En este proceso, la cantidad de alimento que se proporciona, así como las materias primas que lo componen, tienen un papel importante en la maduración del TGI de los lechones recién destetados.

Xylanolytic enzymes production by Aspergillus niger GS1 from solid-state fermentation on corn stover and their effect on ruminal digestibility

Hemicellulosic agricultural by-products such as corn stover (CS) are highly available materials which represent an opportunity to develop value added products. Native Aspergillus niger GS1 was used for solid-state fermentation (SSF) on alkali pre-treated CS (ACS) aimed to optimize xylanolytic enzymes production, and their effect on in vitro ruminal and true digestibility of ACS. Enzyme production was empirically modelled using a fractional factorial design 2(9-5), and the resulting significant factors were glucose, yeast extract and two mineral salts, which were arranged in a Draper-Lin optimization design at two levels. Predicted optimum xylanolytic activity of 33.6 U (mg protein)-1 was achieved at 48 hrs of SSF, and was validated by confirmatory experiments. ACS was incubated with a semipurified enzymatic extract (EE) showing a xylanolytic activity of 1600 U kg-1 dry ACS for 12 hrs before exposure to cow's ruminal liquid for 72 hrs, which led to 5 percent and 10 percent increase of in vitro ruminal and true digestibility, respectively. CS is a readily available by-product in different regions which after alkaline treatment and partial hydrolysis with the EE, may be advantageously used as supplement for ruminant feed.