D. Sklan

Establishment of immune competence in the avian GALT during the immediate post-hatch period.

Population dynamics of intestinal lymphocytes and the temporal development of lymphocyte functions were studied in broiler chicks during the first 2 weeks post-hatch. This period is of major immunological importance as the chick is immediately exposed to environmental antigens and pathogens. We show that the gut-associated lymphoid tissue contains functionally immature T and B lymphocytes at hatch, and that function is attained during the first 2 weeks of life as demonstrated by mRNA expression of both ChIL-2 and ChIFNgamma. Functional maturation occurred in two stages: the first-during the first week post-hatch, and the second during the second week, which was also accompanied by an increase in lymphocyte population, as determined by expression of antigen receptor genes. Evidence is presented to show that in the intestinal milieu cellular immune responses mature earlier, and are a prerequisite for humoral responses. Hence, the lack of antibody response in young chicks is primarily due to immaturity of T lymphocytes.

Development of the digestive tract of poultry

Hatching birds which have been dependent on the yolk for their energy supply during much of the embryonic period must undergo a rapid transition to utilising carbohydrate rich exogenous feed. This change is accompanied by the preferential growth of the small intestine and activation of digestive enzymes and absorption pathways. The ontogeny of these processes is described and includes the intense development immediately after hatching. The effect of delayed access to feed on intestinal development is also discussed.

Comparison of energy and protein efficiency among three fish species gilthead sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax) and white grouper (Epinephelus aeneus): energy expenditure for protein and lipid deposition

This study was carried out in order to compare the daily energy needs in three fish species: gilthead sea bream, European sea bass and white grouper. The requirements for maintenance and growth and the efficiencies for protein and lipid deposition were estimated. The energy requirement for maintenance is proportional to the metabolic body weight in the form of a x BW(kg) b , whereas the requirement for growth is dependent on the amount and the composition of the added tissue. The exponent b of the metabolic body weight was determined by energy loss during starvation using fish ranging from 1 to 400 g. Similar values of 0.82, 0.80 and 0.79 were determined for the three species. The efficiencies of digestible energy for growth were determined by feeding fish at increasing levels, starting at zero and up to close to maximum voluntary feed intake. Digestible energy intake and the subsequent energy gain partitioned into protein and lipid gain were measured by comparative slaughter technique. Plotting the relationships (x=DE intake, y=energy gain) for each fish species, the resulting equations proved to be linear throughout, defining the efficiency of utilization of energy by the value of the slope. As the energy gain consists of protein, as well as lipid energy, a multiple regression was employed to determine the energy coefficients for protein and lipid deposition simultaneously with the maintenance requirement: DE intake (kJ) = DE maint + 1/k p x protein energy (kJ) + 1/k L x lipid energy (kJ). The calculated energy cost for protein gain (1/k P ) ranged from 1.79 to 1.90 kJ per kJ protein energy deposited. Energy cost (1/k L ) for lipid gain was lower than the energy cost for protein gain and ranged from 1.10 to 1.31 kJ per kJ lipid deposited. Therefore, we conclude that utilization of energy and protein for growth does not appear to be very different across the species examined. Differences were found, however, in the magnitude and the composition of the weight gain, which ultimately determines the amount of energy and protein required.

The effect of fasting at different ages on growth and tissue dynamics in the small intestine of the young chick.

The small intestines of hatching chicks undergo rapid developmental changes in the immediate post-hatch period when the birds are making the transition from endogenous nutrient supply from yolk to dependence on exogenous feed. This transition usually only begins 48 h or more after hatching, owing to logistical considerations of production. The effects of fasting for 48 h at different times during this critical period on small intestinal development and enterocyte dynamics were examined by morphometric determinations and use of staining for proliferative-cell nuclear antigen and 5-bromo-2-deoxyuridine. The effects of fasting were specific to both time of fasting and the intestinal segment examined. Decreased development was found in the duodenum and jejunum, but was less apparent in the ileum. Fasting between 0 and 48 h decreased crypt size in the duodenum and jejunum, the number of crypts per villus, crypt proliferation, villus area and the rate of enterocyte migration. Fasting at later times resulted in smaller effects, although the jejunum appeared to be the most sensitive of the intestinal segments. Growth was correlated with the number of cells in the crypts, the number of cells along the villus and the segment surface area. The common practice whereby feed is first available to chicks more than 48 h post-hatch may depress subsequent development.

Cell proliferation in chicken intestinal epithelium occurs both in the crypt and along the villus

Abstract The location of cell proliferation and differentiation in chicken small intestinal epithelium was examined using immunostaining, measurement of DNA synthesis and brush-border enzyme activities. Chicken enterocytes were removed sequentially from the villus using a modification of the Weiser (1973) method. Alkaline phosphatase activity was relatively constant along the villus tip-crypt axis but decreased in the crypt fractions, whereas sucrase and maltase activities showed higher activity in the upper half of the villus and lower activity in the lower half of the villus and in the crypt. Immunostaining of proliferating cell nuclear antigen indicated the presence of proliferating cells both in the crypt and along the villus, including some activity in the upper portion; the crypt region exhibited a significantly higher number of proliferating cells. Labelled thymidine incorporation into cell fractions after 2 h incubation exhibited a similar pattern of proliferation, with the most active region observed in the crypt and proliferation activity decreasing along the villus. However, some activity was found in the upper half of the villus. After 17 h incubation, cells from the middle region of the villi showed greater proliferation ability than the 2 h incubation. These results indicate that, unlike mammals, chicken enterocyte proliferation is not localized only in the crypt region, and that the site of enterocyte differentiation is not precisely localized.

The effect of dietary (n-3) polyunsaturated fatty acids on growth, survival and swim bladder development in Sparus aurata larvae.

Abstract The requirement for dietary ( n −3) PUFA for growth, survival and swim bladder development in gilthead seabream, Sparus aurata , larvae was tested using rotifers with various levels of ( n −3) PUFA. Four rotifer treatments differing in their ( n −3) PUFA content (0.8, 3.2, 5.1 and 8.4 mg/g dry body weight, DBW) were prepared by feeding them combinations of various oil emulsions and dried squid (rich in both EPA (20:5 n −3) and DHA (22:6 n −3)). A fifth treatment consisted of rotifers enriched on the algae Nannochloropsis sp. Regression analyses, from the emulsion treatments, were performed on various relationships between rotifer ( n −3) PUFA levels and larval phospholipid and growth. The equations describing these correlations were then used to examine whether the same parameters in larvae fed Nannochloropsis -enriched rotifers were a result of the dietary ( n −3) PUFA levels they consumed or some other nutritional factor. The results indicate that dietary ( n −3) PUFA significantly ( P n −3) PUFA (8.4 mg/g DBW) showed a four-fold increase in growth (1263% vs. 312%) over larvae offered rotifers with the lowest levels of ( n −3) PUFA (0.8 mg/g DBW). In contrast, there was no compelling evidence that EPA and/or DHA significantly ( P Nannochloropsis treatment was strongly associated with EPA and implies that, despite other sources of nutrition in the algal media, this fatty acid determines the dietary value of these rotifers for growth in Sparus aurata larvae.

Small intestinal development in the young chick: Crypt formation and enterocyte proliferation and migration

1. Post-natch mucosal development was examined in the chick small intestinal epithelium using immunostaining with proliferating cell nuclear antigen (PCNA) and 5-bromo-2-deoxyuridine (BrdU). 2. On the day of hatching jejunal crypts were small and a single crypt per villus was observed. However, during the 108 h post-hatch crypts developed rapidly, branching and increasing in size, cell numbers and cell size. 3. Almost all epithelial cells in the small intestine of the hatching chick were proliferating, as indicated by PCNA and BrdU, while more than 80% of proliferating cells were localised in the crypts after 108 h post hatch. 4. Estimate of villus cell transit time using BrdU was only possible from 48 h post-hatch when villus transit time was 72 h in the jejunum, whereas at 336 h transit time was 96 h. 5. In the 108 h post hatch a rapid transition occurs from total jejunal epithelial cell proliferation and immature crypts to a defined proliferative zone in the crypts, with constant division and migration.

Optimization of feeding regimes for European sea bass Dicentrarchus labrax: a factorial approach

Requirements for dietary energy and protein in growing fish can be quantified using the factorial approach, which assumes that the requirement is the sum of growth and maintenance. Thus dietary intake can be calculated using the respective partial efficiencies of utilization. Growth for Dicentrarchus labrax as a function of body weight and temperature was predicted by the equation: y=0.64×BW (kg)0.587×exp0.07×T (where y=weight gain in g fish−1 day−1, BW=body weight in kg and T=temperature in °C). The composition of the gain was measured by analyzing whole fish ranging from 1 to 400 g. The energy content was dependent upon fish weight and increased from 5.4 to 10 MJ kg−1 body mass, whereas the protein content remained constant at 171 g kg−1. The comparative slaughter technique was used to determine the loss in the fish during starvation and the values amounted to 33.7 kJ BW (kg)−0.79 day−1 and 0.39 g BW (kg)−0.69 day−1 for energy and protein, respectively. The efficiencies of utilization of digestible energy (DE) and digestible protein (DP) for maintenance and growth in D. labrax were determined by feeding fish of various sizes at increasing feeding levels, from zero to maximum voluntary feed intake. DE intake and the subsequent energy gain were measured. The relationship between DE intake and energy gain was found to be linear and was independent of feed intake and body weight. The requirement for digestible energy for maintenance was calculated to be 43.6 kJ BW (kg)−0.79 day−1 and for digestible protein 0.66 g BW (kg)−0.69 day−1. The partial efficiency of utilization for growth was 0.68 and 0.52 for digestible energy and digestible protein, respectively. Using these values allows optimization of practical feeding at different growth rates for D. labrax culture.

The effect of dietary lecithin and lipase, as a function of age, on n-9 fatty acid incorporation in the tissue lipids of Sparus aurata larvae

The present study tested the effect of dietary lecithin and exogenous lipase on the incorporation of oleic acid in the tissue lipids of gilthead seabream larvae (Sparus aurata). Two of four microdiets were prepared by the addition of [14C]oleic acid as free fatty acid (FFA) to diets containing either 5% cuttlefish liver oil (CLO) or 5% soybean lecithin. Glycerol tri[1-14C]oleate was similarly incorporated in two other diets identical in lipid (4% cuttlefish liver oil, 1% soybean lecithin) and non-lipid composition but differed in that one contained a supplement of 0.05% porcine lipase. The effect of these diets was tested by following the incorporation of the label (dpm/mg larvae DBW) in the neutral and phospholipid fractions of seabream larvae at four different ages (21, 27, 32 and 45 days after hatching).A significant (p<0.05) effect of dietary lecithin on the incorporation of labelled FFA in both larval neutral and phospholipid fractions was demonstrated at all ages. This was particularly pronounced during early development (day 21) where fish fed the lecithin supplement incorporated 6.75 times more label than the diet containing [14C]oleic acid in CLO. The dietary lecithin enhancing effect diminished with age but was still significant at day 45 (2.17 times more label). In addition, the label was considerably higher in the phospholipid fraction compared to the neutral lipid, reflecting the high demand for membrane synthesis during rapid growth. Lecithin fed larvae demonstrated a higher consumption rate and efficiency of incorporation than fish consuming the cuttlefish liver oil diet, suggesting an emulsifying function for dietary phospholipid.In contrast, the supplementation with lipase showed a clear effect only in older fish where 45 day old larvae fed the lipase diet demonstrated a 3.42 times increase in radioactivity in their tissue lipids. This late lipase response may be the result of an insufficient level of dietary lecithin (M) and a short intestinal length being ineffective, in the early larval stages, in incorporating labelled free fatty acid from dietary glycerol tri[1-14C]oleate breakdown.

Yolk utilisation in the newly hatched poult

1. Routes of yolk utilisation and some aspects of intestinal digestion and absorption were determined in the hatching poult and compared to the chick. 2. Transfer from yolk to blood was observed pre-hatch and up to 72 h post-hatch. From hatch the transport pattern was similar to the chick. 3. Transport from the yolk sac into the intestine via the yolk stalk was observed up to 120 h after hatch. Secretion was initially to the proximal ileum and reflux occurred, transporting contents to the proximal small intestine and gizzard. Antiperistaltic movements increased after hatch and secretion continued for longer post-hatch than in the chick. 4. In situ uptake of glucose per unit of duodenum did not change with age, whereas uptake of methionine and oleic acid decreased with age. In contrast, in the chick glucose and methionine uptake capacity increased slightly between hatch and 7 d. 5. The lipid class distribution of intestinal contents resembled that of yolk close to hatch, however, some lipolysis was observed in the duodenum. With age the proportion of free fatty acids increased rapidly, first in the duodenum then in the ileum and finally in the caecum. Yolk in the distal small intestine close to hatch did not appear to be utilised.