Z. Uni

Methods for early nutrition and their potential

Several factors may limit the development and viability of late-term embryos and hatchlings: 1) The nutrient content of the egg needed for the development of tissues and nutrient reserves (glycogen, muscle, yolk) of the embryo through to hatch; 2 The ability of the gastrointestinal tract to digest utilize nutrients from an external carbohydrate and protein-rich diet; and 3) The ability of chicks and poults to rely on the residual nutrients in the yolk sac during the first few days post-hatch. These limitations are manifested by in the “chick or poult quality” phenomena. Approximately 2% to 5% of hatchlings do not survive the critical post-hatch “adjustment” period and many survivors exhibit stunted growth, inefficient feed utilization, reduced disease resistance, or poor meat yield. These limitations can be alleviated by the administration of food in the hatchery immediately post-hatch, a technology termed “Early Feeding”, or by administration of food into the amnion of late term embryo, what we define as “In Ovo Feeding”. A great potential exists in “combining” the early feeding and the in ovo feeding methods. Since the modern broiler increases its body weight by 50-fold from hatch until market age at 42 days, the first few critical days of “adjustment” represent a much greater proportion of the birds life span than in the past. Consequently, early feeding methods will have a great impact on overall growth and well-being of the bird, particularly as genetic selection for increased growth performance continues in the future.

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.

β-hydroxy-β-methylbutyrate (HMB) stimulates myogenic cell proliferation, differentiation and survival via the MAPK/ERK and PI3K/Akt pathways

Beta-hydroxy-beta-methylbutyrate (HMB), a leucine catabolite, has been shown to prevent exercise-induced protein degradation and muscle damage. We hypothesized that HMB would directly regulate muscle-cell proliferation and differentiation and would attenuate apoptosis, the latter presumably underlying satellite-cell depletion during muscle degradation or atrophy. Adding various concentrations of HMB to serum-starved myoblasts induced cell proliferation and MyoD expression as well as the phosphorylation of MAPK/ERK. HMB induced differentiation-specific markers, increased IGF-I mRNA levels and accelerated cell fusion. Its inhibition of serum-starvation- or staurosporine-induced apoptosis was reflected by less apoptotic cells, reduced BAX expression and increased levels of Bcl-2 and Bcl-X. Annexin V staining and flow cytometry analysis showed reduced staurosporine-induced apoptosis in human myoblasts in response to HMB. HMB enhanced the association of the p85 subunit of PI3K with tyrosine-phosphorylated proteins. HMB elevated Akt phosphorylation on Thr308 and Ser473 and this was inhibited by Wortmannin, suggesting that HMB acts via Class I PI3K. Blocking of the PI3K/Akt pathway with specific inhibitors revealed its requirement in mediating the promotive effects of HMB on muscle cell differentiation and fusion. These direct effects of HMB on myoblast differentiation and survival resembling those of IGF-I, at least in culture, suggest its positive influence in preventing muscle wasting.

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.

Routes of yolk utilisation in the newly‐hatched chick

1. This study was conducted to study the routes by which yolk is utilised in the chick during the initial posthatch phase. 2. Transfer from yolk to blood was examined by injecting, in the form of labelled compounds, oleic acid, triolein, inulin and dextran into the yolk; movement from yolk to blood was observed up to 72 h posthatch. 3. Transport of these molecules from blood to yolk was also observed by injecting them into the circulation and determining label in yolk. The yolk sac membrane was permcable in both directions for all labelled materials tested. 4. In the newly-hatched chick, blue dextran injected into the yolk sac could be seen moving in pulses into the intestine at irregular intervals. Transport of labelled materials from the yolk sac into the intestine was observed up to 72 h after hatching, and marker was found in the proximal small intestine and gizzard. The yolk stalk provided a pathway for transport to the intestine until lymphoid cells began to accumulate, with passage becoming partially occluded at 72 h posthatch. 5. Yolk utilisation was more rapid in fed than in fasted birds suggesting that the transport of yolk through the intestine could be increased by the greater intestinal activity found in fed chicks.

Important metabolic pathways in poultry embryos prior to hatch

Growth performance and meat yield of commercial broilers and turkeys has improved linearly each year during the past four decades (Havenstein et al., 2003b; Havenstein et al., 2003a; Havenstein et al., 2007), and this trend is likely to continue in the future as new technologies in genetics, biotechnology and developmental biology are adopted by the poultry industry. As the time it takes meat birds to achieve market size decreases, the period of embryonic development becomes a greater proportion of a birds productive life. Therefore, incubation and embryonic development towards hatch is of greater relative importance to the successful rearing of meat poultry than ever before (Hulet 2007; Foye et al., 2007b). Consequently, anything that supports or limits growth and development during the incubation period will have a marked effect on overall growth performance and health of modern strains of meat poultry. Many poultry researchers now realize that future gains in genetic and production potential of poultry will come from advancements made during the incubation period and embryogenesis (Elibol et al., 2002; Peebles et al., 2005; Christensen et al., 2007; Collin et al., 2007; Leksrisompong et al., 2007). The urgent need to explore and understand the biology of incubation has been emphasised by several symposia: two held at the annual conference of the U.S. Poultry Science Society (July 2006-Edmonton, Alberta, Canada “Managing the embryo for performance”, and July 2007-San Antonio, TX Informal Nutrition Meeting “The impact of imprinting on biological and economical performance in animals”), and one held by the European Federation of World Poultry Science Society (October 2007-Berlin, Germany “Fundamental physiology and perinatal development in poultry), which were specifically devoted to demonstrating the importance of the embryonic period on poultry performance. This review will summarise the metabolic events and pathways in four of the most active tissues of embryos during the period just prior to hatch, and the hormonal control that coordinates the marked changes as the embryo prepares for its post-hatch life.

Activity of intestinal mucosal brush border membrane enzymes in relation to the feeding habits of three aquaculture fish species

Abstract The activity of intestinal mucosal enzymes in various parts of the intestine and the pyloric caeca of adult fish from three different species was examined. Selection of the fish for the study was based on their aquacultural importance and the different feeding habits they exhibit: carnivorous hybrid striped bass ( Morone saxatilis × Morone chrysops ); omnivorous tilapia ( Oreochromis niloticus × Oreochromis aureus ) hybrids and herbivorous silver carp ( Hypophthalmichthys molitrix ). The results show marked differences among the different fish species corresponding to their feeding habits. Sucrase and maltase activities were found to be highest in the midgut of all species compared to other regions of the intestines. The lowest activity of γ-glutamyltranspeptidase (γ-GT) was found in the foregut of all species compared to other regions of the intestines. Alkaline phosphatase and γ-GT activities in the pyloric caeca of tilapia and bass were similar to those found in the intestines, indicating that these organs are an extension of the intestines where active protein degradation takes place.

Development of the small intestine in heavy and light strain chicks before and after hatching

1. Intestinal development was examined in Arbor Acres and Lohmann chicks from one week before hatching until one week after. Changes in morphology and concentrations of DNA, RNA and protein in the duodenal tissue were determined. 2. Villus height and perimeter increased 9 to 11 fold from day 14 of incubation until 7 d after hatching. Arbor Acres chicks had values which were consistently higher than Lohmann chicks. 3. DNA concentration of duodenal tissue increased with age in parallel to the increase in the number of enterocytes per villus. In the pre-hatch period tissue activity as indicated by RNA/DNA, and ribosomal capacity as shown by the RNA/protein ratios, were high for both strains; values for Arbor Acres embryos and chicks were greater than for Lohmann. 4. DNA concentrations, RNA/DNA, RNA/protein and protein/DNA ratios correlate with morphological measurements and can be used as additional criteria for evaluating development in chick intestine. 5. In the last week of incubation and immediately after hatching, intestinal growth appears to arise mainly from cellular hyperplasia and not from cellular hypertrophy. Intestinal development patterns were similar for both strains but growth was more rapid in Arbor Acres chicks.

Effect of in ovo feeding and its interaction with timing of first feed on glycogen reserves, muscle growth, and body weight

Chicks are commonly fasted for the first 36 to 72 h posthatch because of the logistics of commercial production. Fasting for 48 to 72 h posthatch results in retarded BW, delayed intestinal development, and lower pectoral muscle weight. This study is focused on the first 36 h of fasting and its interaction with feeding before hatch. Four treatment groups, differing in time of first feed, 6 h [early feeding (EF)] or 36 h [standard feeding procedure (SP)] posthatch, with or without in ovo feeding (IOF) with dextrin and β-hydroxy-β-methylbutyrate-calcium salt in a saline solution, were examined for glycogen status in the liver and pectoral muscle, myogenic cell proliferation, and myofiber diameter in embryos and chickens on various days posthatch. In addition, chicken BW, ADG, pectoral muscle weight, and pectoral muscle percentage of BW until 35 d of age were recorded. Results showed that delaying the first feed for 36 h posthatch (SP group) led to an irreversibly reduced growth rate compared with the EF group. However, IOF affected the growth of chickens in the SP group, whereas the control embryos had depleted glycogen reserves in the liver; IOF-treated embryos had elevated hepatic glycogen contents on embryonic day (E) 19, E20, and the day of hatch. In addition, on d 2 posthatch, although hatchlings in the SP group showed the predicted low levels of glycogen in their livers, birds in the EF group exhibited more than 30-fold and 3-fold increases in liver and muscle glycogen, respectively. In ovo-fed birds in the SP group also exhibited higher glycogen reserves, BW, pectoral muscle weight, and BW gain than control birds in the SP group. In ovo feeding had an immediate effect on promoting myoblast proliferation on E19, whereas on d 3 posthatch, the effect was pronounced only in the EF groups. On d 5, although myoblast proliferation in all groups declined, it remained higher in both IOF groups. These effects were expressed on d 3 and 35 by myofiber diameter. Together, IOF had a long-term supportive effect on BW and posthatch muscle growth when first feed was delayed by 36 h.