Changes in yolk sac membrane absorptive area and fat digestion during chick embryonic development.

The capacity of yolk sac (YS) utilization by the chick embryo may be affected by structural changes in the YS membrane (YSM) and by the mechanisms within its cells for digestion, absorption, and transfer of nutrients. Two experiments were conducted to examine structural and digestive changes in the YS of the broiler chick embryo; weights of embryo, YS, and YSM, as well as the total area of the YSM and the absorptive area of the YSM, were measured between embryonic day (E) 5 and E21. In addition, fat content, lipase activity, and bile acid concentration in the YSM and YS contents (YSC) were measured between E11 and E21. Results showed that YSM weight increased from 0.19 g on E5 to 6.46 g on E15, and decreased by 3.74 g between E17 and E21. The absorptive YSM area increased from 536 mm² on E5 (51% of total YSM area) to 6,370 mm² (86% of total area) on E17, and decreased to 4,439 mm(2) on E21 (85% of total area). The smaller YSM area between E17 and E21 did not decrease the rate of YS fat utilization, which could suggest that YSM mechanisms for fat absorption, digestion, and secretion increased during that period. Total YSM lipase activity relative to fat content (units per g of YSM fat) increased from approximately 1,000 units on E15 to 1,500 units on E21. The detection of lipase in the YSM lends support to the hypothesis that YS lipids are hydrolyzed in the lipolysosomes of the YSM. The current study also confirmed for the first time that bile acids are present in the YS, with levels that ranged from 0.61 to 1.06 µmol/g in the YSM, and may suggest that bile is synthesized in the YSM of the chick embryo. Results of the current study contribute to our understanding of the developmental changes that affect YS functionality and could give insight into the coordination between the embryo's demands and YSM morphological, absorptive, digestive, and secretive changes.

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 ß-hydroxy-ß-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.

A school-based program of physical activity may prevent obesity.

An organized intervention program in pre-pubertal children based on increased physical education and activity together with nutritional advice to the children and their families may prevent obesity. Children aged 9 to 11 received double hours of weekly physical education lessons and additional nutritional advice for 2 years. They were compared with a similar group who received standard physical education lessons only. A total of 82 study and 26 control children completed the 2 years of the project. Boys in the control group gained significantly more weight than the corresponding study group (8.4 kg vs 3.2 kg, respectively (P<0.016)), control delta body mass index (BMI) 1.02 vs study 0.44 (P<0.012). There was no significant change in the weight or BMI in the girls. We conclude that the prevention of obesity may be attained by similar programs. Hormonal effects and compliance at this age may be responsible for the sex differences in this study.

Yolk sac nutrient composition and fat uptake in late-term embryos in eggs from young and old broiler breeder hens.

In the present study, we examined the composition, amount, and uptake of yolk nutrients [fat, protein, water, and carbohydrates (COH)] during incubation of eggs from 30- and 50-wk-old broiler breeder hens. Eggs were sampled at embryonic d 0 (fresh eggs), 13, 15, 17, 19, and 21 (hatch). Egg, embryo, yolk content, and yolk sac membrane were weighed, and the yolk sac (YS; i.e., yolk content + yolk sac membrane) composition was analyzed. From 30 to 50 wk of age, the albumen weight increased by 13.3%, whereas the yolk increased by more than 40%. The proportion of fat in the fresh yolk of the 30-wk-old group was 23.8% compared with 27.4% in the 50-wk-old group, whereas the proportion of protein was 17.9% compared with 15.6%, respectively. During incubation, results indicated that water and protein infiltrated from other egg compartments to the YS. Accordingly, the calculated change in the content of water and protein between fresh yolk and sampled YS does not represent the true uptake of these components from the YS to the embryo, and only fat uptake from the YS can be accurately estimated. By embryonic d 15, fat uptake relative to embryo weight was lower in the 30-wk-old group than in the 50-wk-old group. However, by embryonic d 21, embryos of both groups reached similar relative fat uptake, suggesting that to hatch, embryos must attain a certain amount of fat as a source of energy for the hatching process. The amount of COH in the YS increased similarly during incubation in eggs from hens of both ages, reaching a peak at embryonic d 19, suggesting COH synthesis in the YS. At hatch, the amount of protein, water, and COH in the residual YS, relative to the weight of the yolk-free chick, was similar in eggs from young and old hens. However, chicks from the younger hens had less fat in the YS for their immediate posthatch nutrition compared with those from the older hens.

In ovo feeding improves energy status of late-term chicken embryos.

Maintenance of glucose homeostasis during late-term embryonic development is dependent upon the amount of glucose held in reserve primarily in the form of glycogen in the liver and upon the degree of glucose generated by gluconeogenesis from protein first mobilized from amnion albumen and then from muscle. Insufficient glycogen and albumen will force the embryo to mobilize more muscle protein toward gluconeogenesis, thus restricting growth of the late-term embryo and hatchling. We hypothesize that administration of available carbohydrates to the amnion will improve glycogen reserves and spare muscle protein mobilization for gluconeogenesis during late-term embryonic and posthatch neonatal development. Our hypothesis was tested by comparing BW gain, liver glycogen reserves, and muscle weight of in ovo fed and control embryos during last days of embryonic incubation until 25 d after hatching. We examined, using 600 birds from 2 different strains of commercial boilers, body and muscle weights and glycogen reserves following feeding embryos at d 17.5 of incubation with a solution containing maltose, sucrose, dextrin, and beta-hydroxy-beta-methylbutyrate (HMB). Providing carbohydrates and HMB to late-term embryos increased hatching weights by 5 to 6% over controls, improved liver glycogen by 2- to 5-fold, and elevated relative breast muscle size by 6 to 8%. These weight advantages were sustained through the end of the experiments at 25 d of age. It is reasonable to assume that the elevated glycogen levels in the in ovo treatment reduce the need to produce glucose via gluconeogenesis and, therefore, contribute to less use of muscle protein and hence a greater percentage of pectoral muscle weight in the in ovo birds.

Seasonal changes in bovine fertility: relation to developmental competence of oocytes, membrane properties and fatty acid composition of follicles.

Follicle dynamics and oocyte viability in Holstein primiparous and multiparous cows and the relationships between fertility and the biochemical and physical properties of oocyte membranes with season were examined. The conception rates of primiparous (n = 70 885) and multiparous (n = 143 490) cows differed, peaking in the winter and decreasing in the summer. The number of follicles 3-8 mm in diameter per ovary was higher in winter (19.6) compared with summer (12.0). However, in winter the percentage of ovaries with fewer than ten follicles per ovary was 16%, in contrast to 50% in summer. After aspiration of follicles, 7.5 oocytes per ovary were found in winter and 5.0 oocytes per ovary in summer. Cleavage to the two- to four-cell stage after chemical activation was greater in winter than in summer; this was enhanced at the morula stage and embryo development to the blastocyst stage was significantly higher in winter than in summer. Determination of the lipid phase transition in oocyte membranes revealed a shift of 6 degrees C between summer and winter. Fatty acid composition of phospholipids from follicular fluid, granulosa cells and oocytes indicated that there was a higher percentage of saturated fatty acids during the summer and that the percentages of mono-unsaturated and polyunsaturated fatty acids were higher in oocytes and granulosa cells during the winter. Oocytes and granulosa cells had similar fatty acid compositions, in contrast to follicular fluid. These results may explain the differences in the ability of oocytes to develop to the blastocyst stage at different seasons. Thus, temperature changes may lead to changes in membrane properties, which, in turn, can influence oocyte function and fertility.

Retinoid metabolism in human leucocytes.

Leucocytes from subjects from 0 to 80 years old were separated into mononuclear and granulocyte fractions and the retinoids and retinoid-binding fractions were examined. Both leucocyte fractions were found to contain retinol, retinoic acid and an additional retinoid; retinoic acid comprised 40% of retinoids in some samples. The protein fractions containing retinoids included a 200 kDa protein and several 14-18 kDa proteins. Plasma concentrations of retinol changed little with increasing age. In contrast, leucocyte concentrations of retinoids and retinoid-binding proteins increased quadratically with age. However, in granulocytes from young children retinoids were almost undetectable.

Absorption of protein, fatty acids and minerals in young turkeys under heat and cold stress.

1. Absorption of protein, fatty acids, calcium, phosphate and potassium by young turkeys maintained at thermoneutral (24 degrees C), hot (35 degrees C) and cold (8 degrees C) conditions was examined. 2. Non-acclimatised, heat-stressed birds absorbed less potassium and phosphate, whereas absorption of nitrogen, fatty acids and calcium was not altered, as compared with birds at 24 degrees C. Non-acclimatised, cold-stressed birds absorbed less calcium than control birds and more nitrogen than non-acclimatised, heat-stressed birds. 3. Heat acclimatization might reduce the adverse effect of heat stress on potassium and phosphate absorption.