Prefeeding Levels Research Articles

Assessment of chromium tripicolinate supplementation and dietary protein level on growth, carcass, and blood criteria in growing pigs

This study was conducted to evaluate potential interactive effects of supplemental Cr and dietary protein levels in growing pigs. Thirty-six individually penned barrows, 22 to 63 kg, were used in a 2 x 3 factorial arrangement of supplemental Cr (0 or 200 ppb from chromium tripicolinate) and protein level (76, 83, or 90% of lysine requirement). A corn-soybean meal basal diet was designed to supply all mineral and vitamin needs, 90% of the estimated metabolizable energy need, and 76% of the estimated protein need at 70% of ad libitum feed intake. Additional protein to 83 or 90% of the lysine requirement was provided by a soy protein isolate supplement. Growth data were collected for a 50-d period, and pigs were killed at a mean of 63 kg BW. Increasing lysine levels linearly (P < 0.01) increased ADG and liver weight. Lysine level had a quadratic effect on 10th rib backfat thickness (P < 0.05) and cooler shrink (P < 0.01) with the highest responses at the 83% lysine level. Increasing lysine level linearly decreased (P < 0.05) carcass content of ash and lipid and quadratically increased the carcass water content (P < 0.01). Carcass accretion rate showed a linear increase for protein (P < 0.01) and water accretion (P < 0.01). Dry matter composition of the longissimus muscle showed linear increases of ash (P < 0.05) and protein (P < 0.01) and a linear decrease of lipid content (P < 0.01) resulting in a linear increase (P < 0.05) of the protein to lipid ratio based on the increasing lysine levels. Pre-feeding insulin levels were increased (P < 0.05) with increasing level of lysine. One hour post-feeding, a quadratic lysine response for plasma glucose (P < 0.05) was observed with the lowest concentration at 83% lysine. Cr addition increased 10th rib backfat thickness (P < 0.10). There was no Cr x lysine level interaction (P > 0.10) observed for any of the growth or carcass traits. Plasma glucose concentrations pre-feeding were lower for Cr-supplemented pigs (P < 0.01). As expected, increasing protein levels in protein-deficient diets increased protein accretion while decreasing lipid accretion in 22 to 63 kg growing pigs; however, these effects were more clearly seen in the longissimus muscle than in the entire carcass. Supplementation of Cr exerted only minor effects with few Cr x lysine interactions observed in this study.

The effects of temperature on metabolic rate and protein synthesis following a meal in the isopod Glyptonotus antarcticus Eights (1852)

Seawater temperatures in Antarctica are low, and typically rather stable seasonally. Associated with this, many marine invertebrates have low resting metabolic rates with a limited aerobic scope, and are often stenothermal. We have therefore investigated the response of metabolic rate and protein synthesis to feeding in the large Antarctic isopod, Glyptonotus antarcticus, at two different temperatures. The resting oxygen consumption of starved Glyptonotus was low, and comparable with a previous measure for this species and other Antarctic marine invertebrates. Resting metabolic rate exhibited a Q 10 of 2.18 between 0°C and +4°C. After feeding at 0°C, oxygen consumption increased by a factor of 2.5 and ammonia excretion eightfold, before returning to prefeeding levels, in a classic if somewhat prolonged SDA (specific dynamic action) response. At 4°C, the postprandial factorial increase in both oxygen uptake and ammonia excretion was reduced. Whole-body protein synthesis rates for prefeeding animals showed a similar Q 10 to oxygen consumption. Rates of synthesis increased significantly after feeding, and there was an associated drop in the O:N ratio, indicating that protein formed the primary metabolic substrate during the SDA response. The contribution of the costs of protein synthesis to the overall SDA was estimated to be 68%, although this estimate is based on a previous estimate of the costs of protein synthesis in Glyptonotus which is higher than typical values for temperate-water crustaceans. The fraction of ingested energy utilised in the SDA was, however, low (2–3%). Further work is needed to determine whether these unusual features in Glyptonotus are typical of polar marine invertebrates in general.

Ghrelin in domestic animals: distribution in stomach and its possible role

Ghrelin, a novel growth-hormone-releasing acylated peptide, was recently isolated from rat and human stomachs. In rat, peripheral or central administration of ghrelin stimulates the secretion of growth hormone (GH) from the pituitary gland. Recent work suggests that ghrelin plays an important role in energy homeostasis, body weight, and food intake. We examined the distribution of cells immunoreactive to ghrelin in the stomachs of domestic animals and rats, using a polyclonal antibody for the N-terminal fragment of rat ghrelin [1–11]. We measured the plasma levels of ghrelin before and after feeding in cows, and GH levels after central administration of ghrelin in Shiba goats, to elucidate the possible role of ghrelin. Immunostained cells were widely distributed from the neck to the base of the oxyntic gland in all animals. The plasma ghrelin concentration in cows decreased significantly 1 h after feeding, and then recovered to pre-feeding levels. Administration of ghrelin into the third ventricle in Shiba goats dramatically increased the plasma GH concentration dose-dependently. These results suggest that ghrelin plays an important role in GH secretion and feeding regulation in domestic animals.

Influence of pre partum and post partum plane of nutrition on the performance of crossbred suckler cows and their progeny

The objective of the experiment was to study the effects of two pre partum and four post partum feeding levels on the performance of 28 Hereford-Ayrshire and 30 Limousine-Ayrshire spring-calving mature cows in calf to Limousin and their calves from the beginning of indoor feeding until the end of grazing under Finnish climatic conditions. A 2 H 2 factorial design experiment consisted of a low (L) and moderate (M) pre partum feeding levels based on hay and straw and two post partum concentrate feeding levels, 1.5 and 3.5 kg/d (1 and 2, respectively). The treatments were replicated across the genotypes. For feeding level L the amount of roughage offered was restricted to proportionately 0.7 on a dry matter (DM) basis of feeding level M. Milled barley was offered at 1.3 kg DM/d to all cows 72 days pre calving. The experiment was divided into two parts, an indoor feeding (215 days) and grazing period (114 days). The indoor feeding period included three periods, from start of the study to the beginning of additional concentrate feeding (P1) and feeding additional concentrate supplements both pre (P2) and post calving (P3). On feeding level M cows had a daily intake of 9.1 and 10.4 kg DM during periods P1 and P2, respectively. During period P3 intake was 10.4 and 12.0 kg DM for 1 and 2. Corresponding values for feeding level L were 6.7, 8.0, 8.0 and 9.7 kg DM, respectively. At the onset of grazing, cows on feeding level M were 47 kg heavier (P

Immunomodulation by dietary β-1, 3-glucan in the brooders of the black tiger shrimpPenaeus monodon

The present study evaluated the effectiveness of β-1,3-glucan derived from Schizophyllum commune in enhancing shrimp survival as well as haemocyte phagocytosis and superoxide anion production in brooder Penaeus monodon. Pond-reared P. monodon adults (135±25g) stocked in outdoor or indoor tanks were fed either a test diet containing β-1,3-glucan (2·0g kg−1) or a glucan-free control diet for 40 days. Their survival was compared. The brooders reared in indoor tanks were analysed at days 0, 1, 3, 6, 12, 24, 30 and 40 for their haemocyte phagocytic activity and superoxide anion production. The results showed that regardless of indoor or outdoor rearing the survival rate of shrimp fed the glucan diet was significantly higher (P< 0·001) than that of the control group. The brooders showed enhanced haemocyte phagocytic activity, cell adhesion and superoxide anion production when glucan was administered in their diets. The immunostimulatory enhancement peaked at day 24 after starting the dietary exposure and subsequently decreased to the pre-feeding level at the end of the 40 days feeding trial.

Effects of feeding frequency and dietary moisture content on growth, body composition and gastric evacuation of juvenile Korean rockfish ( Sebastes schlegeli)

A 7-week feeding experiment was conducted to determine the optimum feeding frequency for growth, body composition and gastric evacuation of the juvenile Korean rockfish. Three replicate groups of the fish (average weight of 5.7 g) were fed to visual satiety either dry pellets (DP) or moist pellets (MP), at different feeding frequencies (two meals a day, one meal a day or one meal every 2 days). At the end of the feeding trial, gastric evacuation rate of the fish was monitored after feeding. Weight gain and daily feed intake of the fish were not affected by dietary moisture content, whereas they were significantly affected by feeding frequency ( P<0.05). Weight gain and daily feed intake of the fish fed DP or MP once a day and twice a day were significantly higher than once every 2 days ( P<0.05). Feed efficiency and protein efficiency ratio in the fish fed MP were not affected by feeding frequency ( P>0.05), but these variables in the fish fed DP once every 2 days were significantly higher than once a day or twice a day ( P<0.05). As feeding frequency decreased, moisture content of muscle and liver increased. Both feeding frequency and dietary moisture content had no significant effect on protein content of muscle and viscera ( P>0.05). As feeding frequency increased, lipid content of muscle, viscera and liver significantly increased ( P<0.05). Gastric contents peaked at 4 h after feeding, then gradually decreased until the 20th h and reached the pre-feeding level within 24 h. It is concluded that one meal a day is more effective than two meals a day or one meal every 2 days for improving growth performance of juvenile Korean rockfish grown from 6 to 20 g.

Effects of incremental changes in forage: concentrate ratio on plasma hormone and metabolite concentrations and products of rumen fermentation in fattening beef steers

AbstractAs part of an investigation of factors responsible for a previously reported lower efficiency of carcass lean gain in steers offered grass silage diets, 16 Simmental × Friesian steers (515 (s.e. 6·4) kg) were offered perennial ryegrass silage ad libitum (C0) or silage plus rolled barley at 200 (C20), 400 (C40) or 600 (C60) g/kg total diet dry matter (DM). Barley-supplemented diets were intake-restricted to provide equal DM and metabolizable energy (ME) intakes to those offered C0. Eight steers were selected at random to determine the ME contents of the diets by open-circuit respiration calorimetry. The other eight steers were offered the same diets and were blood-sampled at 20- to 60-min intervals, for 10 h, to monitor changes in the concentrations of a number of nutritionally related plasma metabolites and hormones. Estimated ME intakes in these steers were 85·7, 83·1, 84·4 and 86·2 (s.e. 0·91) MJ/day from diets C0, C20, C40 and C60 respectively. Rumen-fistulated Hereford × Friesian steers provided 24-h rumen data for the same diets offered at equal amounts of ME per kg metabolic live weight.Mean 24-h plasma concentrations of insulin and insulin-like growth factor 1 (IGF-1) were linearly and positively related (P &lt; 0·01 and P &lt; 0·001 respectively) and glucagon quadratically related (P &lt; 0·05) to the proportion of barley in the diet. Plasma insulin increased after feeding on all diets but concentrations on diets C40 and C60 were significantly higher than those on C0 and C20 at all post-feeding sampling times up to 9 h after feeding. Plasma IGF-1 concentrations increased above pre-feeding levels following feeding of the higher barley diets (C40 and C60; P = 0·053) but remained unchanged in steers offered C0 and C20. Mean plasma concentrations of glucose were unaffected by diet but those of β-hydroxybutyrate (BOHB) and urea were positively and negatively related respectively (both P &lt; 0·001) to the proportion of barley in the diet. Plasma BOHB and urea concentrations also changed with time after feeding (P &lt; 0·001). Amongst the rumen parameters measured (pH; ammonia and volatile fatty acid concentrations and proportions) only the mean 24-h concentrations and proportions of butyrate were positively related to the proportion of barley in the diet (P = 0·051 and P &lt; 0·05 respectively). All rumen parameters were affected by time after feeding (acetate, P &lt; 0·01; others, P &lt; 0·001) but there was no interaction between treatment and time for any parameter.

Integrated physiological responses to feeding in the blue crab Callinectes sapidus.

The passage of a barium meal (15 % by mass) was followed through the digestive system of the blue crab Callinectes sapidus by flash-freezing crabs at set intervals, followed by radiography of specimens. Food moved from the oesophagus into the stomach region within 15 min. After 1-2 h, food was visible in the midgut, at 6 h it had reached the hindgut, and material was still present in the stomach at this time. The stomach was emptied between 8 and 10 h after feeding, and the entire digestive system was cleared of material after 18 h. A pulsed-Doppler flowmeter was used to monitor cardiac variables and arterial haemolymph flows during a 4 h control and 24 h postprandial period. Heart rate increased immediately upon food detection and remained elevated for 16-18 h after food ingestion. There was no significant change in stroke volume of the heart, and total cardiac output increased significantly and remained elevated above pre-feeding levels for 24 h after feeding. There was no change in haemolymph flow through the anterior or posterior aorta, but flow increased in the sternal, anterolateral and hepatic arteries. These changes in haemolymph flow reflected the use of the chelae and mouthparts in feeding, contraction of the visceral muscle surrounding the gut system and mobilisation of enzymes from the hepatopancreas. There was also a postprandial increase in the rate of oxygen uptake (apparent specific dynamic action). The rate of oxygen consumption (M(dot)(O2)) reached maximal levels 4 h after feeding and decreased slowly thereafter, reflecting the increased use of oxygen in digestion and absorption.

Respiratory consequences of feeding in the snake Python molorus

Snakes can ingest large meals and exhibit marked increases in metabolic rate during digestion. Because postprandial oxygen consumption in some snakes may surpass that attained during exercise, studies of digestion offers an alternative avenue to understand the cardio-respiratory responses to elevated metabolic rate in reptiles. The effects of feeding on metabolic rate, arterial oxygen levels, and arterial acid–base status in the snake Python molorus are described. Four snakes (180–250 g) were cannulated in the dorsal aorta and blood samples were obtained during 72 h following ingestion of a meal (rat pups) exceeding 20% of body weight. Oxygen consumption increased from a fasting value of 1.71±0.08 to 5.54±0.42 ml kg −1 min −1 at 48 h following feeding, and the respiratory gas exchange ratio increased from 0.67±0.02 to a maximum of 0.92±0.03 at 32 h. Plasma lactate was always less than 0.5 mM, so the postprandial increase in metabolic rate was met by aerobic respiration. In fasting animals, arterial PO 2 was 66±4 mmHg and haemoglobin-O 2 saturation was 92±3%; similar values were recorded during digestion, but haematocrit decreased from 15.8±1.0 to 9.8±0.8 due to repeated blood sampling. Plasma [HCO 3 −] increased from a fasting level of 19.3±0.8 to 25.8±1.0 mmol l −1 at 24 h after feeding. However, because arterial PCO 2 increased from 21.1±0.5 to 27.9±1.4 mmHg, there was no significant change in arterial pH from the fasting value of 7.52±0.01. Acid–base status returned to pre-feeding levels at 72 h following feeding. The increased arterial PCO 2 is most likely explained by a reduction in ventilation relative to metabolism, but we predict that lung PO 2 does not decrease below 115 mmHg. Although ingestion of large meals is associated with large metabolic changes in pythons, the attendant changes in blood gases are relatively small. In particular, the small changes in plasma [HCO 3 −] and stable pH show that pythons respond very differently to digestion than alligators where very large alkaline tides have been observed. It is unclear why pythons and alligators differ in the magnitude of their responses, but given these interspecific differences it seems worthwhile to describe arterial blood gases during digestion in other species of ectothermic vertebrates.

Effects of ruminal infusion of volatile fatty acids on plasma concentration of growth hormone and insulin in sheep

In an initial experiment we observed postprandial changes in plasma concentrations of growth hormone (GH), insulin, glucagon, and somatostatin (SRIF) in sheep. We then examined whether increasing the rumen concentration of volatile fatty acids (VFA) by infusing a VFA mixture at three rates (53.5, 107, and 214 μmol/kg/min for 4 hr) mimicked the postprandial changes in hormone secretion. Feeding significantly (P < 0.05) suppressed the plasma GH concentration for 6 hr, whereas it significantly (P < 0.05) increased plasma concentrations of insulin, glucagon, and SRIF. Plasma glucose levels tended to decrease after feeding but then gradually increased over the prefeeding level (P < 0.05). Intraruminal infusion of the VFA mixture at 107 μmol/kg/min caused similar changes in ruminal VFA concentrations to those seen after feeding. The infusion significantly (P < 0.05) suppressed GH secretion in a dose-dependent manner, whereas it caused a significant (P < 0.05) increase in insulin and glucose concentrations without changing glucagon concentrations. From these results, we conclude that the postprandial change in ruminal VFA concentration may be a physiological signal which modifies GH and insulin secretion in sheep.

The Nuts and Bolts of Captive Chimpanzee Diets and Food as Enrichment: A Survey

Beyond planning for good nutrition, one of the Cornerstones of a successful captive-chimpanzee wellness program is the opportunity for the nonhuman primates to express normal feeding and foraging behaviors. This study presents the results of a survey of 11 institutions—8 zoological and 3 research facilities—given to ascertain how daily diets and feeding enrichments were accomplished. Information represents 806 captive chimpanzees, and entails a composite of captive chimpanzee daily diets, forage and browse materials, periodic treats, medicating and supplemental foods, alternative feeding techniques, and food devices. Results suggest facilities are moving away from timed feeding schedules, which tend to increase prefeeding levels of agonism, to feeding a wide variety of foods throughout the day and using a wide variety of feeding techniques.

Effects of body weight, water temperature and ration size on ammonia excretion by the areolated grouper ( Epinephelus areolatus) and mangrove snapper ( Lutjanus argentimaculatus)

The effects of body weight, water temperature and ration size on ammonia excretion rates of the areolated grouper Epinephelus areolatus and the mangrove snapper Lutjanus argentimaculatus were investigated. Under given experimental conditions, L. argentimaculatus had a higher weight-specific ammonia excretion rate than E. areolatus. Weight-specific ammonia excretion rates of fasted individuals of both species showed an inverse relationship with body weight ( W, g wet wt.), but a positive relationship with water temperature ( t, °C). The relationships for total ammonia nitrogen (TAN) were: E. areolatus: TAN (mg N kg −1 d −1)=21.4·exp 0.11 t · W −0.43 ( r 2=0.919, n=60); L. argentimaculatus: TAN (mg N kg −1 d −1)=121.5·exp 0.12 t · W −0.55 ( r 2=0.931, n=60). Following feeding, the weight-specific ammonia excretion rate of E. areolatus increased, peaked at 2 to 12 h (depending on temperature), and returned to pre-feeding levels within 24 h. A similar pattern was observed for L. argentimaculatus, with a peak of TAN excretion being found 6 to 12 h after feeding. Stepwise multiple regression analysis indicated that weight-specific TAN excretion rates of both species increased with increasing temperature and ration ( R, percent body wt. d −1): E. areolatus: TAN (mg N kg −1 d −1)=22.8· t−28.8· R−378.2 ( r 2=0.832, n=24); L. argentimaculatus: TAN (mg N kg −1 d −1)=22.9· t−25.4· R−216.4 ( r 2=0.611, n=24). The effect of body weight on weight-specific postprandial TAN excretion was not significant in either species ( p>0.05). This study provides empirical data for estimating ammonia excretion of these two species under varying conditions. This has application for culture management.

NASOGASTRIC FEEDING ENHANCES NUTRITIONAL STATUS IN PAEDIATRIC LIVER DISEASE BY A MECHANISM WHICH IS INDEPENDENT OF CHANGES IN CIRCULATING IGF-I AND IGFBPs

163 Introduction 50% of children with cirrhosis have abnormal growth or malnutrition. This is associated with major changes in the insulin-like growth factor (IGF) - IGF binding protein (IGFBP) axis. Previous controlled studies suggested that intense enteral feeding can enhance nutritional status. The aim of the study was to ascertain whether nutritional status can be improved by nasogastric (NG) feeding in clinical practice and to assess the effects of NG feeding on the IGF-IGFBP axis. Methods 35 children(median age 0.6 yrs, range 0.1-8.0) with biliary atresia and failure to thrive were treated with NG feeding. Target daily intake was 150 Kcal/kg. Height(Ht), weight (Wt) & triceps skin fold thickness (TSF) were measured prior to starting feeding and then regularly for 1 yr or until NG feeding was stopped. Serum IGF-I, IGFBP-1 to -3 were assayed at the same intervals.Results The median duration of feeding was 3.7 mo (range 0.2-31.3). 1 boy died from ischaemic hepatitis. 24 stopped NG feeding after liver transplantation while 10 stopped electively. The median energy intake by NG feeding was 141 Kcal/kg/day (range 41-205). Complications occurred in 15 children (diarrhoea 9, pneumonia 5, persistent vomiting 4, variceal bleeding 3, others 3). No complication required the stopping of NG feeding. Before NG feeding, the children were losing weight & falling off their height centile. TSF & Wt SDS improved significantly after 8 wks & 4 mo of feeding respectively. Baseline IGF-I (69.6±6.4μg/L) & IGFBP-3(0.71±0.08mg/L) were low & non-fasting IGFBP-1(310±33μg/L) & IGFBP-2 (1.46±0.07mg/L) were raised. There was no change in IGF-I or IGFBP-1 during the study. IGFBP-2 fell to 1.32±0.07mg/L (p=0.02) by 2 mo of NG feeding & reached a nadir by 3 mo. By 6 wks, IGFBP-3 rose to 1.38±0.25mg/L (p=0.02) before falling back to pre-feeding levels. IGFBP-2 was negatively correlated with the change in TSF SDS after 4, 6 & 8 wks of feeding but not with changes in weight SDS. IGFBP-3 correlated with the change in TSF SDS after 4 & 6 wks.Conclusion NG feeding reversed the adverse nutritional changes seen in chronic liver disease. However, there was no change in IGF-I or IGFBP-1. IGFBP-2 fell with NG feeding & levels correlated with changes in TSF SDS. IGFBP-3 rose temporarily before falling to pre-feeding values. This suggests that circulating IGF-I & IGFBPs do not play a major role in mediating the NG induced changes in body composition in paediatric liver disease. This does not, however, exclude a paracrine or autocrine effect of IGF-I.

Digestion of host immunoglobulin and activity of midgut proteases in the buffalo fly Haematobia irritans exigua

The digestion of blood by the buffalo fly ( Haematobia irritans exigua) was monitored for 6 h at 33°C after a single meal. Following the meal, the concentration of soluble protein within the midgut increased to a peak at 2 hours then decreased steadily over the next 4 h. The magnitude of the increase in soluble protein at 2 h indicated a release of protein from another source; most likely from lysed red blood cells. The immunoglobulin (IgG) fraction of the blood meal was digested rapidly (50% within one hour of feeding) and fully digested within 4 h. This is indicative of its accessibility to digestive enzymes within the midgut. In contrast, when flies had continuous access to blood, the concentration of IgG in the midgut remained at a more constant level. The loss of antigen-binding activity of a specific antibody was more rapid than complete degradation of the IgG, with 70% of binding activity lost within one hour of feeding. The level of trypsin activity in the midgut increased from pre-feeding levels to reach a peak at 2 h before returning to basal levels after 6 h. The pattern of trypsin activity follows closely that of the concentration of soluble protein in the midgut ( r=0.88). The activity of leucine aminopeptidase in the midgut also increased immediately after feeding and remained elevated for 4 h before declining to a basal level after 6 h. The rapid digestion of IgG and subsequent loss of antibody activity suggests that for a specific anti-buffalo fly antibody to be effective it would need to be able to either evade the digestive system or induce a rapid response.

Protein Synthesis and Degradation Change Rapidly in Response to Food Intake in Muscle of Food-Deprived Mice ,

The short-term changes in muscle protein synthesis and degradation after food intake are unclear. We investigated muscle protein metabolism after food intake in mice that were starved for 18 h and refed for 1 h. Protein synthesis activity was estimated by the polysome profiles, and protein degradation was estimated by plasma Nτ-methylhistidine (MeHis) concentration, reflecting translational activity and myofibrillar protein degradation, respectively. MeHis is an index of myofibrillar protein degradation because it is not reused for protein synthesis and it is not metabolized. Stimulation of protein synthesis (polysome profile) and the reduction of protein degradation (plasma Nτ-methylhistidine concentration) were observed immediately after feeding began. Protein synthesis returned to the prefeeding level by 6 h after refeeding, whereas protein degradation remained at a low level. The decreased plasma MeHis concentration after refeeding was not due to a decrease in MeHis release from muscle cells and an increase in the free MeHis pool size, because the changes in free MeHis concentration in muscle were similar to that of plasma. Plasma insulin concentration immediately rose with feeding and it returned to the prefeeding level by 3 h after refeeding. These results suggest that responses of postprandial protein metabolism are very rapid and that protein synthesis is regulated by insulin, whereas degradation is regulated by insulin and other dietary factors. Thus the ability of skeletal muscle to use nutrients more effectively by stimulating protein synthesis and reducing protein degradation may cause the accelerated rate of protein accretion in skeletal muscle during the short postprandial period.

Plasma cholecystokinin concentrations in 3-day-old lambs: effect of the duration of fasting preceding a sucking bout.

Cholecystokinin (CCK) is a regulatory peptide released into the circulation after the ingestion of food. Our knowledge concerning the factors affecting its pattern of secretion in the mammalian neonate is scanty. Therefore, in this work we studied plasma concentrations of CCK in 3-day-old lambs after a sucking bout that followed either a short (2 h) or a long fasting period (9 h). Plasma concentrations of CCK were measured by radioimmunoassay in blood samples collected from jugular veins 10 min before, immediately after a sucking bout, and then at 10-min intervals during the following hour. In the first experiment a period of fasting of 2 h before allowing the lambs to suck did not lower the levels of CCK. On the other hand, a significant decrease was recorded 10 min after feeding ended. Between 20 and 50 min after the end of sucking, the mean CCK concentration rose back to the pre-feeding level before decreasing again at 60 min. In the second experiment a period of fasting of 9 h, on the other hand, significantly lowered the levels of CCK. Plasma levels also tended to decrease immediately after sucking was ended. This was followed by a substantial rise and levels remained high during the rest of the sampling period. It was concluded that the decrease recorded immediately after a sucking bout could be due to an inhibitory effect of the oral phase while the following rise reflected the stimulatory effect of milk nutrients on intestinal CCK-producing cells.

Gastric evacuation time and digestive enzyme activity in abaloneHaliotis midaefed a formulated diet

Gut evacuation time and enzyme activity were monitored over 46 h in juvenile Haliotis midae fed a formulated diet. Gut fullness peaked 6 h after feed was offered and returned to pre-feeding levels within 24 h. Enzyme secretion began with the onset of feeding and continued for at least 6 h after peak gut fullness was attained. Protease activity increased significantly following ingestion, whereas amylase activity was maintained at a fairly constant level. A low level of lipase activity was observed, suggesting that the ability of H. midae to digest fat is limited. When formulated food is used, a feeding frequency of once per day is recommended.

Effects of feeding and starvation on the metabolic rate of the necrophagous Antarctic amphipod Waldeckia obesa (Chevreux, 1905)

The marked seasonality of high latitude marine ecosystems means that the relationship between nutrition and metabolism is of particular interest, for many polar organisms must survive long periods without food. One hundred individuals of the scavenging lysianassoid amphipod Waldeckia obesa (Chevreux, 1905) were collected from Antarctica and then maintained in cold-water aquaria at the British Antarctic Survey in Cambridge. One group were fed and then starved for 64 days, during which time oxygen consumption fell to 60% of the initial value, and ammonia excretion to 20%. The initial decrease in metabolism occurred in about 5 days, after which time ammonia excretion remained roughly constant whereas oxygen consumption (and hence O:N atomic ratio) oscillated. O:N ratio and proximate composition estimated stoichiometrically from elemental composition both indicated the use of protein and lipid as metabolic substrates during starvation. Fed amphipods exhibited a classic post-prandial increase in metabolism (specific dynamic action, SDA): oxygen consumption and ammonia excretion increased rapidly to a level between 4 and 7.5 times the prefeeding levels, respectively. These are the largest increases of metabolic rate with feeding so far reported for a marine invertebrate and the overall SDA response lasted 8–10 days. O:N ratios indicated that metabolism 2–4 days after feeding was dominated by protein metabolism.

Effects of feeding on set point temperatures and thermoregulatory behaviour in the lizards

Abstract Feeding resulted in immediate upward shifts of between 0.62 and 3.00 K in the mean set points at which basking started and ceased (Tbask and Tmove) in P. muralis allowed to thermoregulate beneath tungsten bulbs giving three different levels of radiant heat, except for Tmove in lizards at the highest level (70 mW cm-2 measured in the range 8 000-14 000 nm). Mean bask durations decreased following feeding, but mean forage durations also decreased and the overall times spent basking increased. Values for all four variables declined gradually, returning to pre-feeding levels after 30-50 min. Feeding had no effect on mean heating rates. Feeding in Lacerta vivipara also resulted in increases in set point temperatures, but mean bask durations increased following feeding in this species.

Salivary gland apyrase in black flies ( Simulium vittatum)

Apyrase enzyme activity was demonstrated in the salivary glands of a colonized strain of Simulium vittatum. Activity was maximum (8.5 ± 0.7 mU/pair of gland equivalents) at pH 8.0, with ADP as substrate and Ca 2+ as the divalent cation. Activity was minimal in newly emerged females (1.6 ± 0.5 mU/pair of gland equivalents) but increased by 48 h. Activity in male salivary glands was marginally detectable (0.7 ± 0.8 mU/pair of gland equivalents), even 72 h after emergence. When newly emerged females were maintained at 4°C, salivary apyrase activity accumulated at a slow rate. Transferring females to warmer temperatures increased the rate of apyrase accumulation, but 27°C did not yield greater activity than 20°C. Apyrase activity was decreased when females engorged on whole bovine blood or on a simulated blood meal. Activity remained low 6 h after feeding, but increased to prefeeding levels by 48 h. During the second, anautogenous gonotrophic cycle, apyrase activity was not greater than during the first, autogenous gonotrophic cycle. Apyrase activity was not related to long term colonization as total salivary gland apyrase activity and pH profile in wild S. vittatum was not different from colonized S. vittatum.