Effect of weaning terms and protein deficit in rat pup nutrition on activities of digestive enzymes

Restriction of protein in nutrition of rat pups weaned at different terms has been found to produce changes in activities of digestive enzymes (maltase, alkaline phosphatase, aminopeptidase M, and glycyl-L-leucine dipeptidase) in the small and large intestine both at once after cessation of nutrition with low-protein diet for 10 days and 4 months later. In adult animals after the earlier or later weaning there are observed not only a decrease or increase of the enzyme activities, but also a different type of distribution of the alkaline phosphatase activity along the small intestine, which is more pronounced in the lately weaned rats. Thus, disturbance of metabolic programming of enzyme systems of the small and large intestine due to a change of quality of nutrition in early ontogenesis depends on terms of weaning of animals.     

Effect of milk deprivation during the lactation period on performance and digestive enzyme activities of the piglets following weaning

Post-weaning performance of piglets from systems where lactation is disrupted (e.g. from multisuckling systems) is superior to conventionally reared piglets. The objective of this study was to establish whether restricted growth prior to weaning caused by disruption of suckling was an important factor in post-weaning performance and also whether there were related changes in gastro-intestinal development. Ten litters of eight piglets were used in a split-plot design. Half of each litter (limited suckling, LS) had suckling disrupted by separation from their dam for 7 h/day from day 14 to 28 after farrowing. The remainder of each litter was allowed to suck normally (normal suckling, NS). The same amount of creep feed was offered to LS piglets as consumed by NS littermates on the previous day. There were no differences in weight between LS and NS piglets at 14 days of age, but restricting access to the sow reduced weaning weight at 28 days of age (7.96 v. 9.00 kg; LS v. NS; P < 0.01; s.e.d. 0.23). Feed intakes were greater for LS than NS piglets over the first 28 days post weaning, particularly in the 1st week after weaning when feed efficiency was also improved (0.91 v. 0.62 kg gain per kg feed; P < 0.01; s.e.d. 0.08). As a result, LS piglets grew more rapidly in the first 28 days post weaning, particularly in the first 7 days after weaning. Subsequent performance to 8 weeks was similar for both groups. Digestive organ weights were not different at 2 and 9 days after weaning; nor were small intestine specific enzyme activities significantly different ( P>0.05). Pancreatic trypsin activity was, however, greater ( P < 0.01) for LS pigs on both days 2 and 9 post weaning. In conclusion the restriction of growth as a result of limited suckling itself is an important factor in determining post-weaning performance and may be related to development of pancreatic trypsin activity.     

Effect of different weaning ages (21, 28 or 35 days) on production, growth and certain parameters of the digestive tract in rabbits

The effect of different weaning ages, that is, 21 (G21), 28 (G28) or 35 (G35) days, on growth and certain parameters of the digestive tract was examined in rabbits to assess the risk of early weaning attributable to the less-developed digestive system. On days 35 and 42, G35 rabbits had 10% to 14% and 10% higher BW, respectively (P < 0.05), than those weaned at days 21 and 28. In the 4th week of life, early weaned animals had 75% higher feed intake than G28 and G35 rabbits (P < 0.05). The relative weight of the liver increased by 62% between 21 and 28 days of age, and thereafter it decreased by 76% between 35 and 42 days of age (P < 0.05), with G21 rabbits having 29% higher weight compared with G35 animals on day 35 (P < 0.05). The relative weight of the whole gastrointestinal (GI) tract increased by 49% and 22% after weaning in G21 and G28 rabbits, respectively (P < 0.05). On day 28, the relative weight of the GI tract was 19% higher in G21 than in G28 rabbits, whereas on day 35 G21 and G28 animals had a 12% heavier GI tract compared with G35 rabbits (P < 0.05). Age influenced the ratio of stomach, small intestine and caecum within the GI tract; however, no effect of different weaning age was demonstrated. The pH value of the stomach and caecum decreased from 5.7 to 1.6 and from 7.1 to 6.3, respectively, whereas that of the small intestine increased from 6.8 to 8.4 (P < 0.05); the differences between groups were not statistically significant. Strictly anaerobic culturable bacteria were present in the caecum in high amounts (108), already at 14 days of age; no significant difference attributable to weaning age was demonstrable. The concentration of total volatile fatty acids (tVFA) was higher in G21 than in G28 and G35 throughout the experimental period (P < 0.05). The proportion of acetic and butyric acid within tVFA increased, whereas that of propionic acid decreased, resulting in a C3 : C4 ratio decreasing with age. Early weaning (G21) resulted in higher butyric acid and lower propionic acid proportions on day 28 (P < 0.05). No interaction between age and treatment was found, except in relative weight of the GI tract and caecal content. In conclusion, early weaning did not cause considerable changes in the digestive physiological parameters measured, but it resulted in 10% lower growth in rabbits.     

Effect of ragi and Lxxx-lactate-producing cultures on enteric pathogens in a rice-based weaning food

The use of the Southeast-Asian starter culture ragi in enhancing the safety of a rice-based model weaning food is described and compared with the use of diastatic malt extract. Ragi was shown to be an effective saccharifying agent convenient for use in weaning-food preparation on a domestic scale. Saccharification and fermentation with ragi alone produced some antimicrobial effect against the three enteric bacterial pathogens tested but this was much improved when ragi was used in conjunction with the Lxxx-lactate-producing Lactococcus lactis or Lactobacillus bavaricus. The latter showed the greatest inhibition of pathogens, reducing viable numbers by more than a factor of 10⁴ within 4 h. The antibacterial effects observed correlated with the total acid produced (ragi alone giving 0.2%; ragi with Lc. lactis giving 0.3% and ragi with Lb. bavaricus giving 0.4%). The proportion of the physiological Lxxx-lactate isomer was highest in Lc. lactis fermentations (>99% compared with 80% with Lb. bavaricus). There was no evidence of any pronounced antimicrobial effect due to the nisin produced during fermentation by Lc. lactis (150 IU/g). Whereas bacteriocin production may play little role in pathogen control, it may be desirable as a way of preventing fermentations conducted non-aseptically from becoming dominated by lactic acid bacteria producing unacceptable amounts of Dxxx-lactate.R.M. Yusof is with the Department of Nutrition and Community Health, Faculty of Human Ecology, University Pertanian Malaysia, 43400 UPM, Serdang, Selangor, Malaysia. T.A. Baker, J.B. Morgan and M.R. Adams are with the School of Biological Sciences, University of Surrey, Guildford, Surrey GU2 5XH, UK.     

Adaptability of the digestive function according to age at weaning in the rabbit: II. Effect on nutrient digestion in the small intestine and in the whole digestive tract

The ability of young rabbits to digest a solid diet was evaluated according to the weaning age: 21 (W21, 12 litters) or 35 (W35, 12 litters) days of age. From 14 days onwards, the rabbits were fed the same pelleted feed. Three methods were compared to estimate the faecal digestibility in the young rabbits, between 24 to 28 and 38 to 42 days. Digestive balance at ileal and faecal levels was determined for the main nutrients provided by milk and solid feed. The W21 rabbits increased their solid feed intake only 2 days after their weaning, when compared with suckling rabbits. Thus, their crude protein (CP) intake remained lower until 26 days compared with the W35 rabbits (from 41%, P < 0.01), as well as their crude fat intake until 28 days (from 72%, P < 0.001). On the contrary, the W35 rabbits increased their solid feed intake without a delay after weaning, quickly reaching the intake level of the W21 rabbits. The amounts of organic matter (OM) and CP reaching the caecum were increased on day 28 by 56% and 42% in the W21 rabbits compared with the W35 rabbits, respectively (P < 0.05), and were similar between groups on day 42. Starch ileal digestibility coefficients were 94·2% and 95·4% in 28- and 42-day-old rabbits, respectively, irrespective of the weaning age. The amount of starch flowing through the ileo-caecal junction was low and only tended to be higher on day 28 in the W21 group (0.20 v. 0.15 g/day in the W35 group, P = 0.10). The digestive balance pointed out that the digestible energy intake was similar between weaned and suckling rabbits from 23 to 27 days, a phenomenon partly explained by a high ability of the W21 rabbits to digest starch (98%) and NDF (36%). Indeed, the amounts of starch and NDF digested by the W21 group were 2.0- and 2.4-fold higher than those of the W35 rabbits at this period (P < 0.001). However, they ate 20% less digestible proteins than still-suckling rabbits (P < 0.001). From 38 till 42 days, only a lower ability of the W21 rabbits to digest lipids was detected (P < 0.05). In conclusion, early-weaned rabbits were able to adapt quickly to digest large amounts of starch and fibres.     

Milk production and composition,and progeny performance in young ewes with high merit for rapid growth and muscle and fat accumulation

In ewe lambs, acceleration of growth and accumulation of both muscle and fat leads to earlier sexual maturity and better reproductive performance. The next stage in the development of this theme is to test whether these aspects of growth in young ewes affect milk production in their first lactation and the growth of their first progeny. We studied 75 young Merino ewes that had known phenotypic values for depth of eye muscle (EMD) and fat (FAT), and known Australian Sheep Breeding Values for post-weaning weight (PWT) and depths of eye muscle (PEMD) and fat (PFAT). They lambed for the first time at 1 year of age. Their lambs were weighed weekly from birth to weaning at 10 weeks to determine live weight gain and weaning weight. Progeny birth weight was positively associated with live weight gain and weaning weight (P<0.001). The PWT of the mothers was positively associated with birth weight (P<0.01), live weight gain and weaning weight of the progeny (P<0.05); however, these progeny traits were not influenced by EMD, FAT, PEMD, PFAT of the mothers (P>0.05). The PWT of the sire was positively associated with live weight gain (P<0.05) and weaning weight of the progeny (P<0.01). At around day 20 postpartum, we measured milk production and milk composition (fat, protein, lactose, total solids). Milk production was influenced positively by birth type (single or twin; P<0.05) and negatively by birth weight (P<0.05), but not by mother phenotype or genotype, sire genotype of the mother or the sex of the progeny (P>0.05). The concentrations of fat, protein, lactose and total solids in the milk were not affected by the phenotype or genotype of the mothers or of the sires of the mothers, or by the sex of the progeny (P>0.05). We conclude that selection of young Merino ewes for better growth, and more rapid accumulation of muscle and fat, will lead to progeny that are heavier at birth, grow faster and are heavier at weaning. Moreover, milk production and composition do not seem to be affected by the genetic merit of the mother for post-weaning live weight or PEMD or PFAT. Therefore, Merino ewes can lamb at 1 year of age without affecting the production objectives of the Merino sheep industry.     

Absorption of food in Heterotis niloticus (Cuvier) (pisces: osteoglossidae) from a small tropical man-made lake in Ibadan, Nigeria

The protein, carbohydrate and lipid contents of the food ingested and their absorption in the intestine of Heterotis niloticus inhabiting a small man-made lake; Awba Lake, in Ibadan were investigated.The ingested food had mean total protein, mean total carbohydrate and mean total lipid contents of 53.0%, 28.8% and 15.5% of the organic content, respectively. Calculated percentages absorbed were 56.4–72.7% (mean — 64.9%) total protein, 32.2–50.8% (mean — 40.3%) total carbohydrates and 71.9–87.3% (mean = 78.3%) lipid.Absorption mostly occurred in the fore-gut (the first one-third of the intestine) and least in the hind-gut (the last one-third of the intestine). Different sizes of fish showed different dietary protein, carbohydrate and lipid contents. Absorptive capacity for these components of the food also varied with fish size.     

Effects of weaning and finishing feeding treatment on fatty acids, especially cis and trans C18:1 isomers, in the Longissimus thoracis muscle of Galician Blond calves

Seven- to 10-month-old calves are the typical production of Galician Blond (GB), the most important bovine local beef breed in Spain. As meat lipid repercussions on human health depend on their fatty acid (FA) profile, this study aimed at analysing the individual FA at weaning and at the end of the feeding finishing period, especially trans and cis 18:1 isomers in total lipids of the Longissimus thoracis muscle in GB male calves. Distribution of main FA in veal lipids was characterized by gas-liquid chromatography (GLC) analysis on a high polar glass capillary column. Total trans and cis 18:1 isomers were purified, from total FA (TFA) methyl esters, by preparative reversed-phase high-performance liquid chromatography, to allow subsequent specific analysis of their different isomers by GLC. Calves stayed with their mothers at pasture for 2 or 5 months in intensive or semi-extensive systems, followed by an indoor feeding period. The weaned (W) group was finished on concentrate and hay, whereas the non-weaned (NW) group was finished on concentrate and hay and it continued suckling until slaughter. The studied effects did not present interactions. The duration of the indoor finishing period hardly had a significant influence on the parameters analysed. Compared to W calves, NW calves had higher proportions (% TFA) of 18:3n-3 (+38%, P < 0.0001), 20:5n-3 (+22%, P = 0.005), 22:5n-3 (+13%, P = 0.042), cis monounsaturated FA (MUFA; +8%, P = 0.032), total MUFA (+8%, P = 0.013), n-3 polyunsaturated FA (PUFA; +25%, P = 0.0001) and conjugated linoleic acid (CLA; +48%, P < 0.0001) to the detriment of 18:0 (-10%, P = 0.002), 18:2n-6 (-25%, P = 0.004) and n-6 PUFA (-20%, P = 0.011). With regard to cis and trans 18:1 isomers, NW calves had higher proportions (% total cis or trans 18:1) of Δ11trans and Δ16trans (+25% and +22%, respectively, P < 0.01) and Δ13 + 14trans (+13%, P < 0.05) and lower proportions of Δ6 to 8 and Δ10trans (-28% and 58%, respectively, P < 0.001). NW calves' meat might be more suitable for human health than W calves' meat due to the increase of anti-atherogenous FA such as n-3 PUFA, CLA and 18:1 Δ11trans.     

Alterations in the activities of rat tissue hexose monophosphate dehydrogenases in response to premature weaning and dietary restriction at mid-lactation

Summary The activities of the hexose monophosphate dehydrogenases increased in adipose tissue, remained unchanged in liver and decreased in mammary gland following the weaning of rats at mid-lactation (day 14). When dietary intake was restricted at mid-lactation, the activities of the hexose monophosphate dehydrogenases increased in adipose tissue, decreased in liver, but were unaltered in mammary gland. Premature weaning on day 14 postpartum resulted in maternal increases in both plasma insulin and glucose, which peaked at day 16. The plasma insulin levels decreased from day 14 to day 18 postpartum in the normal lactating rat, and a similar trend was observed for animals on a restricted dietary intake. Daily food consumption in the lactating rat decreased from 50 g to 20 g after premature weaning. The live weight of pups raised on dams given a restricted food intake from day 14 had decreased by day 17 postpartum, whereas an increase in daily live weight gain was recorded for the litters from the lactating controls. The results demonstrate that the activities of the hexose monophosphate dehydrogenases are regulated differentially between tissues of the lactating rat.     

Early weaning programs rats to have a dietary preference for fat and palatable foods in adulthood

The objective of this work was to study the effect of early weaning on alimentary preference for the macronutrients protein, carbohydrate and fat in adult rats. Male Wistar rat pups were weaned by separation from the mother at 15 (D15) or 30 (D30) days old. Body weight and food intake were measured every 30 days until pups were 150 days old. At 110 days of age, the alimentary preference was evaluated for 1 h on 3 consecutive days. At 120 days of age, the palatable diet test was conducted during 3 consecutive 24-h periods. Body weight and food intake were not altered, but early weaning in rats induced an alimentary preference to fat and hyperphagia of a palatable diet. In conclusion, early weaning, although did not modify body weight or basal food intake, promoted an increased preference for palatable and fatty foods. This demonstrates that early weaning is not capable of promoting perceptible alterations of alimentary behavior under normal laboratory conditions. However, in the presence of a stimulating factor such as a choice of nutrients or a palatable diet, a possible latent effect on dietary preferences may become apparent. Over the long term, this preference for foods with high caloric density can lead to obesity and metabolic perturbations.     

Early weaning in bighorn sheep, Ovis canadensis affects growth of males but not of females

Theories of parental investment and parent-offspring conflictassume that investment involves a cost to the parent and a benefitto the offspring, but for herbivorous mammals, behavioral andnutritional weaning are gradual processes that are difficultto define, and little is known about the consequences of individualvariation during weaning. To study the effects of late maternalcare on offspring fitness, we removed female bighorn sheep (Oviscanadensis) from a marked population in Alberta, Canada, andmonitored the survival, growth, and reproductive success oforphan and nonorphan lambs. Mothers were removed when lambswere 3.5–4.0 months, about 2–4 weeks before thesuspected time of nutritional weaning. Femaleorphans and nonorphanshad the same weight as yearlings, the same probability of producingtheir first lamb at 2 years of age, the same lifetime reproductivesuccess (lambs produced or lambs that survived to early autumn),and the same longevity. Male orphans from most cohorts weresmaller as yearlings compared to nonorphans from the same cohort.They were unable to compensate for this early weight differencein later life: at 4 years, orphan males had smaller horns andwere lighter than nonorphans. Small horn and body size likelylowered the reproductive success of orphaned males comparedto nonorphans from the same cohort. We suggest that in thissexually dimorphic species late maternal care is more importantfor males than for females. Because late maternal care had nomeasurable benefit for daughters, we suggest that parent-offspringconflict over the duration of maternal care may not exist formother-daughter pairs. or mother-son pairs it remains to beshown whether late maternal care involves a cost to the mother,but the assumption of a benefit to the son was met.     

Growth pattern of the polypeptide-YY cell population in the upper digestive tract of the rat during the perinatal period and after weaning

Summary The distribution of polypeptide-YY cells within the gastric and duodenal mucosa of the rat and the development of their populations were examined daily from 3 days before birth until day 8 postpartum and after weaning, on day 25 postpartum, using a precise technique of quantification. Polypeptide-YY cells appeared in the stomach around the 19th day of gestation. They were always more numerous in the antral mucosa and particularly in the pyloric sphincter area than in the fundic mucosa. Immunogold staining at the electron-microscopic level revealed that, in the antrum, polypeptide-YY was colocalised with gastrin in endocrine cells mainly of type G and, more rarely, in cells of intestinal type IG. Comparison of the gastrin and polypeptide-YY cell populations in the same rats indicated that, except at day 6 postpartum, there were fewer gastric polypeptide-YY cells than immunoreactive gastrin cells and that polypeptide-YY cells were 8 times less numerous than gastrin cells at day 25 postpartum. Polypeptide-YY cells were clearly present in the duodenum of the 19-day-old embryo. This population increases with age until day 8 postpartum, then significantly decreases (by 87%) between days 8 and 25 postpartum. Because polypeptide-YY may inhibit secretion of gastric acid, it is possible that the presence of significant population of polypeptide-YY cells in the upper digestive tract during the first postnatal week of life may play a role (endocrine or paracrine) in the decreased acid secretion occurring in the newborn rat.     

Transient changes of enzyme activities and expression of stress proteins in the small intestine of piglets after weaning

To determine the transient effects of weaning on the small intestine, 16 piglets were slaughtered at days 0, 1, 4 and 7 after weaning. Jejunal samples were collected to examine different enzyme activities and mRNA expressions of two stress protein families, namely, heat-shock proteins (HSP) and trefoil factors (TFF). Results showed that the activities of ceruloplasmin, alkaline phosphatase and lactate dehydrogenase, were significantly changed at Day 1 and/or Day 4. The mRNA expressions of HSP10, HSP60 and HSP90 showed a pattern of increased expression with time after weaning. Expression significantly differed between Day 0 and Day 7 after weaning. The mRNA expression of HSP70 was significantly increased on Day 1 only. Similarly, the mRNA expressions of TFF1 and TFF2 were significantly increased on Day 7 compared with those on Day 0. Expression of TFF3 was not affected by time after weaning. In conclusion, the present study indicated that weaning induced transient injury to small intestinal morphology and function. Particularly it changed enzyme activities and gene expression of stress proteins in the small intestine of piglets. At first time, a change in the gene expression of HSP10 and a gene overexpression of TFF1 in the small intestine of piglets after weaning was found.     

Association between body energy content in the dry period and post-calving production disease status in dairy cattle

The transition from gestation to lactation is marked by significant physiological changes for the individual cow such that disease incidence is highest in early lactation. Around the time of calving, cows rely on mobilisation of body energy reserves to fill the energy deficit created by an increase in nutrient demands at a time of restricted feed intake. It is well established that monitoring of body energy reserves in lactation is an important component of herd health management. However, despite their influence on future health and productivity, monitoring of body energy reserves in the dry period is often sparse. Further, there is increasing concern that current dry off management is inappropriate for modern cattle and may influence future disease risk. This study aimed to identify candidate indicators of early lactation production disease from body energy data collected in the dry period and production data recorded at the time of dry off. Retrospective analysis was performed on 482 cow-lactations collected from a long-term Holstein-Friesian genetic and management systems project, the Langhill herd in Scotland. Cow-lactations were assigned to one of four health groups based on health status in the first 30 days of lactation. These four groups were as follows: healthy, reproductive tract disorders (retained placenta and metritis), subclinical mastitis and metabolic disorders (ketosis, hypocalcaemia, hypomagnesaemia and left displaced abomasum). ANOVA, employing a GLM was used to determine effects for the candidate indicator traits. Cows which were diagnosed with a reproductive tract disorder in the first 30 days of lactation experienced a significantly greater loss in body energy content, body condition score and weight in the preceding dry period than healthy cows. The rate of change in body energy content during the first 15 days of the dry period was −18.26 MJ/day for cows which developed reproductive tract disorder compared with +0.63 MJ/day for healthy cows. Cows diagnosed with subclinical mastitis in the first 30 days of lactation had significantly greater milk yield at dry off in the previous lactation than cows that developed a reproductive tract disorder or metabolic disease in addition to a significantly higher yield to body energy content ratio at dry off than healthy cows. Physiological and production traits recorded in the lactation and dry period preceding a disease event differed between cows which developed different diseases post-calving. Differences in these traits allow the development of new disease indicators for use in models for the prediction of disease risk in the transition period.     

Morphological and physiological aspects of digestive processes in the graminivorous primate Theropithecus gelada-a preliminary study

Hindgut fermentation has been suggested to contribute significantly to the digestive process in the gelada (Theropithecus gelada). We therefore hypothesized that in an in vitro fermentation test (Hohenheim gas test, using gas production as measure of microbial digestion) inoculum based on fresh gelada feces would degrade grass to a similar degree as zebra (Equus burchelli chapmani) feces and to a higher degree than that of hamadryas baboons (Papio hamadryas). Additionally, morphology of gelada tongue, salivary glands, stomach, and intestine were examined in this study. Gas production was measured between 4 and 96 hr using animal feces incubated with 200 mg of air-dry hay or mixed concentrate sample. For grass hay, 12-hr gas production was as follows: T. gelada (19.9 ml)>Papio (18.4 ml)>Equus (15.7 ml). After 24 hr, gas production changed: Papio (35.1 ml)>T. gelada (31.9 ml)>Equus (27.9 ml). At 96 hr, Papio was unexpectedly the most effective species with the highest gas production (53.1 ml)>zebra (51.2 ml)>gelada (49.4 ml). With a concentrate standard, 12-hr gas production was as follows: T. gelada (38.5 ml)>Equus (36.8 ml) = Papio (36.4 ml). At 24 hr, gas production differed: Papio (51.7 ml)>Equus (47.0 ml) = T. gelada (46.8 ml). At 96 hr, zebra was the most effective species with the highest gas production (63.9 ml)>Papio (60 ml) = T. gelada (59.9 ml). In conclusion, the results show that the microbial population present in gelada feces is able to ferment forage and concentrate substrates in vitro, although this fermentation did not occur with the expected effectiveness. Future studies should therefore focus also on the bacteria species involved.     

Arousal and re-feeding rapidly restores digestive tract morphology following aestivation in green-striped burrowing frogs

During aestivation, the gut of the green-striped burrowing frog, Cyclorana alboguttata undergoes significant morphological down-regulation. Despite the potential impact such changes might have on the re-feeding efficiency of these animals following aestivation, they appear to be as efficient at digesting their first meals as active, non-aestivating animals. Such efficiency might come about by the rapid restoration of intestinal morphology with both arousal from aestivation and the initial stages of re-feeding. Consequently, this study sought to determine what morphological changes to the intestine accompany arousal and re-feeding following 3 months of aestivation. Arousal from aestivation alone had a marked impact on many morphological parameters, including small and large intestine masses, small intestinal length, LF heights, enterocyte cross-sectional area and microvilli height and density. In addition, the onset of re-feeding was correlated with an immediate reversal of many morphological parameters affected by 3 months of aestivation. Those parameters that had not returned to control levels within 36 h of feeding generally had returned to control values by the completion of digestion (i.e. defecation of the meal). Re-feeding was also associated with several changes in enterocyte morphology including the incorporation in intracytoplasmic lipid droplets and the return of enterocyte nuclear material to the 'active' euchromatin state. In conclusion, morphological changes to the gut of aestivating frogs which occur during aestivation are transitory and rapidly reversible with both arousal from aestivation and re-feeding. The proximate causes behind these transitions and their functional significance are discussed.     

黑腹绒鼠消化道长度和重量的季节变化

能量获得与分配的效率和速率是决定动物能量收支的主要因子,对于动物的生存和繁殖是至关重要的（Karasov, 1986;Weiner,1992）.动物的消化道容纳和处理食物的能力,以及消化和吸收营养物质的能力是限制其能量收支的重要因素,也是理解生活史进化和最优资源分配理论的关键（Derting and Bogue,1993;Derting and Noakes,1995）.     

Neuropeptides,food intake and body weight regulation: a hypothalamic focus

Energy homeostasis is controlled by a complex neuroendocrine system consisting of peripheral signals like leptin and central signals, in particular, neuropeptides. Several neuropeptides with anorexigenic (POMC, CART, and CRH) as well as orexigenic (NPY, AgRP, and MCH) actions are involved in this complex (partly redundant) controlling system. Starvation as well as overfeeding lead to changes in expression levels of these neuropeptides, which act downstream of leptin, resulting in a physiological response. In this review the role of several anorexigenic and orexigenic (hypothalamic) neuropeptides on food intake and body weight regulation is summarized.     

Morphology of the digestive tract and feeding habits of Loricaria lentiginosa Isbrücker, 1979 in a Brazilian reservoir

The present study describes some aspects of the morphology of the digestive tract and the feeding patterns of Loricaria lentiginosa. Sixty‐three specimens with gut contents were captured quarterly from November 2001 to August 2002 in Porto Colômbia reservoir, Rio Grande basin, southeastern Brazil. The species has bicuspid teeth inserted in the lips, unicuspid teeth in the dentary bone and pharyngeal teeth, besides having short, numerous and slightly separated gill rakers. The stomach is rudimentary and the intestine is relatively short (Intestinal Quotient = 1.32 ± 0.15). Molluscs, especially bivalves, represented the most important item on the diet of this species, followed by organic matter. The characteristics of the digestive tract as well as the dietary pattern, suggest that L. lentiginosa is able to explore bottom food resources, being classified as benthophagous with a tendency to malacophagy, and utilizing organic matter as an associated or additional food resource. Loricariidae species are able to use not only algae, sediment and detritus, but also plant and invertebrate items.