True grit? Comparative anatomy and evolution of gizzards in fishes.

Gut morphology frequently reflects the food organisms digest. Gizzards are organs of the gut found in archosaurs and fishes that mechanically reduce food to aid digestion. Gizzards are thought to compensate for edentulism and/or provide an advantage when consuming small, tough food items (e.g., phytoplankton and algae). It is unknown how widespread gizzards are in fishes and how similar these structures are among different lineages. Here, we investigate the distribution of gizzards across bony fishes to (1) survey different fishes for gizzard presence, (2) compare the histological structure of gizzards in three species, (3) estimate how often gizzards have evolved in fishes, and (4) explore whether anatomical and ecological traits like edentulism and microphagy predict gizzard presence. According to our analyses, gizzards are rare across bony fishes, evolving only six times in a broad taxonomic sampling of 51 species, and gizzard presence is not clearly correlated with factors like gut length or dentition. We find that gizzard morphology varies among the lineages where one is present, both macroscopically (presence of a crop) and microscopically (varying tissue types). We conclude that gizzards likely aid in the mechanical reduction of food in fishes that have lost an oral dentition in their evolutionary past; however, the relative scarcity of gizzards suggests they are just one of many possible solutions for processing tough, nutrient-poor food items. Gizzards have long been present in the evolutionary history of fishes, can be found in a wide variety of marine and freshwater clades, and likely have been overlooked in many taxa.

Histomorphology and ultrastructure of the proventriculus of the broad breasted white turkey (Meleagris gallopavo, Linnaeus 1758).

This study aims to examine the functional morphology of the proventriculus of the broad breasted white turkey (BBWT) (Meleagris gallopavo, Linnaeus 1758) using gross anatomy, light microscopy, gross/histomorphometric analysis, and scanning and transmission electron microscopy. The proventriculus was characterized internally by many elevated papillae with a mound, leafy flower, and lotus flower-shapes. Each papilla was enclosed by concentrically organized mucosal folds with distinct or indistinct proventricular gland openings on its top. Longitudinal folds and grooves at the junction of the proventriculus with the esophagus exhibited various sized and shaped openings of esophageal glands with irregular outlines. Histologically, the surface epithelium of the proventriculus was covered by a thin layer of cuticle, particularly evident at its junction with the gizzard. The lamina epithelialis and propria, and secretory units of proventricular lobules were infiltrated by aggregations of lymphocytes and lymphoid follicles (nodules). Variably shaped glandular lobules of proventricular glands occupied the submucosa, surrounded by thin strands of smooth muscle fibers derived from muscularis mucosa. Triangular, cuboidal, or columnar-shaped secretory oxyntico-peptic cells lined the secretory units. Many telocytes (pyramidal or fusiform-shaped cell bodies with lengthy telopodes) were observed in interstitial tissue. Further, two types of argyrophilic endocrine cells were identified within the glandular epithelium. The morphology of the M. gallopavo proventriculus reflects its dietary habits and behavior.

Histomorphological, histochemical and scanning electron microscopic investigation of the proventriculus (Ventriculus glandularis) of the hooded crow (Corvus cornix).

The current investigation aimed to clarify the histomorphological features, scanning electron microscopy (SEM) and histochemistry of the proventriculus in the adult hooded crow (Corvus cornix). Twenty-two adult birds of both sexes were collected from El-Fayoum and Beni-Suef governorates, Egypt; ten were used for anatomical investigation, two were scanned using SEM, and ten were subjected to routine histological technique. The obtained anatomical results revealed a small-sized spindle-shaped proventriculus obliquely located in the left ventral part of the body cavity with an average body weight, length and diameter of 1.689 ± 0.231 gm, 1.54 ± 0.383cm and 3.51 ± 0.416cm, respectively. The histological examination revealed a typical tubular organ. The mucosa exhibited several plicae and sulci that were lined with simple columnar cells. The lamina propria was composed of collagenous connective tissue infiltrated by lymphocytes, lymphatic aggregations and tubular glands. The submucosa consisted of collagenic fibres and compound tubuloalveolar glandular lobules lined with oxynticopeptic cells and enteroendocrine cells. The oxynticopeptic cells reacted negatively with PAS and Alcian Blue stains, whereas the ductal cells reacted positively with PAS only. Enteroendocrine cells were seen singly in the lamina epithelialis mucosae and were abundant in submucosal glands. The tunica musclaris was arranged in two layers covered by serosa. The proventricular glands' openings were noticed by SEM as raised tubes with regular circular outlines surrounded by anastomosed microscopic folds. The obtained histomorphological structure of the hooded crow's proventriculus revealed some shared morphological features with most species of birds and some variations that might be attributed to their diet and feeding behaviour.

Brain mass explains prey size selection better than beak, gizzard and body size in a benthivorous duck species.

Prey size selection in some bird species is determined by the size of the beak. However, we assumed for bird species swallowing whole prey that a cognitive process may be involved. As cognitive feature, brain mass was used. We hypothesized that the mass of the brain was more strongly positively correlated with prey size than morphological features such as beak volume, gizzard mass and body mass. We tested this hypothesis on eiders Somateria mollissima that swallow the prey whole, by using mean and maximum size of nine prey categories. Eiders were collected at the main wintering grounds in Denmark. As index of brain mass we used head volume, which is positively correlated with brain mass (r2 = 0.73). Head volume of eiders was significantly, positive correlated with mean and maximum size of blue mussels Mytilus edulis, razor clams Ensis directus and all prey sizes combined and the maximum size of draft whelk Hinia reticulata and conch Buccinum undatum. Gizzard mass was also significantly positively correlated with maximum size of draft whelk and conch. Beak volume and body mass was not significantly correlated with the size of any of the nine food items. Analyses of effect size for organs showed that head volume was positively related to prey size, whereas beak volume, gizzard mass and body mass did not show a significant positive relationship. These results indicate that cognitive processes connected to brain mass may be involved in prey size selection by eiders.

Seasonal variation in body composition in an Afrotropical passerine bird: increases in pectoral muscle mass are, unexpectedly, associated with lower thermogenic capacity.

Phenotypic flexibility in avian metabolic rates and body composition have been well-studied in high-latitude species, which typically increase basal metabolic rate (BMR) and summit metabolism (Msum) when acclimatized to winter conditions. Patterns of seasonal metabolic acclimatization are more variable in lower-latitude birds that experience milder winters, with fewer studies investigating adjustments in avian organ and muscle masses in the context of metabolic flexibility in these regions. We quantified seasonal variation (summer vs winter) in the masses of organs and muscles frequently associated with changes in BMR (gizzard, intestines and liver) and Msum (heart and pectoral muscles), in white-browed sparrow-weavers (Plocepasser mahali). We also measured pectoral muscle thickness using a portable ultrasound system to determine whether we could non-lethally estimate muscle size. A concurrent study measured seasonal changes in BMR and Msum in the same population of sparrow-weavers, but different individuals. There was no seasonal variation in the dry masses of the gizzard, intestines or liver of sparrow-weavers, and during the same period, BMR did not vary seasonally. We found significantly higher heart (~ 18% higher) and pectoral muscle (~ 9% higher) dry mass during winter, although ultrasound measurements did not detect seasonal changes in pectoral muscle size. Despite winter increases in pectoral muscle mass, Msum was ~ 26% lower in winter compared to summer. To the best of our knowledge, this is the first study to report an increase in avian pectoral muscle mass but a concomitant decrease in thermogenic capacity.

Histological and histochemical study of the proventriculus (Ventriculus glandularis) of common starling (Sturnus vulgaris).

The histological and histochemical structures of the proventriculus of starling (Sturnus vulgaris) were examined using haematoxylin and eosin and special staining, that is periodic acid schiff (PAS), Masson's trichrome, Alcian blue, Orcein and Reticulin. All three cranial, middle and caudal parts of the proventriculus were also studied. The study results showed that the wall of the proventriculus consisted of mucosal, submucosal, muscular and serosal tunics. The mucosal tunic presented folds and sulci on its luminal surface. In the first third of the proventriculus, the tunica mucosa characterized by presence of folds lined by stratified squamous epithelium and presence of simple tubular glands in the lamina propria. In the middle and caudal thirds of the proventriculus, the surface was covered by a columnar epithelium, and the branched tubular glands were extended through the lamina propria. From the base of the branched tubular glands, the deep proventricular glands were observed that were compound tubuloalveolar lobules. The surface epithelium of the tunica mucosa and the cells lining the proventricular glands showed a positive reaction to PAS and Alcian blue stainings. In addition, the epithelial cells of the tubular and branched tubular glands showed Masson's trichrome-positive reaction. The submucosal tunic was thin in the proventricular wall. The tunica muscularis was formed by a thin inner layer of longitudinal smooth muscle fibres and a thick outer layer of circular fibres. The serosa consisted of loose connective tissue, rich in blood vessels and covered by mesothelium.

Within-Individual Canalization Contributes to Age-Related Increases in Trait Repeatability: A Longitudinal Experiment in Red Knots.

Age-related increases in the repeatable expression of labile phenotypic traits are often assumed to arise from an increase in among-individual variance due to differences in developmental plasticity or by means of state-behavior feedbacks. However, age-related increases in repeatability could also arise from a decrease in within-individual variance as a result of stabilizing trait expression, that is, canalization. Here we describe age-related changes in within-individual and among-individual variance components in two correlated traits-gizzard mass and exploration behavior-in a medium-sized shorebird, the red knot (Calidris canutus). Increased repeatability of gizzard mass came about due to an increase in among-individual variance, unrelated to differences in developmental plasticity, together with decreases in within-individual variance consistent with canalization. We also found canalization of exploration but no age-related increase in overall repeatability, which suggests that showing predictable expression of exploration behavior may be advantageous from a very young age onward. Contrasts between juveniles and adults in the first year after their capture provide support for the idea that environmental conditions play a key role in generating among-individual variation in both gizzard mass and exploration behavior. Our study shows that stabilization of traits occurs under constant conditions: with increased exposure to predictable cues, individuals may become more certain in their assessment of the environment allowing traits to become canalized.

Comparative anatomical studies on the glandular stomach of the rock pigeon (Columba livia targia) and the Egyptian laughing dove (Streptopelia senegalensis aegyptiaca).

The rock pigeon (RP) and the laughing dove (LD) are common and widely distributed species in African countries, including Egypt. The present work was carried out to characterize the comparative features of the glandular stomach (proventriculus) in these two birds, which share diets and habitats. In both species, the proventriculus is an elongated spindle obliquely situated in the cranial two-thirds of the body cavity. The length and weight of the proventriculus in the RP were about one and half times greater than that of the LD. Histologically, the proventricular wall generally consisted of the mucosa (thickest), submucosa, muscular and serosa layers. The proventricular glands occupied most of the wall of the proventriculus within the lamina propria of the mucosa. The glands are tubuloalveolar in type, consist of variable shaped lobules and are more condensed in LD than in RP. At the proventricular-gizzard junction (PGJ), the proventricular glands were observed external to the tubular glands of the gizzard in the RP, whereas in LD, these glands end abruptly and are separated from the tubular glands of the gizzard by a short distance. A scanning electron microscopy (SEM) of the proventricular lumen in RP revealed that the openings of the proventricular glands have an irregular outline surrounded by concentrically arranged mucosal folds that resemble a rosette shape. In the LD, these openings have a regular outline surrounded by thinner, widely spaced mucosal folds. To our knowledge, these results identified the structure of the proventriculus in RP and LD for the first time.

The foregut and its manipulation via feeding practices in the chicken.

The digestive system of a chicken is simple, short, and extremely efficient. In the upper gastro-intestinal tract (GIT) or foregut, in particular when feed is not continuously available, moistening of feed occurs in the crop followed by chemical and physical digestion in the proventriculus and gizzard, respectively, as a preparation for nutrient absorption which occurs in the distal portions of the GIT-duodenum, jejunum, ileum, and to a lower extent in the ceca and colon. Broiler husbandry practices in the past have focused on achieving high intakes of readily digestible nutrients and largely failed to consider the ancestral purpose of the foregut. Besides holding important digestive functions, the rich bacterial communities in both the crop and the gizzard transform these organs in barriers preventing the invasion of the GIT by pathogens. However, the amount of time feed spends in the foregut-and therefore the environment in this gut segment-is extremely variable and can be manipulated by different feeding practices, such as feed structure and composition, frequency of feeding, and/or light regimes.With further progress in terms of performance and health of broiler chickens being sought, and following decades of research focusing on distal GIT segments, it is about time to explore how the foregut can contribute to achieve these goals. This review revisits morphological, physiological, and microbiological characteristics of the foregut; explores the importance of this GIT portion as feed intake regulator; and discusses how husbandry and feeding practices such as lighting regimes and feed structure may be adapted to activate the crop and the gizzard, which results in performance and health improvements. Finally, interactions of these feeding practices with exogenous enzymes are discussed and suggestions for further research are made.

Developmental morphology study on the stomach of African ostrich chicks.

This study investigates the developmental morphology changes on the proventriculus and gizzard of African ostrich chicks using gross anatomy, and light and transmission electronic microscopy. The body weight; the weight of the proventriculus and gizzard; the thickness of simple tubular glands, muscularis mucosae, compound tubular glands, and muscular layer of the proventriculus; and the thickness of the gizzard glands and muscularis mucosae were measured on postnatal d one, 45, 90, and 334. Under transmission electronic microscopy, the oxynticopeptic cells, mucous cells, and endocrine cells were observed in the proventriculus on postnatal d one, 45, and 90. Our results revealed that the weights of the proventriculus and gizzard (relative to the body weight) both peaked on d 90, respectively, and declined thereafter. The thicknesses of the simple tubular glands, muscularis mucosae, compound tubular glands, muscular layer of the proventriculus, and gizzard glands increased with increasing bird age. However, the thickness of the muscularis mucosae in the gizzard peaked on d 90 and gradually decreased thereafter. The result of transmission electron microscopy revealed that the glands in the submucosa layer of the proventriculus did not differ from other cell types, aside from an increase in cell diameter and an increase in cytoplasmic content. A significant increase in the number of mitochondria and smooth endoplasmic reticulum was noted, as well as an in granules secreted by endocrine cells. Therefore, to improve brood rates of reared African ostrich chicks, feed management ought to be enhanced between postnatal d one and day 90.

Uncoupling Basal and Summit Metabolic Rates in White-Throated Sparrows: Digestive Demand Drives Maintenance Costs, but Changes in Muscle Mass Are Not Needed to Improve Thermogenic Capacity.

Avian basal metabolic rate (BMR) and summit metabolic rate (Msum) vary in parallel during cold acclimation and acclimatization, which implies a functional link between these variables. However, evidence suggests that these parameters may reflect different physiological systems acting independently. We tested this hypothesis in white-throated sparrows (Zonotrichia albicollis) acclimated to two temperatures (-8° and 28°C) and two diets (0% and 30% cellulose). We expected to find an uncoupling of Msum and BMR where Msum, a measure of maximal shivering heat production, would reflect muscle and heart mass variation and would respond only to temperature, while BMR would reflect changes in digestive and excretory organs in response to daily food intake, responding to both temperature and diet. We found that the gizzard, liver, kidneys, and intestines responded to treatments through a positive relationship with food intake. BMR was 15% higher in cold-acclimated birds and, as expected, varied with food intake and the mass of digestive and excretory organs. In contrast, although Msum was 19% higher in cold-acclimated birds, only heart mass responded to temperature (+18% in the cold). Pectoral muscles did not change in mass with temperature but were 8.2% lighter on the cellulose diet. Nevertheless, Msum varied positively with the mass of heart and skeletal muscles but only in cold-acclimated birds. Our results therefore suggest that an upregulation of muscle metabolic intensity is required for cold acclimation. This study increases support for the hypothesis that BMR and Msum reflect different physiological systems responding in parallel to constraints associated with cold environments.

Morphometric traits of gizzard in relation to feeding habits of wild Sardinian partridges (Alectoris barbara barbara, Bonnaterre, 1790) with particular regard to clast selection.

Housing and feeding practices of wild birds for conservation management of biodiversity or restocking play a crucial role in determining the survival rates of animals when released into nature. Failure in coping with the environment might be one of the main flaws captive animals can experience when put into natural habitat. The present investigation aimed at exploring feeding habits and related morphometric traits of gizzard with respective content from wild partridges in comparison with captive ones. A total of 52 hunted wild Sardinian adult partridges (Alectoris barbara barbara Bonnaterre, 1790) were used. By comparison, 42 captive adult partridges reared in cages were enrolled. From each animal, the morphology of gizzard was investigated and respective content analysed for gross composition and taxonomical determination of fractions. Wet sieving analysis of each gizzard content was carried out (four-sieve towers with different mesh sizes: 1 mm, 500 µm, 250 µm and 125 µm), and relative and absolute weight of fresh filled and empty gizzards were recorded. Thickness of muscular layer of gizzard wall was measured by stereomicroscope. Carcass weight significantly (p < 0.05) differed between captive vs. wild partridges (478 ± 21 and 305 ± 35 g respectively). Post-mortem inspection highlighted gross morphological differences of gizzards between the two groups. Fresh weight of empty gizzards was 6.37 ± 0.80 vs. 11.25 ± 1.82 g, with average pH values of digesta 4.97 ± 0.11 vs. 4.38 ± 0.28 in captive vs. wild partridges respectively. Gizzard content from wild partridges accounted a 61.7% vs. 38.3% of biological vs. non-biological material proportions (DM basis). The non-biological material was mostly represented by lithic fragments and minerals (quartz, feldspar, calcite and mica) with specific peculiarities in terms of granulometry and morphometry. Feeding the captive partridges should point to support morphological and functional adaptation of gizzards to the feeding stuffs naturally available in the environment.

Effects of thermo-resistant non-starch polysaccharide degrading multi-enzyme on growth performance, meat quality, relative weights of body organs and blood profile in broiler chickens.

This research was conducted to study the performance and carcass parameters of broiler chickens fed diets supplemented with heat-treated non-starch polysaccharide degrading enzyme. A total of 432 one-day old Ross 308 broiler chickens were allocated to five treatments: (i) CON (basal diet), (ii) E1: CON + 0.05% multi-enzyme, (iii) E2: CON + 0.1% multi-enzyme, (iv) E3: CON + 0.05% thermo-resistant multi-enzyme and (v) E4: CON + 0.1% thermo-resistant multi-enzyme, each treatment consisted of six replications and 12 chickens in each replication. The chickens were housed in three floor battery cages during 28-day experimental period. On days 1-7, gain in body weight (BWG) improved by feeding the diets supplemented with thermo-resistant multi-enzyme. On days 7-21 and 1-28, chickens fed the diets containing thermo-resistant multi-enzyme showed improved (p < 0.05) BWG and feed conversion ratio (FCR) compared to CON group. Supplementing the diets with multi-enzyme or thermo-resistant multi-enzyme affected the percentage of drip loss on d 1 (p < 0.05). Drip loss percentage on days 3 and 5 and also meat colour were not affected significantly. Supplementing the diets with multi-enzyme or thermo-resistant multi-enzyme did not affect the relative weights of organs but compared to CON group, relative weight of breast muscle increased and abdominal fat decreased (p < 0.05). Among measured blood constituents, chickens fed supplemented diets with thermo-resistant multi-enzyme showed higher (p < 0.05) IgG. Counts of red and white blood cells and lymphocyte percentage were not affected. In conclusion, the results demonstrated that supplementing pelleted diets with thermo-resistant multi-enzyme improved performance of broiler chickens.

The Effect of Digestive Capacity on the Intake Rate of Toxic and Non-Toxic Prey in an Ecological Context.

Digestive capacity often limits food intake rate in animals. Many species can flexibly adjust digestive organ mass, enabling them to increase intake rate in times of increased energy requirement and/or scarcity of high-quality prey. However, some prey species are defended by secondary compounds, thereby forcing a toxin limitation on the forager's intake rate, a constraint that potentially cannot be alleviated by enlarging digestive capacity. Hence, physiological flexibility may have a differential effect on intake of different prey types, and consequently on dietary preferences. We tested this effect in red knots (Calidris canutus canutus), medium-sized migratory shorebirds that feed on hard-shelled, usually mollusc, prey. Because they ingest their prey whole and crush the shell in their gizzard, the intake rate of red knots is generally constrained by digestive capacity. However, one of their main prey, the bivalve Loripes lucinalis, imposes a toxin constraint due to its symbiosis with sulphide-oxidizing bacteria. We manipulated gizzard sizes of red knots through prolonged exposure to hard-shelled or soft foods. We then measured maximum intake rates of toxic Loripes versus a non-toxic bivalve, Dosinia isocardia. We found that intake of Dosinia exponentially increased with gizzard mass, confirming earlier results with non-toxic prey, whereas intake of Loripes was independent of gizzard mass. Using linear programming, we show that this leads to markedly different expected diet preferences in red knots that try to maximize energy intake rate with a small versus a large gizzard. Intra- and inter-individual variation in digestive capacity is found in many animal species. Hence, the here proposed functional link with individual differences in foraging decisions may be general. We emphasize the potential relevance of individual variation in physiology when studying trophic interactions.

The effects of the supplementation of Bacillus subtilis RX7 and B2A strains on the performance, blood profiles, intestinal Salmonella concentration, noxious gas emission, organ weight and breast meat quality of broiler challenged with Salmonella typhimurium.

An experiment was conducted to evaluate the effects of B. subtilis RX7 and B. subtilis B2A on growth performance, blood profiles, intestinal Salmonella population, noxious gas emission, organ weight and breast meat quality of broilers under S. typhimurium challenge. A total of 120, one-day-old Ross 308 male broiler chicks were assigned to four dietary treatments, composed of six replications, with five birds per replication, for 10 day. The dietary treatment groups were negative control (NC; no antibiotic, no B. subtilis), positive control (PC; NC + 0.1% virginiamycin), B. subtilis RX7 (NC + 0.1% B. subtilis RX7 1.0 × 10(9) cfu/g) and B. subtilis B2A (NC + 0.1% B. subtilis 1.0 × 10(9) cfu/g). All birds were orally challenged with 2 ml suspension, containing 10(4) cfu/ml of S. typhimurium KCCM 40253. Results indicated that the body weight gain, feed intake and feed conversion did not differ, among all comparative treatments. Serum haptoglobin concentration was lower in Bacillus treatments (RX7 + B2A) than the NC treatment (p < 0.05). Intestinal and excreta Salmonella number, and excreta ammonia gas emission in the PC treatment or Bacillus treatments, was lower than the NC treatment (p < 0.05). Breast pH, colour and water-holding capacity were not affected by supplementation of B. subtilis RX7 and B2A. However, drip loss at 1 day post-slaughter from birds fed with B. subtilis RX7 and B2A decreased, compared with the positive control birds (p < 0.05). Relative gizzard weights of birds fed B. subtilis RX7 and B2A were significantly higher than the NC birds under S. typhimurium challenge. It is concluded from the results that B. subtilis RX7 and B2A increased the gizzard weight and decreased the intestinal and excreta Salmonella population and excreta ammonia gas, and drip loss of breast meat after being stored for 1 day, under stress caused by the S. typhimurium challenge.

The gastric isthmus from D+ and D- broiler lines divergently selected for digestion efficiency shows histological and morphological differences.

Previous results suggested that the gastric function plays a paramount role in digestive efficiency differences between D+ and D- broiler lines divergently selected for AMEn (more feed efficient and less feed efficient, respectively). In this paper we show an histological analysis of the gastric isthmus located between the proventriculus and the gizzard in the D+ and D- lines. Cross-sections were performed using a cryostat (Leica CM30505) and stained with a routine procedure using Mayer's Hematoxylin and Eosin Stain. The surface and shape of the constitutive gastric isthmus tissues were quantified using the image analysis software Image J. The lumen occupied 11% of the whole D- isthmus cross-sectional area against 24% for D+ (P < 0.01). The mucosa relative area (cm(2)/total cross-sectional area) was higher in D- than in D+ [47% (D-) and 39% (D+), P < 0.01]. It was significantly more oval and more folded on the lumen side in D- than in D+ chickens; the muscle layer (muscularis mucosae) of the mucosa was relatively more developed in D- than in D+ (16 and 11% of the section, respectively; P < 0.01). A relationship between these observations and increased gastric motility reported in D- compared with D+ is discussed.

Is gastrointestinal plasticity in king quail (Coturnix chinensis) elicited by diet-fibre or diet-energy dilution?

Phenotypic plasticity of organ size allows some animals to manage fluctuations of resource quality or availability. Here, we examined the phenotypic plasticity of the gastrointestinal tract of king quail (Coturnix chinensis) in a diet-fibre manipulation study. Quail were offered either a control low-fibre (high-quality) food (8.5% neutral-detergent fibre; NDF), or one of two experimental diets of higher fibre contents of 16% NDF (i.e. low-quality food). To examine whether phenotypic plasticity of organ size was associated with the fibre content per se, or as a consequence of diluting the diet energy contents by adding fibre, one of the high-fibre feeds was 'balanced' with additional energy to match that of the low-fibre control diet. Total empty dry mass of the gastrointestinal tract was significantly heavier among birds offered the unbalanced high-fibre diet as compared with those offered the control diet, with birds offered the fibrous but energy-balanced diet having guts of intermediate size. The heavier entire-gut mass (dry) of quail offered the unbalanced high-fibre diet was associated mainly with these birds having significantly heavier gizzards. Notably, the larger gizzard in the birds offered the unbalanced high-fibre diet was associated with marked increases in their metabolisability (digestion) of diet fibre. Our findings suggest that the available energy in the diet may be more important for eliciting phenotypic changes in the gut of these herbivorous birds rather than simple physical effects of diet fibre on feed intakes or on muscular compensation to fibrous ingesta.

Personality drives physiological adjustments and is not related to survival.

The evolutionary function and maintenance of variation in animal personality is still under debate. Variation in the size of metabolic organs has recently been suggested to cause and maintain variation in personality. Here, we examine two main underlying notions: (i) that organ sizes vary consistently between individuals and cause consistent behavioural patterns, and (ii) that a more exploratory personality is associated with reduced survival. Exploratory behaviour of captive red knots (Calidris canutus, a migrant shorebird) was negatively rather than positively correlated with digestive organ (gizzard) mass, as well as with body mass. In an experiment, we reciprocally reduced and increased individual gizzard masses and found that exploration scores were unaffected. Whether or not these birds were resighted locally over the 19 months after release was negatively correlated with their exploration scores. Moreover, a long-term mark-recapture effort on free-living red knots with known gizzard masses at capture confirmed that local resighting probability (an inverse measure of exploratory behaviour) was correlated with gizzard mass without detrimental effects on survival. We conclude that personality drives physiological adjustments, rather than the other way around, and suggest that physiological adjustments mitigate the survival costs of exploratory behaviour. Our results show that we need to reconsider hypotheses explaining personality variation based on organ sizes and differential survival.

Effects of lactulose supplementation on performance, blood profiles, excreta microbial shedding of Lactobacillus and Escherichia coli, relative organ weight and excreta noxious gas contents in broilers.

This study was to evaluate the effects of lactulose supplementation on performance, blood profiles, excreta microbial shedding of Lactobacillus and Escherichia coli, relative organ weight and excreta noxious gas contents in broilers. A total of 720 ROSS 308 broilers with a body weight of 46 ± 0.1 g (1 day of age) were used in a 28-d experiment. Broilers were randomly allotted to 4 experiment diets with 12 replicate pens and 15 birds per pen. Dietary treatments were as follows: NC, negative control (without antibiotic); PC, NC + 0.1% tiamulin; L1, NC + 0.1% lactulose; and L2, NC + 0.2% lactulose. Broilers were fed with phase 1 (1-8 day), phase 2 (9-18 day) and phase 3 (19-28 day) diets in the form of mash. During day 1-8, broilers fed the PC and L2 diets had higher (p < 0.05) body weight gain than those fed the NC diet. During day 19-28, broilers fed the L1 and L2 diets had lower (p < 0.05) feed intake than those fed the NC diet. The feed conversion ratio (FCR) was decreased (p < 0.05) in L1 treatment compared with NC treatment. Overall, the FCR was improved (p < 0.05) in all supplementation treatments compared with NC treatment. The apparently metabolizable nitrogen in L1 treatment was higher (p < 0.05) than that in NC treatment at day 28. The excreta Lactobacillus was increased and E. coli was decreased in PC and L2 treatments compared with NC treatment at day 28 (p < 0.05). The excreta NH3, H2S and acetic acid contents were decreased (p < 0.05) in L1 and L2 treatments compared with NC treatment. The relative weight of abdominal fat of broilers fed the PC diet was lowest (p < 0.05) compared with other treatments. In conclusion, this study indicated that dietary supplementation of 0.1% or 0.2% lactulose could improve growth performance, decrease excreta E. coli and excreta NH3 and H2S contents.

Effect of dietary levan fructan supplementation on growth performance, meat quality, relative organ weight, cecal microflora, and excreta noxious gas emission in broilers.

A total of 720 1-d-old male Ross broilers (BW of 48.0±0.3 g) were used to evaluate the effects of dietary levan fructan supplementation on growth performance, meat quality, relative organ weight, cecal microflora, and excreta noxious gas emission in broilers. This experiment lasted 31 d. Broilers were randomly allotted to 1 of 3 dietary treatments: 1) CON, basal diet, 2) CON+0.25% fructan (FC1), and 3) CON+0.50% fructan (FC2). Each treatment contained 16 pens with 15 chicks per pen. Broilers on levan fructan supplementation treatments (FC1+FC2) had a lower (P=0.005 for d 15 to 31) ADFI and greater (P=0.005 for d 15 to 31 and P=0.022 for d 1 to 31) G:F than those on the CON. A decreased (P=0.031) relative spleen weight was observed with levan fructan supplementation treatments compared with the CON. Cecal E. coli and C. perfringens concentrations in levan fructan treatments were decreased, while cecal Lactobacillus, as well as Bifidobacteria, concentrations in levan fructan treatments were increased compared with the CON. However, excreta NH3 concentrations were decreased (P=0.013) in levan fructan treatments compared with the CON. In conclusion, fructan supplementation improved later stage growth performance, increased cecal Lactobacillus and Bifidobacteria concentrations, and decreased cecal E. coli and C. perfringens concentrations, as well as excreta NH3 concentrations, in broilers.