Comparison of the cost of short flights in a nectarivorous and a non-nectarivorous bird.

Although most birds are accustomed to making short flights, particularly during foraging, the flight patterns during these short periods of activity differ between species. Nectarivorous birds, in particular, often spend time hovering, while non-nectarivorous birds do not. The cost of short flights is likely therefore to differ between nectarivorous and non-nectarivorous birds because of the different energetic contributions of different flight types to the behaviour. The 13C-labelled bicarbonate technique was used to measure the energy cost of short flights in the nectarivorous Palestine sunbird Nectarinia osea (mean mass 6.17+/-0.16 g, N=8) and the non-nectarivorous starling Sturnus vulgaris (mean mass 70.11+/-1.11 g, N=9). The technique was initially calibrated in five individuals for each species at temperatures ranging from 1 to 35 degrees C, by comparing the isotope elimination rate to the metabolic rate measured simultaneously by indirect calorimetry. The cost for short intermittent flight was then measured by encouraging birds to fly between two perches at either end of a narrow corridor (perch distance for sunbirds, 6 m; for starlings, 5 m), and measuring the amount of isotope eliminated during the flight. The isotope elimination rate was interpolated onto the calibration equation to predict flight cost, as a direct calibration could not be performed during flight. Mean energy expenditure during flight was 1.64+/-0.32 W in sunbirds, while in starlings the flight costs averaged 20.6+/-0.78 W. Energy cost of flight relative to basal metabolic rate was substantially greater in the starling than the sunbird. Phylogenetic analysis of different modes of flight in these and additional species suggests that differences in flight behaviour may cause these elevated costs in slow flying non-nectarivores such as starlings, compared to birds that are more prone to short intermittent flights like the sunbirds.

The energy cost of loaded flight is substantially lower than expected due to alterations in flight kinematics.

The effect of experimentally increased wing loading on the energy cost of flight was examined in cockatiels Nyphicus hollandicus. Five individuals were flown for periods of approximately 2 min, while carrying additional payload mass amounting to between 5 and 20% of unloaded body mass. The energy cost of flight was measured using the 13C-labelled bicarbonate technique, which was also calibrated in a separate experiment on resting birds, by comparing the elimination rate of 13C in breath with a simultaneous measurement of oxygen consumption by indirect calorimetry. It was not possible to perform a similar calibration during flight when energy costs were higher, so we extrapolated the relationship from the resting calibration to predict flight cost. Flight cost in the pre-manipulated individuals averaged 16.7+/-1.8 W. Flight cost in the pre-manipulated birds was significantly related to the interaction between downstroke duration and flight speed. There was no significant increase in flight cost with increases in payload mass. The birds responded to payload masses between 5 and 15% of their unloaded body mass by decreasing flight speed relative to unloaded birds, while maintaining wing beat frequency (Fb). At a payload mass equivalent to 20% of body mass, however, the birds flew at higher speeds than unloaded controls, and had a significantly higher Fb, generated by a reduction in both the upstroke and downstroke durations. Wing amplitude was unaffected by the increase in loading. Using the measured flight parameters, the effect of loading was not significantly different than predicted using aerodynamic models.

The energetic cost of variations in wing span and wing asymmetry in the zebra finch Taeniopygia guttata.

Asymmetry is a difference in the sizes of bilaterally paired structures. Wing asymmetry may have an effect on the kinematics of flight, with knock-on effects for the energetic cost of flying. In this study the 13C-labelled bicarbonate technique was used to measure the energy expended during the flight of zebra finches Taeniopygia guttata, prior to and after experimental manipulation to generate asymmetry and a change in wing span by trimming the primary feathers. In addition, simultaneous high-speed video footage enabled differences in flight kinematics such as flight speed, wing amplitude, up- and downstroke duration and wing beat frequency to be examined. In 10 individuals, the primary feathers on the right wing were trimmed first, by 0.5 cm, and then by an additional 0.5 cm in six of these individuals. In a separate 'control' group (N=7), approximately 0.25 cm was trimmed off the primary feathers of both wings, to produce the same reduction in wing span as 0.5 cm trimmed from one wing, while maintaining symmetry. When birds were manipulated to become asymmetric they maintained flight speed. They also increased the left wing amplitude and decreased the right up- and downstroke durations to counteract the changes in wing shape, which meant that they had an increase in wing beat frequency. When the wing area was reduced while maintaining symmetry, birds flew with slower flight speed. In this case wing amplitude did not change and wing upstroke slightly decreased, causing an increased wing beat frequency. The mean flight cost in the pre-manipulated birds was 1.90+/-0.1 W. There was a slight increase in flight cost with both of the asymmetry manipulations (0.5 cm, increase of 0.04 W; 1.0 cm, increase of 0.12 W), neither of which reached statistical significance. There was, however, a significantly increased flight cost when the wing span was reduced without causing asymmetry (increase of 0.45 W; paired t-test T=2.3, P=0.03).

Age-related changes in the metabolism and body composition of three dog breeds and their relationship to life expectancy.

We measured body composition and resting metabolic rates (RMR) of three dog breeds (Papillons, mean body mass 3.0 kg (n = 35), Labrador retrievers, mean body mass 29.8 kg (n = 35) and Great Danes, mean body mass 62.8 kg (n = 35)) that varied between 0.6 and 14.3 years of age. In Papillons, lean body mass (LBM) increased with age but fat mass (FBM) was constant; in Labradors, both LBM and FBM were constant with age, and in Great Danes, FBM increased with age but LBM was constant. FBM averaged 14.8% and 15.7% of body mass in Papillons and Labradors, respectively. Great Danes were leaner and averaged only 10.5% FBM. Pooling the data for all individuals, the RMR was significantly and positively associated with LBM and FBM and negatively associated with age. Once these factors had been taken into account there was still a significant breed effect on RMR, which was significantly lower in Labradors than in the other two breeds. Using the predictive multiple regression equation for RMR and the temporal trends in body composition, we modelled the expenditure of energy (at rest) over the first 8 years of life, and over the entire lifespan for each breed. Over the first 8 years of life the average expenditure of energy per kg LBM were 0.985, 0.675 and 0.662 GJ for Papillons, Labradors and Great Danes, respectively. This energy expenditure was almost 60% greater for the smallest compared with the largest breed. On average, however, the life expectancy for the smallest breed was a further 6 years (i.e. 14 years in total), whereas for the largest breed it was only another 6 months (i.e. 8.5 years in total). Total lifetime expenditure of energy at rest per kg LBM averaged 1.584, 0.918 and 0.691 GJ for Papillons, Labradors and Great Danes, respectively. In Labradors, total daily energy expenditure, measured by the doubly labelled water method in eight animals, was only 16% greater than the observed RMR. High energy expenditure in dogs appears positively linked to increased life expectancy, contrary to the finding across mammal species and within exotherms, yet resembling observations in other intra-specific studies. These contrasting correlations suggest that metabolism is affecting life expectancy in different ways at these different levels of enquiry.

The effect of varying percentage hydroxyapatite in poly(ethylmethacrylate) bone cement on human osteoblast-like cells.

Poly(ethylmethacrylate) (PEMA) bone cement has been developed, and the cements mechanical properties are improved by the incorporation of particulate fillers, such as hydroxyapatite (HA). In this in vitro study, human osteoblast-like (HOB) cells were used to examine the effect on cellular behavior of the addition of HA to PEMA using a plain PEMA control. Thymidine uptake ((3)H-TdR) and total DNA were used to assess cell growth and proliferation. Confocal laser scanning microscopy (CLSM) was used to study focal contacts and actin cytoskeletal organisation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess cell morphology and cellular ultrastucture. The early time points showed preferential anchorage to the HA exposed on the cement surface, but no difference in adhesion or proliferation. These results have been attributed to increases in residual monomer with HA incorporation, as shown by proton nuclear magnetic resonance (H(1)-NMR) spectra.

Cost of flight in the zebra finch ( Taenopygia guttata): a novel approach based on elimination of (13)C labelled bicarbonate.

On three separate occasions, five zebra finches ( Taenopygia guttata) were injected intraperitoneally with 0.2 ml 0.29 M NaH(13)CO(3)solution and placed immediately into respirometry chambers to explore the link between (13)C elimination and both O(2) consumption (VO(2)) and CO(2) production (VCO(2)). Isotope elimination was best modelled by a mono-exponential decay. The elimination rate (k(c)) of the (13)C isotope in breath was compared to VO(2) (ml O(2)/min) and VCO(2) (ml CO(2)/min) over sequential 5-min time intervals following administration of the isotope. Elimination rates measured 15-20 min after injection gave the closest relationships to VO(2) ( r(2) =0.82) and VCO(2) ( r(2)=0.63). Adding the bicarbonate pool size (N(c)) into the prediction did not improve the fit. A second group of birds ( n=11) were flown for 2 min (three times in ten birds and twice in one) between 15 min and 20 min following an injection of 0.2 ml of the same NaH(13)CO(3) solution. Breath samples, collected before and after flight, were used to calculate k(c) over the flight period, which was converted to VO(2) and VCO(2) using the equation generated in the validation experiment for the corresponding time period. The energy expenditure (watts) during flight was calculated from these values using the average RQ measured during flight of 0.79. The average flight cost measured using the bicarbonate technique was 2.24+/-0.11 W (mean+/-SE). This average flight cost did not differ significantly from predictions generated by an allometric equation formulated by Masman and Klaassen (1987 Auk 104:603-616). It was however substantially higher than the predictions based on the aerodynamic model of Pennycuick (1989 Oxford University Press), which assumes an efficiency of 0.23 for flight. The flight efficiency in these birds was 0.11 using this model. Flight cost was not related to within-individual variation [general linear model (GLM) F(1,31)=1.16, P=0.29] or across-individual variations in body mass (GLM F(1,31)=0.26, P=0.61), wingspan (regression F(1,10)=0.01, P=0.94) or wing loading (regression F(1, 31)=0.001, P=0.99) in this sample of birds.

Increasing hydroxyapatite incorporation into poly(methylmethacrylate) cement increases osteoblast adhesion and response.

Poly(methylmethacrylate) (PMMA) is the current standard for cement held prostheses. It forms a strong bond with the implant, but the bond between the cement and the bone is considered to be weak, with fibroblastic cells observed at the implant site, rather than direct bone contact, a contributing factor leading to implant failure. Incorporation of hydroxyapatite (HA) increases the biological response to the cement from tissue around the implant site, thus giving increased bone apposition. In this study, PMMA discs with 0, 4.6 and 8.8 vol%. HA were examined. Primary human osteoblast-like cells (HOBs) were used for the biological evaluation of the response to the cements in vitro. Morphology was observed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Measurement of tritiated thymidine (3H-TdR) incorporation and alkaline phosphatase (ALP) activity were used to assess proliferation and differentiation. A synergy between increasing focal contact formation, cytoskeletal organisation, cell proliferation and expression of phenotype was observed with increasing HA volume. Preferential anchorage of HOBs to HA rather than PMMA was a prominent observation.

In vitro adhesion and biocompatability of osteoblast-like cells to poly(methylmethacrylate) and poly(ethylmethacrylate) bone cements.

A bone cement, poly(ethylmethacrylate)/n-butylmethacrylate (PEMA/nBMA) has been developed with lower exotherm and monomer leaching compared to the traditional poly(methylmethacrylate)/methylmethacrylate (PMMA/MMA) cement. This study compares the in vitro biological response to the cements using primary human osteoblast-like cells (HOB). Cell attachment was qualified by immunolocalization of vinculin and actin cytoskeleton, showing more organization on PEMA/nBMA compared to PMMA/MMA. Proliferation was assessed using tritiated thymidine incorporation, and phenotype expression determined by measuring alkaline phosphatase (ALP) activity. An increase in proliferation and ALP activity was observed on PEMA/nBMA compared to PMMA/MMA. The results confirm the biocompatability of PEMA/nBMA, and an enhanced cell attachment and expression of differentiated cell phenotype.

The use of P-aminobenzoic acid and chromic oxide to confirm complete excreta collection in a carnivore, Felis silvestris catus.

Complete excreta collection is a pre-requisite for several protocols in protein metabolism, and lack of confidence in achieving this may be increased when working with carnivores. Recovery of p-aminobenzoic acid (PABA) as a check for complete urine collection and chromic oxide for complete faeces collection were assessed in the cat. A single oral dose of PABA (4 mg/kg BW) was excreted more slowly than has been reported in the human (82% recovery at 6 h). A daily dose of PABA proved a useful method for confirming complete urine collection in the cat, and was 99% excreted in 72 h. Chromic oxide (500 mg/cat) was administered orally and recovery of chromium in the faeces was 90% after 96 h. A HPLC method for the analysis of PABA in cat urine was developed, and from the application of the techniques to a nitrogen balance study, it was concluded that PABA and chromic oxide are useful checks for complete excreta collection in the cat.

Effects of feeding regimens on bodyweight, composition and condition score in cats following ovariohysterectomy.

The effects of ovariohysterectomy on bodyweight, composition and condition score were evaluated in 49 cats that were fed ad libitum and 11 cats that had their food allowances controlled with the aim of maintaining a stable bodyweight. In cats fed ad libitum, bodyweight increased by an average of 31 per cent in the 12 months following ovariohysterectomy compared with 3.1 per cent over the 12 months before surgery, and this was largely due to increased body fat content. There was no difference in weight gain between cats fed dry or canned foods, but weight gain was inversely related to age and bodyweight at the time of neutering. Mean bodyweight increased by 7.5 per cent in the controlled feeding group, compared with 3.6 per cent over the 12 months before surgery, and individual bodyweights were maintained to within 10 per cent of pre-neutering values in nine cats. The other two cats experienced substantial weight gain (+20 per cent and +36 per cent), despite being fed only 40 kcal/kg/day. There were no significant changes in body composition of cats with controlled dietary allowances and their condition scores were significantly lower than those of cats fed ad libitum. The results confirm a link between ovariohysterectomy and the development of obesity in cats with free access to food, and indicate that substantial reductions in energy intake are required to prevent weight gain in such cats.

Initial interaction of osteoblasts with the surface of a hydroxyapatite-poly(methylmethacrylate) cement.

Failure of the bone/cement interface in cemented joint prostheses is a contributor to implant loosening. The introduction of a bioactive phase, such as hydroxyapatite (HA), to cement may enhance fixation by encouraging direct bone apposition rather than encapsulation of the implant by fibrous tissue. The effect of poly(methylmethacrylate) (PMMA) bone cement (incorporating 17.5% HA wt.) on bioactivity has been investigated using primary human osteoblast-like cells (HOB). A significantly higher cell proliferation and differentiation was seen on the PMMA/HA cement compared to the PMMA cement alone, with retention of phenotype up to 21 days of culture on both materials.

Tensile characteristics of ten commercial acrylic bone cements.

The mechanical properties of acrylic bone cement, used in orthopedic surgery, are very influential in determining successful long-term stability of a prosthesis. A large number of commercial formulations are available, differing in chemical composition and physical properties of both powder and monomer constituents. In this study, the static and dynamic tensile characteristics of a number of the most commonly used bone cements (Palacos R, Simplex P, CMW 1 & 3, Sulfix-60, Zimmer Dough), along with some newer formulations (Endurance, Duracem 3, Osteobondtrade mark and Boneloc), have been investigated under the same testing regimes. Testing was performed in air at room temperature. Significant differences in both static and fatigue properties were found between the various bone cements. Tensile tests revealed that Palacos R, Sulfix-60, and Simplex P had the highest values of ultimate tensile strength, closely followed by CMW 3, while Zimmer Dough cement had the lowest strength. Fatigue testing was performed under stress control, using sinusoidal loading in tension-tension, with an upper stress level of 22MPa. The two outstanding cements when tested in these cyclic conditions were Simplex P and Palacos R, with the highest values of Weibull median cycles to failure. Boneloc bone cement demonstrated the lowest cycles to failure. While the testing regimes were not designed to replicate exact conditions experienced by the bone cement mantle in vivo, there was a correlation between these results and clinical outcome.

Nutrition and energetics of the canary (Serinus canarius).

Canaries appear to be primarily seed-eaters, although there are no reports of their feeding ecology in the wild. In captivity, they are offered seed-based diets, preferring to consume seeds such as canary, rapeseed and millet. The mean daily dry-matter intake ranges from 3 to 4 g, which corresponds to a mean gross energy intake of approximately 70 kJ per bird per day. The efficiency of dietary metabolism is high (0.85), which equates to individual metabolizable energy intakes of 45-75 kJ per bird per day. For a canary of average body weight (22 g) the data can be fitted to a regression equation to predict a requirement of 62 kJ ME per day. This corresponds to published information on the energy requirements of other passerine species, but deviates from the predictive equation for poultry. The digestibility values for protein, fat and carbohydrate are similar to those obtained for the budgerigar, although it is likely that the digestibility coefficient is dependent upon the seed type and alimentary tract lipase and amylase activities. Nutrient requirements of canary chicks have not yet been determined, although recent studies have provided data on the nutrient intakes of developing chicks. The newly-hatched canary chick has a rapid growth rate, achieving 90% of its asymptotic body mass by 11 days of age. Gross energy intake is approximately 3 kJ per day following hatching and by day 10 is equivalent to that of an adult canary. It appears that the protein intake should lie between 16.5 and 21.9% of the diet (as is), with peak intake occurring between 8 and 10 days of age.

Age-related changes in apparent digestibility in growing kittens.

The ability of the growing kitten to digest protein, fat, carbohydrate, dry-matter and energy were assessed. Kittens were divided into two groups; one group was fed a wet diet, the other a dry diet. Both groups were allowed ad libitum access to food. Apparent digestibility of the two diets, and kitten bodyweights were measured over a 24-week period. There were no significant differences in mean bodyweight between the two groups. Digestible energy intake of the kittens decreased with increased age; regression analysis of the data generated two fitted models which appeared to accurately predict the digestible energy intake between 39 and 41 weeks of age. There was a significant (P < 0.05) effect of diet on the apparent digestibility of protein, organic-matter and dry-matter. Age had a significant (P < 0.05) effect on the apparent digestibility of all the parameters measured. Newman-Keuls multiple range tests showed that apparent digestibility of carbohydrate, organic-matter and total energy significantly (P < 0.05) increased in kittens older than 19 weeks. This suggests that the digestive capacity of the younger cat may be affected by the physiological development of the gut, and dietary induced enzyme modulation.

Gastrointestinal transit times in young and old cats.

Ageing results in a decrease in apparent nutrient digestibility in the gastrointestinal (GI) tract. The aim of this study was to investigate whether the rate of gastric emptying or total GI transit times differed between young (3.0+/-0.9 years) and senior (11.6+/-1. 4 years) cats. Gastric emptying rates were measured using [1-(13)C]octanoic acid and total transit times with chromium oxide. No significant differences (P>0.05) were observed in either the rate of gastric emptying or total transit time between young and senior cats although senior cats exhibited a larger variability in total transit time compared to the younger cats (35.71+/-14.06 and 26. 46+/-5.80 h, respectively). The results of this study indicate that the observed reduction in nutrient digestibility in ageing cats is not due to alterations in the rate of passage of digesta through the GI tract.

Influence of feeding regimen on body condition in the cat.

The influence of feeding regimen on body condition in the cat was studied in a sample of the UK domestic cat population (n = 136). Data were collected by interviewing cat owners and assessing body condition of cats in the owners' homes. Four main factors were identified which were related to body condition. These were, in descending order of significance: neuter status, age, frequency of treat feeding, and ad libitum feeding. Feeding regimen as a risk factor in feline obesity is discussed.

Urea kinetics of a carnivore, Felis silvestris catus.

The effect of two levels of dietary protein energy, moderate (20%; MP) and high (70%; HP), on urea kinetics in eleven domestic cats was studied. After a 3-week prefeed, a single dose of [(15)N(15)N]urea was administered, and urine and faeces collected over the subsequent 5 d. For each 24 h period, total urea and enrichment of [(15)N(15)N]- and [(15)N(14)N]urea in urine were determined, and a model applied to calculate urea production, entry into the gastrointestinal tract, recycling to urine or faeces and, by difference, retention by the body and potentially available for anabolism. Urea production and excretion increased with dietary protein level Most of the urea produced was excreted, with only a small proportion entering the gut, and with the pattern of urea disposal not significantly different between the HP and MP diets. Thus, the percentages of urea production available to the gut were 15% (MP) and 12% (HP), of which 57% (MP) and 59% (HP) was recycled in the ornithine cycle, 40% (MP and HP) was potentially available for anabolism and the rest lost as faecal N. As a percentage of urea produced the amount potentially available for anabolism was very low at 6.41% (MP diet) and 4.79% (HP diet). In absolute terms urea entering the gut, being recycled in the ornithine cycle and potentially available for anabolism was significantly higher on the HP diet These results show that cats operate urea turnover, but at a lower rate, and with less nutritional sensitivity than has been reported for other species.

Mechanical properties of hydroxyapatite reinforced poly(ethylmethacrylate) bone cement after immersion in a physiological solution: influence of a silane coupling agent.

PEMA-based bone cement has previously been shown to possess many advantages over traditional PMMA cements. One of these is the option of adding up to 40 wt % HA without a decrease in static mechanical strength, thus providing the potential for enhanced bioactivity. Bone cement, in vivo, is subjected to an aqueous environment and therefore, it is important to understand the influence of this upon the mechanical integrity of experimental cements. In this current investigation the static and dynamic properties of PEMA cement, with and without 30 wt % untreated and silanated HA, were examined after periods of immersion in Ringer's solution. A commercial PMMA cement was also tested in a similar manner. Relatively small changes in static mechanical properties were observed after 12 weeks storage for the PEMA cements, the largest change being for the PEMA cement reinforced with silanated HA. The PMMA cement exhibited the largest change in static strength with a decrease of 16.6%. In contrast to these results, the fatigue properties of the PEMA cements were found to decrease significantly after storage in Ringer's solution, again with the largest changes to the PEMA cement reinforced with silanated HA. This effect was attributed to the reduction in efficiency of the silane coupling agent in the presence of water. The fatigue resistance of the PMMA cement was not reduced after immersion in a saline environment.

The effect of ageing on nutrient digestibility by cats fed beef tallow-, sunflower oil- or olive oil-enriched diets.

Nutrient digestibility and absorption decline with age in several mammalian species. The aim of this study was to compare apparent fat digestibility of different dietary fats in young and senior cats. Three diets enriched with either beef tallow (high in saturated fatty acids), olive oil (high in monounsaturated fatty acids) or sunflower oil (high in polyunsaturated fatty acids) were fed to 6 young (3.0+/-0.9y) and 6 senior (11.6+/-1.4y) cats at 300kJ metabolisable energy/kgBW0.75/d in a 3*3 Latin square design. Food and faecal samples collected over two consecutive 7d periods were analysed for fat, protein, moisture, ash, gross energy and fatty acid content. Apparent digestibilities of fat and energy were significantly lower (P=0.03) in senior cats compared to young cats (fat: 0.922 compared to 0.944; energy: 0.848 compared to 0.885, for senior and young cats, respectively) in all three diets. Senior cats exhibited a lower apparent digestibility for all fatty acid groups compared to the younger cats (saturated: 0.932 compared to 0.952; monounsaturated: 0.964 compared to 0.982; polyunsaturated: 0.980 compared to 0.987, for senior and young cats, respectively). Saturated fatty acids had the lowest apparent digestibility in both young and senior cats, and shorter chain fatty acids were digested more easily than the longer chain fatty acids. These results suggest that the age-related reduction in apparent fat digestibility was a general phenomenon affecting all fatty acids, and was not due to one particular fatty acid group.