Significant Differences In Body Condition Research Articles

Body condition of three autochthonous canid species from Serbia

The body condition of three autochthonous canid species in Serbia (wolf- Canis lupus, jackal-Canis aureus, and fox-Vulpes vulpes) was assessed based on the value of Kidney Fat Index (KFI). A total of 1232 specimens (147 wolves, 711 jackals, and 375 foxes) were collected during a ten years period. Data were analyzed according to multiple factors such as sex, age, seasons, species, and genus. The results indicate that the adult members of the Canis genus have a significantly better body conditional status than the yearlings as well as the representatives of the Vulpes genus (F (2, 900) = 71.465, p = 0.000). Significant differences in KFI across seasons are recorded in jackal (F (3, 542) = 6.912, p < 0.001) and fox (F (3, 371) = 2.675, p < 0.05) populations. Jackals have the highest KFI during winter when females are in significantly better body condition than males. None of these three canid species has shown a significant difference in body condition between sexes, although females had slightly higher KFI. Among adult female jackals, a difference in KFI between nursing ones and other adult and pregnant females is observed (H (2, n = 220) = 8.339, p = 0.016). Food deprivation which occurs naturally during the winter months does not affect the body conditional status of these predators which are well prepared for the upcoming breeding season. Considered as a whole, in spite of the differences observed at the genus level, the body condition status of these autochthonous canids measured through KFI index indicates decent average fitness status in wolves, jackals, and foxes in Serbia.

Noninvasively Collected Fecal Samples as Indicators of Multiple Pesticide Exposure in Wild Birds.

Pesticide use poses a potential hazard to wild birds that use agricultural farmland as their foraging habitat. Whereas most current pesticide studies have found residues in liver samples and single active substances, noninvasive sampling methods and data on a wide variety of agrochemicals are needed to determine pesticide exposure of living wild birds for postregistration monitoring. We collected feces during autumn migration of Eurasian skylarks (Alauda arvensis), a species that commonly forages in winter cereal crops. Birds were kept in paper bags until we measured their body condition, individually marked and released them. We analyzed the feces dropped in paper bags for the presence of 80 pesticides including rodenticides and degradation products. Nine active substances from fungicides and herbicides commonly used in grain and maize fields were detected individually, or in combination, in 25% of the samples. We found no significant differences in body condition between exposed and unexposed birds, but Eurasian skylarks without pesticide residues had a better body condtion score on average than birds with pesticide residues. Pesticide determination in noninvasively collected fecal samples allows a refined risk analysis, which takes pesticides used in the habitats of birds into account. It allows the search for the sources of pesticide contamination, but also enables research into potential deleterious effects on the fitness of farmland birds. Environ Toxicol Chem 2022;41:201-207. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Stable isotopes of carbon reveal flexible pairing strategies in a migratory Arctic bird

Many birds change their partners every year and pairing may occur before arrival on the breeding grounds. Early pairing strategies can benefit mates by strengthening pair-bonds and increasing the rate of pre-breeding resource acquisition, leading to increased reproductive output and success, especially for migratory species breeding in seasonally-constrained environments like the Arctic. Despite the theorized and documented advantages of early pairing, we know rather little about pairing phenology in many species. Here, we test the use of a stable isotope (carbon δ13C) method to assign geographic origin of paired birds to examine pairing phenology in Arctic-breeding Common Eiders (Somateria mollissima borealis). During two consecutive years, we captured paired individuals upon their arrival at breeding grounds approximately 2–3 weeks before laying. Pairs with similar δ13C in their claws indicates that they paired during winter, while similar blood values (with no similarity in claws) would reveal pairs formed much later, during the pre-breeding period near or on the breeding grounds. While a large proportion of pairs (43%) appeared to pair on wintering grounds, an almost equal number (52%) likely paired within 1 month prior to arrival on the breeding grounds. The remaining 5% did not have an obvious pairing time. Despite this variability in pairing phenology, we found no significant differences in body condition between females or males which paired in winter or spring. In the year characterized with more challenging winter conditions, pairs formed in spring tended to have a higher breeding propensity than those formed in winter, although there were no detectable links to body condition. Delaying pairing until spring may be advantageous for Arctic-breeding eiders, although a specific mechanism is unknown. Future research focusing on the energetic costs and benefits for male eiders during these periods would help further understand pairing phenology and potential impacts on males of female breeding decisions.

Measures of Health Provide Insights Into the Coping Strategies of Urban Lizards

Abstract The rapid rate of urbanization worldwide and its consequences for affected species and ecosystems urgently warrants research and action. Whether animals are effectively coping from urbanization is hotly debated, especially since interpretations are based on different measures of animal responses. Here, we take a physiology-centric view of animal coping strategies, and set up predictions for distinguishing urban adaptors and exploiters using multiple markers of health. Our study compares rural and urban populations of a tropical lizard species, the Indian rock agama (Psammophilus dorsalis), that lives in a rapidly changing and highly threatened semi-arid ecosystem in Southern India. Contrary to expectations, we did not find any significant differences in body condition, number of ectoparasites, and degree of cell-mediated immune response between lizards from urban and rural areas, despite previously documented differences in aspects of their behaviour. However, urban lizards had lower heterophil to lymphocyte ratios, as well as lower testosterone levels compared to rural lizards, which suggest active physiological coping responses. Notably, we find no correlation between the different physiological measures within individuals; strongly reflecting the flexible and independent axes of health responsiveness. Overall, the considerable overlap in responses by urban and rural lizards highlights the importance of using multiple measures of immunity to evaluate health status. These data collectively indicate that P. dorsalis is an urban adaptor, and that the tropical urban environment is not associated with harmful consequences for their health.

Four Plasma Glucose and Insulin Responses to a 75 g OGTT in Healthy Young Japanese Women.

The incidence of diabetes has been gradually increasing, not only in middle-aged individuals but also in young individuals. However, insulin and glucose patterns have not been investigated in apparently healthy young individuals, as they are typically grouped as controls. In this study, we investigated and classified glucose and insulin patterns in healthy young women. Sixty-two nonobese women without metabolic disease were recruited. The subjects underwent a 75 g oral glucose tolerance test (OGTT), physical measurements, and a biochemical examination. Two subjects displayed impaired glucose tolerance. The 62 subjects were categorized into four patterns by plasma glucose and insulin peak time during OGTT: normal type (n = 39), insulin-late type (n = 11), insulin- and glucose-late type (n = 7), and insulin-very late type (n = 5). OGTT glucose and insulin levels at all time points, insulinogenic index, HOMA-IR, and glucose area under the curve (AUC) significantly differed among the four groups. However, insulin AUC did not significantly differ. We did not detect significant differences in body condition or biochemical measurements. Our study demonstrated that some healthy young individuals might have delayed insulin secretion by OGTT. Early detection of altered glucose metabolism might be helpful to improve lifestyle choices and prevent progression to diabetes.

HEMATOLOGIC AND BIOCHEMICAL PARAMETERS OF KELP GULLS (LARUS DOMINICANUS) CAPTURED IN THE CITY OF TALCAHUANO, CHILE

In order to provide tools for future health-based monitoring programs, we developed reference intervals for hematology and plasma biochemistry and partitioned data for sex and season (winter and autumn). Ninety-one physically healthy kelp gulls (Larus dominicanus) were sampled in the city of Talcahuano, Chile, during winter (July-September) of 2007, autumn (April-June) and winter of 2008, and autumn of 2009. After blood sampling, the kelp gulls were euthanized by cervical dislocation. Packed cell volume (PCV), hemoglobin, total plasma protein (TPP), and complete blood count were performed. Alanine amino transferase, gamma-glutamyl transpeptidase, lactate dehydrogenase, alkaline phosphatase (ALP), creatinine, urea, calcium, phosphorus, and uric acid were analyzed. No significant differences were found between sexes (P>0.05). When a comparison was made between the two seasons, the values of PCV, TPP, white blood cell, heterophils, eosinophils, and monocytes were significantly higher in winter than in autumn (P<0.05) while and urea and uric acid concentrations were higher in autumn. Heterophils were the predominant circulating leukocyte for all birds. There was no significant difference in body condition between autumn and winter nor between sexes. Body condition showed a significant relationship with TPP and basophil concentration and ALP activity.

Reverse Movements of Red KnotsCalidris canutusDuring Northward Migration in Argentina

Migratory birds are sometimes known to make reverse movements to seek better fuelling sites before undertaking long-distance migratory flights across ecological barriers. Red knots Calidris canutus rufa regularly make prodigious migratory flights of ∼ 8,000 km from southern South America to North America; these flights depend critically on the birds being able to store adequate fuel at southern staging sites. Knots staging at San Antonio Oeste (SAO) in northern Patagonia in Argentina could potentially backtrack ∼200 km southwards to complete refuelling at Península Valdés (PV). We therefore analysed resightings of birds individually marked in SAO or the flyway at these two staging sites in 2006, 2007, 2009 and 2010 to investigate whether reverse movements occurred between them. In the four-year period, 63 detected individuals backtracked south from SAO to PV in one or more years. These movements occurred in all years of the study thus demonstrating the annual occurrence of flights of ∼200 km in the opposite direction to the normal northward migration. There was no significant difference in body condition (mass), sex or day of first sighting in SAO between birds that made or did not make reverse movements to PV. However, individuals (N = 11) that backtracked to PV from SAO had significantly lower hematocrit levels at the time of capture than SAO resident birds (N = 205). Because migrating shorebirds have been shown to restore low hematocrit levels before undertaking rapid fuel storage to power long flights, we hypothesise that red knots backtracking to PV were probably behind schedule on migration, and thus may have traded-off the small cost of a ∼200 km flight for the increased foraging time and high quality soft-shell prey available late in the season at PV. This hypothesis helps to explain the later staging phenology of red knots using PV, and its role as an alternative staging area in the northward migration.

Sex identification and PIT‐tagging: tools and prospects for studying intersexual differences in freshwater fishes

This study evaluated a technique to allow the long-term monitoring of individual fishes of known sex in the wild using sex confirmation in close proximity to the reproductive period combined with individual tagging. Hundreds of partially migratory roach Rutilus rutilus were tagged with passive integrated transponders (PIT) following sex determination in spring and various performance measures were compared with fish tagged outside the reproductive period in autumn. Short-term survival was >95% for R. rutilus sexed and tagged under natural field conditions. Total length (LT ) did not affect the probability of survival within the size range tagged (119-280 mm), nor were there differences in timing of migration the following season between individuals sexed and tagged in spring and individuals tagged in autumn (i.e. outside the reproductive period). Also, a similar per cent of R. rutilus sexed and tagged in spring and tagged in autumn migrated the following season (34·5 and 34·7%). Moreover, long-term recapture data revealed no significant differences in body condition between R. rutilus individuals sexed and tagged in spring, individuals tagged in autumn and unmanipulated individuals. The observed sex ratio of recaptured fish did not differ from the expected values of equal recapture rates between males and females. Hence, there is no observable evidence for an adverse effect of tagging close to the reproductive period and therefore this method is suitable for studying intersexual differences and other phenotypic traits temporarily expressed during reproduction at the individual level in fishes.

Invasive Ants Alter Foraging and Parental Behaviors of a Native Bird

Introduced species can exert outsized impacts on native biota through both direct (predation) and indirect (competition) effects. Ants frequently become established in new areas after being transported by humans across traditional biological or geographical barriers, and a prime example of such establishment is the red imported fire ant (Solenopsis invicta). Introduced to North America in the 1930's, red imported fire ants are now firmly established throughout the southeastern United States. Although these invasive predators can dramatically impact native arthropods, their effect on vertebrates through resource competition is essentially unknown. Using a paired experimental design, we compared patterns of foraging and rates of provisioning for breeding eastern bluebirds (Sialia sialis) in unmanipulated (control) territories to those in adjacent (treated) territories where fire ants were experimentally reduced. Bluebirds inhabiting treated territories foraged nearer their nests and provisioned offspring more frequently than bluebirds inhabiting control territories with unmanipulated fire ant levels. Additionally, nestlings from treated territories were in better condition than those from control territories, though these differences were largely confined to early development. The elimination of significant differences in body condition towards the end of the nestling period suggests that bluebird parents in control territories were able to make up the food deficit caused by fire ants, potentially by working harder to adequately provision their offspring. The relationship between fire ant abundance and bluebird behavior hints at the complexity of ecological communities and suggests negative effects of invasive species are not limited to taxa with which they have direct contact.

Sheep fed only silage or silage supplemented with concentrates. 1. Effects on ewe performance and blood metabolites

In Scandinavia, winter diets for sheep are forage-based, with concentrates commonly being added in the latter part of pregnancy and during lactation. In organic production, however, the level of concentrates is restricted and rations are sometimes purely forage-based. It is uncertain if feeding only forage fulfils the nutritional requirements of high producing ewes. The aim of this project was to compare the performance and nutrient status of ewes fed only silage from mid-pregnancy until the end of lactation (SIL), or silage and a maximum of 40% concentrates before lambing, and 50% afterwards (CON). The study was conducted during two consecutive indoor feeding seasons (Y1 and Y2), with 41 and 51 ewes, respectively. In Y1, the silage was of high nutrient quality, whereas the silage used in Y2 had a lower content of energy and protein and more fibres. The general level of feed intake was lower in Y2 than Y1. There were significant differences in body condition between SIL and CON ewes in both years. Blood samples from the ewes were analyzed for betahydroxybutyrate (BHB), non-esterified fatty acids (NEFA) and urea. In both years, SIL ewes had higher NEFA and BHB than CON ewes two weeks after lambing, In Y2, urea was lower in SIL ewes than in CON ewes after lambing. Litter size also had a significant impact on the blood metabolites. In conclusion, feeding only silage is not recommended for ewes with more than one lamb, unless the silage is of a very high nutritional quality.

Hantavirus ecology in rodent populations in three protected areas of Argentina

In this study, we identified hantavirus genotypes and their reservoirs and evaluated the spatial and temporal distribution of the virus in rodent population in three protected areas of Argentina over 3 years (2007-2010). A total of 837 rodents were captured with an effort of 22 117 trap-nights. We detected the genotype Lechiguanas in Oligoryzomys nigripes and O. flavescens and Pergamino in Akodon azarae. There was no correlation between seroprevalence and trap success of the host. The proportion of seropositive males was significantly higher than the proportion of seropositive females. The total length of seropositives was higher than that of seronegatives in each host species. Seropositive individuals were observed in warm months and not in cold months, which suggests an infection cycle. This investigation confirms that protected areas of central east Argentina are places with a variety of sylvan rodents species associated with different hantavirus genotypes where reservoirs are numerically dominant. Although there was more than one known reservoir of hantavirus, only one species had antibodies in each area. This can be explained because the transmission of the virus does need not only the presence of a rodent species but also a threshold density. Longevity of even a small proportion of the host population in cold months may provide a trans-seasonal mechanism for virus persistence. The seroprevalence detected was higher than the one found before in rodent populations of Argentina, and this explains the appearance of human cases in two of these three areas.

Influence of signalment on developing cranial cruciate rupture in dogs in the UK

To investigate risk factors associated with cranial cruciate ligament rupture in dogs. Retrospective case-control study: medical records of a first-opinion veterinary practice were searched for dogs diagnosed with cranial cruciate ligament rupture (1995 to 2007). For each case, six unaffected dogs were randomly selected from all dogs presenting that day for comparison. Multi-variable binary logistic regression was performed to assess the association of variables on likelihood of cruciate rupture. Frequency of cranial cruciate ligament rupture was 1·19% [95% confidence interval (CI) 1·02 to 1.36%]. West Highland white terriers (n=17), Yorkshire terriers (n=14) and Rottweilers (n=11) were at significantly increased risk of cranial cruciate ligament rupture (P≤0·002). Rottweilers were at five times greater risk compared with other pure breeds (OR 5·12, 95% CI 2·281 to 11·494, P<0·001), obesity quadrupled the risk of cranial cruciate ligament rupture (OR 3·756, 95% CI 1·659 to 8·502, P=0·001) and females were twice as likely to suffer cranial cruciate ligament failure compared to males (OR 2·054, 95% CI 1·467 to 2·877, P<0·001). Dogs less than two years old were statistically less likely to sustain cranial cruciate ligament rupture than dogs older than eight years (OR 0·246, 95% CI 0·127 to 0·477, P<0·001). There was no significant difference in median weights (in kilograms) of neutered dogs, compared to their entire counterparts in either the case group (P=0·994) or in the control group (P=0·630). There was also no significant difference in body condition (-underweight/normal weight/overweight/obese) of neutered versus entire dogs among the cases (P=0·243), or the controls (P=0·211). Cranial cruciate ligament rupture is more likely in Rottweilers and in female dogs, older dogs and obese dogs. Following multi-variable analysis, it was established that neutering was not associated with increased risk of cranial cruciate ligament rupture.

Sunflower Based Rations for Small-Medium Milk Producing Dairy Cows

Two dairy concentrates (ram press sunflower and sunflower heads) were formulated locally and their effects on the performance of crossbred dairy cows were compared with that of a commercial dairy concentrate. There were no significant differences in body condition and milk production responses by crossbred dairy cows to sunflower based diets compared to commercial dairy concentrates (p > 0.05). It was suggested that the sunflower based rations can be used as cheaper alternatives to conventional dairy concentrates. The ram press sunflower cake, in particular is an option that may be used by smallholder dairy farmers to formulate local dairy concentrate, which influence dairying to a similar extent as the commercial dairy concentrate but cheaply. More research is required to determine fermentation patterns, rumen microbial protein synthesis, true intestinal digestibility and absorption of nutrients from sunflower-based diets at the small intestines in crossbred dairy cows.

Food limitation and low-density populations of sympatric hamster species in North China

Although food has been proposed as a possible factor on population regulation of small mammals, evidence of food restriction in field conditions is still lacking. Food restriction is generally thought to occur in high-density years of oscillating populations of small mammals. By using two body condition indices (muscle protein concentration and cleaned carcass index), we investigated variations of body condition of the greater long-tailed hamster (Tscherskia triton) and the striped hamster (Cricetulus barabensis) in the Raoyang County of the North China Plain during a population decline- and low-phase from 1998 to 2003. Our laboratory experiments showed that food restriction reduced muscle protein concentration and cleaned carcass index of greater long-tailed hamster. We found there were significant differences in body condition of hamsters over the six years. Both the muscle protein concentration and cleaned carcass index of T. triton were significantly and positively correlated with its yearly trap successes, which reflected yearly population densities. Muscle protein concentration of C. barabensis was positively correlated with the total yield of the wheat. This observation supported the hypothesis on the in-phase relation between food resources or availability and rodent abundances. During the four seasons, muscle protein concentration of two species was highest in autumn, and lowest in summer. These two body condition indices of wild T. triton in summer and in low phases were similar to 60% food restricted animals raised in the laboratory, but significantly lower than nonfood- restricted animals. Our results indicated that malnutrition occurred in summer when food was not abundant, and in low density years with low grain production (an index reflecting food abundance of rodents) in our study region. Therefore, we concluded that food limitation may play an important role in seasonal and inter-annual population fluctuation of these two hamster species.

Long-term study of Sarcoptes scabiei infection in Norwegian red foxes ( Vulpes vulpes) indicating host/parasite adaptation

The red fox ( Vulpes vulpes) population, in Norway, was naïve to Sarcoptes scabiei prior to the late 1970s when this parasite was first recorded and a still ongoing epidemic started. During the course of this protracted epidemic some degree of host/parasite adaptation, with the occurrence of healthy antibody positive foxes, might be expected. In the present study the prevalence of sarcoptic mange and serologically identified S. scabiei exposure was investigated in 363 Norwegian red foxes, shot by hunters during two different study periods (1994–1995 and 2002–2005). The sarcoptic mange diagnosis was based upon the presence of clearly visible lesions in the skin of the cadaver with confirmatory demonstration of S. scabiei. The serodiagnosis was based on an indirect-ELISA. There was a significant decrease in prevalence of both mange cases and seropositive animals from the first to the second study period. Whilst the mange prevalence fell more than threefold, from 30.0% to 6.6%, the seroprevalence dropped less dramatically from 53.3% to 19.1%. The smaller decrease in seroprevalence compared to mange cases reflected a significantly higher ratio of seropositive-mange negative versus seropositive-mange positive foxes, during the second study period, 40:18, compared to the first, 14:18. These findings indicate that the red fox population is adapting to live with the parasite and that low-grade or sub-clinical infections, and even recoveries, occur amongst exposed foxes. Mange positive foxes had significantly poorer body condition than those without sarcoptic mange. No significant difference in body condition was seen between seropositive-mange negative versus seronegative-mange negative foxes. The ELISA sensitivity was found to be 95% and proved a useful tool for investigating the exposure to S. scabiei in wild foxes. This study is believed to be the first pointing to a long-term Sarcoptes/fox adaptation, combining long-term prevalence studies of clinical sarcoptic mange and serological evidence of exposure to the parasite in the general fox population.

No evidence of genetic benefits from extra-pair fertilisations in female sand martins (Riparia riparia)

Genetic parentage studies of socially monogamous birds reveal a widespread prevalence of extra-pair paternity. Variation in extra-pair paternity among individuals may depend on how different individuals benefit from extra-pair fertilisations and on the opportunity to pursue extra-pair copulations. A long-term study of sand martins (Riparia riparia) in Hungary allowed us to examine patterns of extra-pair fertilisations in a large colony of over 3,000 breeding pairs with many known age individuals. We used multi-locus DNA fingerprinting to determine whether extra-pair fertilisations occur when females are paired to (1) presumably low quality mates, or (2) genetically similar or dissimilar mates, and whether extra-pair fertilisations result in offspring of higher quality. Extra-paternal young were found in 38% of 47 broods and comprised 19% of 190 offspring. Males that lost paternity did not differ significantly from others in age or body condition. Social mates of broods containing extra-pair offspring did not differ in genetic similarity from pairs without extra-pair offspring. Furthermore, there was no significant difference in body condition between extra-pair young and their maternal half-siblings. We were unable to assign paternity and therefore cannot exclude the possibility that extra-pair males differed from the within-pair males they cuckolded, in age, body condition or genetic similarity with the female. We found a positive relationship between paternity losses and breeding density, suggesting that low breeding density may constrain opportunities for seeking extra-pair copulations.

Condition dependence of a multicomponent sexual signal in the field cricket Gryllus campestris

In choosing a breeding partner, females in many animal species select between available males on the basis of several signalling traits. Some theoretical models of signalling evolution predict that multiple ornaments convey specific information on different aspects of male quality, such as current nutritional condition. We investigated the effect of nutrition on the calling song of male field crickets Gryllus campestris. This song is a multicomponent sexually selected signal. Adult males were kept on one of three feeding regimes, which resulted in significant differences in body condition between experimental groups. We found significant increases in calling rate and chirp rate and a significant decrease in interchirp duration with increasing food level. Other song characters, such as chirp duration, syllable number, chirp intensity and carrier frequency, were not affected by the food treatment. Furthermore, carrier frequency was correlated with harp area, which is an index of structural size in adult males. The calling song of the field cricket may thus serve as a multicomponent sexual signal, which contains discrete information on past growth and juvenile development as well as present nutritional condition. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Biparental mouthbrooding of the catfish Phyllonemus filinemus in Lake Tanganyika

This article reports biparental mouthbrooding of the bagrid catfish Phyllonemus filinemus in Lake Tanganyika, based on analysis of specimens collected during SCUBA diving. This catfish was nocturnally active, and in the daytime it was concealed singly or in pairs beneath rocks. Within a breeding pair, the male or female alone incubated all the brood in the mouth until the offspring attained 12 mm or so in total length, but thereafter joint mouthbrooding or guarding by both parents took place. Most females of nonbrooding pairs showed high values of gonadosomatic index (GSI), whereas all females of brooding pairs and most single females showed low GSI values. This fact indicated that a pair is formed at a time near the gonadal maturation of the female and separates after the brood is reared. No significant difference in body condition among parents of different reproductive states was observed, which suggested that their condition does not deteriorate markedly as the result of foraging by an off-duty parent.

Sex, diet and feeding method‐related differences in body condition in the Oystercatcher Haematopus ostralegus

Measurements were made of Oystercatcher corpses to find the most reliable measure of body condition in live birds. Total body weight was as accurate as muscle thickness in assessing the weight of the pectoral muscles, a major store of protein reserves. Total body weight was also a good indicator of fat reserves. Wing‐length was the most reliable measure of body size. Body condition in live birds was measured as an individual's residual weight derived from a general linear model of (loge) body weight against age, month, (loge) wing‐length and time since capture. On the Exe estuary in autumn, there was no significant difference in body condition between same‐age Oystercatchers of different diets and feeding methods. In the winter months, however, body condition differed significantly between mussel feeders using different feeding methods, and between mussel feeders and birds that fed on worms and clams. Differences between diet/feeding methods were not the same for each age group. Birds with the highest mean body condition index in adults were mussel hammerers, in immatures mussel stabbers and in juveniles, worm/clam feeders. No significant difference in body condition was found between the sexes in any age group in autumn. In winter, when birds with the same diet/feeding method were considered, females were significantly heavier than males. However, when birds of all diets and feeding methods were combined, weight differences between the sexes were not apparent. We examine reasons why birds with certain diets and feeding methods may be heavier than others in winter, and why females are sometimes heavier than males. We conclude that, in most cases, it is due to differences between birds in their ability to achieve a common target weight. However, we conclude that adult females try to achieve a higher target weight than males, probably as a premigratory and prebreeding strategy. In the light of this, we consider the consequences for adult females, in terms of reproductive success and survival, of specializing in diets and feeding methods associated with lower body weights in winter.

Biostimulatory effects of estrous cows and bulls on resumption of ovarian activity in postpartum anestrous Zebu ( [formula omitted]) cows in the humid tropics

Suckled postpartum Zebu ( Bos indicus ) cows were exposed either to estrous females alone or together with bulls to determine if this regimen would stimulate the resumption of ovarian activity. The study was carried out on 60 Zebu cows. The animals were allocated at parturition to 1 of 3 treatment groups. Group FB cows (n=14) were exposed to progestogen treated females (approximately 3 cows per progestogen treated cow) and a bull for 42 d. Group F cows (n=31) were exposed to progestogen treated females and after 21 d a bull was introduced and remained with the group until the end of the experiment 21 d later. Estrus was induced with Syncro Mate B treatment and the cows were in estrus when introduced into Groups FB and F. Group N cows (n=15) were introduced to a bull 21 d after the treatments had begun in Groups FB and F, and the bull remained with these cows until the end of the study. On average, resumption of ovarian activity occurred in 57% ( 8 14 ), 19% ( 6 31 ) and 7% ( 1 15 ) of the cows in Group FB, F and N, respectively, within 21 d after the start of treatments. The difference was significant between Group FB and Groups F and N (P<0.05). During the second part of the experiment, in which the bull was introduced to Groups F and N, an additional 32% ( 10 31 ) of the cows in Group F and 33% ( 5 15 ) in Group N resumed ovarian activity. No cows in Group FB resumed ovarian activity during this period. There were significant differences in body condition between cows that resumed ovarian activity and those that remained in anestrus (P<0.05). We conclude that biostimulation effectively enhanced resumption of ovarian activity in anestrous suckled Zebu cows. This technique offers a potentially useful and practical way to improve reproductive efficiency in anestrous Zebu cattle in the tropics.