Female Birds Research Articles

Effect of Stocking Density on Growth Performance and Carcass Characteristics of Broilers Grown to 3 Kg under Antibiotic Free Diets1,2

Background: Stocking densities could have a significant impact on birds when reducing or eliminating antimicrobials (antibiotic-free; ABF) in poultry diets. This study investigated the effects of stocking densities on growth performance and carcass characteristics of broilers fed antibiotic-free diets grown to 3 kg. Methods: A total of 888 1-d-old Ross × Ross 708 chicks were randomly distributed into 24 pens. The treatments were four stocking densities including 29, 33, 39 and 42 kg of BW/m2; each treatment was represented by six replicates. Treatments were blocked within the room to account for any variations in room conditions. Treatment assignments were randomized within each block. Used bedding was obtained from commercial farms to simulate commercial conditions and litter microflora. Birds were fed antibiotic-free (ABF) diets and provided a three phase-feeding program (Starter: 0-14 d, Grower: 15-28 d and Finisher: 29-42 d). Feed and water were provided ad libitum. Birds and feed were weighed on 1, 14, 28 and 42 d of age to measure growth performance. On d 43, 10 (5 males and 5 females) birds from each pen were processed to determine weights and yields. Result: The BW and BW gain, live weight, carcass weights and carcass yield percentage were not affected by stocking density. Also, mortality was not affected by stocking density. However, FI and FCR for the starter period were significantly elevated (P less than 0.001 and P less than 0.001, respectively) at lower stocking densities, but were not different for the remainder of the growout. In conclusion, stocking densities evaluated from 29 to 42 kg/m2 with appropriate environmental management has a negligible effect on overall production and processing yield in ABF broilers.

Bacillus licheniformis and phytase combination in broiler chicken diets: Effects on growth performance, digestibility coefficients, gut microbiome activities, and bone quality

In the present study, B. licheniformis was added to broiler chicken diets alone or in combination with 6-phytase and the effects on growth performance, coefficients of ileal nutrient digestibility, morphometrical measurements of selected internal organs, gut microbial activity, and bone quality were determined. Four hundred 1-day-old female birds (Ross 308) were randomly allotted to 4 dietary treatments (10 replicate pens, 10 birds each). The trial was set up as follows: negative control (NC), basal diet without any feed additive; NC+Pro, basal diet with B. licheniformis (500 g/t of diet); NC+Phy, basal diet with 6-phytase (400 g/t of diet); and NC+Pro+Phy, basal diet in which both experimental factors were added at the same levels as above. The interaction between treatments was noted in each evaluated period regarding BWG and FI. In the entire experiment, an increased body weight gain (P < 0.001) was observed in the NC+Pro+Phy treatment compared to the other groups. The birds that received both feed additives combined were characterized by an increased feed intake (P < 0.001), contrary to NC+Pro and NC+Phy. Moreover, in terms of microenvironment modulations, interactions (P < 0.05) were observed in the jejunal and cecal digesta pH, short-chain fatty acid (SCFA) level, and microbial enzyme activities. However, the impacts of B. licheniformis and phytase on cecal SCFA concentrations and bacterial enzymes were mainly opposite. There were no interactions (P < 0.05) in terms of geometrical, mechanical, and structural selected tibia and femur indices. However, 6-phytase addition improved bone structure, stiffness, and elasticity. In conclusion, the interactions between 6-phytase and B. licheniformis positively affect growth performance via microbial activity changes; however, the supportive bone quality maintenance properties are only connected to 6-phytase supplementation.

Effect of increasing supplementation of dietary glycine on growth performance, meat quality, liver characteristics, and intestinal health in broiler chickens raised under heat stress conditions

The current study aimed to investigate the effect of increasing supplementation of dietary glycine (Gly) on growth performance, meat quality, liver characteristics, and intestinal health in broiler chickens raised under heat stress (HS) conditions. A total of one thousand six hundred 25-d-old broiler chickens were randomly allotted to 1 of 5 dietary treatments with 8 replicates. Each replicate comprised 20 male and 20 female birds. A negative control (NC) diet was prepared to meet or exceed energy and nutrient requirement estimates, whereas a positive control (PC) diet was formulated to contain increasing concentrations of AMEn by 50 kcal/kg as well as those of digestible amino acids, total Ca, and available P by 10% compared with the respective concentrations in the NC diet. Three additional diets were prepared by supplementing the NC diet with 0.4, 0.8, or 1.6% Gly. All chickens were raised under cyclic HS conditions at 29°C ± 0.89°C for 10 h/d and 23°C ± 1.45°C for the remaining time over an 18-d feeding trial. Results indicated that broiler chickens fed the NC diet had a greater (P < 0.05) FCR than those fed the PC diet under HS conditions. Increasing supplementation of up to 1.6% Gly in diets decreased (linear, P < 0.001) FCR in broiler chickens. Increasing supplementation of dietary Gly tended to increase (linear, P = 0.070) water holding capacity in the breast meat. Increasing supplementation of dietary Gly decreased (linear, P < 0.05) serum aspartate aminotransferase concentrations and tended to decrease blood heterophil:lymphocyte (linear, P = 0.083) and liver malondialdehyde concentrations (quadratic, P = 0.084). A tendency for increased villus height (linear, P = 0.086) and a significant increase in villus height:crypt depth ratio and goblet cell numbers (linear, P < 0.05) were identified following increasing Gly supplementation. In conclusion, increasing supplementation of dietary Gly improved feed efficiency, meat quality, liver health, and intestinal morphology possibly by mitigating oxidative stress and stress response in broiler chickens raised under HS conditions.

PSII-19 Effect of dietary supplementation of xylanase alone or combination of xylanase and β-glucanase on growth performance and intestinal measurements in broiler chickens

Abstract Poultry feeds primarily comprise plant ingredients such as cereal grains and cereal by-products that are high in non-starch polysaccharides (NSPs). However, poultry has limited digestive enzymes to efficiently utilize NSPs, and therefore, exogenous NSP-degrading enzymes (NSPase) are typically supplemented to poultry diets. Xylanase is the most widely used as NSPase in poultry diets because xylanase degrades arabinoxylans which is in increased amounts in most feed grains like corn and wheat, thereby improving dietary nutrient utilization and subsequent productive performance. β-glucanase is another potential exogenous NSPase used to degrade β-glucans present in plant ingredients. Although the benefits of dietary xylanase are well-documented, limited information regarding effects of dietary xylanase and β-glucanase complex is available. Therefore, this study aimed to investigate the effect of dietary supplementation of xylanase alone or combination of xylanase and β-glucanase on growth performance and intestinal measurements in broiler chickens. A total of four hundred 8-d-old male and female Ross 308 broiler chicks were randomly allotted to 1 of 4 dietary treatments with 10 replicates. Each replicate had 5 male and 5 female birds. Dietary treatments included a positive control (PC) diet with adequate energy and nutrients, a negative control (NC) diet with high NSP-containing ingredients and less AMEn by 100 kcal/kg than PC diet, and 2 NC-based diets supplemented with 0.1% xylanase (4,000,000 units/kg) or 0.1% xylanase-glucanase complex (4,000,000 units/kg xylanase and 2,000,000 units/kg β-glucanase). The experiment lasted for 28 d. For intestinal measurements including jejunal morphology and ileal digesta viscosity, 1 male chicken per replicate was selected based on the body weight at the end of the experiment. Results indicated that birds fed PC diets had less (P &amp;lt; 0.05) FCR than those fed NC diets (Table 1). Birds fed diets supplemented with xylanase alone or combination of xylanase and β-glucanase had also less (P &amp;lt; 0.05) FCR than those fed NC diets. No difference in FCR was observed between birds fed PC diets and those fed diets supplemented with xylanase alone or combination of xylanase and β-glucanase. However, dietary treatments had no effects on body weight, body weight gain, and feed intake of broiler chickens. Jejunal villous height to crypt depth ratio (VH:CD) was greater (P &amp;lt; 0.05) for birds fed PC diets or diets supplemented with combination of xylanase and β-glucanase than those fed NC diets (Table 2). Feeding diets supplemented with xylanase alone or combination of xylanase and β-glucanase decreased (P &amp;lt; 0.05) ileal digesta viscosity as compared with feeding NC diets (Table3). In conclusion, feeding high NSP and low energy diets supplemented with either 0.1% xylanase alone or 0.1% xylanase and β-glucanase complex results in similar productive performance of broiler chickens as compared with feeding typical corn-soybean meal-based diets possibly due to improved intestinal structure and decreased digesta viscosity.

Sex identification of sun conure (Aratinga solstitialis) using loop-mediated isothermal amplification of W and Z spindlin chromosomes.

The sun conure (Aratinga solstitialis), a bird belonging to the Psittaciformes family, is a popular pet because of its bright color and beautiful appearance. The sun conure is a monomorphic bird with similar appearances between males and females, making sex identification difficult by observing the external morphology. Therefore, molecular techniques are utilized. Loop-mediated isothermal amplification (LAMP) is a molecular technique that is often applied for sex identification in birds and is a quick and simple method that can be used in the field. This study used the LAMP technique to improve sex identification in sun conures by observing the color change of hydroxy naphthol blue. Two primer sets, SunSpin-W and SunSpin-Z, were designed for sex identification in sun conures using the LAMP technique specific to the spindlin gene. The developed LAMP reaction was tested for optimal conditions, sensitivity, and specificity compared with the polymerase chain reaction (PCR) technique. The SunSpin-W primer set amplified only female birds, whereas the SunSpin-Z primer set amplified DNA from both male and female birds. The primer sets were optimized at 62°C for 45 min. A positive result was visible to the naked eye from the color change of the reaction. In the LAMP assay, the lowest detectable concentration was 10 pg/μL and in the PCR assay, it was 1 ng/μL, while a 100% accuracy rate in sex identification was observed when comparing the LAMP assay results with the PCR assay. This study successfully developed a LAMP technique for sex identification of sun conure, which took 45 min to complete and can be expanded for use in the field.

Investigation of Glandula Uropygialis in Different Avian Species Using Morphometric and Histological Methods.

The aim of this study was to identify the glandula uropygialis's macroanatomical and histological structure in male and female birds (stork, goose, eagle, pigeon, crow and sparrowhawk) that belong to different populations. A total of 58 specimens were used in the study. The study materials were delivered to our laboratory by nature conservation and national parks, and no animals were euthanised for this study. The longitudinal and transversal lengths, dorsoventral heights and feather length of the glandula uropygialis and papilla uropygialis were measured with a digital calliper. Haematoxylin-eosin and Masson trichrome staining were performed for histological examinations. The shape of the glandula uropygialis was found to be pear-shaped in pigeons and sparrowhawks, heart-shaped in geese, kidney-shaped in eagles and oval-fascule-shaped in storks. In the crow, the shape of the glandula uropygialis was different from the other species in that it was located dorso-caudally. Histomorphological examination of the glands of these species revealed that the gland generally consisted of two lobes, right and left, surrounded by connective tissue from the outside. The parenchyma of these lobes consisted of tubulo-alveolar secretory glands with a radial arrangement from the periphery to the centre. The glands within the lobes differed from the periphery to the centre and although the general histomorphological appearance was similar between bird species, some differences were observed between species. Similar stromal structure was observed in all bird species evaluated in the study. However, the reticular connective tissue forming the roof of the gland was found to be more developed in pigeons, especially in Masson's trichroma staining. The degenerative layer in the glands was more prominent in the eagle, followed by the goose and crow. Although a common general histological structure was observed among bird species, simple histomorphological differences were found between these formations, but no differences were found between the sexes. The results obtained will be compared with the findings of the aves class and will provide a data source for this special gland specific to birds. It is thought that the results obtained may help to determine the functional properties of the gland and contribute to the science of ornithology.

Family flock size and age-sex structure of indigenous village chickens.

Indigenous village chickens (IVCs) significantly contribute to rural development. There is considerable variation in family flock size and age-sex structure of IVCs. This study reports the family flock size, age-sex group structure, and demographic history of IVCs. This work involved a cross-sectional study conducted using face-to-face general informants' individual interviews with 119 smallholder farmers in highland and lowland agroecological zones. The average family flock size of the sampled households was small (mean = 7.28, range: 1-38). Female birds (hens and pullets) represented the largest proportion of the family flocks (50.2%). The proportion of chicks (26.4%) and pullets (14.4%) was lower than that of hens (35.8%), which creates a considerable challenge in producing replacement breeding flocks. Similarly, the proportion of cockerels (9.1%) was lower than that of cocks (14.3%). The average cock-to-hen ratio (one cock to seven hens) was better than the commonly recommended proportion (1 cock to 8-10 hens). As a result, smallholder farmers have not faced the problem of producing infertile eggs. The estimated effective population size (Ne) of 4.02 and the corresponding inbreeding coefficient of 0.12 at the family flock level show that to some extent inbreeding may occur at the family flock level; besides, the estimated Ne represents 55.2% of the census size. However, inbreeding could be offset by the high rate of flock turnover and uncontrolled mating among scavenging birds. Family flocks contain a few birds, which may lead to consanguineous mating. Inbreeding is, however, considerably reduced by uncontrolled breeding among birds that share a common scavenging ground. The driving factors behind the low proportion of chicks and juvenile birds and the family flock size need to be further investigated to improve the contribution of local chickens to rural livelihoods.

Correction to: Scope and adaptive value of modulating aggression over breeding stages in a competitive female bird

Correction to: Scope and adaptive value of modulating aggression over breeding stages in a competitive female bird

Research Progress in the Establishment of Sterile Hosts and Their Usage in Conservation of Poultry Genetic Resources

Many local chicken breeds are rapidly declining and even facing extinction due to a variety of factors such as indiscriminate crossbreeding, climate fluctuations, epidemic outbreak, and environmental changes. Developing effective preservation strategies is important to address this situation. The special reproductive characteristics and gamete morphology of chickens pose challenges for preserving genetic heritage through the cryopreservation of genetic materials. Currently, gonad and primordial germ-cell cryopreservation and transplantation are the most promising approaches, especially for the genetic information in the W chromosome of female birds. The study of establishing sterile recipients is crucial for increasing the efficiency of the colonization of transplanted donor tissues and cells. Several classical methods, including ovariectomy and testectomy, busulfan, and irradiation, have been employed to deplete endogenous germ cells in recipient males before transplantation. These methods rely on the toxicity of chemical reagents and physical stimulation to kill germ cells. Recent advances in gene-editing technology have introduced sterile hosts via the knocking out of genes relevant to germ cells’ development. This review explores state-of-the-art technologies for preparing infertile avian recipients (mainly chickens) and aims to provide guidance for the conservation of poultry genetic material and breed restoration.

Stay or go? Changing breeding conditions affect sexual difference in colony attendance strategies of Atlantic puffins Fratercula arctica.

Male and female birds have different roles in reproduction and, thereby in their reproductive investment, which in turn may increase negative effects of poorer breeding conditions caused by e.g., climate change or ecosystem regime shifts. By using a 33-year time series of resightings of Atlantic puffins Fratercula arctica individually colour-ringed as breeders in previous years, we showed that the difference in colony attendance of male and female birds depended on the environmental conditions for raising young, proxied by the average duration of the chick period and size of the herring Clupea harengus fed to the chicks in the colony each year. The longer the chick period, the more was the sex ratio of adults sitting visibly in the colony biased in favour of males. An increase in herring size, indicating better feeding conditions for raising chicks, led to more observations of both sexes. Additionally, we found that birds were observed less with age and females more so than males. We discuss the results in relation to general life-history theory on sexual differences in trade-offs between individual investment in breeding and own survival. Our results suggest that females are increasingly more willing than males to invest in provisioning for the chick the more and longer the chick needs such care.

Breeding pairs with color aberrations in oriental reed warblers.

In 2017, one pair of Oriental reed warblers (Acrocephalus orientalis) with color aberrations was found in Yongnianwa National Wetland Park, Hebei, China. The female bird exhibited white feathers on the head, neck, and upper back, and the base of the beak was flesh-red in color. The male had a few feathers on the outer edges of the left and right primary wing coverts that were white, which was determined to be leucism after analysis. The breeding pairs laid their first egg on May 29, with a clutch size of four eggs. After an incubation period of 13 days, two chicks hatched on June 13, 2017. The nest was found empty on June 20 when the chicks were 7 days old and before fledging age; therefore, it was presumed that the chicks had been predated. A white parrot egg was added to the nest during the incubation period to test the egg recognition ability of breeding pairs and was successfully rejected. To the best of our knowledge, this is the first report of color aberrations in the Oriental reed warbler, and we found that this color aberrations did not affect some reproductive and antiparasitic behaviors of the birds, but whether it affects their breeding success needs to be further studied.

Principal Component Analysis (PCA) of Body Measurements and Its Relationship with Body Weight in Jowo Super (Bangkok × Layer) Chicken

The aim of this study was aimed to determine the total variation of the body weight (g) by using principal components analyses (PCA) of body measurements (cm) in 156 Joper (Bangkok × Layer) crossbred chickens consisting of 60 males and 96 females. In total twelve traits including body weight (BW), head circumference (HC), neck length (NL), wings length (WL), back length (BL), chest circumference (CC), chest width (CW), femur length (FL), tibia length (TiL), shank length (SL), shank circumference (SC) and third toe length (TL) were measured in each bird. The PCA of body measurements was performed by using a SPSS 16.0 package. Results determined three PC’s in each sex group based on the body measurements. Five body measurements of WL, BL, FL, TiL and SL were included in the first component (PC1) in both sex group which were able to explain the BW variation by 76% in male and 61% in female. The first three PC explained 67.78% and 65.93% of total variance of the morphostructure of male and female birds, respectively. The Kaiser-MeyerOlkin (KMO) value in both sex group was 0.80 which indicated the results of PC analyse were accurate. In conclusion, the body measurements of PC1 were influenced to BW of birds study.

Social Environment Alters the Duration of Rapid Yolk Deposition in Eggs of Domestic Hens.

AbstractThe social environment can drive female birds to alter their investment in reproduction in the form of greater incubation behavior, more parental care, and greater allocation of physiological mediators to yolks. However, less is known about how social variables impact the speed at which females grow ovarian follicles in preparation for ovulation. We hypothesized that the social environment would influence how long ovarian follicles remain in rapid yolk deposition before reaching the size necessary for ovulation. For 8 d, we tested the effects of three types of social interactions: no social engagement (control), engagement with the same four females (social group 1), or engagement with the same four females plus six randomly selected roosters (social group 2). Starting on day 5 of engagement, we collected eggs and measured egg and yolk masses and yolk diameters. Then we stained the yolks with potassium dichromate to quantify the number of days the ovarian follicle spent accumulating yolk. We compared the results of the treatment groups with those of the control hens that were kept in individual laying cages throughout the study. The number of eggs laid, the yolk mass, and the yolk diameter did not differ among any of the three groups, but hens exposed to both females and males produced yolks with significantly more rings than hens in the other groups. Thus, the presence of males appeared to lengthen the time it took for ovarian follicles to reach the size needed for ovulation but did not result in larger or heavier yolks.

First nesting record of Black-necked Stork Ephippiorhynchus asiaticus (Aves: Ciconiiformes) in Kumana National Park, Sri Lanka

Black-necked Stork is a tall, long-necked wading bird of the stork family (Ciconiidae). It is a rare breeding resident and fewer than 50 birds inhabit the island of Sri Lanka. This study was conducted in Kumana National Park from August 2022 to August 2023 to observe nesting characteristics of Black-necked Storks. Nesting locations were searched during three predefined periods each day. During the study, the first recorded Black-necked Stork nest in Sri Lanka was observed, with both male and female birds engaging in nesting behavior. The findings provide important insights for conserving this nationally critically endangered bird species.

Brain Gene Regulatory Networks Coordinate Nest Construction in Birds.

Nest building is a vital behavior exhibited during breeding in birds, and is possibly induced by environmental and social cues. Although such behavioral plasticity has been hypothesized to be controlled by adult neuronal plasticity, empirical evidence, especially at the neurogenomic level, remains limited. Here, we aim to uncover the gene regulatory networks that govern avian nest construction and examine whether they are associated with circuit rewiring. We designed an experiment to dissect this complex behavior into components in response to pair bonding and nest material acquisition by manipulating the presence of mates and nest materials in 30 pairs of zebra finches. Whole-transcriptome analysis of 300 samples from five brain regions linked to avian nesting behaviors revealed nesting-associated gene expression enriched with neural rewiring functions, including neurogenesis and neuron projection. The enriched expression was observed in the motor/sensorimotor and social behavior networks of female finches, and in the dopaminergic reward system of males. Female birds exhibited predominant neurotranscriptomic changes to initiate the nesting stage, while males showed major changes after entering this stage, underscoring sex-specific roles in nesting behavior. Notably, major neurotranscriptomic changes occurred during pair bonding, with minor changes during nest material acquisition, emphasizing social interactions in nest construction. We also revealed gene expression associated with reproductive behaviors and tactile sensing for nesting behavior. This study presents novel neurogenomic evidence supporting the hypothesis of adult neural plasticity underlying avian nest-construction behavior. By uncovering the genetic toolkits involved, we offer novel insights into the evolution of animals' innate ability to construct nests.

Meat Quality Traits and Blood Biochemistry of Three Chicken Genotypes Reared under Different Production Systems

In the recent modernization, the consumer is becoming choosier regarding the quality and nutritional aspects of meat. A study was planned to evaluate meat quality attributes from different chicken genotypes reared in three different housing systems. For this, 54 female birds (52 weeks old) from 3 different genotypes i.e., two crossbreds [Rhode Island Red × Naked Neck (RNN), Black Australorp × Naked Neck (BNN), and purebred Naked Neck (NN)] reared under three housing systems (Intensive, Semi-Intensive, and Free-range) were slaughtered and subjected to nutritive, qualitative and sensory evaluation. Significant differences among genotypes, housing systems, and their interactions were observed regarding carcass yield, breast, wings, drumsticks, neck, ribs, and back weight. Regarding sensory evaluation, significant variations were observed among genotypes, housing systems, and their interaction except for juiciness. In terms of proximate analysis, significant differences were observed regarding moisture, dry matter, ash, and ether extract among different genotypes, housing systems, and their interactions. Regarding blood biochemistry, birds reared under the intensive housing system had the higher glucose values whereas albumen and globulin was higher in semi-intensive reared bird; BNN showed higher cholesterol levels among genotypes. In conclusion, carcass traits, meat proximate, and mineral composition were affected by genotypes and housing systems.

Characteristics of Several Qualitative Traits of Betet Chickens Raised by Fighting Cock Fans in Central Lombok

The study was conducted to determine the characteristics of betet chickens kept by fighting cock enthusiasts in Central Lombok. Determining the research area was carried out using the cluster sampling method, and sampling of farm was carried out non-randomly using the snowball method, and determining the number of chicken samples for observation was carried out using the accidental sampling method. Observations were made on 74 male Betet and 26 female Betet birds The variables observed were: body posture, feather color, beak color, beak shape, shank color and comb shape. The data obtained were tabulated, the frequency was calculated and analyzed using descriptive analysis. The results of the research found that the feather color of male betet chickens was dominated by bing (black), followed by green, brumbun and the smallest frequency of lurik colors. The feather color of female betet chickens was dominated by the alap color, followed by the kelawu color and the lowest frequency of the berumbun color. The highest frequency of beak color was yellow, followed by black, and the majority was sharply curved. The highest frequency of shank color in male betet chickens was yellow, followed by black and the lowest frequency was white. There were no white shanks found in female betet birds. The highest frequency of the comb shape for male betet chickens was without a comb because it is cut, followed by the single shape, then the lowest frequency was the pea shape. The majority of female betet chickens have a single comb, the rest do not have a comb (the comb does not develop). It was concluded that betet chickens kept by fighting cock enthusiasts

Scope and adaptive value of modulating aggression over breeding stages in a competitive female bird

Abstract In seasonally breeding animals, the costs and benefits of territorial aggression should vary over time; however, little work thus far has directly examined the scope and adaptive value of individual-level plasticity in aggression across breeding stages. We explore these issues using the tree swallow (Tachycineta bicolor), a single-brooded bird species in which females compete for limited nesting sites. We measured aggressiveness in nearly 100 females within 3 different stages: (1) shortly after territory-establishment, (2) during incubation, and (3) while caring for young chicks. Based on the timing, direction, and magnitude of behavioral changes between stages, we used k-means clustering to categorize each female’s behavior into a “plasticity type.” We then tested whether plasticity type and stage-specific aggression varied with key performance metrics. About 40% of females decreased aggressiveness across consecutive breeding stages to some degree, consistent with population-level patterns. 33% of females exhibited comparatively little plasticity, with moderate to low levels of aggression in all stages. Finally, 27% of females displayed steep decreases and then increases in aggression between stages; females exhibiting this pattern had significantly lower body mass while parenting, they tended to hatch fewer eggs, and they had the lowest observed overwinter survival rates. Other patterns of among-stage changes in aggressiveness were not associated with performance. These results reveal substantial among-individual variation in behavioral plasticity, which may reflect diverse solutions to trade-offs between current reproduction and future survival.

The potential of in ovo-fed amino acids to alleviate the effects of heat stress on broiler chickens: effect on performance, body temperature, and oxidative status during the finisher phase

The aim of the current study was to investigate the potential of in ovo-fed amino acids (AA) to reduce the effects of heat stress on finishing broiler chickens. To achieve this, a total of 1,400 fertile hatching eggs were randomly distributed into 5 groups (n = 280/group) and injected with one of the following in ovo treatments on embryonic day 18: 52 µL of sterile diluent/egg (CTRL), CTRL + 1.0 mg of L-Leucine (T1), CTRL + 0.45 mg of leucine + 1.15 mg of methionine (T2), CTRL + 3.0 mg of methionine + 2.0 mg of cysteine (T3), and CTRL + 0.40 mg of leucine + 1.60 mg of methionine + 1.60 mg of cysteine (T4). After hatch, chicks were allocated according to a complete randomized block design comprising 2 thermal conditions: thermoneutral (24°C, 45% RH) and heat stress (34°C, 55-60% RH) with 5 pens/group/condition. The cyclical heat stress regimen (10 h/d) was then applied from d 29 to d 34. Compared to the CTRL group, T3 and T4 exhibited a higher BW during the starter phase (P < 0.001). T4 also had a lower feed conversion ratio (FCR) than CTRL during this same phase (P = 0.03). During the grower phase, males of all treatment groups consistently exhibited higher BW compared to the CTRL group, which was not observed among female birds (PSex × TRT = 0.005). During the finisher phase, the in ovo treatment effect on performance was not significant. However, heat-stressed birds from treatment group T3 and T4 exhibited lower facial temperatures (Pday × TRT < 0.001) as well as lower plasma (Pcondition x TRT = 0.039) and liver (Pcondition x TRT < 0.001) malonaldehyde concentrations compared to the CTRL group. In conclusion, in ovo-fed AA have the potential to modulate the effects of heat stress on finishing broiler chickens by limiting its detrimental consequences, including increased body temperature and oxidative damage.

Developmental stage-dependent effects of perceived predation risk on nestling tree swallows (Tachycineta bicolor).

The risk of predation directly affects the physiology, behavior, and fitness of wild birds. Strong social connections with conspecifics could help individuals recover from a stressful experience such as a predation event; however, competitive interactions also have the potential to exacerbate stress. Few studies have investigated the interaction between environmental stressors and the social landscape in wild bird populations. In 2 years of field studies, we experimentally simulated predation attempts on breeding female tree swallows (Tachicyneta bicolor). At the same time, we manipulated female breast plumage color, a key social signal. Simulated predation events on tree swallows early in the nestling period reduced young nestlings' mass by approximately 20% and shortened telomere lengths. Ultimately, only 31% of nestlings in the predation group fledged compared with 70% of control nestlings. However, the effects of experimental manipulations were timing dependent: the following year when we swapped the order of the experimental manipulations and simulated predation during incubation, there were no significant effects of predation on nestling condition or fledging success. Contrary to our expectations, manipulation of the social environment did not affect the response of tree swallows to simulated predation. However, manipulating female plumage during the nestling period did reduce nestling skeletal size and mass, although the effects depended on original plumage brightness. Our data demonstrate that transient stressors on female birds can have carry-over effects on their nestlings if they occur during critical periods in the breeding season.